Simulation of a flood event in a catchment

[KaiHeckel]

Hello!

For a scientific project I want to simulate a rising of the groundwater in a river catchment of the Yangtze.

What is the easiest way to do this?

I got the basin from a SRTM DEM.

[ThomasDilts]

There are lots of ways to simulate floods and the method that you choose should depend on the spatial extent and resolution of your data, the question that you are trying to resolve, and the consequences (e.g. are people going to lose their homes due to a decision that you are making?).

For fine scale flood modeling you should look into using HEC-geoRAS or some other hydraulic model that does a good job of modeling water "behavior".  For larger scale problems I've used a methodology that basically involves detrending a DEM using local weighted averaging and then picking a threshold flood height value and reclassifying the raster into flood and non-flood categories.  Some of the methodology is described here: www.esri.com/news/arcuser/0110/mapping-with-lidar.html
and tools are available here: http://arcscripts.esri.com/details.asp?dbid=16792
With that in mind, you'll probably need to convert stage heights into some flood interval (people often use a 50 year flood for mapping riparian areas) and you'll probably need to use different stage heights for different parts of the catchment (stage height of a 50 year flood typically increases with accumulation area).

I'm also making the assumption that you are trying to model the inundation area not some other property of flooding such as velocity, volume of water, etc.

-Tom Dilts

[KaiHeckel]

Primarly I want to simulate the inundation of the land that is adjacent to the Yangtze's lower reaches. The DEM I have has a 90m resolution but the area it contains is pretty big. I tried to do it with HEC-geoRas but there are to many requested files that I don't have and which I don't know where to find...

Isn't there a simple way to rise the groundwater level in arcmap?