Flow accumulation straight lines, flow direction problems

Question

Hi. I am having some difficulties in revealing flood channels in my study area.

The problem begins with the flow direction raster (input to flow acc.), where there is a -blue- region (picture attached) without flow direction being calculated. I don't want to exclude the area of course.

Please advise, how to solve it.

Thanks!

flowdirectionissue.png

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AkosKalman · Answer

Dear Dan,

Thank you for your answer and my apologies for the late answer. The problematic blue area is a flat area, the white is the northernmost Gulf of Aqaba - Eilat that was taken out by setnull from the raster. I have downloaded and tried Arc Hydro Tools-->DEM Manipulation-->Fill SInks, Sink Prescreening, furthermore Flow Direction with sinks as well as fill.

Did I miss something?

DanPatterson_Retired · Answer

is it a lake? a flat area? were sinks filled prior to doing anything with the dem?

Do you have some results to show if there is a problem?