Steps in building a channel-network dataset.
1.Build a contiguous DEM over entire watershed (IfSAR, LiDAR, NED).
Decisions: resolution, coordinate system.
2.Calibrate synthetic channel-network extent.
Decisions: length scale for topographic attributes, channel density.
3.Hydrologic conditioning.
a)Build a water mask.
b)Identify road crossings (LiDAR).
c)Existing line work for hydrologic enforcement.
d)Drain or fill closed depressions.
e)Define flow directions.
4.Build linked channel-node dataset.
5.Build GIS output files.
a)Routed channel network.
Decisions: reach length, upslope extent.
b)Attributes (contributing area, gradient, flow length, etc.)
c)Flood-plain polygons.
d)Drainage wings.
e)Run other needed analyses (road erosion, etc.)
6.Verify (field surveys, other data sets), Quality Control. Iterate.
Ensure all subsequent analyses properly functional.
All processing on separate DEM; original data unaltered.
We’ll go through all these steps in subsequent slides.