How to correct the incorrect watershed delineation caused by artificial or natural barriers in high-resolution DEMs (e.g., 1-meter resolution) using the Burning Streams method in HEC-HMS.
When using a high-resolution DEM (e.g., 1 m), the increased level of detail may introduce obstacles such as roads, embankments, or walls that block water flow. As a result, the delineated watershed might be smaller than expected, compared to results obtained with coarser DEMs (e.g., 10 m).
To fix this, a dense stream network is generated and "burned" into the DEM, guiding water through artificial obstructions.
1. Generate a Dense Stream Network
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Go to GIS > Identify Streams (follow this tutorial).
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Use a low flow accumulation threshold to create a very detailed stream network.
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The output will be a dense vector stream network.
2. Extract the Stream Network as a Shapefile
3. Terrain Reconditioning (Burning the Streams)
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Go to GIS > Terrain Reconditioning...
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A step-by-step wizard will appear.
In the Burning Walls section:
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Leave this field empty — do not load any shapefile here.
In the Burning Streams section:
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Load the shapefile of the stream network you extracted earlier.
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Set an appropriate burning depth (e.g., 5–10 meters depending on DEM resolution).
This step modifies the DEM by carving channels along the provided stream lines, allowing water to conceptually drain through them — even across otherwise blocking terrain features.
4. Complete the Wizard
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Proceed through the wizard and let the tool finish the process.
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You will obtain a new conditioned DEM, with the streams burned into it.
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