Müller wrote in Fri Nov 22, 2013 1:57 pm: roads within rivers, rough terrain or lack or excess
If you see an excess of terrain... pull up!
Just kidding, just kidding. Some pictures of these errors would be very useful. For example, check that you really have roads on rivers, and not "rivers on rivers". i.e., a small water stream inside a larger water surface. Check also if bridges are correctly labeled in the area: http://www.openstreetmap.org
ICAO airports had many repeated, only from an airport with the name of a farm had repeated 8
This is a limitation (actually, it is a bug) of current fgrun: if it finds an airport in the scenery but not in the apt.dat, it repeats the name of the last airport. This means that the scenery includes more airports than the internal FlightGear database! You can update the database manually (my choice), wait for an update of FlightGear, or try to fix fgrun.
To update the database, download the last data from X-Plane (version 9, if I recall correctly) and substitute FGDATA/Airport/apt.dat with earth_apt.dat from X-Plane. You can also update nav.dat and fix.dat. Remember compressing these files using GZip format!