[GRASS-user] calculation valley floor width in GRASS or some index indicating valley floor width?

Blumentrath, Stefan Stefan.Blumentrath at nina.no
Tue Apr 1 02:20:13 PDT 2014

Hei Helumt,

In that case I would probably try r.param.scale in order to identify flat areas at maybe different scale levels.

V-valleys have a higher variation in aspect at the bottom (sides are almost facing each other and nearly "meet" at the lowest point in a V-valley). While sides are more or less steep. So slope and aspect at a coarser level (also available through r.param.scale) could help to distinguish V- and U-valleys.

Depending on scale U-Valleys have a TPI of ~0 at the bottom and ~0 at the middle of the sides (equaly much terrain above and below a focal cell in the given neighborhood).

Some background material on TPI can be found here: http://www.jennessent.com/arcview/tpi.htm 
Jenness used ArcView. Yet TPI is a simple combination of r.neighbors and a mapcalc.

Good luck with your modelling.


-----Original Message-----
From: grass-user-bounces at lists.osgeo.org [mailto:grass-user-bounces at lists.osgeo.org] On Behalf Of Helmut Kudrnovsky
Sent: 1. april 2014 10:33
To: grass-user at lists.osgeo.org
Subject: Re: [GRASS-user] calculation valley floor width in GRASS or some index indicating valley floor width?

Hi Stefan,

thanks your response.

>If you think of valleys in a hydrological perspective I would have a 
at r.stream. modules for having a kind of threshold above streams (in m), and then use r.grow.distance for an inverted valley representation.

>If you think of valleys in a geomorphometric context things might be a 
more complex (esp. for U-valleys, compared to V-valleys).

it's maybe a mixing of both... ;-)

given is a habitat typical for gravel beds/braided river in mountain regions. it seems the probability of the occurrence of the needed habitat structure is greater in wider valleys floors than in narrow valley floors, and greater in U-valleys than in V-valleys.

the idea is to get some measure/index to handle this probability ...

best regards
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