Hy,

Can anybody help me with a little problem. I am quite new with Grass, and i need
to make a hydro simulation using GIS.

In Grass Gis - the SIMWE Overland Flow modelling - there are some requirements
that i do not understand :

x - derivatives raster map
y - derivatives raster map.

If you have any idea about this, please help me. How can these rasters can be
made.

Thx.

Daimon