Side channel dynamics

Side channels are commonly constructed to increase the discharge capacity of a river during peak flow conditions or to increase the ecological value of the river. Observations show that large aggradation occurs in the side channels. Therefore, such channels require regular and costly maintenance. The aim of this research is to better understand the mechanisms that drive the morphodynamic development of side channels and thereby, improve the design of side channels and reduce their maintenance needs. We studied the development of side channel in various ways and found that mechanisms such as a length difference between the downstream channels, sediment sorting at the bifurcation and varying hydrodynamic conditions have a large effect on the morphodynamic development of a side channel system. The mechanisms that are important are not the same for each side channel and can vary in time. Therefore, we propose three categories of side channel based on how the sediment that is deposited in the side channel is transported in the main channel: (1) bed load supplied, (2) suspended bed-material load supplied and (3) wash load supplied side channels. These categories can help in determining the main mechanisms that affect the development of a side channel system. In addition, we propose a method based on the categorization that can aid the design, operation and maintenance of side channels.