> What modules are appropriate for these data to model flow paths to the
> culvert inflow?
Flow accumulation can be modeled with r.watershed or r.terraflow, with the
former as a preference for drainage networks.
r.stream.extract will vectorize the drainage network.
> Or, should I convert the raster or vector files to a
> different type?
The above mentioned modules (r.watershed/r.terraflow) work on continuous
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