topic Problems delineating flood area with a DEM in Water Resources Questions

Problems delineating flood area with a DEM

iankirschner — Sat, 13 Apr 2013 13:07:05 GMT

Hello
I am doing a flood model for a town. I have created the river geometry using a 50cm DEM. When I bring the RAS layers back into ArcMap I am unable to delineate the flood area when using the DEM. Any suggestions?
Ian Kirschner
BGIS Student
SAIT polytechnic
Calgary, AB

Re: Problems delineating flood area with a DEM

iankirschner — Mon, 22 Apr 2013 13:04:55 GMT

Hi Steve
The problem that I was having was with the the final step in ArcGIS, delineating the flood plain area. Since I wrote the post I was able to create an accurate output. I converted my DEM into a TIN and it seemed to work. Thanks for getting back to me. Perhaps you could shed some light on another issue that I am having though. I am having difficulty with modelling low flows. When comparing my outputs with historical floods my flood inundation area that I created at 200cms is comparable with the historical flood area of 340cms. I suspect that the elevation information that I have for the river bed is not very precise and that is part of the reason. When I enter very low flows, even 1cms, I still have flooding occurring outside of the river banks?
Any suggestions that you could give to explain would be greatly appreciated.

Ian Kirschner

Re: Problems delineating flood area with a DEM

ketakiagarwal — Tue, 01 Oct 2013 05:35:25 GMT

Am facing a similar issue but with a different process. The initial steps, i.e exporting data to HEC GeoRAS and then exporting it back to GIS, all went fine.
Could even create the water surface profiles also.But when I try to delineate flood plain , after a long runtime process of 45 mins it shows the following error, as in the depth profile is created but the the boundary profile is not created. Please refer the attachment and kindly help.

Re: Problems delineating flood area with a DEM

anitaYeeting — Mon, 11 Nov 2013 01:56:51 GMT

I am doing the same thing here...delineate flood zones...and calculating land area loss from flooding.

I managed to create a DEM and then select contours which marks flood areas. however I do not know how to delineate these contours as flood zones.

After that I will be calculating land area loss from flooding....any ideas on how to do this?

Many thanks

Jay