| Abstract: | It is often believed that extreme but infrequent events are most important in the development of landforms. When evaluating the overall effect of large floods on floodplain sedimentation, quantitative measurements of both high- and low-magnitude events should be considered. To analyse the role of flood magnitude on floodplain sedimentation, we measured overbank sedimentation during floods of different magnitude and duration. The measurements were carried out on two embanked floodplain sections along the rivers Rhine and Meuse in The Netherlands, using sediment traps made of artificial grass. The results showed an increase in total sediment accumulation with flood magnitude, mainly caused by enhanced accumulation of sand. At low floodplain sections the increase in sediment deposition was smaller than expected from the strong increase in suspended sediment transport in the river. Spatial variability in sediment accumulation was found to depend both on flood magnitude and duration. Deposition of sand on natural levees mainly takes place during high-magnitude floods, whilst low floods and slowly receding floods are important for the deposition of silt and clay in low-lying areas, at greater distance from the main channel. © 1998 John Wiley & Sons, Ltd. |
