D-Infinity Concentration Limited Acccumulation

Title  D-Infinity Concentration Limited Acccumulation

Summary

This function applies to the situation where an unlimited supply of a substance is loaded into flow at a concentration or solubility threshold Csol over a region indicated by an indicator grid (dg). It a grid of the concentration of a substance at each location in the domain, where the supply of substance from a supply area is loaded into the flow at a concentration or solubility threshold. The flow is first calculated as a D-infinity weighted contributing area of an input Effective Runoff Weight Grid (notionally excess precipitation). The concentation of substance over the supply area (indicator grid) is at the concentration threshold. As the substance moves downslope with the D-infinity flow field, it is subject to first order decay in moving from cell to cell as well as dilution due to changes in flow. The decay multiplier grid gives the fractional (first order) reduction in quantity in moving from grid cell x to the next downslope cell. If the input outlets is used, the tool only evaluates the part of the domain that contributes flow to the locations given by the outlets. This is useful for a tracking a contaminant or compound from an area with unlimited supply of that compound that is loaded into a flow at a concentration or solubility threshold over a zone and flow from the zone may be subject to decay or attenuation.


Usage

Command Prompt Syntax:

mpiexec -n <number of processes> DinfConcLimAccum -ang <angfile> -dg <dgfile> -dm <dmfile> -ctpt <ctptfile> -q <qfile> [ -csol ] [ -o <outletfile>] [ -wg <wgfile>] [ -nc] [ -lyrname <layer name>] [ -lyrno <layer number>]

angfile:Dinf flow direction input grid

dgfile: Input disturbance indicator grid

dmfile: decay multiplier grid

ctptfile: Output concentration grid.

qfile: Specific discharge grid.

wgfile: Input weight grid (optional)

outletfile: input outlets file (OGR readable dataset)

csol: Concentration threshold

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

DInfConcLimitedAcccum (Input_D-Infinity_Flow_Direction_Grid, Input_Effective_Runoff_Weight_Grid, Input_Disturbance_Indicator_Grid, Input_Decay_Multiplier_Grid, {Input_Outlets}, Concentration_Threshold, Check_for_Edge_Contamination, Input_Number_of_Processes, Output_Overland_Flow_Specific_Discharge_Grid, Output_Concentration_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 can be created by the tool D-Infinity Flow Directions . The 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_Effective_Runoff_Weight_Grid Dialog Reference

A grid giving the input quantity (notionally effective runoff or excess precipitation) to be used in the D-infinity weighted contributing area evaluation of Overland Flow Specific Discharge.

 Raster Layer
Input_Disturbance_Indicator_Grid Dialog Reference

A grid that indicates the source zone of the area of substance supply and must be 1 inside the zone and 0 or "no data" over the rest of the domain.

 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 or decaying substance. If travel (or residence) times t(x) associated with flow between cells are available d(x) may be evaluated as exp(-k t(x)) where k is a first order decay parameter.

 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 the area upslope of these outlets.

 Feature Layer
Concentration_Threshold Dialog Reference

The concentration or solubility threshold. Over the substance supply area, concentration is at this threshold.

 Double
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. 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_Overland_Flow_Specific_Discharge_Grid Dialog Reference

The grid giving the specific discharge of the flow carrying the constituent being loaded at the concentration threshold specified. This is the D-infinity weighted accululation of the Effective Runoff Input Weight Grid.

 Raster Dataset
Output_Concentration_Grid Dialog Reference

A grid giving the resulting concentration of the compound of interest in the flow.

 Raster Dataset

Code Samples

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