<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"></head><body >Rich,<div><br></div><div>Maybe have a look at r.lake: https://grass.osgeo.org/grass70/manuals/r.lake.html. This module fills the area upstream a dam or a blocked stream.</div><div><br></div><div>Cheers,</div><div>Johannes</div><br><br><br><br><div>-------- Original message --------</div><div>From: Thomas Adams <tea3rd@gmail.com> </div><div>Date:04/10/2016 04:32 (GMT+01:00) </div><div>To: Rich Shepard <rshepard@appl-ecosys.com> </div><div>Cc: grass-user@lists.osgeo.org </div><div>Subject: Re: [GRASS-user] r.flow: define contributing area </div><div><br></div><div dir="ltr"><div><div>Rich,<br><br></div>The only way to -correctly- do this is with hydrodynamic modeling, such as with HEC-RAS. It can be very crudely approximated with r.damflood (<a href="https://grass.osgeo.org/grass70/manuals/addons/r.damflood.html">https://grass.osgeo.org/grass70/manuals/addons/r.damflood.html</a>).<br><br></div>Tom<br><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Oct 3, 2016 at 7:39 PM, Rich Shepard <span dir="ltr"><<a href="mailto:rshepard@appl-ecosys.com" target="_blank">rshepard@appl-ecosys.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> Reading the r.flow manual page suggests that the use of the '-u'<br>
(upstream) option allows determination of flowlines and lengths that can be<br>
used to delineate the area that would drain to a specific point. Is this<br>
correct?<br>
<br>
To determine the area flooded if an outlet is plugged would require the<br>
inverse of r.drain. That module calculates the area flooded with surface<br>
water originating from a specific point; e.g., a hole in a dike or dam. The<br>
closest I've seen to do the opposite seems to be r.flow. The quantity of<br>
surface water and the rate of accumulation and infiltration into the vadoz<br>
zone are not of interest, only the area flooded is needed.<br>
<br>
The modules listed under the Natural Hazards application page all appear<br>
to delineate the area flooded from a point source. Can any of these be used<br>
backwards to delineate the area flooded if an outlet is blocked?<br>
<br>
I'd appreciate pointers and suggestions based on cumulative experience<br>
here for appropriate module(s).<br>
<br>
TIA,<br>
<br>
Rich<br>
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