Alluvial responses to the changing Earth system

Alluvial systems are complex, self-organizing and hierarchical in structure. They represent stored and transitory sediment bodies transported by rivers that have eroded their catchments and created multiscalar landforms and sedimentary architectures over a range of time-scales. The central question we address in this paper is how environmental signals are autogenically processed and recorded by the fluvial sediment system. We compare databases of alluvial units that are well constrained in terms of dating control with direct or proxy records of environmental change. River system responses to environmental change are evaluated over three nested time periods spanning the past 200 000 years. First, focusing on Mediterranean European and African catchments, river responses to relatively abrupt and short-term Late Pleistocene Dansgaard-Oeschger and Heinrich climate events are examined. Second, the effects of rapid and globally significant episodes of Holocene climate change on European rivers, together with anthropogenic land-use impacts, are assessed. Last, 'Little Ice Age' flooding and alluvial responses to modern climate warming are reviewed with particular reference to upland Britain. These studies are shown to have significant implications for modelling local, regional and global-scale alluvial responses to future environmental change. They highlight the necessity for numerical simulation models to be fully informed by field-based knowledge and understanding of the memory effects of whole fluvial sediment systems, particularly those that have experienced repeated phases of environmental change. Copyright (c) 2008 John Wiley & Sons, Ltd.