2 replies to this topic

[Luigi]

I have a DEM off a study area and I would like to make a flood map out of it...

I want to obtain all the cells that are below value X. So far so god.
My problem is that I only want to obtain "connected cells" this is, cells that are below the the value X and that are connected whit other cells of the same value (at least 4 more cells)

can anyone HELP?

I'm trying to build raster calculator expression

[gregory]

the solution isn;t exaclly the way you asked for but should give the same result;
dissolve your raster by cell value,
then compute area for you new aggregated raster for each agregation you got
order in ascending way
there is some area of singel pixel - check whose of agregation are 4 and more.

[merft]

I would recommend using HEC-GeoRAS from the Army Corps of Engineers. There is a tutorial that explains how to use it. I believe it requires both Spatial and 3D Analyst to funtion. Good luck. -Tom