How To: Delineate a watershed based on an elevation grid
This article contains a basic procedure for delineating a watershed from a grid of elevation values.
- Remove localized sinks using FILL:
Grid: FILL demraw demfill SINK 4.5
- Create FLOWDIRECTION grid:
Grid: demfdir = FLOWDIRECTION(demfill)
- Create FLOWACCUMULATION grid:
Grid: demfacc = FLOWACCUMULATION(demfdir)
- Find cells of highest accumulation:
Grid: strm = CON(demfacc gt 300,demfacc)
- Find the outlets with SNAPPOUR. A prompt appears requesting a graphical selection of the outlet point at the bottom of the watershed.
Grid: outlet = SNAPPOUR(*,demfacc,5000)
- Use WATERSHED to find watershed of stream networks:
wshed = WATERSHED(demfdir,outlet)
Article ID: 000002160
Software: ArcInfo Workstation 7.0.4, 7.1.1, 7.1.2, 7.2.1, 8.0.1, 8.0.2, 8.1, 8.1.2, 8.2, 8.3, 9.0, 9.1