D-Infinity Decaying Accumulation

Title  D-Infinity Decaying Accumulation

Summary

The D-Infinity Decaying Accumulation tool creates a grid of the accumulated quantity at each location in the domain where the quantity accumulates with the D-infinity flow field, but is subject to first order decay in moving from cell to cell. By default, the quantity contribution of each grid cell is the cell length to give a per unit width accumulation, but can optionally be expressed with a weight grid. The decay multiplier grid gives the fractional (first order) reduction in quantity in accumulating from grid cell x to the next downslope cell.


Usage

Command Prompt Syntax:

mpiexec -n <number of processes> DinfDecayAccum -ang <angfile> -dm <dmfile> -dsca<dscafile> [ -o <outletfile>] [ -wg <wgfile>] [ -nc] [ -lyrname <layer name>] [ -lyrno <layer number>]

angfile: Dinf flow direction input file

dmfile: Input decay multiplier grid (distance down grid)

dscafile: Output decayed specific catchment area grid

outletfile: input outlets file (OGR readable dataset)

wgfile: Input weight grid (optional)

nc: Flag for edge contamination

layer name: OGR layer name if outlets are not the first layer in outletfile (optional)

layer number: OGR layer number if outlets are not the first layer in outletfile (optional)

Layer name and layer number should not both be specified.


Syntax

DInfDecayingAccumulation (Input_D-Infinity_Flow_Direction_Grid, Input_Decay_Multiplier_Grid, {Input_Weight_Grid}, {Input_Outlets}, Check_for_Edge_Contamination, Input_Number_of_Processes, Output_Decayed_Specific_Catchment_Area_Grid)

Parameter Explanation Data Type
Input_D-Infinity_Flow_Direction_Grid Dialog Reference

A grid giving flow direction by the D-infinity method. Flow direction is measured in radians, counter clockwise from east. This grid can be created by the function D-Infinity Flow Directions . The D-infinity algorithm is 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.

 Raster Layer
Input_Decay_Multiplier_Grid Dialog Reference

A grid giving the factor by which flow leaving each grid cell is multiplied before accumulation on downslope grid cells. This may be used to simulate the movement of an attenuating substance.

 Raster Layer
Input_Weight_Grid (Optional) Dialog Reference

A grid giving weights (loadings) to be used in the accumulation. If this optional grid is not specified, weights are taken as the linear grid cell size to give a per unit width accumulation.

 Raster Layer
Input_Outlets (Optional) Dialog Reference

This optional input is a point feature defining outlets of interest. If this input is used, the tool will only evaluate ther area upslope of these outlets.

 Feature Layer
Check_for_Edge_Contamination Dialog Reference

This checkbox determines whether the tool should check for edge contamination. Edge contamination is defined as the possibility that a value may be underestimated due to grid cells outside of the domain not being considered when determining contributing area. This occurs when drainage is inwards from the boundaries or areas with no data values for elevation. The algorithm recognizes this possibility and reports no data for the result. It is common to see streaks of no data values extending inwards from boundaries along flow paths that enter the domain at a boundary. This is the desired effect, and indicates that values for these grid cells is unknown due to it being dependent on terrain outside of the available data. Edge contamination checking may be overridden in cases where you know it is not an issue, or want to ignore the problems, if for example, the DEM has been clipped along a watershed outline.

 Boolean
Input_Number_of_Processes Dialog Reference

This input indicates 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 piece of the domain.

 Long
Output_Decayed_Specific_Catchment_Area_Grid Dialog Reference

The D-Infinity Decaying Accumulation tool creates a grid of the accumulated mass at each location in the domain where mass moves with the D-infinity flow field, but is subject to first order decay in moving from cell to cell.

 Raster Dataset

Code Samples

Tags

Credits

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