distance and cost raster, along river network?

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06-05-2013 01:40 PM
DavidMedeiros
Occasional Contributor II
Is there a way to generate a pixel by pixel distance accumulation of a raster river network, where the distances accumulate along the river pixels from headwaters to outlet?

This would be similar to running Euclidean or Path Distance tools except only on the river pixels, and with distance increasing along the river network, not away from it.

The ultimate goal would be to create a set of rasters for the river network: 1)distance along the network 2)upstream travel cost 3)down stream travel cost.
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5 Replies
ChrisSnyder
Regular Contributor III
Yes, the tool is in Spatial Analyst and called Flow Length: http://resources.arcgis.com/en/help/main/10.1/index.html#//009z00000053000000
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DavidMedeiros
Occasional Contributor II
Yes, the tool is in Spatial Analyst and called Flow Length: http://resources.arcgis.com/en/help/main/10.1/index.html#//009z00000053000000


Thanks, unfortunately as with all of these tools they rely on creating a river network (or a flow direction surface) from the DEM. I was looking to calculate these distances along an existing river network that has been rasterized.

I tried faking it by buffering my streams and extracting the DEM values inside the buffer as the input to the Flow Direction tool. But the results are irregular. I think Flow Direction needs a large surface to run on.

I'm trying again with larger buffers, or extracting the buffer area of the full Flow Direction raster. Will report back.
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DavidMedeiros
Occasional Contributor II
As I'm working through this I'm beginning to realize why this won't work. How can you have a distance value in a pixel that is different distances away from multiple upstream sources?

You could do it stream segment by segment. Or from the bottom of the network, but not the top I guess. This is for a student I'm helping here and I think I'm at the point where I need to know more about what question he's trying to answer with this before proceeding.

Stream Order or Network Analyst may have be substituted.

I'm still curious though, as this has come up before. When thinking about a cost path analysis and modelling river networks into that, how can you model directionality? Flow? So that the cost model takes into account the benefit from traveling down stream if that's allowed by your model, but the added cost of traveling up stream?
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ChrisSnyder
Regular Contributor III
Hmmm.... I think you would then have to use Network Analyst or some other "routing" approach. The trick is having a way to establish flow direction. In the Hydrology Spatial Analyst tools this is done using a D8 (8 possible dircetions) flow direction raster (created from a Filled DEM). In Network Analyst it is done via defining a route, destinations, and source/incidents.

Another option: Do all your stream segments "flow" in the correct orientation (i.e the from node is upstream of the to node)? If so, then you could just parse the geometry in a cursor to establish "distance from headwater".
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JimTenbrink
Esri Contributor

Hi David

You might be able to use the Distance Accumulation tool in arcgis pro for this. Your stream network rasterization will need to be good enough so that different stream reaches use distinct sets of cells. You will also need to explicitly identify your starting locations (sources) for the measurements.

 

Let me know if it works.

Regards,

-Jim TenBrink

spatial analyst team

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