1

I'm working with ArcMap 10.2 and I'm pretty new in this area.. What I want to do is compute the river slope for a lot of rivers from a DTM...I know that there is a way to do it manually passing by excel..but I was wondering if there was an automatic way to do it..also maybe using other programs.. I have all the territory of Swizerland to analyse..

  • Seems to me you need a peer-accepted heuristic to even calculate the slopes. I mean, do you use the average slope observed over N equal-interval stream segments? Or perhaps elevations at 10% and 85% of the stream length? I suppose because it's not a relatively large area, most of Switzerland's rivers have alot in common with one another and therefore a single approach to calculating slope may suffice, but in many places--like Arkansas or Missouri (USA)--the rivers in the northwest have extraordinary differences with rivers in the southeast, and different approaches have to be used. – elrobis Oct 17 '14 at 15:07
  • thank you very much for your answer, i'm not sure about wich method is better..what do you suggest me? i tried to use arc hydro tool as jbosq suggested me, but i don't know wich function is better to use. i heard also something about geo hms tool bar, but i think that there is no version for arcgis 10.2..is it right? thanks – irene Oct 21 '14 at 9:41
  • If you're just experimenting with your options right now, look into something called Whitebox GAT, it's got a variety of Hydrology functions that might benefit you. – elrobis Oct 21 '14 at 14:04
2

If you are new to hydrology/arc I'd suggest using arc hydro (for 10.2 try download and documentation). This will give you average slope and 10-85 using Watershed Processing - Flow Path Parameters - Flow Path Parameters from 2D Line.

elrobis's is correct that you may need to sample the slope more often depending on: (1) how the rivers were defined (think length, although it is usually accumulation based) (2) change in slope in the area (3) how you are using your results. However, if this is the case you can use the same slope determination method but on finer river segments/definitions.

  • thank you very much for your answer, i installed arc hydro, and under arc hydro tools-terrain preprocessing-vector QC i found a command called slope.Is it that one that i can use? i mean that slope correspond to the river slope right? not the one of the ground.. thanks again – irene Oct 21 '14 at 8:38
  • or is -assign stream slope? but in that case what i have to put as input? thanks again – irene Oct 21 '14 at 8:53
  • "Slope" gives slope values across your DEM as a raster, "Flow Path Parameters from 2D Line" will give you slope info for your line (stream) in its attribute table based on your DEM as well as creating points for the 10-85 values (where it was sampled along the line). GeoHMS is meant for formatting data for export to a hydrologic tool (HMS) it uses arcHydro for most of its processing and is only available up to 10.1 at this time. – jbosq Oct 21 '14 at 13:47

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.