The Derive Continuous Flow tool generates a raster of accumulated flow into each cell from an input surface raster with no prior sink or depression filling required.
The output is a hosted imagery layer.
Learn more about how Derive Continuous Flow works
Examples
Example scenarios for the use of this tool include the following:
- Determine flow accumulation and flow direction from a surface raster without prior sink or depression filling required.
- Determine flow accumulation at each cell of the surface raster considering locations where water can flow into but not outward.
Usage notes
Derive Continuous Flow includes configurations for input layers, flow direction settings, and the result layer.
Input layers
The Input layers group includes the following parameters:
Input surface raster is the elevation raster that will be used for calculation. It can be a digital elevation model (DEM) with no prior sinks filled or a hydroconditioned DEM.
The tool is not sensitive to errors in the surface raster that can act as depressions or sinks where flow terminates; filling sinks or depressions is not necessary.
If the input surface raster contains real depressions, the locations of the depressions must be specified in the Input depressions raster or features parameter to be considered cells where water can flow into but not out from.
NoData cells in the input surface raster do not have an associated value. These cells are ignored when identifying the direction of the least steep uphill neighbor, as well as the determination of flow direction and accumulation.
- The Optional layers group includes the following parameters:
Input depressions raster or features is the dataset that defines real depressions or sinks, where water can flow into but not out of.
You can choose a layer using the Layer button, or use the Draw input features button to create a sketch layer to use as the input. For feature inputs, a count of features is displayed below the layer name. The count includes all features in the layer, except features that have been removed using a filter. Environment settings, such as Processing extent, are not reflected in the feature count.
If the input is a raster layer, the depression cells must have a valid value, including zero, and the areas that are not depressions must be assigned NoData.
If the input is a feature layer, it can be point, polyline, or polygon. Feature input will be converted to a raster internally before performing the analysis.
Input weight raster is a raster layer that defines the fraction of flow that contributes to flow accumulation at each cell.
The weight is only applied to the accumulation of flow.
If no accumulation weight raster is provided, a default weight of 1 will be applied to each cell.
Flow direction settings
The Flow direction settings group includes the following parameters:
Flow direction type specifies the type of flow method that will be used when computing flow direction.
D8—The D8 method assigns flow direction to the steepest downslope neighbor 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). The values in the Output flow direction raster name layer will be integer values in the range of 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 will be undefined. In this case, the value for such cell will be the sum of the possible directions.
This is the default.
MFD—The MFD flow method partitions the flow direction across downslope neighbors according to an adaptive partition exponent. The adaptive component is estimated as a function of maximum slope gradient, which considers local terrain conditions (Qin et al., 2007). The values in the Output flow direction raster name layer will be integer values in the range of 1 to 255, 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 values in the Output flow accumulation raster name layer reflect accumulation based on the flow partition scheme.
Force edge cells to flow outwards specifies whether edge cells will always flow outward or follow normal flow rules.
- Unchecked—The flow direction will be toward the inner cell with the steepest drop in z-value. However, if the drop is less than or equal to zero, the cell will flow outward from the surface raster. This will be the same for all cells across the raster.
- Checked—Flow direction at edge cells will always be outward from the surface raster.
Result layer
The Result layers group includes the following parameters:
Output flow accumulation raster name is the name of the output raster that will contain the flow accumulation result.
The name must be unique. If a layer with the same name already exists in your organization, the tool will fail and you will be prompted to use a different name.
The Optional layers group includes the Output flow direction raster name parameter, which is the name of the output raster that will contain the flow direction result.
The name must be unique. If a layer with the same name already exists in your organization, the tool will fail and you will be prompted to use a different name.
- Save in folder specifies the name of a folder in My content where the result will be saved.
Environments
Analysis environment settings are additional parameters that affect a tool's results. You can access the tool's analysis environment settings from the Environment settings parameter group.
This tool honors the following analysis environments:
- Output coordinate system
- Processing extent
Note:
The default processing extent is Full extent. This default is different from Map Viewer Classic in which Use current map extent is enabled by default.
- Snap raster
- Cell size
- Mask
Outputs
This tool includes the following outputs:
The Output flow accumulation raster name layer stores the value of accumulated flow as determined by accumulating all upstream cells that flow into each cell. The target cell is not included in the accumulation value. If an input weight raster was specified, the weight at each cell is considered in the accumulation value.
The Output flow direction raster name layer stores the value of flow direction at each cell.
The output flow direction raster is of integer type. If MFD was specified for the Flow direction type parameter, the value of each cell shows the predominant flow direction, which is toward the cell that receives the largest fraction of flow according to the partition scheme.
Usage requirements
This tool requires the following user type and configurations:
References
- Ehlschlaeger, C. R. 1989. "Using the AT Search Algorithm to Develop Hydrologic Models from Digital Elevation Data." International Geographic Information Systems (IGIS) Symposium 89: 275-281.
- 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.
- Metz, M., Mitasova, H., & Harmon, R. S. 2011. "Efficient extraction of drainage networks from massive, radar-based elevation models with least cost path search." Hydrology and Earth System Sciences 15(2): 667-678.
- 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.
Resources
Use the following resources to learn more:
- How Derive Continuous Flow works
- Derive Continuous Flow in ArcGIS REST API
- Derive Continuous Flow in ArcGIS Pro in ArcGIS Pro with the Spatial Analyst extension