Hi Rotor dude
There is a fix provided by a modified terrain.cfg file-
http://library.avsim.net/download.php?DLID=93289This will fix the rocky rivers so feel free to download this, try it and let me know if it helps (it changes the default rocky remap on higher slopes)
If there are river polygons which are actually missing (I.e. the shoreline is there but the water polygon isn't), then I would like to know about them
There are a few I'm aware of (which have been fixed in my data and will be supplied with the patch) but its possible there are more caused by errors in the source data)
Cheers