Stability Index

A grid of terrain slope expressed as 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.

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 Dinfinity contributing area function to obtain this.

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.

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)

Lower bound of steady state recharge used to compute soil profile saturation (m/hr).

SINMAP stability index. Stability index values are 0.0 or greater, with values greater than 1.0 indicating some level of stability.

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/Tsinqis 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/sinq), a number between 0 and 1 which represents the wettest the cell could get given the range of R/T specified.