function MainClass::IsRiverTile(tile)
// pfff, finally a solve to detect river
{
	if (!AITile.IsWaterTile(tile)) return false;
	if (AITile.GetMinHeight(tile) == 0 && AITile.GetMaxHeight(tile) == 0) return false;
	if (AIMarine.IsWaterDepotTile(tile)) return false;
	if (AIMarine.IsCanalTile(tile)) return false;
	if (AIMarine.IsLockTile(tile)) return false;
	return true;
}