Hydraulic Design of the Box Inlet Drop Spillway

Abstract

This paper contains sufficient information to permit the complete hydraulic design of a box inlet drop spillway and explains briefly the various factors that influence the design. Its four major sections deal with the free flow capacity, the outlet design, the submerged flow capacity, and the utilization of the preceding information in the design of box inlet drop spillways.

The box inlet drop spillway may be described as a rectangular box open at the top and at the downstream end. The spillway is shown in the Frontispiece and in Figure 1. Storm runoff is directed to the box by dikes and headwalls, enters over the upstream end and two sides, and leaves through the open downstream end. An outlet structure is attached to the downstream end of the box. The long crest of the box inlet permits large flows to pass over it with relatively low heads, yet the width of the spillway need be no greater than that of the exit channel.