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SINMAP - David Tarboton

1. Steps selection is that the number of natural terrain points used for plotting may be specified When the plot is created with the Compute Steps selection the default number of points 2 000 or the number of points previously established by the user is displayed on the plot Selection of the SA Plot menu item allows an on the fly change to the number of points to be plotted in a dialog box The number of points plotted is only approximate and does not include landslide points Creating the SA Plot first creates the file damnamesap dbf which is an X Y table of slope area data and other attribute landslide and location data for each cell Data from this file table provide the basis for the SA Plot The SA Plot is then created named SA Plot Demname and resized along with the DEM map view so that both windows may be viewed at the same time The SA Plot menu item becomes enabled after the calibration regions slope and contributing area grid themes are added to the map view It is disabled after the SA Plot is created and added to the study In some situations it may become necessary to create a new SA Plot For example if new landslide data become available and are added as data points to the Landslides Seeps theme it is necessary to rebuild dannamesap dbf with the added data points for these landslides The creation of a new SA Plot requires that the user delete the existing SA Plot from the study This is accomplished by acti
2. A 26 B U b b The cumulative distribution function of A is obtained for a particular a by evaluating the area below the hyperbola defined by a yb that is within the box Figure 2 that defines the domain b b y relative to the total area of the box Conditional statements are used dependent upon which sides the hyperbola intersects Symmetry is invoked as the hyperbola intersecting the left and right edges which is only possible when y b lt y b is equivalent to the hyperbola intersecting the top and bottom edges bottom edges when y b gt y b if y and b are interchanged We choose to work with the case y b lt y b Before evaluation of F a if y b gt b and y are interchanged Then F a is given by ifa yb F a Prob A lt a 0 if y b lt a lt a In a yjb a yb y yi b bi if y b lt a lt yab F a aln b b b b y y y b b if yb lt a lt yb F a 61 SINMAP USER S MANUAL APPENDIX 1 aln b y a a biy biy b y F E y b ifa yb F a 1 This defines a generic function which with parameters is denoted Fy Yv y b by a Prob A lt a A 27 a yb bi b FIG URE A 2 Evaluation of CDF for product of uniform random variables Now the combination given by A 25 has density function the convolution of the density functions of A and X namely f z jt f z
3. LS Density tt km 2 Region 8 Area km 2 of Region HLandslides of Slides LS Density km 2 6 A Stait ay Exploring Norrish BY Microsoft Word Documenti ArcView GIS Version 3 0a a Statistical Summary f FIGURE 12 summary statistics for the eight calibration regions of the Bumt Creek D rainage 50 SINMAP USER S MANUAL PART 111 2 ArcView GIS Version 3 0a Edit View Iheme Analysis SinMap uz Windoi BY Ese Wo AAAA 80 0 z Fare TT web 70 Hg 2 SA Plot Chetelev BEE 1e 006 100000 c m 10000 1000 4 Contributing Area Slope degrees Astan Exploring Norrish BY Microsoft Word Documenti ArcView GIS Version Statistical Summary for Ch Ch 257PM FIGURE 13 Slope area plot for all eight calibration regions of the Burnt Creek D rainage Figure 14 is an ArcView screen showing a portion of the wetness map derived by the SINMAP analysis for the Burnt Creek Drainage Figure 15 is an ArcView screen that shows a portion of the stability index map calculated in the analysis Table 5 summarizes the classification results for the entire study area The results indicate that the upper threshold stability class has the highest landslide density of 11 05 landslides per square kilometer This stability class represents a total area of 3 5 square kilometers which is only 1 596 of the total study area It i
4. If no is selected the existing files are backed up by adding b to their names prior to creating the new grids From the SinMap menu choose Contributing Area as the final step This selection generates the contributing area grid and adds it to the map view The grid file generated will have the name dennamesa where demname is the name of the original DEM grid If dennamesa exists a Yes No dialog box will ask whether to use the existing grid as the basis for the grid theme If no is selected the existing file is backed up as dannamesa b prior to the creation of the new grid Note An additional grid called demnamesca2 is created by this operation See Section 7 7 for an explanation of this grid s purpose 4 8 Stability Analysis SINMAP theory discussed in Part I of this document is implemented within the program with results displayed as saturation and stability index grid themes and the creation of an SA Plot These results are generated using menu items in the Stability Analysis menu item group Option 1 From the SinMap menu in the Stability Analysis group choose Compute Steps The Compute All Steps menu item becomes ungrayed enabled after slope contributing area and calibration regions grid themes have been created and added to the view The Compute All Steps menu item sequentially executes routines for generating the Stability Index and Saturation grids adds these grids to the map view as grid themes and creates t
5. TABLE 1 Stability Class D efinitions Condition Class Predicted State Parameter Range Possible Influence of Factors Not Modeled SI gt 15 1 Stable slope zone Range cannot model Significant destabilizing factors are instability required for instability 1 5 gt SI gt 1 25 2 Moderately stable zone Range cannot model Moderate destabilizing factors are instability required for instability 1 25 gt SI gt 1 0 3 Quasi stable slope Range cannot model Minor destabilizing factors could zone instability lead to instability 1 0 gt SI gt 0 5 4 Lower threshold slope Pessimistic half of range D estabilizing factors are not zone required for instability required for instability 0 5 gt SI gt 0 0 5 Upper threshold slope Optimistic half of range Stabilizing factors may be zone required for stability responsible for stability 0 0 gt SI 6 D efended slope zone Range cannot model Stabilizing factors are required for stability stability 2 2 The Infinite Slope Stability Model The infinite slope stability model factor of safety ratio of stabilizing to destabilizing forces is given by simplified for wet and dry density the same from Hammond et al 1992 _ Cc C cos Olp g D D p 8 Dy tan 1 D p gsin0cos0 FS where C is root cohesion N m C is soil cohesion N m is slope angle p is wet soil density kg m p is the density of water kg m g is
6. computed from digital elevation model D EM data The other input parameters are recognized to be uncertain so are specified to SINMAP in terms of upper and lower bounds on the ranges they may take The stability index SI is defined as the probability that a location is stable assuming uniform distributions of the parameters over these uncertainty ranges This value ranges between 0 most unstable and 1 least unstable Where the most conservative destabilizing set of parameters in the model still results in stability the stability index is defined as the factor of safety ratio of stabilizing to destabilizing forces at this location under the most conservative set of parameters This yields a value greater than Terrain stability mapping practice in British Columbia Province of British Columbia 1995 requires that broad stability classes be identified and mapped based upon relatively coarse information to quickly identify regions where more detailed assessments are warranted SINMAP is intended for this purpose Table 1 gives an example of how broad stability classes may be defined in terms of the stability index SI The selection of breakpoints 1 5 1 25 1 0 5 0 0 is subjective requiring judgement and interpretation in terms of the class definitions In the example given we use the terms stable moderately stable and quasi stable to classify regions that according to the model should not fail with the most conserv
7. ArcView extension files If sinmap avx is not in the ArcView extension search path SINMAP will not be available for selection in the Extensions dialog box sinmap dll is the dynamic link library file containing SINMAP routines It must be placed in the arcview bin32 directory where arcview exe and all ArcView D LL files are located Other files included that can be placed anywhere include 16 SINMAP USER S MANUAL PART III sinmap pdf copy of this user s manual in Adobe Acrobat format sample asc small test ASCII file of DEM data samplels shp samplels s ArcView shape files for point landslide sample data samplels dhf C source files area c avcalls c flood c gioapi h gridio c gridio h Ismcom c lsm h sindex c setdir c areamn c floodmn c setdirmn c sinmn c avcalls null c gridio null c See section 8 modifying the source code for information on using the source code files 3 0 Quick start tutorial This section provides a quick introduction to the steps required to undertake a SINMAP analysis Each of these procedures is explained in more detail in Section 4 Sample data files are provided for use with the tutorial The file sampleasc is a small ASCII file of DEM data and the files samplds shp samplds shx and samplds dbf are a point shapefile coverage of landslides These files should be copied to a directory where you want the SINMAP output files to be created 1 Start up ArcView From the Project window Fi
8. Created by SINMAP File Location dannamedp is automatically placed in the study directory in which denname is located Slope is calculated for each grid cell using the methods presented in Part I Section 3 3 Be aware that the slope algorithm used by SIN MAP differs from that implemented by ESRI in the Spatial Analyst extension 7 7 Theme Name Contributing Area Theme Type Grid theme File Name demnamesca and demnamesca2 where demname is the name of the original D EM grid file File Type G rid File Source Created by SINMAP File Location demnamesca and demnamesca2 are automatically placed in the study directory in which demname is located This is the specific catchment area and is equal to the upslope area draining to the cell per unit length of contour through which that area drains Calculation of specific catchment area is discussed in Part I Section 3 4 Two specific catchment area grids are created The grid demnamesca contains the actual specific catchment area values In the grid named demnamesce2 all contributing area values greater than 100 000 are reduced to 100 000 for display purposes This was done due to some apparent limitations in ArcView for presenting a wide range of floating point grid data For terrain stability mapping studies this should pose no problem as the areas that have greater 100 000 m of specific catchment area are usually within the lower watershed along perennial streams The data source for
9. a cess cbs ctt e dta e a hata oS ae 11 3 2 Pit Filling Corrections uc iH t He od ae Ge ete tte 11 3 3 Slopes and Flow 11 3 4 Specific Catchment Area eese eese m Sa 13 3 5 SINMAP Stability Index and Wetness eene eene nnne 13 PART II SINMAP SOFTWARE USER S GUIDE 14 EOINTRODUCTION 3 35 5 A 5 0 s a IDEE E EE 14 EIDEM Map View saa asna au aq Dundee 15 1 2 Slope Area Plot Chart eee itu eei t n eee 15 2 0 INSTAEDATION 1 2 renidet n 15 2 1 Hardware and Software Requirements eese nne nnne 15 2 2 Installation Procedure 4e eet dee d ee ed ene 16 3 0 QUICK START TUTORA D o ee reee p P exte Eo Ee eae EXE ER EUN eye Ee PP RR AN EN YN PANNIS 17 40 DETAILED TUTORIAL 2 2 2 3 Erie dus EE ED eter ER E e EP RE 18 4 1 Starting ArcView and Loading ener 18 42 Adding a New dde Ree e te e b e ee ee t edo e ess 19 4 3 Establishing Model Parameters eese nennen 19 4 4 Importing and Selecting DEM 20 4 5 Creating the Calibration Regions Grid esee 22 4 6 Adding Landslides to the View eese eene enne nennen nenne 22 4 7 Preparatory Grid Processing 23 4 6 St bility Analysis i a ae e d e e eda
10. a da A 28 Since X U x x this can be written Z X aO da 00 50 82 A 29 To get the cumulative distribution function of Z we need the integral of F which will be denoted Then Fa z xi Fa z x5 X X F z A 30 Integrating F the expressions between equations A 26 and A 27 we obtain fa lt yb a F a C F n a C a lt a lt yb 62 SINMAP USER S MANUAL APPENDIX 1 2 2 y ba Fa a C F a C Al y y b b 2 AI2 2 if yib amp lt a lt ybi a 2 a b bi y a Fy z C FA FC 9 Sd if yb z a lt a yb a a 3a In b y POS OA b y b y a 2 y y b bi F a C ifa yb a FAi 8 a C Fus a C In the above the argument a values defining the domain are defined together with generic expressions over each domain segment The constants of integration need to be specified so that F is continuous because it is the integral of a bounded function The first constant is arbitrary because the use of F is in a difference expression equation A 29 Therefore define C 20 C Faifa C Farla fori 2 5 to ensure this continuity It is possible when or b equals 0 for some of the intervals between sequential a s to reduce to alength of 0 In these cases the subscript i 1 must be un
11. and Dietrich 1994 when upper and lower uncertainty bounds of the parameters are specified as equal and cohesion is set to zero The range of uncertainty of the hydrologic wetness parameter may in an approximate sense substitute for the dynamic modeling over a range of storm events used by Wu and Sidle 1995 without requiring analysis and input of weather data We believe that the complexity and additional computational burden of analyzing sequences of weather data is unwarranted 1 3 Applicability and Limitations The SINMAP approach applies to shallow translational landsliding phenomena controlled by shallow groundwater flow convergence It does not apply to deep seated instability including deep earthflows and rotational slumps It is not intended to be used in the absence of field information needed for calibration and is most profitably implemented in conjunction with other terrain stability mapping methods The data required to implement the theory include soil and climate properties that can be highly variable in both space and time The theory does not require numerically precise input and accepts ranges of values that represent this uncertainly Stability indices output by the analysis should not be interpreted as numerically precise and are most appropriately interpreted in terms of relative hazard SINMAP USER S MANUAL PART I The methods implemented in the software rely on grid based data structures rather than vector based polyg
12. ata Computer V ision G raphics and Image Processing 28 328 344 O Loughlin E M 1986 Prediction of surface saturation zones in natural catchments by topographic analysis W ater R esearch 22 5 794 804 Pack R T 1995 Statistically based terrain stability mapping methodology for the Kamloops Forest Region British Columbia Proceedings of the 48th Canadian eotechnical Conference Canadian G eotechnical Society Vancouver B C 67 SINMAP USER S MANUAL REFERENCES Province of British Columbia 1995 Mapping and Assessing Terrain Stability Guidebook Forest Practices Code of British Columbia Quinn P K Beven P Chevallier and O Planchon 1991 The Prediction of Hillslope Flow Paths for Distributed Hydrological Modeling Using Digital Terrain Models H ydrological Processes 5 59 80 Sidle R 1992 A Theoretical Model of the Effects of Timber harvesting on Slope Stability W ater Resources R esearch 28 7 1897 1910 Sidle R C AJ Pearce and C L O Loughlin 1985 Hillslope Stability and Land Use Water Resources Monograph 11 Edition American G eophysical Union 140p Tarboton D G 1989 The analysis of river basins and channel networks using digital terrain data ScD Thesis Department of Civil Engineering M LT Cambridge MA Also available as Tarboton D G R L Bras and I Rodriguez Iturbe Same title Technical report no 326 Ralph M Parsons Laboratory f
13. gravitational acceleration 9 81 m s D the vertical soil depth m D the vertical height of the water table within the soil layer m and the intemal friction angle of the soil The slope angle 0 is the arc tangent of the slope S expressed as a decimal drop per unit horizontal distance Figure 1 illustrates the geometry assumed in equation 1 SINMAP USER S MANUAL PART I atan S FIGURE 1 Infinite slope stability model schematic Our approach with the hydrologic model is to interpret the soil thickness as specified perpendicular to the slope rather than soil depth measured vertically Soil thickness h m and depth are related as follows h D cos0 2 With this change FS reduces to _ 1 wr tan 0 sin 0 FS where w D D h h 4 is the relative wetness C C h p g 5 the combined cohesion made dimensionless relative to the perpendicular soil thickness and T Py Ps 6 the water to soil density ratio Equation 3 is the dimensionless form of the infinite slope stability model that we use This is convenient because cohesion due to soil and root properties is combined with the soil density and thickness into a dimensionless cohesion factor C equation 5 This may be thought of as the ratio of the cohesive strength relative to the weight of the soil or the relative contnbution to slope stability of the cohesive forces Figure 2 illustrates this concept The second term i
14. is relatively homogeneous and similar textures were observed in both glacial and colluvial soils across the area Calibration parameters were derived by fitting calibration curves to the landslide data within the slope area plot Though no independent analysis of soil properties was completed the 36 to 45 degree soil friction angles used in the calibration are considered realistic for the coarse subangular tills and colluvium found in the study area Interestingly this is a similar 45 SINMAP USER S MANUAL PART 111 range to that used in the Kilpala Watershed on Vancouver Island T R parameter was set at between 1500 m and 2500 m in the calibration On a 30 slope this equates to a length of planar slope required for saturation of between 750 and 1250 meters Figure 10 is an ArcView screen that shows a portion of the wetness map calculated in the analysis 2 ArcView GIS Version 3 0a File Edit View Theme Analysis SinMap Graphics Window Help Bo Es jr E J gt J EERS T ici COT Landslides Seeps _ Tm 8 NE KB Natural Landslide m 7 d n vii ig a W Fa D Ya a 3m eet 2 by LI asss sa a dd s es E quiate x Te al 2 lusu a r rm n ES AL TEN m fi S ees S n No D ata _ Contributing Area _ Slope rn _ Flow Direction NN _ Pitfilled DEM LN S M wil Calib
15. oe eg 24 4 9 Calibration Methods itii teet de ete tette d tdeo eie ether oet 25 4 9 1 Adjusting parameters in the DEM view emen mener 25 4 9 2 Adjusting parameters in the SA plot sese nennen 26 4310 Statistical SUmmdky e apnd elei de three ut 27 ASP The Rex Tool tes ee rre An u DTP Er ES S EH UNS 28 5 0 BONUS GRID EDITING TOOLS u kuu nn n VEE a E WARS S nene ener 28 54 Merge Grids ii naspa u Ea pe mon re er IS Su u Usa 28 SINMAP USER S MANUAL PART I 5 2 SUDSEL OF Grid itt e tee od 28 5 3 Grid Cutter oe S ted ed a e 29 6 0 7USBEULD TIPS ERR ni s hae OD eI ak DH 29 6 1 Create a Calibration Region Outside Study Area eese 29 6 2 Using an Existing Calibration Region 30 6 3 Changing Colors Data ranges and Names eese 30 7 0 DATA STRUCTURE REFERENCE u isane entere then 31 7 1 Theme Name Original DEM 1 apana aaa h enne nnne 3l 7 2 Theme Name Calibration Regions eese eene nennen nennen 3l 7 3 Theme Name Landslides noize neroni oie ed tede erede eee 32 7 4 Theme Name Pit filled DEM 33 7 5 Theme Name Flow Direction eese esee eene ener nennen 33 74 6 Theme Names eate dete aims kus 33 7 7 Theme Name Contributing Area
16. of Nimpkish Lake and to the south of Port McNeill B C The soils are predominantly coarse granular glacial tills and colluvium of variable thickness derived from basaltic bedrock of the Karmutsen Formation Few fine grained fluvial or lacustrine sediments were observed and none were noted to be associated with landslides during a brief two day field reconnaissance of the area The majority of landslides were noted to be shallow translational debris slides some of which subsequently mobilized into debris flows Many of the landslides originate in steep colluvial and bedrock dominated slopes and are frequently found in swales However it was also observed that some landslides originate in local zones of weathered bedrock 40 SINMAP USER S MANUAL PART III 2 2 Input Data DEM data were obtained from the Englewood Division of Canadian Forest Products Ltd Canfor These data were digitally complied from 1 45 000 scale photographs at an accuracy appropriate for a 10 meter contour interval map ie spot elevation accuracies of plus or minus 2 5 meters The data were then interpolated to a 10 m gid DEM using raw irregularly spaced elevation points and a triangulated network interpolation method O rthophotos rectified using this D EM are also available for the area and have a one meter pixel size These orthophotos were found to be particularly useful for accurately locating landslides A previous landslide inventory had been completed for the
17. or minus 5 meters This data was then 48 SINMAP USER S MANUAL PART III interpolated to a 15 m grid DEM using raw irregularly spaced elevation points and a triangulated network interpolation method A total of 266 landslides were inventoried using 1 15 000 scale black and white photography dated August 1994 Of the 266 landslides only 3 were determined to be associated with forest road construction All were classified as debris slides meaning that they are shallow translational and composed of a mixture of coarse and fine grained soils Any shallow landslides associated with the formation of talus at the base of rock cliffs mainly in alpine areas were disregarded in the inventory The landslides were classified into three broad size classes e Small less than 15 m wide by less than 75 m long e Large wider than 30 m or longer than 75m Medium between the small and large size Of the 266 landslides 129 were small 79 medium and 58 large It was also estimated that 5 were single occurrences 78 likely occur every one to five years and 183 likely occur less frequently than every five years The landslides located on aerial photographs were digitized using manual methods Because no orthophotos were available for this area at the time of this study the landslide locations were carefully plotted using T RIM contour form as a guide At the time of the transfer it was noted that the TRIM data frequently failed to pick up sma
18. subject area and was supplied in digital form by Canfor These landslide point locations were overlain on the orthophotos and carefully compared with obvious headscarp locations It was found that many of the inventory points were originally placed within the landslide scar but not within the zone of initiation Because the SINMAP methodology applies to failure locations within a zone of initiation the landslide inventory points were moved to this zone This editing was found to have a marked improvement on model results and is therefore deemed very important Z ArcView GIS Version 3 0a File Edi Table Field Window Help WE aga w AKH 53 i Goff 1 selected 7 SA Plot Kelevation of Region 38 137 Statistical Summary for Kelevation ly Quasi L Stable of Slides 0 0 LS Density km 2 00 1 006 S 150 125 10050 00 HA ER eiua Ai 1117932 Region 100000 200000 000 _ 100000 j lt 100004 dU a 2 m P a ru I a Saturated I E 2 4004 fede po s s t We E t es E d Unsaturated o al om Ic ZO Wetn ss 1096 10 BE 0 10 20 30 40 50 60 Slope degrees sa 22 51 R ArcView GIS Version 3 08 Exploring Desktop J Statistical Summary f Cj 10 03 4M FIGURE 6 ArcView screen showing the analytic results of a SINM
19. the theme that is displayed is the demnamesca2 grid Calculations involving specific catchment area however access the demnamesca grid The default color scheme for this theme illustrates the drainage network with drainage divides represented in yellow small catchment areas in green and mainstem streams in blue 7 8 Theme Name Stability Index Theme Type Grid theme File Name dennamsi where dannameis the name of the original D EM grid file 34 SINMAP USER S MANUAL PART III File Type G rid File Source Created by SINMAP File Location dennamesi is automatically placed in the study directory in which denname is located Stability index values are 0 0 or greater with values greater than 1 0 indicating some level of stability For display purposes the Stability Index theme is grouped into six classifications as shown in Table 4 TABLE 4 Six default stability index classifications m Stability Index Classification Values SI Stable S gt 15 Moderately Stable 125 lt lt 15 Quasi stable 10 lt S lt 125 Lower Threshold 05 lt SI lt 10 Upper Threshold 00 lt SI lt 05 D efended SI 0 0 Each grid cell contains the actual calculated SI value which may be determined by clicking on the cell with the Identify tool The grouping of the SI values in the legend can be easily modified by the user within ArcView Theory for calculating the stability index is presented in Part I Section 2 4 an
20. the theoretical basis for the calculation of the stability index describes the implementation presents several case studies and describes use of the accompanying software SINMAP has its theoretical basis in the infinite plane slope stability model with wetness pore pressures obtained from a topographicaly based steady state model of hydrology Digital elevation model D EM methods are used to obtain the necessary input information slope and specific catchment area Parameters are allowed to be uncertain following uniform distributions between specified limits These may be adjusted and calibrated for geographic calibration regions based upon soil vegetation or geologic data The methodology includes an interactive visual calibration that adjusts parameters while referring to observed landslides The calibration involves adjustment of parameters so that the stability map captures a high proportion of observed landslides in regions with low stability index while minimizing the extent of low stability regions and consequent alienation of terrain to regions where landslides have not been observed This calibration is done while simultaneously referring to the stability index map a specific catchment area and slope plot of landslide and non landslide points where lines distinguish the zones categorized into the different stability classes and a table giving summary statistics The current implementation of SINMAP is an extension to the ArcVi
21. AL PART III likely that if the DEM data were more accurate many of these landslide locations would actually fall within the higher stability index classes If detailed terrain stability mapping is ever required within a portion of the study area it is highly recommended that detailed 1 5 000 scale topography be compiled Not only would this detailed mapping serve to markedly improve the accuracy of stability index mapping it would also serve to improve most other forest development operations Despite the shortcomings of the results for this study area due to the low resolution DEM data it has been found that the stability index maps are useful as an objective addition to interpretive terrain stability mapping previously completed A separate study has found that in many areas where the DEM data are accurate the stability index map is superior to the subjective polygon based terrain stability maps previously compiled 4 Terratech Consulting Ltd 1998 Comparison of alternative terrain stability mapping methods in a portion of TFL 48 Proprietary report completed for Canadian Forest Products Ltd Chetwynd Division April 1998 55 SINMAP USER S MANUAL APPENDIX 1 Appendix Detailed Derivation of Stability Index Considering Uncertainty The SINMAP stability index is defined by combining the infinite slope stability model Part I section 2 2 and topographic wetness index Part I section 2 3 concepts as described in Part I o
22. AP analysis for the K ilpala Watershed 41 SINMAP USER S MANUAL PART III 2 3 Analytical Results Using the DEM and landslide inventory data the SINMAP software was used to derive a stability index map The analytic results are shown in Figure 6 The figure shows a large slope area plot a small window showing the calibration parameters for the single calibration region used and a larger window showing the statistical results of the analysis A single calibration region was used because no detailed soils mapping results were available Fortunately it was also observed during the brief field visit that the geology is relatively homogeneous and similar textures were observed in both glacial and colluvial soils across the area Calibration parameters were derived by fitting calibration curves to the landslide data within the slope area plot Though no independent analysis of soil properties was completed the 36 to 43 degree soil friction angles used in the calibration are considered realistic for the coarse subangular tills and colluvium found in the study area The T R parameter was set at between 1000 m and 2000 m in the calibration This parameter range when multiplied by the sine of the slope may be interpreted to mean the length of hillslope planar not convergent required to develop saturation In other words with a 30 slope the length of planar hillslope required for saturation would be between 500 and 1000 meters Figure 7 is
23. E ArcView GIS Version pee 10 53 aM FIG URE 14 ArcView screen showing a portion of the wetness map derived by the SINMAP analysis for the Bumt Creek Drainage TABLE 5 Statistical summary for each stability class in the Chetwynd study Landslide density km 52 SINMAP USER S MANUAL PART 111 GIS Ver Edi View ae Analysis SinMap Graphics E t END TE ee rie cia i DEM Chetelev _ Pitfilled DEM _ Calibration Regions _ Original DEM Astart BY Microsoft Word CaseHist Dinbox Microsoft Exchange E ClipBook Viewer Clipboard cView GIS Version CE 1055AM FIGURE 15 ArcView screen showing a portion of the stability index map calculated in the analysis for the Bumt Creek area landslides were found to actually fall within that class For this reason the statistical results for an individual calibration region need to be interpreted with caution Figures 16 and 17 show specific slope area plots for calibration regions 3 and 8 respectively The distribution of landslides on these plots shows a more scattered appearance than the plots of the Kilpala and Rose Creek areas 4 4 Discussion Figures 12 13 16 and 17 as well as Table 5 indicate that a large number of landslides fall within the moderately stable 28 and quasi stable 59 stability index classes This result is quite different than that found for the Kilpala and Rose Creek areas The reas
24. ETAILED DERIVATION OF STABILITY INDEX 56 Onno 66 SINMAP USER S MANUAL PART I Part SINMAP THEORY amp IMPLEMENTATION 1 0 INTRODUCTION 1 1 Purpose The purpose of the SINMAP Stability INdex MA Pping theory implemented by this software is to provide an objective terrain stability mapping tool that can compliment subjective terrain stability mapping methods currently being practiced in the forest sector of British Columbia The theory is also applicable to many other parts of the world that experience shallow translational landsliding This manual provides comprehensive information required to use SINMAP theory in an appropriate manner Part I introduces the fundamentals of the theory and the implementation of that theory Part II provides a user s guide to the software Part III provides three case studies that demonstrate the utility of the theory Detailed mathematical derivations of the theory are provided in Appendix 1 1 2 Background There are many approaches to assessing slope stability and landslide hazards Sidle et al 1985 Dietrich et al 1986 Montgomery and Dietrich 1988 Montgomery and Dietrich 1989 Carrera et al 1991 Dietrich et al 1992 Sidle 1992 Dietrich et al 1993 Montgomery and Dietrich 1994 Wu and Sidle 1995 Pack 1995 The most widely used include Montgomery and Dietrich 1994 1 field inspection using a check list to ide
25. OLS 5 1 Merge Grids This selection will merge two or more grids to create a new grid This is a useful tool if a study area or watershed covers more than one DEM The merge grids menu item is added to the Edit menu of ArcView s view window To use this option add the DEM grids to be merged as themes to a view using usual ArcView methods Then make each of these themes active by using a shift and left mouse button click on each theme in the view s table of contents From the Edit menu choose Merge C rids A new grid called mos where is a number of 1 or greater will be added to the working directory The grid will be added as a grid theme to the view and be called Mosaic of Name where Name is the name of the topmost merged theme in the table of contents The user will normally want to rename and permanently save the grid using the ArcView grid management routines 5 2 Subset of Grid This selection makes a new partial area grid from a larger grid using another small grid as a mask This may be a useful tool if you have a small study area or watershed located within a large DEM Cutting out a small grid and performing SINMAP 28 SINMAP USER S MANUAL PART III procedures on it will be much faster than performing the same tasks on the much larger grid This menu item is added to the Edit menu of ArcView s view window To use this option the two DEM grids must be active themes in a view s table of contents The upperm
26. SINMAP USER S MANUAL PART III 1 1 DEM Map View The final output of most SINMAP studies will be maps that can be used to define areas of potential terrain instability Within ArcView a map is displayed on screen in a view window Most tasks are conducted from SINMAP s DEM map view window Examples of SINMAP s DEM map view window are given in Part IIT Figures 7 8 10 11 14 and 15 These tasks involve the creation use and display of geographic grid data A DEM grid provides the topographic basis for a SINMAP study and a grid of soils hydrologic terrain parameters classified into calibration regions provides non topographic parameter information required for the study Tasks using either one or both of these grids create another six 6 grids that represent the geographic distribution of topography without pits land slope flow direction contributing area saturation and stability index In addition to grid data point data for landslides are required if the user wants to compare locations of predicted instability with areas of actual instability These geographic data sets are added to the DEM map view as themes grid themes for the grid data and as a point theme for landslide data A full SINMAP study will therefore use and or create a total of nine 9 GIS themes 1 2 Slope Area Plot Chart In addition to the geographic display of study data in a EM map view SIN MAP also generates a slope area chart graph of study area dat
27. a to aid in data interpretation and parameter calibration The slope area plot illustrated and defined in Figure 4 is generated by SINMAP routines Examples of SINMAP slope area plots termed SA Plot herein are illustrated in Part III Figures 6 9 13 16 and 17 Plotted on the SA Plot are four types of information 1 Normal cell data Specific catchment area versus slope is plotted for a sampling of grid cell points across the study area that do not have landslides 2 Landslide cell data Landslides are plotted based upon the slope and specific catchment area values of the cell in which each landslide point lies 3 Stability index region lines These five 5 lines provide boundaries for regions within slope specific catchment area space that have similar potential for stability or instability 4 Saturation region lines These three 3 lines provide boundaries for regions within slope specific catchment area space that have similar wetness potential 2 0 INSTALLATION 2 1 Hardware and Software Requirements The current version of SINMAP has been ported to the Windows NT and Windows 95 operating systems You should have the following versions of these two ESRI products 15 SINMAP USER S MANUAL PART III e ArcView GIS Version 3 0a for Windows e ArcView GIS Spatial Analyst Version 1 0a for Windows We have noted that versions earlier than the a version may not work At this time we have not tested Spatial Analyst Ver
28. adjusted Select the Update Grids and Lines menu item to update the grid and enable statistics calculation 27 SINMAP USER S MANUAL PART III 4 11 The Rex Tool When the SINMAP extension is loaded a tool with a dog figure Rex is added to the right side of the tool bar The Rex tool is available for selecting landslide points in either the SA Plot view or the DEM map view and having the same landslide point highlighted in the other view The Rex feature proves useful to the user who is attempting to understand the slope area conditions that lead to the occurrence of a particular landslide You can visualize Rex as your trusty dog that sniffs out the appropriate landslide points On the toolbar click the Rex tool For the Rex button to be activated there must be a Landslides Seeps theme in the map view the landslides should be visible and there must be a SA Plot with an activated visible region theme A landslide is selected by depressing the Rex button moving the target cursor to a landslide symbol on either the map view or the SA plot and dicking the left mouse button The selected landslide changes to the selection color yellow is the ArcView default on both the SA Plot and the DEM map If the study has more than one calibration region and therefore there are multiple region themes in the SA Plot then selected landslides will only appear if they are in the visible activated theme of the SA Plot 5 0 BONUS GRID EDITING TO
29. age name Original File Type Grid polygon coverage or polygon shapefile Original File Source Provided by user Original File Location clrename may be located anywhere Calibration region parameters are stored in the value attribute table VAT of the Calibration Regions grid theme This table is created and populated with default values by SINMAP during creation of the calibration regions grid These values may be changed by the user during the calibration process Fields in the table are Value ArcView assigned value used as calibration region number Numeric Count Number of cells in the calibration region Numeric Region Name of the calibration region String tqmin Minimum T R value Numeric tqmax Maximum T R value Numeric cmin Minimum dimensionless cohesion Numeric cmax Maximum dimensionless cohesion N umeric phimin Minimum Numeric phimax Maximum 9 Numeric 7 3 Theme Name Landslides Theme Type Point theme File Name lsname where Isname is any acceptable ArcView point coverage or point shapefile File Type Coverage or shapefile File Source Provided by user 32 SINMAP USER S MANUAL PART III File Location lsname may be located anywhere It is usually best to store it in the study directory in which denname is a subdirectory Landslide data can come from an ArcView point shapefile or an ARC Info point coverage If you already have your data in an ArcView point feature file y
30. al or geographic nature of SINMAP analyses on screen or printed maps are required for interpreting some computational output Rather than create custom routines to provide standard geographic analysis abilities SIN MAP utilizes off the shelf geographic information system GIS software to handle these tasks SINMAP uses the ArcView GIS from Environmental Systems Research Institute Inc ESRI ArcView is a windows based GIS that ESRI has ported to several environments including the PC Windows environment To use SINMAP you must have ArcView version 3 0a or higher Also you must have the ArcView Spatial Analyst extension which is an add on to the standard ArcView GIS software package Spatial Analyst provides routines for operating upon grid geographic data Finally you must also be using Microsoft Windows NT or Windows 95 operating system software SINMAP adds its capabilities to ArcView through the loading of a custom ArcView extension file ArcView allows encapsulation of customizations program code user interface changes etc in what it terms extensions with extensions saved as extension avx files The SINMAP extension provides links between ArcView and the library of routines in the SIN MAP dynamic link library automates many of the SINMAP data preparation and manipulation tasks and generates maps and charts of user data SINMAP tasks are undertaken in an ArcView session from a DEM map view or a chart of the slope area plot 14
31. an ArcView screen that shows a portion of the wetness map calculated in the analysis It is interesting to note the spatial pattems of wetness on the map and how many of the landslides are located within the areas modeled as being wet 2 ArcView GIS Version 3 0a ile Edit View Theme Analysis SinMap Graphics Window Help HK BIASES No Z J Sees de 58571248 Y CER Ctourtshp Sh N E aM _ Stability Index Stable oderately Stable Qua able _ Contributing Area Slope _ Flow Direction _ Pitfilled DEM _ Calibration Regions _ Original DEM iliStart Qt ArcView GIS Version Exploring Desktop Statistical Summary for Kel BY Microsoft Word Documenti F 10294m FIGURE 7 ArcView screen showing a portion of the wetness map derived by the SINMAP analysis for the K ilpala Watershed 42 SINMAP USER S MANUAL PART 111 Figure 8 is an ArcView screen that shows a portion of the stability index map calculated in the analysis This statistical summary shown in Figure 6 indicates that the defended stability index class light brown in Figure 8 includes 45 landslides or 69 296 of the total inventory At the same time this class includes 17 6 km or only 16 8 of the total study area This class has an average landslide density of 2 6 landslides per square kilometer The upper threshold class represented as red in Figure 8 has an average landslide density of 1 1 land
32. are not met then an error message will be issued specifying the problem The landslides theme is added with legend descriptions of Type 1 Type 2 Type 3 and Type 4 if four distinct landslide types are identified in the data table The user may then modify these legend names as desired 22 SINMAP USER S MANUAL PART 111 From the SinMap menu choose Select Landslide Point Theme A file navigation dialog box is presented from which the landslide theme file can be selected After the theme is added to the View this menu item is grayed 4 7 Preparatory Grid Processing A major part of a SINMAP study is the creation of several derivative grids from the DEM grid These grids are derived solely from the D EM grid and require no other parameters for their construction The processes for creating these several grids are initiated by selecting menu items in the third group of the SinMap menu The grids and associated grid themes that are created by the grid processing steps are Pit Filed DEM e Flow Direction e Slope e Contributing Area Option 1 From the SinMap menu in the Grid Processing group choose Compute All Steps The Compute All Steps menu item becomes ungrayed and available for selection after a DEM grid is selected and added to the view Compute all steps sequentially executes routines for generating the pit filled slope flow direction and contributing area grids and adds these grids to the map view If an
33. ative parameters in the parameter ranges specified SI for these cases is the factor of safety that gives a measure of the magnitude of destabilizing factors e g increased wetness due to road drainage local loading or local enhancement of pore pressures due to soil pipe effects required for instability We use the terms lower threshold and upper threshold to characterize regions where according to the parameter uncertainty ranges quantified by the model the probability of instability is less than or greater than 50 respectively External factors are not required to induce instability in these regions Instability may SINMAP USER S MANUAL PART I arise simply due to a combination of parameter values within the bounds with which uncertainty and variability can be quantified We use the term defended slope to characterize regions where according to the model the slope should be unstable for any parameters within the parameter ranges specified Where such slopes occur in the field they are held in place by forces not represented in the model or the model is inappropriate as in the case of bedrock outcrops In the sections that follow we give the theory that forms the basis for SINMAP in terms of the infinite slope stability model and topographic wetness index These components are combined with an accounting for parameter uncertainty to define the stability index SI Technical details of the derivation are given in Appendix 1
34. available to digitally encode topography comprise 1 G rid Digital Elevation Models D E Ms 2 Triangular irregular networks TINs and 3 contour based storage structures Grid DEMs consist of a matrix data structure with the topographic elevation of each pixel stored in a matrix node TINs store the X Y location as well as elevation at irregularly spaced nodes Contour based data structures store vector data along contour lines Slope and specific catchment area can be computed in each of these frameworks and therefore the theory described above could be implemented in any of these frameworks Within SINMAP grid DEMs were selected for use primarily due to their simplicity and compatibility with ArcView Spatial Analyst grid routines as well as the ready availability of data and prior experience with their use The grid DEM processing routines used are based upon methods described by O Callaghan and Mark 1984 Marks et al 1984 Band 1986 Jenson and Domingue 1988 Tarboton 1989 Tarboton 1997 and Garbrecht and Martz 1997 There are 4 steps involved 1 Pit filling corrections 2 Computation of slopes and flow directions 3 Computation of specific catchment area and 4 Computation of the SINMAP stability index 3 2 Pit Filling Corrections Pits in digital elevation data are defined as grid elements or sets of grid elements surrounded by higher terrain that in terms of the DEM do not drain These are rare in natural topograph
35. c definition in the form of digitized break lines is found in gully and swale areas where landslides initiate This is in contrast to the results discussed in the Chetwynd study in Section 4 47 SINMAP USER S MANUAL PART III 4 0 BURNT RIVER PILOT STUDY AREA 4 1 Physiographic Setting This project area is located approximately 100 km southwest of Chetwynd B C and involves the mapping of two 1 20 000 TRIM map sheets 930 029 and 930 030 The primary watershed within the area is that of the Burnt River The area contains several physiographic and biogeoclimatic zones and is characterised by long cold snowy winters and short cool summers Three biogeoclimatic zones are found within the study area including the Engelmann Spruce Subalpine Fir ESSF Sub boreal Spruce SBS and Alpine Tundra AT A variety of bedrock types of igneous metamorphic and sedimentary origin is found within the study area Faulting is locally common and is usually accompanied by a relatively greater variety of rock types The bedrock geology for the area consists primarily of clastic sedimentary rocks including basal chert pebble conglomerates sandstone mudstone and coal In localised areas metamorphic granitic and volcanic rocks outcrop Outcrops are usually exposed on steep slopes along incised watercourses and glacial meltwater channels and in alpine areas The Burnt River drainage basin has been subject to several glaciations that have left a
36. chment Area a Unit contour length b f Contributing area A FIG URE 3 Definition of Specific Catchment Area depth Instead we assume uniform conductivity of a soil mantle overlying relatively impermeable bedrock In addition we use sin rather than tan This is more correct because the flow distance is actually along the slope The difference between tan and sin which is insignificant for small angles matters for the steep slopes that give rise to landslides Now with assumption 3 the relative wetness is w vi pr 8 1 Tsin 0 The relative wetness has an upper bound of 1 with any excess assumed to form overland flow As illustrated in Figure 1 the relative wetness defines the relative depth of the perched water table within the soil layer The ratio R T in 8 which has units of m quantifies the relative wetness in terms of assumed steady state recharge relative SINMAP USER S MANUAL PART I to the soil s capacity for lateral drainage of water Although the term steady state is used with lateral flux approximated using equation 7 the quantity R is not along term e g annual average of recharge Rather it is the effective recharge for a critical period of wet weather likely to trigger landslides The ratio R T which we treat as a single parameter therefore combines both climate and hydrogeological factors The quantity T R sin m may be thought of as the length of hillslope planar
37. d with ASCII grid files in the format of the sampleasc file provided Y ou will not have the user friendly interface but could still compute a SINMAP grid These standalone programs can be compiled and linked against the source files listed for the sinmap dll but replacing gridio c with gndio_null c and avcalls c with avcalls null c To modify an Avenue script in the sinmap avx file you need to be running Arcview with the SINMAP extension loaded see section 4 1 Any changes you make will be recorded in the projectapr file you are using so be sure to save it and name it appropriately To modify one of the SINMAP avenue scripts use the script manager to select the sinmap script that you want to modify In the project window click on the Scripts button and then select New to create a new script which by default will be 38 SINMAP USER S MANUAL PART III called Script1 Within the script editor select either the Load System Script button or menu item Then within the Script Manager dialog box that pops up scroll down to the scripts that begin with SINMAP These are the SINMAP extension scripts which are briefly described in the script SINMAP a ReadMe Select a SINMAP script to load it into the script editor After you have loaded the script change its name from Script1 to the actual SINMAP script name such as SINMAP aReadMe Make your modifications to the script and then compile it Although the procedure described above will
38. d in Appendix 1 7 9 Theme Name Saturation Theme Type Grid theme File Name dennamsat where danname is the name of the original D EM grid file File Type Gnd File Source Created by SINMAP File Location dannamesat is automatically placed in the study directory in which danname is located 35 SINMAP USER S MANUAL PART III This theme displays the topographic wetness index described in equation 8 of Part I Section 23 Given the range of x R T values x there are 3 possibilities in equation 9 i w is 1 saturated for the full range x x ii wis 1 for part of the range x x i wisnever1 These are used to assign one of the following values to each grid cell in the saturation theme Saturation Z one Always saturated as indicated by w 1 in equation 8 for the full range x This occurs when sin is greater than 1 This is represented coded with a value of 3 T hreshold Saturation Cells having a probability of being saturated E quation 8 returns a value of 1 for some values of x in the range X Le sin0 is greater than 1 but x a sin is less than 1 This is represented coded with a value of 2 Partially W amp and Low Moisture Cells that are never saturated Equation 8 retums a value less than 1 for all values of x R T in the range The level of saturation is encoded here as x a sin a number between 0 and 1 which represents the wettest th
39. del simplified for cohesionless soils to define slope stability classes based upon slope and specific catchment area Wu and Sidle 1995 present a more elaborate model that couples dynamic modeling of the hydrology with the infinite slope stability model in a more complex form accounting for cohesion and varying root strength The SINMAP approach is similar to that of Montgomery and Dietrich 1994 in that it combines steady state hydrologic concepts with the infinite slope stability model There are a few differences 1 Grid based rather than contour based DEM methodology is used following the work of Tarboton 1997 This choice is primarily a matter of convenience Grid based D EMs are more common and their analysis is easier 2 Cohesion is retained in the infinite slope stability model This can be used to account for soil cohesion or root strength as modeled by Wu and Sidle 1995 or it may be set to 0 by a user who wants to consider cohesionless situations 3 Parameter uncertainty is incorporated through the use of uniform probability distributions and lower and upper bounds on uncertain parameters This is akin to the probabilistic approach of the Level I Stability Analysis LISA developed by Hammond et al 1992 for the U S Forest Service The SINMAP approach therefore reflects the real uncertainty associated with estimating parameters in terrain stability mapping The results reduce to the deterministic case equivalent to Montgomery
40. derstood to reference the previous non zero interval to avoid errors in the calculation of F a This defines a generic function which with parameters is denoted FAy b b a F yi y b b a da A 31 The general cumulative distribution function for the generic sum product form of equation A 23 is from A 30 1 X X Fu y yis bo baiz x Fur yis bi bz z x A 32 E Xis X2 y y b bz This expression only works when all three intervals x x Y2 b b have non zero length In the case that the x interval has 0 length this reduces to the general product function equation A 27 In the case that the y or b intervals have zero length it reduces to the generic sum of two variables equation A 18 63 SINMAP USER S MANUAL APPENDIX 1 In region 3 SI is obtained by evaluating this with the appropriate arguments namely sinO sin cos a cosO a 1 1 Vaca sing sin sine sin b b t t SI Prob FS gt 1 ZI E x X2 y Y2 b b l A 33 In region 2 possibly saturated FS is given by _ C cosO l1 wr t FS A 34 sin 0 which is the same as for region 3 However w is given by a w 9 A 35 sin 0 with x U x x and x sin0 gt 1 Therefore w is 1 with probability x a sin0 1 A 36 x5a sin 0 xa sin and uniformly distributed over the range sin0 1 wi
41. dified by the user to provide realistic values for the user s study area The user may come back and modify these values at a later time while conducting the study Other means are also provided within the program described later for more easily modifying most of these values on the fly during the calibration process From the SinMap menu choose the Set D efaults menu item Selecting the Set D efaults menu item displays a dialog box allowing input of several fundamental physical parameter values and modification of a SA Plot display setting Values changeable in this dialog box are Gravity constant D efault value 9 81m s Soil density D efault value 2000 kg m Water density D efault value 1000 kg m Number of points in a SA Plot D efault value 2000 The SA Plot displays all study area landslide points on a slope area plot but only a limited number of grid cells without landslides are normally displayed in order to speed computations and make a less cumbersome graph Remember a 500 by 500 DEM grid has 250 000 cells which is a lot of points to display on an x y graph The number of cells displayed in the plot is approximate 19 SINMAP USER S MANUAL PART 111 From the SinMap menu choose the Set Calibration Parameters menu item Selecting the Set Calibration Parameters menu item displays a dialog box that allows input of several soil parameters and modification of a SA Plot display setting Values cha
42. dslide inventory data the SINMAP software was used to derive a stability index map The analytic results are shown in Figure 9 The figure shows a large slope area plot a small window showing the calibration parameters for the single calibration region used and a larger window showing the statistical results of the analysis Z ArcView GIS Version 30a 8 x Ele Edit Table Field Window jeje EE e m AK E Egzama Moderately Quasi L u n 0 of 1 selected Stable able Stable Threshold Threshold Defended Total Region 1 v 2 38 ag 142 x 26 8 67 1000 2 5 66 30 31 1000 05 64 46 1e 006 Sl 1 50 125 1 00050 0 0 Gi x rate e sain tme mee hime Abax i 00 i 38001 4500 100000 4 amp ha lt 10000 4 h D b amp af Saturated a Rol 1000 4 Unsaturated LI Q Og B 100 d Y Wetness 10 10 T T T 0 10 20 30 40 50 60 Slope degrees Start J Exploring Norrish BY Microsoft Word Documenti ArcView GIS Version 3 0 Statistical Summary f Cj 229PM FIGURE 9 ArcView screen showing the analytic results of a SIN MAP analysis for the Rose Creek Watershed A single calibration region was used because terrain mapping indicated that the soils are similar throughout the watershed Observations during the brief field visit also suggested that the geology
43. e obtained by solving 7 for a for the case where w B 2 X lt lin T sin 0 sin 0 the min expression The solution is 58 SINMAP USER S MANUAL APPENDIX 1 p e A 14 Xr t cos This is used to define a function af 0 C t x r FS EE e A 15 Xr t cos 0 which with appropriate arguments gives the lines corresponding to fixed FS in unsaturated conditions for slope angles 0 ranging between the lower limit defined by equation A 13 and upper limit defined evaluating A 12 with w 0 The equations given thus far are sufficient to compute SI for the region where SI gt 1 and to define the unconditionally stable and unconditionally unstable regions The region in between where SI is defined probabilistically requires derived distributions on the FS given by equation A 7 This is different depending on whether w the min term is 1 saturated or not necessitating separate treatment of the 3 probability regions defined in FigureA 1 In region 1 always saturated FS is given by 0 1 r t FS 16 sin Region 1 KASPA TT S S Sisa S Saturated 7 7 77 o7 wee 1O Region 2 7 A Mixed Sat Unsat e 4 c 1O 9 E lt e Region 3 5 Unsaturated amp o T T T T T 0 0 0 5 1 0 1 5 2 0 Slope FIG URE A 1 Definition of regions for derived distributions 59 SINMAP USER S MANUAL APPENDIX 1 C and t are assumed to be uniformly di
44. e cell could get given the range of x specified Cells with this saturation level greater than the lower wetness threshold set in the Calibration Parameters Input dialog box with default 0 1 are designated partially w amp while cells with saturation level less than this threshold are designated low moisture 7 10 Table Name Attributes of Calregion where Calregion is the name of a calibration region in the SA Plot table of contents File Name dennamsap dbf where danname is the name of the original D EM grid file File Type dBase File Source Created by SINMAP File Location dennamesap dbf is automatically placed in the study directory in which denname is located The SA Plot provides a view of study data in slope area space not in geographic space The data in the plot are derived from a feature table FTab which points to a dBase file created by SINMAP The file is created by extracting data from the Slope 36 SINMAP USER S MANUAL PART 111 theme Contributing Area theme and the Landslides Seeps theme The FTab and underlying dBase file has the following fields East X coordinate for the grid cell from which the data point is derived Numeric North Y coordinate for the grid cell from which the data point is derived N umeric Slope Slope degrees for the grid cell from which the data point is derived Numeric Sca Contributing area m for the grid cell from which the data point is derived Numer
45. each of the six stability classes within each of the eight calibration region as shown in Figure 12 Figure 13 shows the slope area plot for all eight calibration regions combined Because each region has a separate set of calibration parameters it is not possible to place a single set of calibration lines on the plot Z ArcView GIS Version 3 0a aa J LIS M CORO HERO Moderately Quasi Lower Upper Bue AKEJ E EL I Stable Stable Stable Threshold Threshold Defended Total Dof 8 selected X 123 25 d2 1000 i DO 00 3 43 1000 10 28 Regions LS Density t km 2 T 23 Non Landslide Region 2 Debris Avalanche Area km 2 i 07 26 3 of Region l 25 E 100 0 Region fiLandslides 4 5 17 Non Landslide of Slides 23 5 100 0 m Debris Avalanche 61 06 Regione T i 155 gt Non Landslide 1 i ag 1000 1 Debris Avalanche Regions Non Landslide BI Debris Avalanche Regions Landslide Bb Debris Avalanche Regions Non Landslide Bb Debris Avalanche Region2 Non Landslide E Debris Avalanche A Road Landslide Region 1 Non Landslide Debris Avalanche TY Contributing Area 10000 4 of Slides LS Density tt km 2 Region 4 Area km 2 of Region Landslides of Slides LS Density tt km 2 Region Area km 2 of Region HLandslides of Slides LS Density tt km 2 Region 6 of Slides
46. ect area 6 2 Using an Existing Calibration Region Grid If you already have a grid of calibration regions that you would like to use you can incorporate it directly in the analysis However there are a few guidelines need to be followed First place the grid in the same directory as the Original DEM grid and rename it to dannameal where denname is the name of the Original DEM grid This will enable the Use Existing Calibration Region Grid menu item to add this grid to the project as the Calibration Regions Grid The grid must have the data fields described in Section 7 2 These fields must be populated with parameter values as they will not be populated with default values by SINMAP Other data fields are allowed and will not interfere with SIN MAP routines If you are uncertain of the required file structure create a default calibration regions grid and examine its file structure If you are skilled with ArcView you could create a default grid using your original grid as the basis link the default grid VTab to your VTab or the other way around and calculate using existing fields to fill the empty parameter fields If you don t understand what this last sentence meant then stick with the basics WARNING SINMAP does not check to ensure that your calibration regions grid file its fields and data are compliant with SIN MAP If they are not errors may result in the program crashing with loss of unsaved data or changes 6 3 Changing Col
47. ed as a continuous quantity between 0 and 2 This angle is determined as the direction of the steepest downward slope on the eight triangular facets formed in a 3 x 3 grid cell window centered on the grid cell of interest as illustrated in Figure 5 A block centered representation is used with each elevation value taken to represent the elevation of the center of the corresponding grid cell Eight planar triangular facets are formed between each grid cell and its eight neighbors Each of these has a downslope vector which when drawn outwards from the center may be at an angle that lies within or outside the 45 4 radian angle range of the facet at the center point If the slope vector angle is within the facet angle it represents the steepest flow direction on that facet If the slope vector angle is outside a facet the steepest flow direction associated with that facet is taken along the steepest edge The slope and flow direction associated with the grid cell is taken as the magnitude and direction of the steepest downslope vector from all eight facets This is implemented using equations given in Tarboton 1997 Proportion Steepest direction flowing to downslope neighboring Proportion flowing to grid cell 4 is neighboring grid cell 3 001 0 1 002 is 00 00 000 E SA Flow direction measured as counter clockwise angle from east 7 FIG URE 5 Flow direction defined as Steepest downward sl
48. ee stability classes These three classes represent 65 896 of this watershed 2 ArcView GIS Version 3 0a lap Graphics Window Help HK be Saturation Zone Threshold S aturatior artially Wet Low Moisture _ Contributing Area Slope _ Flow Direction _ Pitfilled DEM _ Calibration Regions _ Original DEM iffiStart 3 Exploring Norish EW Microsoft Word Documenti ArcView GIS Version Statistical Summary for Ro Cj 236PM FIGURE 11 ArcView screen that shows a portion of the stability index map for the Rose Creek Watershed 3 4 Discussion When compared to the K ilpala watershed this study area has a much lower proportion of landslides occurring in steep bedrock dominated terrain It was noted during the field reconnaissance that the bedrock is more uniform and therefore the soils are more uniformly thin than at Kilpala Because of this pockets of soil leading to landslides less likely to exist in the steeper terrain The TRIM DEM is less accurate than the DEM in Kilpala Because of this some noticeable interpolation errors can be seen in Figure 11 This error effect is shown by the vertical stripes that represent photogrammetry errors associated with point data collection Though these stripes are indicative of interpolation error they do not appear to have adversely affected the stability index results The reason for this is likely due to the fact that adequate topographi
49. eese eese nennen nnne 34 7 8 Theme Name Stability Index eese eene enne 34 7 9 Theme Name Saturation eniin scales 35 7 10 Table Name Attributes of Calregion where Calregion is the name of a calibration region in the SA Plot table of contents eese eene nenne nennen 36 8 0 MODIFYING SINMAP SOURCE CODE esee eee nennen nennen 37 PART CASE STUDIES 2 qan eene eene 40 1 OINTRODUCTION 2 5 3 5 3 rr tr EP unus re ER ERE Cete e ua FE ED Re ED ERE 0923 40 2 0 KIEPALA PILOT STUDY AREA mieten Pe eene ore eimi Re Ee ae 40 2 1 Physiographic Setting un u u a eak sss 40 22 Input Data ett d 41 2 3 Analytical o iae dee dte e E 42 Z 4 DISCUSSION shoe ette edi eee dedit i date d ete eode ee gt 43 3 0 ROSE CREEK PILOT STUDY AREA eere nennen nre 44 3 1 Physiographic Setting a u 44 SAM LOL Burr ERN EE 44 3 3 Analytical Results i e t e a n te i eee He edad ee dee n 45 E e te e e e E EU IE EHE 47 4 0 BURNT RIVER PILOT STUDY AREA 48 4I Phystographic Setting aaa pi ant aem 48 422 Input Dt eese Ren OR I Ei 46 43 Analytical Results oes ete BIEN ERU EHE BESTE 50 4 4 DISCUSSIOIo i esee eee Dien iei 53 APPENDIX 1 D
50. equired 1 See the Mapping and Assessing Terrain Stability G uidebook 1995 published by the B C Provincial Government SINMAP USER S MANUAL PART I 2 0 SLOPE STABILITY THEORY 2 1 Overview The SINMAP Stability INdex MAPping methodology is based upon the infinite slope stability model e g Hammond et al 1992 Montgomery and Dietrich 1994 that balances the destabilizing components of gravity and the restoring components of friction and cohesion on a failure plane parallel to the ground surface with edge effects neglected The pore pressure due to soil moisture reduces the effective normal stress which through the friction angle is related to the shear strength Pore water pressure is computed assuming a hydrologic steady state with depth of saturated soil computed sufficient to sustain a lateral discharge proportional to the specific catchment area the upslope area per unit contour length SINMAP derives its terrain stability classification from inputs of topographic slope and specific catchment area and from parameters quantifying material properties such as strength and climate primarily a hydrologic wetness parameter Each of these parameters is delineated on a numerical grid over the study area The primary output of this modeling approach is a stability index the numerical value of which is used to classify or categorize the terrain stability at each grid location in the study area The topographic variables are automatically
51. ession in equation A 7 we need to specifically consider the limits on the occurrence of saturation and the consequent use of w 1 rather than w xa sin0 in the min expression Saturation occurs when in equation 8 R a snO sinO lora Be equo A 10 T sin 0 R T X This evaluated for x x defines the upper dashed line on Figure 4 Part I between saturated and possibly saturated This evaluated for x x defines the lower dashed line on Figure 4 between unsaturated and possibly saturated The straight vertical lines on Figure 4 are the slopes that give a particular factor safety under saturated conditions When w 1 FS is independent of specific catchment area and is obtained by solving A 7 for 0 A general solution to A 7 for 0 is obtained by squaring recognizing that sin 0 1 cos0 and solving the resulting quadratic equation to give Cu rw t J FS FS 12 rw C 0 A 11 TB FS 12 mw TM This is used to define a function C 1 rw t JFS FS rw t C csw t w FS cos taa ud y S OATI E A 12 FS c 1 rw t The vertical lines are therefore at slope tan9 values corresponding to evaluation of this function with appropriate arguments namely 1 5 csw t c r 1 1 5 FS in 1 0 csw t 1 1 0 A 13 FS 1 0 csw t 1 1 0 The curves defining a specific factor of safety under unsaturated conditions ar
52. ew geographic information system GIS from Environmental Systems Research Institute Inc ESRI This utilizes ArcView for its standard G IS functionality such as the input and organization of data and the presentation and output of results SINMAP is grid based requiring ArcView version 3 0a or higher with the Spatial Analyst 1 0a extension SINMAP USER S MANUAL PART I Table of Contents THE AUTHORS RH S GANE UEBER RENE h hasa ys pusa 1 DISCLAIMERS EP 1 ACKNOWLEDGEMENTS eee iE A AE au PR ete ee i DISTRIBUTION E PETER ii SUPPORT oe ra ote a m aper ie ete aae e o et ivt eie ii MIU DER EE iii PART I SINMAP THEORY amp IMPLEMENTATION 1 TO INTRODUCTION a eea a A doves pos E E Pete ee E aa Pee E 1 HEIDI 1 1 2 Background in da d Ee da eg teet 1 1 3 Applicability and Limitations n pu uapa uiay ges kaa 2 1 4 Required User Background snien senros ii ea s y nnne 3 2 0 SLOPE STABILITY THEORY L re PEE Co e ER DERE Ferd 4 4 2 2 The Infinite Slope Stability Model eene nnne 5 2 3 Topographic Wetness Index eese eene anal enne 7 2 4 Stability Index Definition niei eee tede d eee Hd ane etes 9 3 0 DIGITAL ELEVATION MODEL 5 11 3S IE Introd ctions
53. f this manual A dimensionless form of the infinite slope stability model is used equation 3 _ 1 wr tan FS Amo A 1 where w D D h h A 2 is the relative wetness C C C h p g A 3 the combined cohesion made dimensionless relative to the perpendicular soil thickness and r A 4 the water to soil density ratio The dimensionless cohesion concept was illustrated in FIGURE 2 see Part I Section 22 Practically the model works by computing slope and wetness at each grid point assuming the other parameters are constant or have the same probability distribution over larger areas With the form of equation A 1 this amounts to implicitly assuming that the soil thickness perpendicular to the slope is constant An alternative definition of C as 56 SINMAP USER S MANUAL APPENDIX 1 C C CJ D p g A 5 would lead to instead of Ai cos 1 wr tan sin 0 cos 0 FS A 6 which implicitly assumes the soil depth D measured vertically is constant implying that soils on steeper slopes are thinner In SINMAP we chose A 1 and A 3 over A 5 and A 6 in part for compatibility with the hydrology where constant soil thickness is consistent with constant transmissivity hydraulic conductivity times thickness and in part because we think it is probably more realistic Combining the topographic wetness concept expressed by equation 8 with equation A 1 leads to fol
54. from the popup menu activated by the right mouse button 10 To view a statistical summary of the data either choose statistics from the SinMap menu or mouse activated menu You have completed a SINMAP study 4 0 DETAILED TUTORIAL 4 1 Starting ArcView and Loading SINMAP Start Arcview within Windows using any of the methods available like double clicking on an ICON or file with extension apr or by selecting it within Start Programs in Windows From the Project window File menu select the Extensions menu item Then check the check box next to SINMAP For SINMAP to operate it must be loaded into ArcView as an ArcView extension The SINMAP extension is loaded from the ArcView application widow If the SINMAP extension does not appear in the Extensions dialog box then the sinmap avx file has not been installed into a default directory as specified in section 2 2 Loading the SINMAP extension changes the default ArcView user interface in several ways A new menu called SinMap is added to the menu bar in an ArcView View Menu items in this menu provide much of SIN MAP s functionality Two menu items are added to a View s Edit menu These items allow merging of multiple grids and extracting a smaller grid from a larger grid using another mask grid Two tools are added to a View s tool bar One tool allows cutting a small rectangular grid from a larger grid The other tool is used for identifying landslide features In the SA Pl
55. he SA Plot If either of the grid files already exist having been previously generated a Y es No Cancel dialog pops up asking if you wish to use the previously computed grids Answering yes will cause existing grids to be used as the basis for grid themes added to the map view Answering no will cause new grids to be created with the existing grids automatically backed up with a b automatically added to the grid name Option 2 From the SinMap menu choose each processing step separately by first choosing Stability Index This selection generates a grid with a stability index at each grid cell location The grid file generated will have the name dennamesi If dannamesi exists a Yes No dialog box 24 SINMAP USER S MANUAL PART 111 will ask whether to use the existing grid as the basis for the grid theme If no is selected the existing file is backed up as demnames b prior to the creation of the new grid This step also generates a saturation grid file dannamesat and a backup saturation grid file dannamesat b if a saturation grid file already existed From the SinMap menu choose Saturation as the next step This selection adds a Saturation grid theme to the map view using the saturation grid that was created in the previous step From the SinMap menu choose SA Plot as the final step The SA Plot menu item creates a slope area plot window The advantage to creating the plot using this menu item in preference to the Compute
56. ic Ter Calibration region containing the grid cell from which the data point is derived This is a integer numeric and is equivalent to the Value field for a region in the Calibration Regions VTab Numeric Ls If this is a landslide seep point then this will be a number between 1 and 4 indicating the type of feature described above If this is a cell without a landslide this will be a 0 Integer Lsrecno This is the ArcView assigned record number in the landslide seep feature theme which is used to connect that theme with the SA Plot region themes for Rex searches Falseslope Because we are using a map type view to create the plot and because X and Y scales must therefore be the same we create a false value for slope and contributing area for log scale plotting purposes Numeric Falsesca False contributing area is also needed for log scale plotting purposes Numeric After the file is created it is added as one or more X Y event calibration region themes to the SA Plot view using Falseslope and Falsesca as the X and Y position values A query is performed for each calibration region so the underlying dBase file may actually be pointed to by the several calibration region themes 8 0 MODIFYING SINMAP SOURCE CODE The Avenue scripts and C source code implementing SIN MAP are available and could be modified by skilled users programmers If this is done then precautions should be taken to back up the original files s
57. ietrich W E C J Wilson D R Montgomery and J McK ean 1993 Analysis of erosion thresholds channel networks and landscape morphology using a digital terrain model The Journal of G eology 101 259 278 Dietrich W E C J Wilson D R Montgomery J McKean and R Bauer 1992 Erosion Thresholds and Land Surface Morphology eology 20 675 679 Dietrich W E C J Wilson and S L Reneau 1986 Hollows colluvium and landslides in soil mantled landscapes chapter 17 in illslope Processes Edited by A D Abrahams Allen amp Unwin Boston p 361 388 Fairfield J and P Leymarie 1991 D rainage Networks from G rid Digital Elevation Models W ater R esearch 27 5 709 717 Garbrecht J and L W Martz 1997 The Assignment of Drainage Direction Over Flat Surfaces in Raster D igital Elevation Models Journal of H ydrology 193 204 213 Grayson B I D Moore and T A McMahon 19923 Physically Based Hydrologic Modeling 1 A Terrain Based Model for Investigative Purposes Water Resources Research 28 10 2639 2658 66 SINMAP USER S MANUAL REFERENCES Grayson R B I D Moore and T A McMahon 1992b Physically Based Hydrologic Modeling 2 Is the Concept Realistic W ater Resouros esearch 28 10 2659 2666 Hammond C D Hall S Miller and P Swetik 1992 Level I Stability Analysis LISA Documentation for Version 2 0 General Technical Repor
58. ility and saturation lines fit the data for a specific region Parameters for each region can thereby be adjusted to eventually calibrate the whole study area Step 3 From either the SinMap menu or the right mouse button activated popup menu choose Update G rids and Lines This updates both the saturation and stability index grids as described in Section 4 9 1 above and the equation lines on the SA plot 4 10 Statistical Summary From either the SinMap menu or the right mouse button activated popup menu choose Statistics This item displays a table of summary statistics for each calibration region by stability class as shown in Table 3 TABLE 3 Example of statistical results of the SIN MAP analysis Moderately Quasi Lower Upper Stable Stable Stable Thresh Thresh Defend Total Area km 41 8 9 8 14 4 11 6 9 6 17 6 104 8 of Region 39 9 9 3 13 7 11 1 9 1 16 8 100 0 of Slides 0 0 1 8 11 45 65 of Slides 0 0 0 0 1 5 12 3 16 9 69 2 100 0 LS Density km 0 0 0 0 0 1 0 7 1 1 2 6 0 6 See Table 1for a definition of stability classes The mouse or shift and arrow keys may be used to select data that can be copied Control C and then pasted into another program Additionally a text file named dannamests is created that may be imported into another program such as a spreadsheet or word processor table If this menu item is disabled then the stability index grid has not been updated since calibration parameters have been
59. is a possibility probability of failure This is a spatial probability due to the uncertainty spatial variability in C tano and T This probability does have a temporal element in that characterizes a wetness that may vary with time Therefore the uncertainty in x SINMAP USER S MANUAL PART I combines both spatial and temporal probabilities In these regions with FSpn lt 1 we define SI Prob FS gt 1 12 over the distributions of C x and t Equations 10 The best case scenario is when C C x x and t t which leads to C cos0 x 2 9 pe FS max 13 sin In the case that FS lt 1 then SI Prob FS gt 1 0 14 Regions with SI gt 1 FS gt 1 0 lt SI lt 1 and SI 0 FS lt 1 are illustrated in Figure 4 in a space defined in terms of slope tan0 and specific catchment area This provides a useful visualization medium for understanding this approach Appendix 1 derives the equations for computing these probabilities and drawing the lines on Figure 4 mM FS min 1 597 FS 12 le Possibly Saturated Higher than pot instability Unstable SI 0 Area Unsaturated 50 100 f i 4 10 Slope FIG URE 4 stability Index defined in Area Slope space 10 SINMAP USER S MANUAL PART I 3 0 DIGITAL ELEVATION MODEL METHODS 3 1 Introduction The data storage structures
60. le menu choose Extensions In the dialog box that pops up click the check box next to SINMAP 2 Create a new view and import the ASCII grid into ArcView format From the View s File menu select the item Import Grids Then select the ASCII import file type choose the file sampleasc name the output grid sample and choose No from the Cell values as integers yes no box 3 In the View menu bar a menu called SinMap was added when the SINMAP extension was loaded From the SinMap menu choose Select DEM Grid for Analysis and then navigate to and select the sample grid 4 From the SinMap menu choose Make Single Calibration Region Theme Accept the default values for the calibration parameters 5 From the SinMap menu choose Select Landslide Point Theme Select the file samplds shp in the file navigator box 6 Under Grid Processing select Compute All Steps to create the pit filled DEM slope flow direction and specific catchment area grid themes 7 Under Stability Analysis select Compute All Steps to create the stability index and saturation grid themes and to create the SA Plot 17 SINMAP USER S MANUAL PART 111 8 Inthe newly created SA Plot activate the Region 1 theme and make it visible 9 From the SinMap Menu choose the item Add D elete Stability Equation Lines to overlay the data points with the SINMAP theory boundary lines Alternatively you may choose the same menu item
61. ll but critical gully walls or terrace faces where landslides commonly originate Because of the wide variety of terrain types within the study area it was necessary to break out several calibration regions The spatial delineation of these regions relies on previous terrain mapping in the areas Eight calibration regions were chosen on the basis of soil depth soil texture and whether or not the area is forested Following are the definitions for each region Region 1 Deep colluvial soils with coarse textures and angular fragments Region 2 Deep morainal soils with mixed textures and subangular to subrounded fragments Region 3 Deep fluvial and glaciofluvial soils consisting of subrounded sands and gravels Region 4 D eep lacustrine and glaciolacustrine silts and clays 3 This mapping was completed by Westroad Resource Consultants Ltd 49 SINMAP USER S MANUAL PART 111 Region 5 Shallow non forested colluvial veneers and rock Region 6 Shallow non forested morainal veneers and rock Region 7 Shallow forested colluvial veneers and rock Region 8 Shallow forested morainal veneers and rock The calibration parameters for each of these regions were determined interactively using the landslide inventory and natural terrain data plotted on slope area plots with the SINMAP software 4 3 Analytical Results The analytical results for each calibration region is given in Figure 12 Statistics have been calculated for
62. lowing equation 9 with simplified notation x R T and t tanq C cos0 1 min xm t sin 0 _ C cosO0 1 w r t sin 0 sin 0 FS A 7 The SINMAP stability index SI is defined from the factor of safety FS as the probability that a location is stable assuming uniform distributions of the uncertain or variable parameters over specified ranges SI Prob FS gt 1 A 8 This probability is evaluated over the distributions of C x and t C U C C x U X x A 9 t U t b This provides the capability to account for inherent uncertainty or natural variability in the parameters In essence it incorporates the probabilistic approach e g Hammond al 1992 while combining the infinite slope stability model with the steady state hydrology approach suggested by Montgomery and Dietrich 1994 Where Prob FS gt 1 1 SI is defined as the minimum deterministic factor of safety equation 11 This assumes that given the most conservative worst case parameters the model still gives FS gt 1 For cases where the best case maximum factor of safety equation 13 is less than 1 the stability index is 0 equation 14 57 SINMAP USER S MANUAL APPENDIX 1 Regions with SI gt 1 FS gt 1 0 lt SI lt 1 and SI 0 FS lt 1 were illustrated in Figure 4 Part I In what follows the equations for computing these probabilities and drawing the lines on Figure 4 are derived Because of the min expr
63. mantle of coarse textured till over most of the area Till texture is variable and generally reflects local bedrock composition Numerous meltwater channels have been cut throughout the area and in places have cut deeply into bedrock Coarse textured gravelly glaciofluvial sediments are locally abundant especially along the lower slopes and valley bottoms Fluvial processes have been active since deglaciation but have not modified the area significantly except for localised down cutting within valley bottoms Recent streams have created gullies on some erosion prone slopes and have undercut older glaciofluvial deposits Veneers and blankets of rubbly and blocky coarse textured colluvial materials are present on moderately steep to steep slopes Colluvial cones have formed at the base of some steep slopes Landslides in unconsolidated materials are commonly associated with seepage on moderate to moderately steep slopes across the study area They are also common on steep terrace faces or gully walls that are actively being undercut by streams Most landslides are shallow debris slides and occur in soil deposits with a variety of thicknesses and textures 4 2 Input Data TRIM DEM data was obtained from the Chetwynd Division of Canfor These data are provided by the B C Provincial Government and were digitally complied from 1 60 000 scale photographs at an accuracy appropriate for a 20 meter contour interval map ie spot elevation accuracies of plus
64. n associated grid produces a single calibration region for the entire study area The region is called Region 1 and the parameter data table for it is populated with default values O ption 2 From the SinMap menu choose Create Multi Region Calibration Theme This method can be used if you have a polygon coverage shapefile or grid theme of calibration regions Selection of this menu item pops up a file navigation dialog box that allows you to pick a grid or polygon feature theme After you select the theme a dialog box listing field names in the selected coverage is presented Pick the field containing the names of the calibration regions A calibration regions grid is then created with each region populated with default parameter values Option 3 From the SinMap menu choose Use Existing Calibration Region G rid This item will be highlighted if there is an existing calibration regions grid in the study directory If you have previously created a calibration regions grid and wish to continue using it this is the selection to choose 4 6 Adding Landslides to the View A landslide point theme coverage or shapefile may be added to the SIN MAP study to allow evaluation of conditions where landsliding has occurred The data table Ftab for the landslide coverage or shapefile must have a numeric field called Type that identifies the type of landslide feature Values for type must range from 1 to 4 If these several conditions
65. n swales 3 2 Input Data B C Terrain Resource Inventory Mapping TRIM DEM data were obtained from the Harrison Operations of Canfor These data produced by the B C Provincial Government were digitally complied from 1 60 000 scale photographs at an accuracy appropriate for a 20 meter contour interval map i e spot elevation accuracies of plus or minus 5 meters The data were then interpolated to a 15 m grid D EM using raw irregularly spaced elevation points and a triangulated network interpolation method Previous landslide inventory work had been completed in the subject area by Mr Don Howes of the B C Provincial Government and had been supplied in hardcopy form by Mr Bruce Thompson of the B C Ministry of Environment Because this inventory data had been compiled in the late 1980 s and marked on a 1 50 000 scale base map it was found that the locations were not sufficiently accurate to directly transfer to the GIS It was therefore necessary to obtain original aerial photographs and use these as the basis for digitizing landslide initiation zones directly into the GIS Because no orthophotos were available for this area the landslide locations were carefully plotted using TRIM contour form as a guide Landslide inventory locations were plotted 44 SINMAP USER S MANUAL PART III within the zone of initiation because the SINMAP methodology applies to failure locations within this zone 3 3 Analytical Results Using the DEM and lan
66. n the numerator of equation 3 quantifies SINMAP USER S MANUAL PART I the contribution to stability due to the internal friction of the soil as quantified by friction angle 6 or friction coefficient tano This is reduced as wetness increases due to increasing pore pressures and consequent reductions in the normal force carried by the soil matrix The sensitivity to this effect is controlled by the density ratio r equation 6 h Combined Cohesion X C C N m independent ofsoil thickness Soil weight h p g Dimensionless cohesion is the cohesive restoring force relative to soil weight C C C h g illustrated here on a vertical face to remove the effect of the normal and friction forces FIG URE 2 Illustration of dimensionless cohesion factor concept Practically the model works by computing slope and wetness at each grid point but assuming other parameters are constant or have constant probability distributions over larger areas With the form of equation 3 this amounts to implicitly assuming that the soil thickness perpendicular to the slope is constant 2 3 Topographic Wetness Index The emergence of the parameter specific catchment area a defined as upslope area per unit contour length m m see Figure 3 has been one of the landmark developments in recent hydrology due to Beven and Kirkby 1979 It is tied closely to recent h
67. name is a subdirectory The Original D EM grid must have units of meters for both elevation Z direction and spatial location X Y plane This version of SinMap does not utilize the ArcView map units designation the assumption is that all units are metric meters However the DEM grid may be either of floating point or integer type In other words elevation values may be input as integer numbers or real numbers If an integer elevation grid is used the derived slope area plots discussed later will show a vertical striping as only a limited number of slope values can be calculated from integer elevation data There are no program limitations on grid cell size but it should be remembered that large grid cells may not adequately represent topography for terrain stability modeling Itis up to the user to determine whether the D EM grid is adequate for the purpose of the intended study Also refer to Table 1 in Section 2 1 to determine the memory requirements for given grid sizes 7 2 Theme Name Calibration Regions Theme Type Grid Theme File Name dennamecal where demname is the name of the original D EM grid file File Type G rid 31 SINMAP USER S MANUAL PART 111 File Source Created by SINMAP File Location dannameal is automatically placed in the study directory in which denname is located subdirectory Original File Name calremame which is any acceptable ArcView grid file name polygon shapefile name polygon cover
68. ncludes a total of 39 landslides The largest number of landslides a total of 59 are found in the quasi stable class comprising 39 3 square kilometers or 16 496 of the entire study area This class has a landslide density of 1 5 landslides per square kilometer An analysis of the statistical results in Figure 12 indicates that Regions 4 and 7 include only 5 and 3 landslides respectively a total of only 3 of the inventory These two regions also only represent 396 of the total area Because of the small sample size the statistical results are suspect For example the lower threshold class of Region 4 yields a landslide density of 79 4 landslides per square kilometer However only 2 51 SINMAP USER S MANUAL PART 111 2 ArcView GIS Version 3 0a Eile Edit View Theme Analysis i Graphics Window Help 2 Ens Sea 10 2 DEM Chetelev 1512 Landslides Seeps Natural Landslide Road Landslide 30entour shp Saturation Saturation Zone Threshold Saturatic Partially Wet Low Moisture No D ata Stability In dex Stable Moderately Stable Quasi stable Lower Threshold Upper Threshold Defended H No Data Contributing Area Slope Flow Direction Pit filled DEM _ Calibration Regions Original DEM 4 3 51 BY Microsoft Word CaseHist E Inbox Microsoft Exchange fj ClipBook Viewer
69. ngeable in the calibration parameter input dialog box are T R lower bound D efault value 2000 m This is the lower bounding value for the ratio of transmissivity to the effective recharge rate T R upper bound D efault value 3000 m This is the upper bounding value for the ratio of transmissivity to the effective recharge rate Dimensionless Cohesion lower bound Default value 0 0 This is the lower bounding value that takes into account both root and soil cohesion Dimensionless Cohesion upper bound Default value 0 25 This is the upper bounding value that takes into account both root and soil cohesion Phi degrees lower bound Default value 30 This is the lower bounding value of the soil friction angle Phi degrees upper bound Default value 45 This is the upper bounding value of the soil friction angle SA Plot lower wetness line percentage Default value 10 This value represents the boundary wetness between the Low Moisture and Partialy Wet zones on the saturation map It is also the wetness of the lowest line on the SA Plot 4 4 Importing and Selecting DEM Data Using a DEM in SINMAP requires two steps 1 creating a grid of DEM data in the ArcView grid format and 2 selecting that grid for the SINMAP analysis Creating an ArcView grid of DEM data is generally undertaken using one of two general methods O btaining D EM grid data files that can be directly imported by ArcView to create an ArcVie
70. ngth taken here as the number of cells times grid cell size cell area divided by cell size This assumes that grid cell size is the effective contour length b in the definition of specific catchment area Figure 3 and does not distinguish any difference in contour length dependent upon the flow direction 3 5 SINMAP Stability Index and Wetness Computation of the SIN MAP stability index is simply a grid cell by grid cell evaluation of the equations in Appendix 1 Wetness computed from equation 8 is also returned as a by product of the stability index calculations 13 ICON KEY Waming 7 Valuable information Keyboard input SINMAP USER S MANUAL PART 111 Part SINMAP Software User s Guide 1 0 INTRODUCTION The SINMAP theory presented in Part I of this report is implemented in computerized form The theory has been incorporated into a library of computer routines that can be called to perform computational tasks including calculating stability index and saturation wetness index Additionally library routines are also available to perform many basic tasks of manipulating digital elevation model D EM grid data including topographic pit filling calculating slopes determining flow directions and defining the area draining to a specific point These various routines are written in the C programming language and are contained within one dynamic link library D LL file Because of the spati
71. not change the original script in the SINMAP extension ArcView will run the modified script in the script editor in lieu of the embedded extension script with the same name In other words when a SINMAP function is run the modified script will be executed in preference to the embedded extension script Saving the project with your modified SINMAP scripts will make them available for future use If want to use the original extension script either rename or delete your version of the script Further information on this topic is available in ArcView online help under the topic How ArcView searches for scripts 39 SINMAP USER S MANUAL PART 111 Part CASE STUDIES 1 0 INTRODUCTION The SINMAP software described in Part II has been used to perform case studies in three separate areas which are presented herein as examples These areas include Kilpala Watershed 104 8 km sub drainage of the Nimpkish Watershed in northern Vancouver Island British Columbia Rose Creek Watershed a small 14 2 km sub drainage of the Norrish Watershed north of Mission British Columbia and Burnt River Watershed 239 2 km within map sheets 930 029 and 930 030 southwest of Chetwynd British Columbia Each of these areas is located within a distinctive physiographic region that is experiencing a varying degree of shallow translational landsliding 2 0 KILPALA PILOT STUDY AREA 2 1 Physiographic Setting This study area lies immediately to the west
72. not convergent required to develop saturation in the critical wet period being considered This concept may be useful for establishing field estimates of R T through the field identification of the limits of surface saturation 2 4 Stability Index Definition To define the stability index the wetness index from equation 98 is incorporated into the dimensionless factor of safety equation 3 which becomes Cocos fi iin T sin 8 9 sin The variables and are from the topography with C tano r and R T parameters We treat the density ratio r as essentially constant with a value of 0 5 but allow uncertainty in the other three quantities through the specification of lower and upper bounds Formally these bounds define uniform probability distributions over which these quantities are assumed to vary at random D enote x tan 0 t and the uniform distributions with lower and upper bounds as C U C X U X X 10 t Ult t The smallest C and t i e C and t together with the largest x i e x defines the worst case most conservative scenario under this assumed uncertainty variability in the parameters Areas where under this worst case scenario FS is greater than 1 are in terms of this model unconditionally stable and we define a Jl r t sin C cos 0 SI FS min 11 sin For areas where the minimum factor of safety is less than 1 there
73. nt EAR 9318977 for the development of the Dee flow directions approach Distribution These programs were developed with government funding and are in the public domain not subject to copyright They are distributed freely with the following requests 1 In any publication arising from the use for research purposes the source of the program should be properly acknowledged and a pre print of the publication sent to the authors at the address below 2 In any use for commercial purposes or inclusion in any commercial software appropriate acknowledgement is to be included and a free copy of this software made available to the authors These programs are available on the Internet from Terratech Consulting Ltd at http www tclbc com or from Utah State University at http www engineering usu edu dtarb Support There is no formal ongoing support for this freely distributed public domain software However we are interested in feedback If you find errors have suggestions or are interested in any later versions contact Terratech Consulting Ltd P O Box 201 1181 6 Avenue N E Salmon Arm B C VIE 4N3 Phone 250 832 3933 Fax 250 832 1117 http www tclbc com SINMAP USER S MANUAL PART I Summary SINMAP Stability Index MAPping is an ArcView extension that implements the computation and mapping of a slope stability index based upon geographic information primarily digital elevation data This report describes
74. ntify sites susceptible to landslides 2 projection of future patterns of instability from analysis of landslide inventories 3 multivariate analysis of factors characterizing observed sites of slope instability 4 stability ranking based on criteria such as slope lithology land form or geologic structure and 5 failure probability analysis based on slope stability models with stochastic hydrologic simulations Each of these is valuable for certain applications None however take full advantage of the fact that debris flow source areas are in general strongly controlled by surface topography through shallow subsurface flow convergence increased soil saturation increased pore pressures and shear strength reduction Montgomery and Dietrich 1994 Recently the availability of digital elevation model D E M data has prompted SINMAP USER S MANUAL PART I the development of methods that take advantage of geographic information system GIS technology to quantify topographic attributes related to slope instability and landsliding GIS technology permits patterns of instability to be resolved and mapped at the scale of the DEM This relatively fine scale mapping which can pinpoint hazard areas has particular value for land management Notable recent contributions are Montgomery and Dietrich 1994 and Wu and Sidle 1995 Montgomery and Dietrich 1994 combine a contour based steady state hydrologic model with the infinite slope stability mo
75. nts the user should understand the concepts and limitations of the SIN MAP theory presented in this document This understanding should include a comprehension of the geomorphic processes which the program is attempting to model and the model s limitations Finally the user should be aware of the accuracy limitations of the DEM soil and hydrologic data used as input for these analyses The authors of SINMAP assume no liability or responsibility for the use of SINMAP the interpretation of SINMAP results or the consequences of management decisions that are based upon SINMAP In no event shall the authors be liable for any damages whatsoever arising out of the use or attempts to use SINMAP The terms ESRI Arc Info ArcView and Avenue are registered trademarks of Environmental Systems Research Institute Acknowledgements SINMAP was developed with the support of Forest Renewal British Columbia in collaboration with Canadian Forest Products Ltd Vancouver British Columbia It relies heavily on the coupling of steady state topographic hydrologic models with the infinite plane slope stability model an approach pioneered by Bill Dietrich and D avid Montgomery We acknowledge discussions and assistance from them The digital elevation model methodology and algorithms have been developed by D avid Tarboton over several years with support from a variety of sources but notably the National SINMAP USER S MANUAL PART I Science Foundation gra
76. o that they can be restored if necessary The Avenue source code is located in an ArcView extension file called sinmap avx The C code which has been compiled in Microsoft Visual Version 5 0 is contained in the following files 37 SINMAP USER S MANUAL PART 111 area c C language source code files for sinmap dll avcalls c flood c gioapi h gridio c gridio h Ismcom c Ism h sindex c setdir c areamn c C language source code files to use programs standalone from floodmn c outside Arcview setdirmn c sinmn c avcalls null c Null library routines to enable programs to be compiled gridio null c without linkage to Arcview To compile the sinmap dll in addition to the files listed in the first panel above you need to link to the following files that are part of Arcview Spatial Analyst avexec32 h These files are part of Arcview usually found in directory avexec32 lib CAESRMAV GIS Arcview lib32 callocate c These files are part of ESRI s gridio applications programmers avgridio lib interface distributed as part of Spatial Analyst usually found in directory CAESRMAV GIS Arcview grdio Gridio is a component of Spatial Analyst that is not installed by default so if you do not have these files you will need to rerun the install program from the Spatial Analyst CD ROM and explicitly select the gridio package If you do not have Arcview with Spatial Analyst the standalone programs can be use
77. on region parameter values and adds updated grid themes to the map view If there are lines on the Saplot these are also updated An alternative means to updating the Stability Index and Saturation grids and grid themes is by selecting the Update G rids and Lines menu item from the SinMap menu If the calibration regions table is closed after editing is complete the right popup menu Update selection is not available so the SinMap menu item provides a means of updating these themes based upon the new table values 4 9 2 Adjusting parameters in the SA plot The SA Plot has several features that allow modification of calibration region parameters updating of SA Plot stability index lines and updating DEM map view saturation and stability index themes Viewing of landslide and cell statistics for calibration regions is described in Section 4 10 These features may be selected as menu items from the SinMap menu when the SA Plot is active Alternatively they may be accessed more conveniently from a popup menu made available by clicking the right mouse button when the mouse cursor is located within the SA Plot window Three menu items are used for parameter adjustment procedures from within the SA Plot Step 1 From either the SinMap menu or the right mouse button activated popup menu choose A dd D elete Stability Equation Line This menu item acts as a toggle that makes the stability equation lines either visible or invisible depending upon their c
78. ons The accuracy of output is heavily reliant on the accuracy of the digital elevation model DEM data input It is also heavily reliant on the accurate positioning of known landslide initiation zones It is therefore important that as much effort a possible be put into obtaining accurate DEM and landslide inventory data SINMAP can be used for forest planning and management forest engineering and other geohazard studies Depending on the accuracy of the DEM data landslide inventory data and field checking used in the analysis it has proven to be a useful tool for both reconnaissance level mapping 1 20 000 scale and detailed mapping 1 20 000 to 1 5 000 scale as defined in the Forest Practices Code of British Columbia Part III provides a brief summary of three case studies at various locations in British Columbia 1 4 Required User Background The software was purposely implemented as a free extension to a popular GIS platform so as to be widely available The ArcView platform was chosen because it provides an intuitive interface for professional mappers with little GIS experience Though the software is simple to use the theory that forms the basis of the software should be thoroughly understood in order to avoid misapplication The user should therefore be experienced with applicable principals of geological engineering and engineering geoscience Some familiarity with basic GIS concepts in general and ArcView software particular is also r
79. ons for this may be twofold 1 the bedrock and surficial geology and landslide processes are considerably more complex than the other two areas and 2 the DEM data fails to pick up many of the small but critical slopes It was observed during the landslide inventory work that many of these landslides are actually located in areas that are obviously steep on aerial photographs but not accurately represented by the TRIM DEM Many of these areas are associated with low but steep terrace faces and gully walls Because of the relatively coarse spacing of the original DEM points 60 m small terrace faces are often not represented It is 53 SINMAP USER S MANUAL PART 111 J AALE 12 amp No ekib 369 2 Statistical Summary for Chetelev 100000 4 10000 4 Contributing Area Moderately Stable Stable 387 96 508 15 0 3 6 4 6 3 1 06 Quasi Lower Upper Stable Threshold Threshold Defended Total 50 08 01 637 78 13 02 100 0 Saturated Uns aturated Wetness 10 ele j A Bae EE 4 Ne ej xir esp TTE 69 1 006 2 Statistical Summary for Chetelev Quasi Lower Upper Stable Threshold Threshold Defended Total Sl 160 125 1405000 100000 Contributing Area Saturated Unsaturated Wetness 10 30 i Slope degrees FIG URE 17 Slope areaplot for calibration regions 8 54 SINMAP USER S MANU
80. ope on planar triangular facets on a block centered grid In the case where no slope vectors are positive downslope the flow direction is set using the method of G arbrecht and Martz 1997 for the determination of flow across flat areas This makes flat areas drain away from high ground and towards low ground These procedures have minimal impact when used in SINMAP because flat areas are always unconditionally stable but are included for completeness and compatibility with other hydrologic uses and to avoid data gaps in the maps produced 12 SINMAP USER S MANUAL PART I 3 4 Specific Catchment Area Upslope area counted in terms of the number of grid cells is calculated using a recursive procedure that is an extension of the very efficient recursive algorithm for single directions Mark 1988 The upslope area of each grid cell is taken as its own area one plus the area from upslope neighbors that have some fraction draining to it The flow from each cell either all drains to one neighbor if the angle falls along a cardinal 0 2 3 2 or diagonal 4 31 4 5 x 4 7 4 direction or is on an angle falling between the direct angle to two adjacent neighbors In the latter case the flow is proportioned between these two neighbor pixels according to how close the flow direction angle is to the direct angle to those pixels as illustrated in Figure 5 Specific catchment area a is then upslope area per unit contour le
81. or Water resources and Hydrodynamics D epartment of Civil Engineering M I T September 1989 Tarboton D G 1997 New Method for the Determination of Flow Directions and Contributing Areas in Grid Digital Elevation Models Water Resources R esearch 33 2 309 319 Wu W and R C Sidle 1995 A Distributed Slope Stability Model for Steep Forested Watersheds W ater R esources R esearch 31 8 2097 2110 68
82. ors Data ranges and Names SINMAP provides default colors and classification data ranges for the grid themes it creates You may modify the various legends as you see fit so as to implement your own color schemes and classifications Y ou can save these legends as ArcView legend files with avl extension and reload them at a later time SINMAP will automatically use your saved legends if you do the following Save the legend files in the directory containing the Original DEM grid Use the following names for the av files for the associated grid theme e dem avl Original DEM e felavl Pit filled Elevations e Slope e Flow Direction e sca wl Contributing Area 30 SINMAP USER S MANUAL PART III e Stability Index e satavl Saturation Legends will be created from these grids in the future instead of using the default SINMAP legends The Calibration Regions theme does not have a default avl file 7 0 DATA STRUCTURE REFERENCE This section provides information regarding naming conventions and file structures for the grids themes and tables used by SINMAP 7 1 Theme Name Original DEM Theme Type Grid theme File Name denname where danname is any acceptable ArcView grid file name File Type G rid File Source Provided by user File Location danname is actually a subdirectory that may be located anywhere It is usually best to store all files required for a study in the directory in which den
83. ost of the two themes in the table of contents must be the grid from which a smaller subgrid will be extracted Then from the Edit menu choose Subset of G rid A new grid called sub where is a number of 1 or greater will be added to the working directory The new grid will be added as a grid theme to the view and be called Sub of Name where Name is the name of the theme from which the subset grid is extracted The user will normally want to rename and permanently save the grid using the ArcView grid management routines 5 3 Grid Cutter This selection makes a new grid from a larger grid based upon a rectangle drawn over the larger grid using this tool This may be a useful tool if you have a small study area or watershed located within a larger DEM that can be cut out as a rectangular area SinMap adds a grid cutter tool to the view tool bar This tool functions similarly to the Subset of G rid menu item in that it allows a smaller grid to be cut from a larger grid To use this option a DEM grid theme must be active in a view s table of contents Then the grid cutter tool button is activated by depressing it A comer of the subset grid is located and the left mouse button is clicked held and dragged to delineate a rectangular box that defines the bounds of the new grid A new grid called sub where is a number of 1 or greater will be added to the working directory The new grid will be added as a grid theme to the vie
84. ot the popup menu that is activated by clicking the right mouse button has several menu items added These menu items provide functions including access to data adjustment dialog boxes and on the fly calculation of landslide statistics 18 SINMAP USER S MANUAL PART III 4 2 Adding a New View From the SINMAP Project window click on the New button to create a new view Many of SINMAP s terran mapping operations are undertaken by accessing and manipulating layers of spatial data from within the DEM map view window Therefore creation of a new view is always the first step in a SINMAP study The menu bar of the view has a menu called SinMap added to it The SinMap menu has 19 menu items that provide for selecting creating and modifying the data used in a terrain stability mapping study These menu items are divided into five 5 groups on the menu with groups distinguished by separator bars A study is undertaken by selecting menu items at the top of the menu and working downward within the menu Menu items are grayed disabled when data are not available for the particular program operation associated with that item 4 3 Establishing Model Parameters Thetop group of two menu items in the SinMap menu provides access to dialog boxes for establishing various program parameters Default values are provided for all parameters so it is not required for a user to input parameter values However calibration region parameters will need to be mo
85. ou can probably use that file with only minor modifications If you have data in an XY event table dBase or ASCII file convert it to a shapefile The only requirement for the landslides file is that it has a numeric field called type where type ranges from 1 to 4 and identifies the type of landslides modeled 7 4 Theme Name Pit filled DEM Theme Type Grid theme File Name dannamdd where denname is the name of the original D EM grid file File Type G rid File Source Created by SINMAP File Location dannamdd is automatically placed in the study directory in which denname is located This grid grid theme is the same as the elevation grid except that it has had internally drained pits removed 7 5 Theme Name Flow Direction Theme Type Grid theme File Type G rid File Name demnamang where demname is the name of the original D EM grid file File Source Created by SINMAP File Location dennameang is automatically placed in the study directory in which danname is located Each cell in this grid represents the compass direction for water flow within the cell down the slope of the steepest triangular facet draining from the cell See Part I Section 3 3 for a complete description of the method used to calculate flow direction 7 6 Theme Name Slope Theme Type Grid theme File Name dennamslp where danname is the name of the original D EM grid file 33 SINMAP USER S MANUAL PART III File Type G rid File Source
86. p SINMAP USER S MANUAL UTAH STATE UNIVERSITY TERRATECH CONSULTING LTD CANADIAN FOREST PRODUCTSLTD C N GOODWIN FLUVIAL SYSTEM CONSULTING SINMAP A STABILITY INDEX APPROACH TO TERRAIN STABILITY HAZARD MAPPING torest 2 WtahState Funded by ee EWAL Bc CONSULTING LTD UNIVERSITY A STABILITY INDEX APPROACH TO TERRAIN STABILITY HAZARD MAPPING SINMAP User s Manual Authored by R T Pack Terratech Consulting Ltd D G Tarboton Utah State University C N Goodwin C N Goodwin Fluvial System Consulting Supported by Canadian Forest Products Ltd Funded by Forest Renewal B C SINMAP USER S MANUAL PART I The Authors Robert T Pack Principal Terratech Consulting Ltd Salmon Arm British Columbia David G Tarboton Associate Professor of Civil and Environmental Engineering Utah State University Logan Utah Craig N Goodwin Principal C N Goodwin Fluvial System Consulting Logan Utah Disclaimers Although care has been taken in developing and testing SINMAP errors and inadequacies may still occur particularly in new applications A user must therefore make the final evaluation as to the usefulness of SINMAP for his her application SINMAP is a tool to be used by investigators who have some knowledge and experience conceming landslide behaviour It requires engineering judgement and common sense in developing input parameters and interpretation of the results In making these judgeme
87. ration Regions 2 lt lal _ Original DEM ne a S mel 2550 T Lr AR r NA p h mA br y lt i ak Start Y Exploring Norrish BY Microsoft Word Documenti ArcView GIS Version Statistical Summary for e 2 33 PM FIGURE 10 ArcView screen showing a portion of the wetness map derived by the SINMAP analysis for the Rose Creek Drainage Figure 11 is an ArcView screen that shows a portion of the stability index map calculated in the analysis This statistical summary shown in Figure 9 indicates that the upper threshold stability index class bright red in Figure 11 includes 37 landslides or 56 1 of the total inventory At the same time this class includes 1 2 km or only 8 5 of the study area This results in an average landslide density of 30 8 landslides per square kilometer This is over 10 times the highest density observed in the Kilpala watershed The defended class light brown and the lower threshold class pink have an average landslide density of 6 4 and 7 7 landslides per square kilometer respectively 2 Similarities in shear strength values in coarse granular glacial tills and colluvium across large areas has been previously noted in elaborate field testing work J Fannin University of British Columbia personal communication 46 SINMAP USER S MANUAL PART 111 Only 2 of the 66 total landslides fall within the lowest thr
88. rid subdirectory It may be useful to create a specific directory for each study where input data files and SIN MA P generated files are stored This is not a program requirement because the D EM base name identifies files associated with a study but it is better housekeeping and will speed up some file Operations 21 SINMAP USER S MANUAL PART III 4 5 Creating the Calibration Regions Grid Theme Calibration regions are areas within which single lower bound and upper bound calibration parameters values can represent T R dimensionless cohesion and friction angle phi Regions are commonly defined using soils geologic vegetation and land use mapping to identify areas having consistent calibration parameters For a SINMAP analysis to provide a realistic assessment of terrain stability the user should understand SINMAP theory and the factors causing the spatial distribution of the calibration parameters There are three menu items that may be chosen to create a calibration regions grid The choice is dependent upon the type of geographic data available and the level of analysis sought Creation of a calibration grid creates the grid subdirectory dannameal and adds the grid theme Calibration Regions to the view Also a table of calibration D emname Calibration Regions is added to the project Option 1 From the SinMap menu choose Make Single Calibration Region Theme This method for creating a calibration regions grid theme and a
89. s of topography We have found TOPOGRID and TIN based interpolation methods available in Arc Info TIN or in ArcView 3 D Analyst software to be preferable After the DEM grid is created the next step is to select the grid for SIN MAP analysis From the SinMap menu choose Select D EM Grid for Analysis Choosing the Select D EM G rid for Analysis menu item displays a file selection dialog box The user navigates through the drives and directories to locate the desired DEM grid and chooses OK The selected D EM grid is added as a grid theme to the view and is automatically renamed to O riginal D EM in the view s table of contents A grid legend is created based upon the default Greens to Reds dichromatic color scheme with 10 equal interval elevation categories This color scheme can be changed at any time without affecting the operation of SINMAP Do not rename this theme or other themes added to the table of contents by the SINMAP Legend names are used to identify data sets within the program The name of the selected D EM is used as the base name for all files created during the study Therefore if the selected DEM is named danname then names of files or grid subdirectories created during the study would have names like demnamedbf and dannamed Throughout the rest of this document danname is used to represent the base name All of the files and subdirectories created during the study will be located in the directory containing the DEM g
90. sion 1 1 You will need enough computer memory usually the more the better In this version of SINMAP we dump the grids into large arrays in memory so as to keep disk input output down and speed up If you do not have enough memory to fully contain all the grids Windows will swap memory pages out to disk This can slow things down dramatically as a lot of swapping and thrashing can occur If you plan on using extremely large grid study areas try to close out all other processes to free up as much memory as possible Check Task Manager to see how much memory you actually have available Table 2 lists the amount of memory your computer needs to run SINMAP with a particular D EM grid size and maintain all operations in memory The values are approximate only for the exact value depends on the specifics of your system configuration and the complexity number of pits and flats of the D EM being processed Table 2 Approximate amount of memory your computer needs to run SINMAP on a particular size D EM grid DEM Grid Size cells Memory Required M egabytes 10 000 100x100 0 16 250 000 500x500 4 1 000 000 1 000x1 000 16 6 250 000 2 500x2 500 100 2 2 Installation Procedure The core of SINMAP employs two files that need to be copied to specific directories on your computer sinmap avx is an ArcView extension file used by SINMAP This file must be placed in the directory called arcview ext32 which is the standard location for
91. slides per square kilometer and includes a total of 11 landslides The lower threshold class includes 8 landslides and the remaining stability index classes representing 62 996 of the total area include just one landslide 2 ArcView GIS Version 3 0a File Edit View heme Analysis SinMap Graphics Window Help Ct 357 AGN BASS 4 Z Esp T1 J Pit filled DEM Calibration Regions Original DEM hey p 7 f 2 y A 33 BIS Version aj Exploring Desktop J Statistical Summary for BY Microsoft Word Documenti 10 27AM FIGURE 8 ArcView screen that shows a portion of the stability index map for the K ilpala Watershed 2 4 Discussion When compared to other areas of the province this area has a relatively high percentage of landslides occurring in steep bedrock dominated terrain During the field reconnaissance it was noted that the bedrock tends to be irregular and the soils variable in depth It is therefore possible that pockets of soil within areas of bedrock outcrop could be a source landslide material in this terrain The SINMAP analysis does a good job of delineating areas that intuitively appear to be susceptible to landsliding In particular SINMAP does a good job of delineating the swales where many landslides originate However it was noted in the field 43 SINMAP USER S MANUAL PART III reconnaissance that several landslides occurred on the noses of a rock
92. stributed random variables equation A 9 thus the combination is a sum of the generic form Z X Y A 17 For X U x x and Y U y y the cumulative distribution function of Z is given by ifz lt x y F z Prob Z lt z 2 0 if x y lt z lt min x y X y 2 F z z y X 2 x X Y yi if min x y X y lt z lt max x y X y lt amp d 2z x y d min x X y yj and d max x X y po 74 2 2 if max x y X y lt Z lt X y 2 xj F z 21 M corem if Z gt X y F z 1 This defines a generic function which with parameters is denoted F X yy Yor z Prob Z lt z A 18 In region 1 SI is obtained by evaluating this with the appropriate arguments namely SI 1 F e orien D A 19 sinO sin sin 0 sin 0 In region 3 never saturated FS is given by FS 1 wr t A 20 sin C and t are assumed to be uniformly distributed random variables equation 9 Also W sin A 21 60 SINMAP USER S MANUAL APPENDIX 1 which with x U x x equation 9 is also a uniformly distributed random variable wed ay A 22 sin sin The combination is therefore of the generic form Z X YB A 23 This requires the combination of the product A YB A 24 with the sum Z X A A 25 where X Y and B are uniformly distributed X U X x Y Uy y
93. t INT 285 USDA Forest Service Intermountain Research Station Jenson S K and J O Domingue 1988 Extracting Topographic Structure from Digital Elevation D ata for Geographic Information System Analysis Photogrammetric E nginering and Remote Sensing 54 11 1593 1600 Mark D M 1988 Network models in geomorphology Chapter 4 in M oddling in eomorphological Systems Edited by M Anderson John Wiley p 73 97 Marks D J Dozier and J Frew 1984 Automated Basin D elineation From Digital Elevation D ata Proossing 2 299 311 Montgomery D and W E Dietrich 1988 Where do channels begin N ature 336 232 234 Montgomary D R and W E Dietrich 1989 Source Areas D rainage D ensity and Channel Initiation W ater Resouros R search 25 8 1907 1918 Montgomery D R and W E Dietrich 1994 A Physically Based Model for the Topographic Control on Shallow Landsliding W ater Resources Research 30 4 1153 1171 Moore I E M Loughlin and C J Burch 1988 Contour Based Topographic Model for Hydrological and Ecological Applications Earth Surface Processes and Landforms 13 305 320 Moore I D and R B Grayson 1991 Terrain Based Catchment Partitioning and Runoff Prediction Using Vector Elevation D ata W ater Resources esearch 27 6 1177 1191 O Callaghan J F and D M Mark 1984 The Extraction of Drainage Networks From Digital Elevation D
94. th probability 1 x a sin 0 A 37 x a sin 0 x a sin In the first case the cumulative distribution function of FS is as for region 1 and in the second case as for region 3 Therefore the resulting cumulative distribution function for the factor of safety in region 2 is F z Prob FS lt z _ x52a sin0 1 C Cy cos0 l r t cos06 1 r t x2a sin 0 xja sin s sino sin sin 0 sin 0 2 1 xa sin C cos0 a X5a sin 0 x a sin 55 sin 0 sin 0 sin 0 ama cos 0 a 1 x t to Z sin I n pta 52 64 SINMAP USER S MANUAL APPENDIX 1 A 38 and SI Prob FS gt 1 1 F z 1 A 39 65 SINMAP USER S MANUAL REFERENCES References References Band L E 1986 Topographic partition of watersheds with digital elevation models W ater Resouros R esearch 22 1 15 24 Beven K J and M J Kirkby 1979 A Physically Based Variable Contributing Area Model of Basin Hydrology ydrologcal Sdences Bulldin 24 1 43 69 Carrera A M M Cardinali R Detti F Guzzetti V Pasqui and P Richenback 1991 GIS Techniques and statistical models in evaluating landslide hazard E arth Surface Processes and L andforms 16 427 445 Costa Cabra M and S J Burges 1994 Digital Elevation Model Networks DEMON A Model of Flow Over Hillslopes for Computation of Contributing and Dispersal Areas W ater esources Research 30 6 1681 1692 D
95. urrent visibility Separate stability equation lines can be plotted for only one active region theme in the SA Plot table of contents at a time If no theme is active or more than one theme is active then an error message is issued Parameters for the stability equations for each activated region theme are obtained from the study s calibration region table NOTE THAT THE VISIBILITY OF A REGION THEME S POINTS HAS NO AFFECT UPON EQUATION LINE PLOTTING More than one set of lines may be plotted by sequentially activating several regions and choosing this menu item Although this allows comparison of different parameters in the stability equation it can become confusing 26 SINMAP USER S MANUAL PART III Step 2 From either the SinMap menu or the right mouse button activated popup menu choose A djust Calibration Parameters Selection of this menu item displays a dialog box that allows changes to be made to the calibration region parameters T R cohesion and phi for the activated calibration region After changes are made to the parameters and the OK button is clicked the previous stability equation and saturation lines are removed if they were visible and a new set of lines based upon the revised parameters is displayed If no theme is active or more than one theme is active then an error message is issued when this item is selected A typical work flow sequence would be to iteratively modify calibration region parameters until the stab
96. vating the project window and deleting the SA Plot Demname view Deletion of the SA Plot enables the SA Plot menu item so that the plot can be recreated 4 9 Calibration Methods 4 9 1 Adjusting parameters in the DEM view The bottom group on the SinMap menu has two items Calibration Parameter Adjust and Update Grids and Lines These two menu items allow the user to change the values of soil parameters in the calibration regions table and then update the Stability Index and Saturation grids and SA plot lines based upon these changes 25 SINMAP USER S MANUAL PART III From the SinMap menu choose Calibration Parameter Adjust Choosing this selection activates the study s calibration regions table making it available for the modification of calibration region parameters Values in the table are edited using the standard ArcView procedures The edit tool is selected from the tool bar the table value to be edited is clicked causing it to highlight and the data value is changed After the editing of calibration region parameters is completed the Stability Index and Saturation grid themes which are dependent upon calibration region parameters are normally updated This may be done from within the calibration regions table by activating the popup menu with a right mouse button click and choosing Update Updating deletes the existing Stability Index and Saturation themes recreates the grids for these themes using the new calibrati
97. w and be called Sub of Name where Name is the name of the theme from which the subset grid is extracted The user will normally want to rename and permanently save the grid using the ArcView grid management routines If a nonrectangular subgrid is required the Subset of Grid Edit menu option should be used 6 0 USEFUL TIPS 6 1 Create a Calibration Region Outside Study Area SINMAP calibrations and statistics are based upon calibration regions If you make a region that incorporates all areas on the D EM that are not part of the study area then the remaining calibration and statistics can be based solely upon the study area For example if you were planning on having only one calibration region then create two one which is called something like Non Project Area and the other called Project Area This can be done by using an ownership or land management base map to create a polygon or grid theme with the attributes Non Project Area and Project Area This theme can then be used as the basis for creation of the Calibration Regions grid theme 29 SINMAP USER S MANUAL PART III The other grids and SA Plot can then be created in the usual manner In the SA Plot you can remove the theme called Non Project Area if you wish Additionally after you have created all the other grids you can go back and use the various Spatial Analyst routines Map Query Map Calculator etc to provide statistics and summaries solely for the proj
98. w grid or Generating an ArcView DEM grid file from a point contour or triangular irregular network data set There are a variety of ways to undertake either of these grid creation strategies One method is to create the data set in the ASCII file format that can be read by ArcView The sample data file sampleasc illustrates this file format 20 SINMAP USER S MANUAL PART 111 From the File menu of the View window choose Import Grids and then select the import file type import file name and name for the output grid to be created Altematively ArcView grids are compatible with ARC Info grids so ARC Info routines for creating grids from point TIN or contour data can be used by users having access to that program In particular the TOPOGRID software available in Arc Info for the generation of grid DEM s from contour or point data while respecting the fluvial drainage morphology of natural topography is recommended The ArcView Spatial Analyst extension also allows creation of grids from a point theme data sets using the following steps Activate a point theme containing elevation points From the Analysis menu choose Interpolate Surface Provide grid values in the O utput G rid Specification dialog box and choose a surface interpolation method in the Interpolate Surface dialog box However we caution users that in our experience the interpolation methods used by Spatial Analyst are often not well suited to certain type
99. y and generally assumed to be artifacts arising due to the discrete nature and data errors in the preparation of the DEM They are eliminated here using a flooding approach This raises the elevation of each pit grid cell within the DEM to the elevation of the lowest pour point on the perimeter of the pit eg Jenson and Domingue 1988 3 3 Slopes and Flow Directions The earliest and simplest method for specifying flow directions is to assign flow from each grid cell to one of its eight neighbors either adjacent or diagonally in the direction with steepest downward slope This method designated D8 8 flow directions was introduced by O Callaghan and Mark 1984 and has been widely used The D8 approach has disadvantages arising from the discretization of flow into only one of eight possible directions separated by 45 e g Fairfield and Leymarie 1991 Quinn et al 1991 Costa Cabral and Burges 1994 Tarboton 1997 These have motivated the development of other methods comprising multiple flow direction methods Quinn et al 1991 Tarboton 1997 random direction methods Fairfield and Leymarie 1991 and grid flow tube methods Costa Cabral and Burges 1994 Tarboton 1997 discusses the relative merits of these SINMAP uses the Deo method the multiple flow direction method developed by Tarboton 1997 11 SINMAP USER S MANUAL PART 1 In this method the flow direction angle measured counter clockwise from east is represent
100. y of the four grid files already exist having been previously generated a Y es No Cancel dialog pops up asking if you wish to use the previously computed grids Answering yes will cause existing grids to be used as the basis for grid themes added to the map view Answering no will cause new grids to be created for map view grid themes with the existing grids automatically backed up with a b automatically added to the grid name Option 2 From the SinMap menu choose each processing step separately by first choosing Pit Filled DEM This selection generates the pit filled DEM grid and adds the grid theme Pit filled DEM to the map view The grid file generated will have the name dennamdd If dannamedd exists a Y es No dialog box will ask whether to use the existing grid as the basis for the grid theme If no is selected the existing file is backed up as dannamdd b prior to creating the new grid 23 SINMAP USER S MANUAL PART 111 From the SinMap menu choose Flow Direction and Slope as the next step Choosing this selection causes generation of the flow direction and slope grids with grid themes of the same names added to the map view The grid files generated will have the names dannameang flow direction and dennamedp slope If either of the grids exist a Y es No dialog box will ask whether to use the existing grids as the basis for the grid themes If yes is selected both grids will be recreated even if one grid already exists
101. y slopes that would not normally be considered susceptible to landsliding On closer examination it was found that locally weathered bedrock may be responsible for these slides The SINMAP methodology missed classifying several of these sites as being landslide prone due to the site specific geologic conditions not modeled It is therefore important to remember that the SINMAP tool should be used in combination with aerial photo analyses and field mapping techniques 3 0 ROSE CREEK PILOT STUDY AREA 3 1 Physiographic Setting This study area lies immediately to the north of Mission B C The soils in the upper portion of the watershed are mostly thin coarse granular glacial tills and colluvium derived from granitic bedrock of the Coast Plutonic Rocks The lower valley slopes have thicker deposits of glacial till and colluvium with pockets of silty glaciofluvial sediments This pilot study focuses on the Rose Creek sub drainage of the Norrish Watershed In this sub drainage the soils are mostly thin colluvium and glacial till The area has a history of landslide problems since the beginning of logging in the late 1970 s and early The majority of landslides observed during a two day reconnaissance of the area were noted to be shallow translational debris slides some of which subsequently mobilized into debris flows As with the Kilpala area many of the landslides originate in steep colluvial and bedrock dominated slopes and are typically found i
102. ydrologic models that represent runoff generation by the saturation from below mechanism TOPMODEL Beven and Kirkby 1979 O Loughlin 1986 TOPOG Moore et al 1988 Moore and Grayson 1991 and THALES Greyson et al 1992a and Grayson et al 1992b These developments follow the field observations that higher soil moisture or areas of surface saturation tend to occur in convergent hollow areas It has also been reported that landslides most commonly originate in areas of topographic convergence Montgomery and Dietrich 1994 Following TOPMODEL and other similar topographically based wetness index models we make the following assumptions SINMAP USER S MANUAL PART I 1 Shallow lateral subsurface flow follows topographic gradients This implies that the contributing area to flow at any point is given by the specific catchment area defined from the surface topography Figure 3 2 Lateral discharge at each point is in equilibrium with a steady state recharge R m hr 3 The capacity for lateral flux at each point is T sin0 where T is the soil transmissivity m hr i e hydraulic conductivity m hr times soil thickness h m Assumptions 1 and 2 together imply that lateral discharge q depth integrated per unit contour length m hr is q Ra 7 Assumption 3 differs from a common TOPMODEL Beven and Kirkby 1979 assumption in that we have not assumed hydraulic conductivity decreasing with Specific Cat

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