Channel degradation and slope adjustment in steep streams controlled through bed sills

Abstract

General, parallel and rotational degradation and the effect of bed sills are investigated with the aid of historical field data and laboratory experiments. The case under consideration is a system of two tributaries and a main river in northeast Spain, characterized by its short length, steepness and ephemeral nature. The comparison of bed profiles since 1962 revealed an incision greater than 5.5 m. The main causes of degradation are thought to be channelization (width reduction) and urban growth. The equilibrium slopes with and without sills were obtained in 111 live-bed flume tests. It is demonstrated that the bed slope is milder with sills than without sills under the same flow and sediment rates. The equations for the calculation of equilibrium slopes, scaled to prototype, are applied to the case-study, with good agreement. Copyright © 2008 John Wiley and Sons, Ltd.