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<div class="moz-cite-prefix">On 17/04/2019 19:34, Mehrdad Varedi
wrote:<br>
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cite="mid:CA+F3BSA5hX6W87-cYhdPLonc2zQMK-TSjhoxG+MQuadPG8XTaQ@mail.gmail.com">
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<div dir="ltr">Hi Everyone,
<div>I would like to know how the flow path, flow accumulation,
or topographic wetness is calculated in cities versus farms.</div>
<div>In other words how to take into account the effect of
non-penetrable areas in forming the above-mentioned layers
based on a DEM and penetrability score for the study area?<br
clear="all">
<div><br>
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<p>No answers yet, so I will give a try:</p>
<p>Each of the variables in your question are geomorphology
characteristics. They depend only on elevation, slope, aspect.
Flow accumulation is an area, TWI is area divided by tan(slope),
etc. These characteristics have nothing to do with infiltration
(i.e. penetrable areas). </p>
<p><br>
</p>
<p>Having said that, the GRASS module r.watershed can take two input
rasters: flow and retention, which change the output flow
accumulation. If you have spatial data on soil retention
properties, or disturbances to surface flow, you can apply them to
r.watershed to get a more "realistic" accumulation grid. The
defaults are 100 for retention (no infiltration, all water flowing
into a cell also goes out) and 1.0 for flow (no disturbances, and
no additional contribution for each cell)</p>
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cite="mid:CA+F3BSA5hX6W87-cYhdPLonc2zQMK-TSjhoxG+MQuadPG8XTaQ@mail.gmail.com">
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<div>
<div>Thanks for your help,</div>
<div><br>
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<div dir="ltr" class="gmail_signature"
data-smartmail="gmail_signature">Mehrdad</div>
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<pre class="moz-signature" cols="72">--
Micha Silver
Ben Gurion Univ.
Sde Boker, Remote Sensing Lab
+972-523-665918</pre>
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