5 to 100 year flood plain

[CadencePhillipe]

Hi,

I have DEM for my country (not usa), soils data, and water surface elevation as points. How do I generate flood plains to show 5 year flood plains, 10, 50 and 100 year flood boundaries?

[ColinConstance]

Hi Cadence,
You'll need good topographic data, good river profile data, good landuse data as well and a good hydrologist who knows how to use HEC-RAS (a 1-D modelling that has a plugin for ArcGIS called HEC-GeoRAS). Also, you will need historical rainfall data as the sorts of flood boundaries you're interested in are statistically calculated. Doing this for a whole country using these tools and data is a big task so you're probably better off starting with a small part of one major river system.
Hope this helps..
regards
Colin Constance