Derive Continuous Flow

Description

The DeriveContinuousFlow task generates a raster of accumulated flow into each cell from an input surface raster with no prior sink or depression filling required.

Example applications of DeriveContinuousFlow include the following:

• Determine flow accumulation from a surface raster without prior sink or depression filling required.
• Specify sink or depression cell locations through the inputDepressionsData parameter and determine flow accumulation at each cell of the surface raster, allowing water flow into depression locations but not outward.

Request parameters

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//Portal item as input raster
"inputSurfaceRaster": {"itemId": <portal item id>}

//URL as input raster
"inputSurfaceRaster": {"url": <image service layer url>}

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"outputFlowAccumulationRasterName":{"serviceProperties":{"name":"testrasteranalysis"}}

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//Output portal item:
"outputFlowAccumulationRasterName":{"itemId": <portal item id>}

//Output url:
"outputFlowAccumulationRasterName":{"url": <image service url>}

//Output raster layer service:
"outputFlowAccumulationRasterName":{"service properties":
  {"name":"testrasteranalysis",
  "serviceUrl":"https://<server name>/server/rest/services/Hosted/testrasteranalysis/ImageServer",
  "itemProperties":{"itemId":"8cfbd3ec25584d0d8f4ed23b8ff7c43b","folderId":"sdfwerfbd3ec25584d0d8f4"}}
}

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"inputDepressionsData":{"url": <image service layer url>}

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//Feature layer URL
"inputDepressionsData":{"url": <feature service layer url>}

//Feature collection
"inputDepressionsData":{"layerDefinition": {}, "featureSet": {}}

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"inputWeightRaster":{"url": <image service layer url>}

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"outputFlowDirectionRasterName":{"serviceProperties":{"name":"testrasteranalysis"}}

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//Output portal item:
"outputFlowDirectionRasterName":{"itemId": <portal item id>}

//Output url:
"outputFlowDirectionRasterName":{"url": <image service url>}

//Output raster layer service:
"outputFlowDirectionRasterName":{"service properties":
  {"name":"testrasteranalysis",
  "serviceUrl":"https://<server name>/server/rest/services/Hosted/testrasteranalysis/ImageServer",
  "itemProperties":{"itemId":"8cfbd3ec25584d0d8f4ed23b8ff7c43b","folderId":"sdfwerfbd3ec25584d0d8f4"}}
}

Flow direction type additional information

The following section contains details on the available flow direction methods in the flowDirectionType parameter.

The DeriveContinuousFlow task supports the D8 and multiple flow direction (MFD) modeling algorithms.

• When the D8 option is specified for flowDirectionType , flow can take a single direction, which is toward the steepest drop. The steepest drop is calculated by taking the difference in z-value divided by the path length between cell centers (1 for cardinal cells and the square root of 2 for diagonal cells) (Jenson and Domingue, 1988). The output raster takes only integer values from 1 to 255. The values from the center of each direction are specified in the following diagram:

  

  If a cell has the same change in z-value in multiple directions, the D8 flow direction is undefined. In this case, the value for such cell in the output flow direction raster will be the sum of the possible directions.

• When the MFD option is specified for flowDirectionType , flow is partitioned across all downslope neighbors. Flow partition across neighboring cells (as a fraction) is estimated as a function of maximum slope gradient, which considers local terrain conditions (Qin et al., 2007). The optional output flow direction raster takes only integer values showing the predominant flow direction (toward the cell that receives the largest fraction of flow according to the partition scheme) for ease of interpretation. However, the output flow accumulation raster reflects the flow partition scheme.

Response

When you submit a request, the task assigns a unique job ID for the transaction.

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{
  "jobId": "<unique job identifier>",
  "jobStatus": "<job status>"
}

After the initial request is submitted, you can use the jobId to periodically check the status of the job and messages as described in Checking job status. Once the job has successfully completed, you use the jobId to retrieve the results. To track the status, you can make a request of the following form:

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https://<raster analysis tools url>/DeriveContinuousFlow/jobs/<jobId>

When the status of the job request is esriJobSucceeded , you can access the results of the analysis by making a request of the following form:

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https://<raster analysis tools url>/DeriveContinuousFlow/jobs/<jobId>/results/<output parameter>

Example usage

Below is a sample request URL for DeriveContinuousFlow .

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https://services.myserver.com/arcgis/rest/services/System/RasterAnalysisTools/GPServer/DeriveContinuousFlow/submitJob

JSON Response example

The response returns the outputFlowAccumulationRaster and outputFlowDirectionRaster output parameters, which have properties for parameter name, data type, and value. The content of value is the output raster dataset itemId and the image service URL.

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{
  "paramName": "outputFlowAccumulationRaster",
  "dataType": "GPString",
  "value": {
    "itemId": "f121390b85ef419790479fc75b493efd",
    "url": "https://<server name>/arcgis/rest/services/Hosted/<service name>/ImageServer"
  }
}

References

• Jenson, S. K., and Domingue, J. O. 1988. "Extracting Topographic Structure from Digital Elevation Data for Geographic Information System Analysis." Photogrammetric Engineering and Remote Sensing 54 (11): 1593–1600.
• Qin, C., Zhu, A. X., Pei, T., Li, B., Zhou, C., & Yang, L. 2007. "An adaptive approach to selecting a flow partition exponent for a multiple flow direction algorithm." International Journal of Geographical Information Science 21(4): 443-458.