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Recent changes to floodplain character and functionality in England
- Entwistle, N.S., Heritage, G.L., Schofield, L.A., Williamson, R.J.
- Catena 2019 v.174 pp. 490-498
- bogs, data collection, ecotones, floodplains, groundwater, highlands, intensive farming, land use, marshes, pastures, plant communities, rivers, sediments, swamps, England
- Regime analysis suggests that temperate alluvial watercourses overtop their banks on average once every 1.5 years transferring water and sediment across the valley floor to form floodplains helping maintain a strong hydrological connection between in-channel and overbank form and process. Flooding also causes erosion, sediment transfer and deposition creating a variety of floodplain morphologic units and functional connectivity with the main river. The result is a morphologically and ecologically varied wetland dominated ecotone where diversity is sustained by the action and flooding and shallow groundwater processes. Floodplains are, however, sensitive to disruption and many have been significantly degraded since the Bronze Age as a result of activities that alter flooding and groundwater processes and manage vegetation communities. The current (2015) floodplain condition and trends of change since 1990, for England are presented here using land use data for 1990, 2000, 2007 and 2015. Floodplain system degradation has been found to be both widespread and severe across the whole of the country. The 1990 data set showed that intensive agriculture occupied around 38% of floodplain zones expanding to 53% by 2000 before slowing slightly to covering 62% in 2007. Between 2007 and 2015 the coverage remained relatively static (64%) with some suggestion that arable areas were being transformed to pasture. Wetland areas in the form of fen, marsh, swamp and bog have been devastated with the data sets indicating that these fundamental floodplain units have been all but lost. Upland and lowland areas are both severely impacted with a near ubiquitous loss of natural floodplain functioning. Despite this some 31% of rivers in England are classified as good or better under the European Water Framework Directive classification system calling into question the UK WFD status classification process.