# Slope Over Area Ratio

(c) 2010 by David G. Tarboton
Calculates the ratio of the slope to the specific catchment area (contributing area). This is algebraically related to the more common ln(a/tan beta) wetness index, but contributing area is in the denominator to avoid divide by 0 errors when slope is 0.

## Parameters

Number of Processes
Integer
  The number of stripes that the domain will be divided into and the number of MPI parallel processes that will be spawned to evaluate each of the stripes.
Slope Grid
Raster Grid
  A grid of slope. This grid can be generated using ether the "D8 Flow Directions" tool or the "D-Infinity Flow Directions" tool.
Specific Catchment Area Grid
Raster Grid
  A grid giving the contributing area value for each cell taken as its own contribution plus the contribution from upslope neighbors that drain in to it. Contributing area is counted in terms of the number of grid cells (or summation of weights). This grid can be generated using either the "D8 Contributing Area" tool or the "D-Infinity Contributing Area" tool.

## Outputs

Slope Divided By Area Ratio Grid
Raster Grid
  A grid of the ratio of slope to specific catchment area (contributing area). This is algebraically related to the more common `ln(a/tan beta)` wetness index, but contributing area is in the denominator to avoid divide by 0 errors when slope is 0.