Calculation of an "alluvial fan"

[TobiasGutmann1]

Hi.

I did not worked with hydrologic tools for a ling time so I need help.
I would like to caluculate the area in front of a small dry valley or wadi (in the DEM) where the water would create an "alluvial fan" after heavy rain. I do not care about the volume I am more or less just interrested with areas will be dangered by the water. In the end a water/rain risk map.
Can anybody give me a hint how to do it? I read a lot of readmes but all I found was watershed and so on what is not what I need.

Thanks a lot

Tobias

[DanPatterson_Retired]

what criteria are you using for alluvial fan delineation?  Perhaps some of the existing tools can be used once these are established.

[TobiasGutmann1]

Well I don't know. I just would like to determine the area endangered by water coming out of a valley or wadi just using the DEM. Imagine planing of settlement which should not be directly in front of the valley. But it would be nice somehow to have an GIS created result. I just mentioned the "alluvial fan" because I thought in the end it will be the same basis.