u see this method for the river i used witch ppl said was 'unusual'
lets me bend the triangles as high/low i want :P.
Okay, I just had to call you out on this. Your method isn't unusual at all - it's the same way everyone else makes terrain for Half-Life. It's quite ordinary, actually.
Anyway, I have a suggestion that would probably improve the terrain a whole lot, and reduce the chance of getting any collision problems (they're not really errors BTW, and they don't show up in the compile process. It'll be more like a random invisible wall that shows up.) First, select every single one of the brushes used for the terrain, then open the texture application tool. hold control and deselect all the top faces of the terrain. This way, all the unseen faces are now selected. Now, go and choose the BEVEL texture (you'll have this if you have zhlt.wad loaded) and apply it. This will cover all the unseen faces of the terrain with the texture.
The BEVEL texture, it's quite a handy little thing, especially for terrain. Most of the problems I was talking about earlier stem from little clipping errors. Even though faces that are hidden against brushes are culled out during the compile process, it seems that CSG still counts them, and thus, the clipping for those faces protrude upward a tiny bit, and you end up running into them. You'll notice what I'm talking about in any map where you've done something similar to this:
This is a little ramp, as you can clearly see. At the point where the angled brush ends, and new brush begins, there's two vertical faces. These won't be rendered at all, but if you compiled this map and ran up the ramp, you would notice a very subtle jolt as your character jumped up over a tiny protruding wall of sorts. The BEVEL texture takes care of this problem, because it basically tells HLCSG that there is no face there, and thus there is no clipping plane generated for it.
Well, that was more long winded than it needed to be, but you get my point now. Try using this technique, and you'll see how smooth everything is. It actually feels strange how you glide over stuff, because most people are so used to the jerky way you normally hop over ridges.