[GRASS-user] floodplain creation

Vaclav Petras wenzeslaus at gmail.com
Fri Sep 28 07:11:28 PDT 2018

On Thu, Sep 27, 2018 at 12:10 PM Shane Carey <careyshan at gmail.com> wrote:

> Is there anyway of the algorithm just being able to create a floodlain for
> actual real rivers as opposed to the derived river dataset?

Yes, just convert your streams to raster (presence-absence) and a raster
for flow direction as I mentioned here:


However, you need to be cautious about fit between the existing streams and
the DEM. Definitively check how your existing streams align with the
derived ones (where there are both streams).

> On Máirt 25 MFómh 2018 at 15:49, Shane Carey <careyshan at gmail.com> wrote:
>> Image attached shows rivers (black line) and floodplain of where it
>> thinks there are rivers and in some cases where there may not be rivers.
To use the derived streams and get rid of parts you don't want, you could
buffer the existing streams and preserve only the derived streams which are
in that buffer.

However, you should really look at why they are different and specifically
what is closer to reality.
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