topic Re: NextDownID = -1 but not outlet in Water Resources Questions

NextDownID = -1 but not outlet

MichelleTischler — Wed, 29 May 2013 14:12:10 GMT

I've built my network; set my flow direction; asigned HydroIDs to my pts, net_junctions & lines; run the From/To nodes for the lines; and lastly NextDownID for the lines. I have 57 line segments with -1 as the NextDownID. I only have one true outlet for the network.

I have no disconnections in the network when I run a trace. All of the From/To Node fields are populated and have the correct HydroID for the next downstream segment. The segments with the -1's are not endpoints but a segment within the total stream length. Unfortunately, this is a fairly large network and takes four hours to run the NextDownID, so it's not an easy test for fixes unless I break out a portion of the network and test on it. I have disconnected the network, stripped out all Hydro/JunctionIDs, and rerun from scratch to see if I missed a step.

Any suggestions are appreciated!

Re: NextDownID = -1 but not outlet

ChristineDartiguenave — Wed, 29 May 2013 22:39:34 GMT

-1 gets assigned to the lines having a TO_NODE that is not assigned to any FROM_NODE. If you look at your lines having NEXTDOWNID=-1 and check their TO_NODE field, can you find other lines having these values in their FROM_NODE field?

Christine Dartiguenave
Esri Water Resources Team

Re: NextDownID = -1 but not outlet

BastianSchmidt — Tue, 02 Jul 2013 18:16:53 GMT

I am experiencing a slightly different yet similar problem with the NextDownID. The entire field (i.e all records) are calculated as -1. I am trying to experimentally introduce "links" into the network (i.e. extra links inbetween confluence points, or non-confluence links) at the raster level. This seems to work upto the NextDownID generation process. My DrainageLines have TO_ and FROM_NODES and they do match up (i.e. the TO_NODE = the FROM NODE of the next downstream line). Is there any other conditions that might result in -1 being calulated for all DrainageLines?

Re: NextDownID = -1 but not outlet

ChristineDartiguenave — Wed, 03 Jul 2013 14:28:05 GMT

What is the type of the FROM_NODE and TO_NODE fields?
If you copy the stream feature class and build a join between the original stream and the new feature class using FROM_NODE/TO_NODE, are the records successfully joined?

Christine Dartiguenave
Esri Water Resources Team

Re: NextDownID = -1 but not outlet

BastianSchmidt — Wed, 03 Jul 2013 15:11:48 GMT

Hi Christine,

The TO_ and FROM_NODE fields are of the LONG [Integer] data type. The "Join" test you suggested is also successful. I have also written an MS-Excel macro to perform the NextDownID attribution and it works with a few exception where network discontinuities exist.

Re: NextDownID = -1 but not outlet

ChristineDartiguenave — Wed, 03 Jul 2013 21:19:27 GMT

I would need to check your data to try to figure out what is going on. Can you post it?

Christine

Re: NextDownID = -1 but not outlet

BastianSchmidt — Tue, 09 Jul 2013 17:19:11 GMT

I have found the problem. It has something to do with my installation of Arc Hydro (ArcGIS 9.3.1) becasue when I ran my data on another computer and it worked just fine!