Question about flattening lakes and Flow direction

[Thomas Wanderer]

I have a general question about the best approach of handling lakes in the DEM pre-processing.

1. As preparation step we flatten lakes with the help of OSM waterbodies with the "FlattenLakes" tool (and also burn OSM streams into the DEM)

2. For flow direction we use the "FlowAccumulationFullWorkflow" tool as we had issues in getting a reliable drainage line network accross many locations and the combined tool proves to work very reliable and deliver good enough results

3. When creating a manual D8 pointer using the flattened lake DEM, we get the following result

4. In comparison the resulting D8 pointer raster of the full FlowAccumulationFullWorkflow adds a lot of unwanted noise to the lake area again, resulting in strange flow directions as shown below

Questions:

- What is causing this added noise in the combined workflow and how can this be avoided

- What is your general experience/recommendation for treating lakes in a DEM. Should we simply neglect the Flattening of lakes in a DEM, turn large lakes (lake of Geneva) simply to void areas (NODATA)

Once again thanks for the great work and help from the Whitebox authors!