Flow Accumulation
Overview
Calculates flow accumulation from an input digital elevation model (DEM) raster and outputs a flow accumulation raster. Flow accumulation represents the amount of upstream contributing flow received by each cell and is commonly used to identify drainage paths and potential stream channels.
Use Cases
- Identify drainage paths, stream initiation zones, and areas with high contributing flow.
- Provide hydrology analysis input for watershed delineation, runoff modeling, and erosion analysis.
- Compare flow routing methods for terrain and watershed studies.
Parameters
| Parameter | Description | Notes |
|---|---|---|
| Input DEM raster file | Input digital elevation model (DEM) raster file. | Required |
| Calculation method | Flow accumulation calculation method. | Required; default: D8; options include Tarboton (Tarboton), D-infinity (Dinf), Quinn (Quinn), Holmgren (Holmgren), Freeman (Freeman), Fairfield-Leymarie D8 (FairfieldLeymarieD8), Fairfield-Leymarie D4 (FairfieldLeymarieD4), and Rho8 (Rho8) |
| Exponent parameter (optional) | Exponent parameter required by some methods, such as Holmgren and Freeman. | Optional |
| Output flow accumulation raster file | Output raster file containing the flow accumulation result. | Required |
Steps
- Start the tool: Open the Geoprocessing Toolbox, go to Thematic Analysis > Hydrology Analysis, and start the Flow Accumulation tool.
- Prepare the input: Select the Input DEM raster file and confirm that the input data is complete and readable.
- Set core parameters: Configure Calculation method and, if needed, Exponent parameter according to the analysis objective.
- Set the output: Specify the Output flow accumulation raster file and confirm that the output path, format, and naming rules meet later workflow requirements.
- Run and inspect results: Click Run to execute the task. After it completes, check whether high-accumulation areas and drainage patterns are as expected.
Notes
- When multiple rasters are used together, first confirm that their coordinate systems, resolutions, extents, and grid alignment are consistent.
- DEM voids, noise, abnormal elevations, and unfilled depressions can interrupt flow paths and affect flow accumulation results.