Establishing a Real-time Meander Observatory

Project Description

Observing the real-time response of meander morphology to the full-range of annual flow conditions is inherently difficult due the rapidity at which these changes occur, and the logistical limitations imposed by the weather and channel flow dynamics. Meander bends progressively erode their outer banks and migrate across their valleys as high-velocity fluid shears across the channel boundary in response to streamline curvature. This process is strongly stage-dependent, with higher flows considered to do the most geomorphic work. Over time, sinuosity increases, and the propensity for meanders to converge or be bypassed by floodplain incision increases, eventually creating oxbow lakes. Meander cutoff – the process responsible for excising bends from the main channel – is seldom observed in the UK over human timescales, due to the long periods over which they develop and considerable modification to natural river systems. However, the River Towy (Wales) provides a unique opportunity monitor and observe the evolution of several high sinuosity bends (with migration rates of >3 m yr-1) as they approach cutoff. The river responds rapidly to multiple flood events each year, which divert flow across the floodplain, increasing bank saturation and collapse and promoting channel incision.