The selection of a grid spacing is a very important step. While you can certainly use a smaller spacing to get a high resolution grid, the more grid points you have, the slower Muk3D will process the grids, and the less interactive they might be in the 3D window.
The rule that we use is to choose a grid spacing that is 1/2 the minimum feature width you're trying to model (e.g. dam crest width).
- Structures/Dams/Draw a dam
- Grid/Merge/Merge dam into grid
- Surface water/Info/Find maximum containment elevation