Stability Index

Summary

Computes terrain stability index (SI) using the SINMAP method based on the infinite plain slope stability model. SI values are written to the output raster file. Refer to documentation on SINMAP web page for an understanding of what this program does. Refer also to documentation on the GRAIP web page for use of this including the impacts of roads on drainage that may alter terrain stability.

Usage

Command Line Options:

1. Python program that takes input from a control file


					StabilityIndex.py --params <control file>

Control file format

# input parameters for combined stability index computation with road impact
# input files
slp=<Slope grid>
sca=<Specific catchment area grid>
cal=<Region grid>
calpar=<parameter attribute table>
# output files
si=<Stability index grid>
sat=<Saturation grid>
# Additional parameters
minimumterrainrecharge=0.0009 
# m/hr
maximumterrainrecharge=0.00135
# m/hr
# temporary output file directory
temporary_output_files_directory=<directory>
is_delete_intermediate_output_files=<Boolean>

2. Direct command line call


					mpiexec –n <number of processes> SinmapSI 
					-slp <Slope grid> 
					-sca <Specific catchment area grid> 
					-calpar <parameter attribute table> 
					-cal <Region grid> 
					-si <Stability index grid> 
					-sat <Saturation grid> 
					-par 0.0009 0.00135 9.81 1000

Syntax

ArcGISStabilityIndex (Input_Slope_Raster, Input_Specific_Catchment_Area_Raster, Input_Parameter_Region_Raster, Input_Parameter_Attribute_Table_Text_File, Minimum_Terrain_Recharge__m_hr_, Maximum_Terrain_Recharge__m_hr_, Output_Stability_Index_Raster, Output_Saturation_Raster, Intermediate_Output_Files_Location, Delete_Intermediate_Output_Files_Upon_Completion)

Parameter	Explanation	Data Type
Input_Slope_Raster	Dialog Reference A grid of terrain slope expressed as drop/distance, i.e. tan of the slope angle. This is recommended to be from the TauDEM D-infinity flow directions function using the method described in Tarboton, D. G., (1997), "A New Method for the Determination of Flow Directions and Contributing Areas in Grid Digital Elevation Models," Water Resources Research, 33(2): 309-319. This is the steepest outwards slope on one of eight triangular facets centered at each grid cell. There is no python reference for this parameter.	Raster Layer
Input_Specific_Catchment_Area_Raster	Dialog Reference A grid of specific catchment area which is the contributing area per unit contour length using the multiple flow direction D-infinity approach. The contributing area of each grid cell is then taken as its own contribution plus the contribution from upslope neighbors that have some fraction draining to it according to the D-infinity flow model. Recommend use the TauDEM D-infinity contributing area function to obtain this. There is no python reference for this parameter.	Raster Layer
Input_Parameter_Region_Raster	Dialog Reference An integer valued raster defining parameter regions. This should have dimensions exactly the same as the input raster, and an accompanying attribute table that specifies SINMAP parameters for each value of this raster. The Create Parameter Region Tool is provided to create this raster. There is no python reference for this parameter.	Raster Layer
Input_Parameter_Attribute_Table_Text_File	Dialog Reference A comma separated attribute table with one row of parameters for each value in the parameter region grid. Example format: SiID,tmin,tmax,cmin,cmax,phimin,phimax,SoilDens 1,2.708,2.708,0.0,0.25,30.0,45.0,2000.0 2,2.208,2.508,1.0,0.25,30.0,45.0,2000.0 Columns are: SiID - Identifier tmin - Transmissivity lower bound (m^2/hr) tmax - Transmissivity upper bound (m^2/hr) cmin - Dimensionless cohesion lower bound cmax - Dimensionless cohesion upper bound phimin - Soil friction angle lower bound phimax - Soil friction angle upper bound SoilDens - Soil density (kg/m^3) There is no python reference for this parameter.	File
Minimum_Terrain_Recharge__m_hr_	Dialog Reference Lower bound of steady state recharge used to compute soil profile saturation (m/hr). There is no python reference for this parameter.	Double
Maximum_Terrain_Recharge__m_hr_	Dialog Reference Upper bound of steady state recharge used to compute soil profile saturation (m/hr). There is no python reference for this parameter.	Double
Output_Stability_Index_Raster	Dialog Reference SINMAP stability index. Stability index values are 0.0 or greater, with values greater than 1.0 indicating some level of stability. There is no python reference for this parameter.	Raster Dataset
Output_Saturation_Raster	Dialog Reference This raster encodes the topographic wetness index described in the SINMAP documentation. Given the range of R/T values there are 3 possibilities: 1. w is 1 (saturated) for the full range (R/T_min, R/T_max). 2. w is 1 for part of the range (R/T_min, R/T_max). 3. w is never 1. These are used to assign one of the following values to each grid cell in the saturation theme. Saturation Zone: Always saturated as indicated by w=1 for the full range (x1, x2). This occurs when Ra/Tsinθ is greater than 1. This is represented (coded) with a value of 3. Threshold Saturation: Cells having a probability of being saturated are represented (coded) with a value of 2. Partially Wet and Low Moisture: Cells that are never saturated. The level of saturation is encoded as ((R/T)_max)(a/sinθ), a number between 0 and 1 which represents the wettest the cell could get given the range of R/T specified. There is no python reference for this parameter.	Raster Dataset
Intermediate_Output_Files_Location	Dialog Reference A folder where intermediate results are written. There is no python reference for this parameter.	Workspace
Delete_Intermediate_Output_Files_Upon_Completion	Dialog Reference Check this to delete intermediate files upon completion (but leave the folder). There is no python reference for this parameter.	Boolean

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Title Stability Index