topic Query about sinks in D8 flow direction model in Water Resources Questions

Query about sinks in D8 flow direction model

SiyangTeo — Wed, 11 Feb 2015 04:43:06 GMT

Hi, I have a few questions about using the hydrology toolset in ArcGIS.

After creating the Flow Direction model, I identified the sinks and found that there were some reservoirs which were not included as sinks. I assume that this is because the DEM did not capture the elevation profile for these areas properly. I have a polygon layer of the reservoirs, but unfortunately with no depth profile. Will this help?
When I eye-balled through the sinks, I realised that a lot of them has the value of "No Data". How do I fill up these sinks for such instances to separate them from the true positives?

Thank you.

Re: Query about sinks in D8 flow direction model

DanPatterson_Retired — Wed, 11 Feb 2015 10:05:21 GMT

if the reservoirs are nodata, then you will have to assign them a reasonable elevation appropriate with the surrounding terrain. This can be accomplished with a combination of IsNull and Con as described in the link. Obviously a value of 1 meter would pretty well make it a deep sink in most parts of the world.

Re: Query about sinks in D8 flow direction model

SiyangTeo — Thu, 12 Feb 2015 02:01:58 GMT

Thanks Pat, that's pretty helpful.

However, when I used the IS NULL tool, areas which the were identified as sinks and have no data values actually have data in the DEM.

Would you know why Sink tool identify them as sinks with no data?

Thank you.

Re: Query about sinks in D8 flow direction model

DanPatterson_Retired — Thu, 12 Feb 2015 12:38:26 GMT

look at the Nibble tool to fill those areas in.