Streams not exiting DEM

Question

Hello,

I'm quite new to hydrological analyses and Arc Hydro and trying to get my head around dealing with streams (artificial ditches rather) not exiting my DEM. I would like to "burn" these ditches into my DEM using "DEM reconditioning" but what I'm wondering is: will I need to apply some kind of sink structure as my ditches are not exiting the DEM? I believe the issue (i.e. the reason the ditches are not exiting the DEM) is that I am working in a semi-urban area and the ditches may actually be ending up in storm water systems. Could these somehow be considered sinks?

I apologize if the questions is a stupid one...I'm just really confused and any help would be really appreciated.

Thanks,

Alex.

AlexanderVentura · Answer

Hi Christine,

I am using the Create sink structure tool for creating my sinks as you suggested. Everything flows smoothly however it seems like the tool only creates a sink polygon and sink polygon grid but no sink point. Do you have any idea of what the problem might be?

Thanks so much.

Alex.

AlexanderVentura · Answer

Hi Christine,

Thanks so much. So I have a vector representing drainage lines on the terrain. I want to "burn" these in so the water will be forced to flow inside of them. But some of the lines (not all of them) in the polyline vector don't "exit" the DEM (as mentioned above in my previous question). Essentially some lines start and end inside the DEM. If I understand it correctly if I follow these steps (to first remove sinks from my raw DEM and then burn in streams):

- Fill sinks

- DEM reconditioning

- Fill sinks

the last steps might fill in the burnt in streams that don't exit the DEM. Is this correct (if burnt streams are not filled can I simply continue with my analysis without bothering with sinks?)? If burnt in streams are filled I need to create a sink at the end of the lines (from the polyline feature) right? I tried to follow the stormwater processing workflow but still feel a bit confused, could you help me get my head around a few steps?

- When you say "buffer by 1.5*cell size to create a draft sink polygon" do you mean a buffer around a new point that I create at the end of the stream?

- In my specific case is it important that the sink is placed at the end of the stream (most downstream location) or it doesn't matter?

- Should Create Sink Structures only generate a sink for the "buffers" that I have generated at the end of the streams that don't exit the DEM?

I tried these steps but I keep getting an error when running the last. Am I getting something wrong here?

Thanks so much again.

Alex.

ChristineDartiguenave · Answer

To avoid being filled back in, a stream must either exit the dem or end in a sink. In your case, create a sink point at the end of the streams, buffer by 1.5*cell size to create a draft sink polygon and then use the Create Sink Structures to create the SinkPolygon/SinkPoint. You can look at the Stormwater processing workflow for help.

Christine Dartiguenave

Esri Water Resources