Broad-crested weirs are control structures. Often, submerged overfall prevails so that the weir is fully submerged in the downstream water. Under certain conditions, broad-crested weirs can be used as measuring weirs.
HM 161.31 contains a cuboid shaped weir body with a sharp edges. Two additional elements can be fixed at the weir body to create rounded edges. Free and submerged overfall can be clearly demonstrated. The effect of the sharp-edged or rounded weir crest on the nappe is easily observable.