How to outline the general area of a raster?

Discussion created by agisguy on Apr 26, 2013
Hi friends, I have a raster (derived from DEM - slope) that I am trying to make represent a floodplain for a catchment.

I would like to be able to convert the raster to polygon eventually, but what I really want is just the outline of the floodplain, and not all of the little bits here and there, and not the channel itself. I want everything inside of the main floodplain area to just be considered floodplain, and all the little bits of data amongst areas of no data outside the floodplain to just become no data.

Anyone have any idea how to do this? It seems simple but I have spent the past 2 days struggling with it....

Eventually I will need to delineate the channel as well, so feel free to provide suggestions on that as well if you have more of a clue than I apparently do.

Thanks friends!