--- a/src/station_cmd.cpp	Wed Jan 23 08:28:19 2008 +0000
+++ b/src/station_cmd.cpp	Wed Jan 23 08:47:49 2008 +0000
@@ -1954,6 +1954,9 @@
 		default: return_cmd_error(STR_304B_SITE_UNSUITABLE);
 	}
 
+	/* Docks cannot be placed on rapids */
+	if (IsRiverTile(tile)) return_cmd_error(STR_304B_SITE_UNSUITABLE);
+
 	if (!(flags & DC_NO_TOWN_RATING) && !CheckIfAuthorityAllows(tile)) return CMD_ERROR;
 
 	if (MayHaveBridgeAbove(tile) && IsBridgeAbove(tile)) return_cmd_error(STR_5007_MUST_DEMOLISH_BRIDGE_FIRST);

--- a/src/water_cmd.cpp	Wed Jan 23 08:28:19 2008 +0000
+++ b/src/water_cmd.cpp	Wed Jan 23 08:47:49 2008 +0000
@@ -285,6 +285,10 @@
 		case SLOPE_NE: dir = DIAGDIR_NE; break;
 		default: return_cmd_error(STR_1000_LAND_SLOPED_IN_WRONG_DIRECTION);
 	}
+
+	/* Disallow building of locks on river rapids */
+	if (IsRiverTile(tile)) return_cmd_error(STR_0239_SITE_UNSUITABLE);
+
 	return DoBuildShiplift(tile, dir, flags);
 }