Dominant Discharges at Platte-Missouri Confluence

Abstract

Principal objectives of river regulation are (1) to secure a stable alinement; (2) to develop a cross section adequate for flood flows; and (3) to maintain a better and deeper channel for navigation. Purpose (3) is often achieved by installing structures along the banks and in the river to direct the flow to form a single, deep channel which will carry the sediment load. The sediment delivered to a river must be carried by widely varying water discharges if a stable channel is to result. The discharge which is the equivalent of the varying river discharges for channel formation is the dominant discharge. One method of determining the dominant discharge is presented. The Platte and Missouri Rivers have been selected as an example and the dominant discharges calculated for each reach above and below their confluence. The effect that regulation by major dams has had on the dominant discharge of the Missouri River, and the stabilizing effect this will have on the bed load transport at the confluence, are described.