Scouring in Long Contractions

Abstract

Based on the continuity of flow and sediment, an analysis on scouring in long contractions is conducted with a formula obtained from measured sediment discharge in long contractions and a formula for the flow resistance related to local scour. The analytical solution shows that the equilibrium scour depth in the contracted section depends only on the ratio of the uncontracted to the contracted channel width, and the approach flow depth. The equation is applicable to both live-bed and clear-water scouring conditions. Previous predictive equations by Straub or Gill can also arrive at the same conclusion, but only for some special cases. A comparison between the measured scour data and various analytical models confirms that the simplified equation is sufficiently accurate for most practical purposes.