Abstract
Abstract. The River Rother, West Sussex, is suffering from excess sediment which is smothering the river bed gravels. This is thought to be exacerbating issues of pollution and degradation of ecosystems. This project aims to identify the severity, extent, possible causes and potential mitigation options available to reduce these pressures on the river. Data have been collected from ten sites to investigate the amount of sediment stored in the river bed gravels and cores obtained from four small reservoirs to establish rates of sedimentation and contribute to the construction of a temporal sediment budget over the last 50–100 years. Evidence suggests that tributary streams have more stored sediment per m2 upstream of their confluence with the River Rother compared to the Rother itself. Reservoir core data indicate that sediment has accumulated more rapidly in the small reservoirs surrounded by mixed agricultural land compared to one surrounded by ancient woodland. These are preliminary results and work is continuing.
Highlights
In the UK, some rivers are failing to meet the criteria for achieving Good Ecological Status (GES) as set out in the European Union (EU) Water Framework Directive (WFD) (Defra, 2014; Official Journal of the European Communities, 2000)
The River Rother catchment is located in West Sussex/Hampshire in the South of England (Fig. 1)
Confirmed in an independent study in the UK by Collins and Walling (2007). It appears that all of the stored sediment estimates plotted in Fig. 2 are high compared with these studies, further suggesting that issues exist with stored sediment in this catchment irrespective of whether the sediment is carrying any contaminants associated with it
Summary
In the UK, some rivers are failing to meet the criteria for achieving Good Ecological Status (GES) as set out in the European Union (EU) Water Framework Directive (WFD) (Defra, 2014; Official Journal of the European Communities, 2000). While fine sand smothers the gravels there is an added issue of silt and clay transporting nutrients and pollutants into the river (Collins et al, 2009). These sediment pressures have been identified as key variables likely to prevent the attainment of GES in the Rother; the specific sources and causes of the problem have yet to be fully evaluated. The soil that erodes from fields can be delivered to waterways and roads where most negative impacts are felt (Boardman et al, 2003; Evans, 2010) This impacts society with financial costs to local authorities, the public and industries which depend on having a healthy river and good communication networks (Collins et al, 2010). If the soil has a reduced infiltration capacity, excess water can create muddy flows that run across the land and into rivers, thereby increasing flood magnitude (Boardman and Favis-Mortlock, 2014)
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