Sèves St. German, Catchment Basins

Catchments prior to calculating flood plain. Using QGIS/GRAS, SRTM30 DEM, and OSM as stream centerline.
Catchments prior to calculating flood plain. Using QGIS/GRAS, SRTM30 DEM, and OSM as stream centerline. Click through to a manipulable 3D model.

Taking out a little time to look at Grass GIS. The objective here is to do a simple (heh-heh) floodplain map for Sèves St. Germain. These are the catchment basis as calculated from SRTM30 data via QGIS/GRASS, which will serve as a basis (I hope) for a flow model. Downstream is to the north east (right in the static image. Here’s a 3D model.)

So why does an historian, even an amateur one care about land areas contributing to runoff toward a given flow? Well, this is the terrain that first and second battalions of 358IR attacked across. The plan called for crossing tanks, only there was a pretty big rainstorm in the evening. The crossing was already contested and the water high, but should have been possible the following morning. If I can track down divisional G2 meteorological information from 1944, I should be able to feed it into the model and come up with a better visualization of exactly how high the water was.

Lots of caveats here. The SRTM was taken in the 1990s and the streambed has probably changed a bit since. Metaled (paved) roads are now the norm, which changes the flow coefficients. But enough. I just want a better idea of how high the water was back then. And it is keeping with my design objective to bring as much data to this design as I can.