[Dhsvm-users] Re: Dhsvm-users Digest, Vol 14, Issue 5

[Keith Norman Adams]

Dear Fahad and Other DHSVMers,

I came across this query in a tidy up of emails, but I can't recall 
seeing a reply to it.

To get a "source area" for my catchment I looked at the DEM in ArcMap, 
with the streams from a 1:50,000 scale map overlain on it.
I looked at a few of the first order streams and counted the number of 
cells contributing to the start of them.
This gave me 0.05 km2 "source area" for a catchment of about 50 km2.

I then checked the stream network obtained from 
'createstreamnetwork.aml', and it seemed about right.

If you have contours (you can use ArcInfo GRID or ArcMap to derive 
contours from the DEM) but not streams, you can use a similar process, 
looking at the contour crenellations that indicate the presence of a stream.

A few further points:
  - The representation of streams on a map depends on the scale of the 
map, so first order streams on a 1:500,000 scale map might be second 
order streams on a 1:50,000 scale map.
  - The shape of contours derived from a DEM will depend on the DEM cell 
size.
  - If you want a simpler (less intricate) stream network, use a larger 
"source area".


I hope this indirect answer helps.


Regards,
Keith Adams.






fahad saeed wrote:

> Dr. Bowling,
>  
> Thanks for replying to my message. I have some doubts in understanding 
> the source area while creating streams for DHSVM which effects the 
> density of stream network. What value of "source area" should I use in 
> for the watershed of 1060 sq. km.
>  
> regards,
>  
> fahad
> 
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-- 
_______________________________________________ 

  Keith Adams,  Ph.D. Candidate
  School of Geography and Environmental Science,
  The University of Auckland		
  Private Bag  92 019, Auckland, New Zealand
  location:  rm. 438  10 Symonds St.
  email:  k.adams at auckland.ac.nz
  phone:  +64-9-373 7599  ext. 84607
  dept. fax:  +64-9-373 7434