Raster smoothing

I am an italian student. I'm using ArcMap 10. For my thesis I need to simulate a debris avalanche, but in my elevation raster the avalanche deposit is included so I'd need to take it off to simulate on a pre-avalanche-like surface. Unfortunately the only data I have is the average (and supposed uniform) thickness of the deposit of 24m. I removed this thickness from my raster using raster calculator ("my raster" - "raster of tickness created from polygon to raster"). What I obtained is a raster without that thickness, but like a valley with sub-vertical walls! I need to smooth these edges to make it look more realistic (now it looks like a print with the shape of the deposit). Which tool can use? What I was able to find is the Filter tool which smooth these edges too mildly or the Smooth Line tool which could work on the contour lines. Is there a tool to smooth directly the raster?

Thank you,

Michele