Thank you all for the replies, with smoothing at inlet boundary (along with a trench) and applying a spatially varied initial water levels, i got the model running.However, the model introduces some errors for steep slope as a wave front moves before the boundary feeds in the domain (see attached).
On other hand, the multi-cell solver is not working fine with blow up errors. i use the coarse grid as 6x6 and fine grid as 2x2. i coarsened the fine grid using the resampling tool (ARCGIS9.3) with Bilinear interpolation.
I appreciate it if anyone can help
Mostafa
