Hi Mark,
Thanks so much for your reply, I really appreciate it.
So if I got this right essentially my approach is valid but it simply would not include the lake area (which is “no data” in my DEM) in the delineated watersheds, correct?
Actually my problem is that I would like all the streams I burn in using “DEM reconditioning” not to be re-filled when I run “fill sinks”. For most of them (the ones “exiting” my DEM) there is no problem, however some of the streams simply start and end somewhere in the middle of the DEM (they end in lakes and are not connected to the “main” stream network). These smaller “isolated” streams get filled when I run “fill sinks” after running “DEM reconditioning”.
I am following the manual you suggested: “Comprehensive Terrain Preprocessing Using Arc Hydro Tools”. According to this, as far as I understand it, in order to maintain the smaller isolated streams and prevent these from getting refilled, they must end into a “sink”. If this sink is a lake (like in my case) and a feature class for these lakes is available (I have this feature class too) one can create a “sink structure” using the lake feature class and the streams ending up in the lakes would then not be re-filled during the “fill sink” operation as they end up in a sink (which as far as I have understood it is equivalent to the streams “exiting” the DEM).
My problem is: how do I create a sink structure from the lake feature class and then use it during the fill operation so that none of the burnt in streams will be filled in?
Could this approach be the correct the one:
1. Use the “create sink structure” tool to create “lake sinks” using my lake feature class.
2. Use the “DEM reconditioning tool” to burn in my streams.
3. Use the “fill sinks” tool to fill sinks but specify that the “deranged polygon” should be the sink structure I created in the first step.
Does this make sense?
Sorry, I have been struggling with this for a while and despite it being a trivial issue (and probably specified in the manual I mention above) I can’t seem to find the solution.
Thanks again.
Alex.