The ability to have the WEIR_HEIGHT set automatically, relative to the WATER_LEVEL of the enclosing water level area. I.e. the WEIR_HEIGHT is WATER_LEVEL + X, relative to datum, where X is user-configurable. The weir height should depend on the highest water level on either side of the weir. The current situation is that the WEIR_HEIGHT’s value is always the weir height relative to datum. If a user wants to relate the weir height to the water level, they have to do so manually. In the requested situation the user can eighter set the height in absolute terms, as is currently the case, or the user can opt to have the weir height set to a value relative to the WATER_LEVEL attribute of the enclosing water level area.