Many large estuaries around the world are engineered to some degree for both flood protection and maintenance of shipping routes. Naturally, planforms of sandy estuaries have the tendency to converge landwards exponentially, where deviations from this shape provide alternating space and constrictions where tidal sandbars and channels form. In the case of embankment by bank protection and dikes, such channels can develop deep scour holes that endanger bank stability. Our objective is to study effects of channel and planform dynamics on scour depth variation near protected banks of estuaries in the tilting tidal flume the Metronome, through three experiments with completely fixed banks and a control run without fixed banks, allowing longer timeseries than available in nature. We observe repeatable patterns of topographic forcing and quasi-cyclic behaviour in channel position and scour depth. Notable variations within and between repeat experiments result from a degree of chaos in the system.
