Inputs:
- A D-infinity Flow Direction raster dataset.
- Stream Initiation Threshold value (optional)
- A D8 Flow Direction raster dataset (optional)
Outputs:
- A Flow Accumulation raster .
Notes:
- The value for each cell in the Flow Accumulation raster is the total number of cells which flow into it including the cell itself. So for a cell with no inflowing cells the value will be 1.
- The D-infinity flow algorithm allows flow divergence. This means that the value accumulated in a cell can be directed to one or two neighboring cells depending on the flow direction angle. This is a better representation of flow on divergent slopes.
- By applying a Threshold value to the Flow Accumulation raster we can determine the cells which form a Stream network. All cells with Flow Accumulation value above the threshold are considered to be part of a stream.
- The flow direction after Stream Initiation is better represented by the D8 single flow algorithm. The function allows for the specification of a Stream Initiation Threshold value and the relevant D8 Flow Direction raster to be used after the threshold accumulation value is reached.
- See Hydrological functions for more information on the hydrological functionality.
- Supported raster formats are File Geodatabase raster, Personal Geodatabase raster and file based raster formats (ESRI GRID, Erdas Imagine and TIFF).
- For file based rasters initially the name of the output raster
defines the raster format
- no extension specified - ESRI binary GRID
- .img extension (for example raster1.img) - ERDAS IMAGINE image.
- .tif extension (for example raster1.tif - Tagged Image File Format (TIFF) image.
- The initial output raster format can be
changed by selecting the desired output in the dialog.
An example of Flow Accumulation D-infinity result (above)
and Flow Accumulation D8 (below).
Note the dispersion of flow in the D-infinity result
compared with the concentrated flow in D8.
Command line syntax
ETS_GPFlowAccumulationDinf <Input D-inf Flow Direction Raster> <Out Flow Accumulation Raster> {Stream Initiation Threshold} {Input D8 Flow Direction Raster}
Parameters
| Expression | Explanation |
|---|---|
| <Input D-inf Flow Direction Raster> | D-infinity Flow Direction raster layer or raster dataset |
| <Out Flow Accumulation Raster> | A String - the full name of the output raster (A raster with the same full name should not exist). The output raster type depends on the extension of the output file(see Notes above) |
| {Stream Initiation Threshold} | A Double representing the Threshold value |
| {Input D8 Flow Direction Raster} | D8 Flow Direction raster layer or raster dataset |
Examples:
-
ETS_GPFlowAccumulationDinf c:\test\FlowDirDinf.img c:\test\FlowAcc.img - all accumulation will be done using the multiple flow D-infinity method
-
ETS_GPFlowAccumulationDinf c:\test\FlowDirDinf.img c:\test\FlowAcc.img 1000 c:\test\FlowDirD8.img - accumulation below value of 1000 will be done using the D-infinity method, above 1000 the D8 Flow Directions will be used
Scripting syntax
ETS_GPFlowAccumulationDinf (Input D-inf Flow Direction Raster, Out Flow Accumulation Raster, Stream Initiation Threshold, Input D8 Flow Direction Raster)
See the explanations above:
<> - required parameter
{} - optional parameter