Watershed Delineation

Delineate the upstream catchment draining to one or more outlet/pour points using a flow-direction raster or DEM-derived flow network.

HydrologyEnd-User DocumentationTheory + Formula + Parameters

1. What This Feature Does

Delineate the upstream catchment draining to one or more outlet/pour points using a flow-direction raster or DEM-derived flow network.

Cloud workflow: choose data → configure the scientific method → run → review the resulting layer/report. No programming is required.

2. Recommended Workflow

Prepare DEM and flow direction. ↓ Define/choose outlet points. ↓ Trace all upstream cells that eventually flow to each outlet. ↓ Generate watershed raster/polygon and inspect outlet placement.

3. Theory, Methods & Equations

Upstream Trace

A cell belongs to a watershed if repeated flow routing from that cell eventually reaches the selected outlet.

W(o)={p : Fk(p)=o for some k}
Best used when: catchment boundaries are needed for hydrology, erosion, water resources or watershed statistics.

4. Input Data

InputTypeRequirementDescription
DEM RasterrasterRequired
Pour PointsvectorRequired

5. Parameters Available in the Application

ParameterDefaultChoices / RangeHow to Use It
Elevation Band——
Fill Sinks FirstOn—

6. Output & Interpretation

The result should be interpreted according to the selected method and the physical meaning of the input data. Preserve source units, coordinate reference information, NoData meaning, acquisition date, and preprocessing level when comparing results.

Scientific interpretation: an algorithm can produce a numerically valid result even when the input data are unsuitable. Always check masks, units, sensor characteristics, spatial resolution and reference data.
Important: Outlet placement is critical. Snapping a pour point to the actual drainage line can materially change the watershed.

7. Best Practices

  • Use analysis-ready inputs and remove invalid/cloud/noise artifacts that are not part of the target phenomenon.
  • Choose parameters from the physical scale of the data, not only from visual appearance.
  • Keep categorical and continuous rasters conceptually separate when selecting interpolation/resampling methods.
  • Compare the result with the source image and independent reference information.
  • Document the settings used when results will be compared across dates, sensors or study areas.
← Flow AccumulationStream Extraction →