Shocked it took me this long to see this.

You're probably going to see more artifacts from four way flow than the mod n. I'd have the erosion increase with slope and decrease a lot under water. Deposition should probably be at a maximum on flat surfaces, decrease with slope and increase under water.

Another improvement once you have slope variation and especially eight way flow, would be a separate hardness raster. Harder surfaces reduce erosion, softer surfaces increase erosion. Hardness wouldn't effect deposition.

I'll watch this with great interest!