RULES: The rules for terrain in the Confrontation booklet are limited is certain ways. Hence when one creates terrain for use with the game the rules should help determine what you are making. Can the average miniature jump the 25cm ravine you are buiding? Will this terrain take too much time to get through? If the terrain is for a different game many aspects may be similar.
    Climable Terrain should be a realistic height as should things troops may wish to jump on. You could even mark numbers on the terrain if you don't want to keep it a secret and force the opponent to judge distance.
    Make a distinction between shallow water and water that requires a swimming feat.
    Some terrain can just be considered impassible. Blocking line of sight is important to keep spells and charges from being too limited.
   You may make a "house rule" which specifies that some figures cannot climb, jump, swim, etc. because they are heavy or encumbered.

The ground is encumbered : forest, shallow water, brushwood… / Each encumbered cm counts for 2.
Ladder, rope… / Each cm counts for 2.
The ground is impassable : wall, deep water, rifts… / IMPOSSIBLE.
    

Of course now the rules for ragnarok may be more important in that regard.