I have a bare earth DEM made from lidar data (A).
It works well and has passed all accuracy tests. It is used in storm surge models. The problem we are having is on underpasses. I need to allow water to flow through underpasses when one road crosses another. My thought is to:
1) Get all roads marked as bridges from OSM.
2) The select all the crossing roads that cross under them (intersect).
3) Then on the new selection of new road segments (2) convert these to raster.
4) Extract all the DEM (A) values under these road segments.
5) Select the minimum of these values under the new road segment (2).
6) Burn this minimum value into the DEM I have to cut a channel through the underpass.
Open to all suggestions, improvements, ideas on how to achieve this including entirely different solutions.
Other options are just get the intersect point and grow this out or maybe identify sinks and work back from this.