Double stream width?

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10-27-2011 01:36 PM
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New Contributor
Hi,

I have calculated possible stream/river locations from a DEM. The streams are 1 pixel wide. My problem is as follows. I'm trying to do a Least Cost Path analysis on the area in question and have created a cost surface that takes into account that I don't want LCP to move over the streams (currently by setting the streams to NODATA). However, since the streams are only 1 pixel wide, the LCPs just go through them diagonally (see the attached screenshot).

Is there a way to fix this? I thought about making the streams 2 pixels wide, to make it impossible to pass through them, but haven't been able to find a suiting method of doing this. I want the LCPs to avoid the streams at all cost. Not sure how the top paths to the target will be created, but that's the idea. Does anyone have an idea how to solve my problem? Any advice is much appreciated!

All the best,
Sander
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3 Replies
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Regular Contributor III
Greetings,

Have a look at the Expand tool.  You can specify the river value as a zone to increase by x number of pixels, then convert (Set Null) the expanded river to nodata.

Regards,
Eric
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New Contributor
Thank you for the quick reply, Eric. I'll give it a go 🙂
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Expand did indeed work. Thanks for the suggestion!
On related question though. Expand expands the given number of cells to both sides, making the streams 3 pixels wide. Is there a way to expand only to one side, to make the streams 2 pixels wide? If not, I'll use this, but adding 1 pixel to the width would already skew my results a little. 3 pixels would do so even more, hence the question 🙂 Thanks again!

Sander
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