Watershed Delineation
Definition
Watershed delineation is the process of computing drainage areas and networks from elevation data or survey inputs for a specified pour point. It includes DEM conditioning, flow-direction and accumulation, stream extraction, and polygon generation for catchments at desired thresholds. Results feed hydrologic models, permitting, and infrastructure design.
Application
Engineers size culverts and detention basins; regulators define construction stormwater areas; researchers compare pre- and post-urbanization hydrology; and emergency teams plan spill containment.
FAQ
How do you choose a flow accumulation threshold for stream initiation?
Calibrate against mapped hydrography and field checks; thresholds vary with climate, terrain, and resolution.
When should pour points be snapped to streams?
Always snap to the highest-accumulation nearby cell to avoid sliver catchments caused by geocoding or digitizing errors.
What is the role of depression filling versus breaching?
Filling raises sinks; breaching cuts through barriers; use breaching when dams or roads are artifacts, but retain true depressions where hydrologically real.
How to communicate delineation uncertainty?
Provide alternative catchments under parameter ranges and note areas sensitive to DEM quality or infrastructure mapping gaps.
SUPPORT
© 2025 GISCARTA