2020 年 8 巻 1 号 p. 178-187
Hydraulics of sharp-crested weirs is investigated in order to obtain the base data for flood control planning in rivers with weir(s). A unique relationship between the dimensionless critical depth and the upstream head from the crest was obtained on the basis of momentum theorem, then the formulas for both discharge and upstream head were derived. In applying the momentum theorem, results of the previous experimental studies on the pressure distribution in the upstream face of the weir and in the flow section immediately behind the weir where the lower nap becomes highest were taken into account. The obtained formulas are much more hydraulically rational than the previous ones, and showed good agreement with experimental data for upstream head up to four times the weir height, which is far wider than the application limit of the previous formulas.