Sediment Storage and Fluvial Sediment Transport Linkages Across an Experimental Flood Sequence

Abstract

River channels are maintained by coordination between flow hydraulics, sediment supply, riparian vegetation, and sediment transport. This coordination is challenging to understand in natural flow regimes, where climatic and environmental drivers produce episodic flood and sediment supply events. To better understand the response of channels to flood sequences, we have undertaken laboratory flume experiments on sediment storage and export across a sequence of alternating hydrographs. Our experiments indicate that accumulated sediment storage before floods predicts sediment transport during floods, with sediment storage depletion during floods causing a nonlinear variation of sediment-transport rates through time. Likewise, sediment storage between floods follows a growth-to-saturation pattern, whereby the sediment transport gradually increases toward the sediment feed rate depending on the occupation of available sediment storage zones. To describe these non-linear variations, we developed a mathematical model which represents sediment transport and storage as a coupled dynamical system. This work highlights the crucial role that within-channel sediment storage and its history play in determining sediment export in rivers.