<div dir="ltr"><div>Hi All,</div><div><br></div><div>This works well, but doesn't capture every river - is it a case of making the threshold value smaller or making a deeper carve in the rivers???</div><div><br></div><div>Thanks in advance - I think this method would will work well, if it were able to "flood" all rivers.</div><div><br></div><div>Thanks<br></div></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div>Le gach dea ghui,<br></div><div><span style="color:rgb(61,133,198)"><b><span style="background-color:rgb(255,255,255)"><i>Shane Carey</i></span></b></span></div><div><span style="color:rgb(61,133,198)"><b><span style="background-color:rgb(255,255,255)"><i>GIS and Data Solutions Consultant</i></span></b></span><br></div></div></div></div></div></div></div></div>
<br><div class="gmail_quote">On Sun, Sep 23, 2018 at 12:55 PM, Shane Carey <span dir="ltr"><<a href="mailto:careyshan@gmail.com" target="_blank">careyshan@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div dir="auto">Thanks, I will compare them and let you know the differences.</div><div dir="auto">Thanks</div><div><div class="h5"><br><div class="gmail_quote"><div>On Domh 23 MFómh 2018 at 02:09, Vaclav Petras <<a href="mailto:wenzeslaus@gmail.com" target="_blank">wenzeslaus@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div><div><div>These are steps based on:</div><div><br></div><div><a href="https://grasswiki.osgeo.org/wiki/From_GRASS_GIS_novice_to_power_user_(workshop_at_FOSS4G_Boston_2017)#Hydrology:_Estimating_inundation_extent_using_HAND_methodology" target="_blank">https://grasswiki.osgeo.org/<wbr>wiki/From_GRASS_GIS_novice_to_<wbr>power_user_(workshop_at_<wbr>FOSS4G_Boston_2017)#Hydrology:<wbr>_Estimating_inundation_extent_<wbr>using_HAND_methodology</a></div><div><br></div><div>You need r.stream.distance module from Addons:</div><br>g.extension r.stream.distance<br><div><br></div><div>Get drainage and streams from your DEM (your carved DEM):<br></div><div><br></div>r.watershed elevation=dem accumulation=flowacc drainage=drainage stream=streams threshold=100000</div><div><br></div><div>Compute height above nearest drainage/stream (HAND):<br></div><div><br></div><div>r.stream.distance stream_rast=streams direction=drainage elevation=elevation method=downstream difference=hand</div><div><br></div><div>Use r.lake not on the original DEM, but on the HAND and start flooding ("lake") from the streams:<br></div><div><br></div><div>r.lake elevation=hand water_level=3 lake=flood_3m seed=streams<br><div><br></div><div>Convert to vector if desired:<br></div><div><br></div><div>r.to.vect -s input=flood_3m output=flood_3m type=area<br></div><div><br></div><div>The difference to the r.grow+r.mapcalc method [1] is that this uses an addon module (there should be no problem installing it) and that r.grow uses euclidean distance for what is later used for height difference while r.steam.distance follows drainage and further that r.lake floods only the cells accessible to water unlike the r.mapcalc expression which just looks at height. The two methodological differences can be summarized as "not respecting the surrounding terrain enough." Anyway, the r.grow+r.mapcalc method can get you quite far and I would be interested in the comparison (will differ for different terrains).<br></div><div><br></div><div>Best,</div><div>Vaclav<br></div><div><br></div><div>[1] <a href="https://lists.osgeo.org/pipermail/grass-user/2018-September/079134.html" target="_blank">https://lists.osgeo.org/<wbr>pipermail/grass-user/2018-<wbr>September/079134.html</a><br></div></div></div></div><div><div><div><div><br></div>On Fri, Sep 21, 2018 at 11:39 AM Shane Carey <<a href="mailto:careyshan@gmail.com" target="_blank">careyshan@gmail.com</a>> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><div>Hi All,</div><div><br></div><div>I have used r.carve to carve out the rivers of a DTM - a really super job. I now need to pour 3meters of water into every cell in the river and see how for this water extends out - onto the floodplain. <br></div><div><br></div><div>I was trying to use r.lake to do this, but unsure as to how r.lake will work to pour 3 meters of water in every cell along the river network. <br></div><div><br></div><div>Any advice on this would be great. It is for the creation of a floodplain.</div><div><br></div><div>Thanks</div><div><br></div><div><br></div><div><div><div class="m_-7146123672366778103m_-2162690350394748460m_110382330510375694gmail-m_-3297281078989513694gmail_signature"><div><div><div><div><div><div>Le gach dea ghui,<br></div><div><span style="color:rgb(61,133,198)"><b><span style="background-color:rgb(255,255,255)"><i>Shane Carey</i></span></b></span></div><br></div></div></div></div></div></div></div>
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</blockquote></div></div></div></div><div dir="ltr">-- <br></div><div class="m_-7146123672366778103gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><span class=""><div>Le gach dea ghui,<br></div><div><span style="color:rgb(61,133,198)"><b><span style="background-color:rgb(255,255,255)"><i>Shane Carey</i></span></b></span></div></span><span class=""><div><span style="color:rgb(61,133,198)"><b><span style="background-color:rgb(255,255,255)"><i>GIS and Data Solutions Consultant</i></span></b></span><br></div></span></div></div></div></div></div></div>
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