Hi, I am modeling soil erosion and sediment transport across a watershed. I have created an erosion map which is a raster layer in which every pixel has a value of soil erosion. In order to route the soil across the watershed I assume that eroded sediment is transferred by surface flow along hydrological flow paths. Hydrological flow paths were determined in arc GIS from a DEM and flow direction. I've considered using the flow accumulation tool with the erosion layer set as the weighted raster in the tool to transport the eroded sediment. The problem with this is that it exports ALL of the sediment from upslope pixels to downslope pixels when in reality this does not occur because some soil is retained by vegetation etc. and is therefore not transported. I have also created a retention surface, which is a raster, the values of which represent different retention factors. I want to be able to apply the retention factor to every pixel that receives sediment, but in a stepwise manner as sediment accumulates from pixel to pixel.