Date:         Tue, 5 Sep 2006 12:12:41 -0700
Reply-To:     Dave Hockman-Wert <[log in to unmask]>
Sender:       Biological Conservation and GIS <[log in to unmask]>
From:         Dave Hockman-Wert <[log in to unmask]>
Subject:      Re: stream gradient graph
In-Reply-To:  <[log in to unmask]>
Content-Type: text/plain; charset=iso-8859-1

Piggy-backing on Geoff's suggestions, I would add that
you could also use the actual elevation value for each
stream pixel as the y-axis value instead of the slope
value.  It would give you a stream "cross-section"
type of graph, rather than a graph of the slope every
10-meters.

Calculating flow distance in the raster environment
would be quicker, but you could also do the following
in a vector environment: convert the "stream network"
raster to a line feature and make it a route, convert
the DEM along the "stream network" raster to a point
feature with the elevation as the value that gets
transferred, "Locate Features Along Routes" (the
points) to add the route distance to the point
feature's DBF, and then you have the x and y values in
one DBF, which could be opened in Excel and graphed. 
I've done this for a whole series of streams.

Dave
Corvallis, Ore.

--- Geoffrey Poole <[log in to unmask]> wrote:

> Oops.  Forgot the line graph part...
> 
> You can calculate flow distance from each pixel in
> the landscape to the 
> outlet -- I can't remember exactly which tool you
> use, but it's either 
> under hydrology or is the least cost path tool using
> a grid derived from 
> topography as the cost grid...  If there's not an
> obvious hydrology 
> tool, check the help under least cost path analysis
> tools.  The help 
> tells you what to use for your cost grid in order to
> get hydrologic flow 
> distance in a watershed.
> 
> Then you can extract flow distance (for use on the x
> axis of your graph) 
> and slope for each stream pixel (for use on the y
> axis).
> 
> -Geoff Poole
> 
> Jeremy Wheeler wrote:
> > Hello List,
> > 
> > I am looking for a way to produce a simple line
> graph of stream gradient
> > for a given watercourse in our watershed.  The x
> axis would be linear
> > distance units of stream reach, and the y axis
> would be elevation above
> > sea level in feet.
> > 
> > I am thinking that this should be relatively easy
> with our 10 meter dem
> > and our streams layer.  I am using ArcGIS
> (ArcInfo) 9.1 (with several
> > extensions).  
> > 
> > Ideas?
> > 
> > Thanks,
> > 
> > Jeremy
> > 
> >
>
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