|Shields Jr, Fletcher|
Submitted to: Journal of Hydraulic Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 15, 2002
Publication Date: September 15, 2002
Citation: KUHNLE, R.A., ALONSO, C.V., SHIELDS JR, F.D. LOCAL SCOUR ASSOCIATED WITH ANGLED SPUR DIKES. JOURNAL OF HYDRAULIC ENGINEERING. 2002. V. 128(12). P. 1087-1093. Interpretive Summary: Streams in agricultural watersheds are often plagued with unstable channel boundaries. Erosion of the unstable channel boundaries threatens valuable agricultural and other lands. Excess sediment from erosion also degrades the habitat for fish and other aquatic organisms. Bank protection measures have the potential to preserve valuable agricultural lands and enhance aquatic habitats. A study was conducted in the laboratory using a model stream channel to test spur dike designs (a structure widely used to protect stream banks) with three different angles to the channel bank. The best design of spur dike was the one that not only protected the stream banks, but also maximized the volume of the scour pool formed by the structure. Stable pools are an important part of improving aquatic habitats in unstable stream channels. It was found that spur dikes constructed with an angle of 135 degrees to the bank had the most potential benefit to aquatic habitat while ones with 90 degree angles yielded the best potential for protection of the banks. This type of information is needed by managers concerned with agricultural watersheds.
Technical Abstract: A series of experiments were conducted in which the volume of the scour hole associated with model spur dikes was measured in a laboratory flume under clear-water overtopping flows. Spur dike models were angled at 45, 90, and 135 degrees to the downstream channel sidewall with contraction ratios of 0.125 and 0.250. The main goals of the experiments were to evaluate the effect of the three angles on aquatic habitat and protection of the streambanks to erosion. The experiments showed that of the three angles tested, the least erosion of the bed in the near bank region was associated with the spur dikes with 90 degree angles, while the greatest volume of the scour hole was associated with the 135 degree spur dikes. It was concluded that spur dikes with 135 degree angles showed the best potential for providing improved aquatic habitats while providing an acceptable level of protection of the banks.