I'm trying to produce a shapefile river network from a flow accumulation raster using the
r.to.vect function and I've overcome some difficulties regarding bit depth and thinned raster.
n.b. I don't have the original DEM from which the flow accumulation raster was derived, so I can't rely on the
Channel Network and Drainage Basins function.
My objective is to obtain a river network with the 'upcells' value of the old HydroSHEDS river network dataset but my result presents some issues that I didn't find a way to solve in an automatic way:
Here we have a thinned boolean raster and the resulted line vector.
- The first issue is the ambiguity between adjacent cells (red circle) that makes the
r.to.vectcreate redundant lines;
- The second issue occurs when there is a right angle between cells, but only in the horizontal/vertical direction (blue circle). In this case, the
r.to.vectfunction splits the lines close to these right angles, as we see from the 'id' label (the element 758 is split from element 755, likewise the element 759 is split from element 764, but this doesn't occur for element 764).
The second issue affects the next step of my workflow when I'm going to use
v.rast.stats to assign for each feature the maximum value of the flow accumulation map raster. This is the result:
The line vectors are now graduated based on the flow accumulation value (red labels) but the
v.rast.stats can't compute statistics for some of these short segments generated by the second issue (elements 759 and 794; the element 799 is not relevant because is redundant)
I've tried some optional configurations of the
r.to.vect function but it doesn't seem able to handle these two issues.
Is there a way to overcome them in an automatic/semi-automatic way?