Ability to have the CULVERT_THRESHOLD checked automatically

The ability to have the CULVERT_THRESHOLD checked automatically, relative to the WATER_LEVEL of the enclosing water level area. If the CULVERT_THRESHOLD is less than or equal to WATER_LEVEL, relative to datum, a warning is displayed. Secondly, if the CULVERT_THRESHOLD + CULVERT_DIAMETER is greater than or equal to WATER_LEVEL, relative to datum, a warning is displayed.