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

[Blumentrath, Stefan]

Hei Helumt,

I guess the main challenge is how to define (or delimit) the valleys (and especially the valley-floor)...

If you think of valleys in a hydrological perspective I would have a look 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 bit more complex (esp. for U-valleys, compared to V-valleys).
A colleague of mine (and to some degree myself too) has been working on a valley map for Norway quite intensively (http://www.nhm.uio.no/forskning/publikasjoner/rapporter/nhm-rapport-11-faglig-grunnlag-for-naturtypeovervaaking-grunnlagsundersoekelser.pdf (pages 99 following, text in Norwegian, map at page 104) and still there are reasonable challenges left in order to properly define valley extents, even though my colleague improved the procedure to a 2.0 version of the valley algorithm. Depends how much effort you like to or can spend on that... In a geomorphometric context r.geomorphon, r.param.scale, or more general Topographic Position Index (TPI) might be worth having a look at. Please note that all these three are heavily scale dependent!

Cheers
Stefan

-----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 09:53
To: grass-user at lists.osgeo.org
Subject: [GRASS-user] calculation valley floor width in GRASS or some index indicating valley floor width?

hi,

any hint or pointer to some grass gis procedure/literature/web link/etc how to caculate valley floor width in GRASS or some index indicating valley floor width.

the idea is to get some measure how wide or narrow a valley is.

thanks in advance!



-----
best regards
Helmut
--
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