How to derive reach breaks

Discussion created by mstead on Apr 10, 2012
Latest reply on Apr 30, 2012 by Hornbydd
I was recently asked to create maps of mainstem stream slopes within a bunch of watersheds classified into 5 slope categories. I was also asked to find changes in slope greater than 2%.

I have done this a few ways, but due to the need to find changes in slope I decided to do this as a routed network so I could manipulate external tables in Excel. I have a 10m DEM so I split my line into ~ 10m sections and converted to points. I used values from the DEM, interpolated for the location of the points to populate this point feature with elevations, and then I used the locate along line tool to create a route event table. I then manipulated this table in excel to be a line event table by making each points F_MEAS the preceding points T_MEAS and then using this to calculate a slope and a change in slope field. From this I can create a line route event layer for segment slope, and a point layer for change in slope.

The person I did this for finds this level of detail the equivalent of noise so I suggested that he define some reaches and I could average the slope. In response I was sent the TFW Stream Segment Identification manual with a methodology involving 3 mylar overlays and no GIS. I subsequently found this methology that uses ArcHydro.

Does anyone out there have any methodology or tools they can point me towards? I have only defined reach breaks in the field.