[GRASSLIST:4457] RE: buffers from roads

[Perret, Didier]

Hello

It depends on what is your definition of the top of a slope. In a project
aimed at determining landslide-prone areas in Eastern Canada we were faced
with a similar problem.  Admitting the base of the slope is known (i.e. as
given by the road level) it remains to locate the top.  Near or at the top
both the curvature of the slope and the local slope angle change.  Although
the absolute values of these two parameters may vary following the shape of
the slope it was possible to isolate what we call a simple slope.  

Things become more complicated when the slope is made up of more than one
segment, for example when there is a small plateau between two or more
sub-slopes as it often happens in man-made cuts. In these cases slope
stability modelling was done to determine the maximum length of such a
plateau for having only one potential failure surface.  The following steps
were to measure the length of these plateaus on the DEM (along maximum slope
angles profiles starting from the base) and reject the parts of the DEM not
corresponding to the length criteria.

Hoping it will help you,

Didier Perret
Natural Resources Canada
Geological Survey of Canada
Terrain Science Division / Landslide Hazards Team
Ottawa K1A 0E8 Canada

Tel. (613) 944-4405 (Ottawa office)
Tel. (418) 654-2686 (Quebec City office)

-----Original Message-----
From: orkun [mailto:temiz at deprem.gov.tr]
Sent: 11 septembre, 2002 06:39
To: GRASSLIST at baylor.edu
Subject: [GRASSLIST:4454] buffers from roads


Hi

I want to create buffers from roads. But extension of buffers
should be limited to slopes which roads cut. That is, buffers
must not overcome the top of slope.

Does anyone give me a hint about how these buffers are created ?

thanks in advance

-- 
Ahmet Temiz
Geological Engineer
General Directorate
of Disaster Affairs
TURKEY




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