Free overall in open channels: state-of-the-art review

Seventy years ago, Hunter Rouse observed that a free overfall in rectangular channels could be used as a simple flow measuring device that requires no calibration. Due to its practical importance, since then many investigators studied the free overfall in various channels. Although the laboratory experimental results are rather simple, the mathematical treatments of free overfall problems have been found to be deceptively complicated. This article presents a comprehensive state-of-the-art review of the important laboratory experimental and theoretical investigations on free overfall in various channels highlighting the hydraulic background and the mathematical treatment of the problem. In this review article, 120 references are included.