A conceptual model of the formation of the meso-scale geomorphology of lowland forested floodplains

Within forested floodplains geomorphological processes are strongly modified by live and dead vegetation. However, interactions between the vegetation, water and sediments are poorly understood. Observations made along semi-natural rivers in the New Forest, UK suggest the presence of particular suites of landforms on the floodplain that owe their formation to such interactions. For example extensive networks of floodplain channels and the development of discrete areas of sand shadows. These features are only found in semi-natural reaches which have a high sinuosity, high frequencies of debris dams, longer sediment and organic matter residence times, and therefore experience relatively high frequencies of overbank flows during the flood season. This research explores the occurrence of such features and proposes a conceptual model for their formation. This model integrates the development of in-channel debris dams with the processes operating on the floodplain. The conceptual model is then applied in order to help set monitoring targets for a habitat restoration programme aimed at restoring wet woodlands along degraded lowland watercourses.