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Department of Geography, University of Cambridge, Cambridge CB2 3EN, UK
The purpose of this paper is to explore the role that drainage basins and networks play in filtering and modulating the effects of environmental change. The record of this change is often inferred from the properties of alluvial stratigraphy in river valleys. However, the variable time lags and smoothing effects caused during the flux of sediment through a drainage basin are very poorly understood, and need to be clarified before the depositional record can be linked to the causes of change. Interactions amongst drainage network elements — main valleys and tributaries — result in complex patterns of storage and delivery in time and space, and these interactions are reviewed in this paper. While the combination of cosmogenic isotopic dating of erosional records, and the use of shallow seismic and ground penetrating radar methods may provide data on the empirical linkages between sediment sources and sinks, a significant research need is for a modelling framework to enable cut-and-fill records to be simulated, and to provide a rigorous connection between the valley-fill depositional record and the environmentally-driven variations in sediment production. This will require a return to the long-neglected analysis of drainage network structure, and an improved understanding of the within-catchment variations in the sediment delivery ratio. Until this is achieved, it will be premature to assume direct connections between environmental change and the record of alluviation in many valleys.
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  L. E. Frostick and S. J. Jones Impact of periodicity on sediment flux in alluvial systems: grain to basin scale Geological Society, London, Special Publications, 2002; 191: 81 - 95. [Abstract] [PDF]
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