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Fluvial Reservoirs |
Department of Geography, University of Aberdeen, Aberdeen AB9 2UF, UK
This paper introduces a forward, 1–2 dimensional model that predicts fluvial depositional sequences in response to (a) variations in runoff and sediment supply regimes of the source catchment, as well as to (b) fluctuations in relative sea-level controlled by eustatic and isostatic changes. Variations in sedimentology and aggradational history are simulated from accommodation principles and unit power relations of flows of varying sediment concentration. The model is applied to the sandurs of Iceland, which have been subject to large-scale environmental changes over the past 10 ka, associated with deglaciation, isostatic uplift and fluctuations in runoff regimes. Flows include not only normal seasonal ablation runoff from glaciers, but also repeated glacier burst floods generated by sudden volcanic activity. Simulation of 100-year runoff events has allowed prediction of the stratigraphy, sedimentology and geomorphic history of the sandurs. The model has been successfully tested at the smaller Solheimasandur, and then applied to Skeidararsandur, the largest of the Icelandic outwash plains. In both deposits, the predicted stratigraphy and geomorphic history highlight the significance of extreme events for the development of the alluvial sequences. The results indicate that, since alluvial stratigraphy can be so highly dependent on fluctuations in runoff and sediment supply regimes, these factors should be essential components in development of quantitative models of alluvial sequences used for reservoir exploration.
