Reducing bed scour in meandering channel bends using spur dikes

Abstract

A river's planform pattern changes due to erosion of banks and the bed near the outer bend. The primary cause of these planform changes is the formation of helical flow patterns in response to centrifugal forces. Uncontrolled bed scouring can have a negative impact on the river's geometry, aquatic habitat, and floodplains. To alleviate this scouring, various structures, such as spur dikes, can be placed at any accessible location along the bend. The current research was accomplished by installing two meandering models with different sinuosities of 1.3 and 1.5, in a flume. For both sinuosities, the maximum bed scour was observed at an approximate angle of 45° relative to the bend apex. Thus, the main objective was to control this maximum scour by installing spur dikes with varying porosities, ranging from 0% to 75%, at five locations along the outer bend. The spur dikes were found to divert the helical flow regime away from the outer bend and protect the riverbed from severe scouring. However, the results show that the effectiveness of spur dikes decreases as sinuosity increases. Furthermore, for both meandering models, a 50% permeable spur dike installed at the +30° location yielded the best performance. Finally, a regression-based predictive equation is proposed to determine the proportion of scouring around a spur dike in a meandering channel.