Laboratory experiments on lateral hyporheic exchange in riverbanks with curved bank morphology

As an important component of stream-subsurface exchange processes, lateral hyporheic exchange plays a crucial role in maintaining health of river and riparian ecosystems. In order to reveal the discipline of lateral hyporheic exchange induced by bank morphology, 10 runs of circulation flume experiments with idealized sinusoidal curved bank and 4 runs of comparison experiments with straight bank were conducted in varying flow conditions. The experimental results showed that the lateral hyporheic exchange also consisted of advection (pumping exchange), diffusion and micro-circulation, which was similar to the vertical hyporheic exchange. The increasing stream Reynolds Number Re intensified the effect of diffusion and micro-circulation. The presence of curved bank morphologies produced additional exchange under all flow conditions. With increasing bank amplitude and flow velocity, the pumping exchange (advective exchange) gradually became the main exchange pattern in the earth time of hyporheic exchange.