Fill Depressions
Overview
Fills depressions in an input digital elevation model (DEM) raster and outputs a depression-filled DEM for subsequent hydrology analysis. Filling depressions removes local sinks that can interrupt flow routing and flow accumulation calculations.
Use Cases
- Preprocess a DEM before hydrology analysis, especially flow direction and flow accumulation workflows.
- Remove spurious depressions caused by data voids, noise, or interpolation artifacts.
- Prepare terrain input for watershed delineation, runoff simulation, and drainage network extraction.
Parameters
| Parameter | Description | Notes |
|---|---|---|
| Input DEM raster file | Input digital elevation model (DEM) raster file. | Required |
| Apply epsilon gradient | Specifies whether to apply an epsilon gradient to all flat areas. | Optional; default: False |
| Topology indicator | Flow direction algorithm used for depression filling. | Required; default: D8; options: 8-direction flow direction algorithm (D8), 4-direction flow direction algorithm (D4) |
| Output filled DEM file | Output digital elevation model (DEM) raster file after depressions are filled. | Required |
Steps
- Start the tool: Open the Geoprocessing Toolbox, go to Thematic Analysis > Hydrology Analysis, and start the Fill Depressions tool.
- Prepare the input: Select the Input DEM raster file and confirm that the input data is complete and readable.
- Set core parameters: Configure Apply epsilon gradient and Topology indicator according to the analysis objective.
- Set the output: Specify the Output filled DEM 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 the filled DEM surface and value distribution are as expected.
Notes
- When multiple rasters are used together, first confirm that their coordinate systems, resolutions, extents, and grid alignment are consistent.
- Voids, noise, and abnormal elevation values in the DEM can create false depressions and affect downstream hydrology analysis results.