Sediment pressures and impacts mean that sediment mitigation represents a priority management issue in many parts of England and Wales. Effective sediment management requires reliable information on the principal sources of the problem and on the efficacy of the mitigation options being deployed. Sediment source identification has traditionally been difficult, using conventional indirect procedures, due to logistical constraints, problems of representativeness and the costs involved. However, in recent years sediment source fingerprinting techniques have proved to offer a reliable direct alternative. The fingerprinting approach avoids many of the logistical problems and uncertainties associated with conventional sediment sourcing procedures by providing a reliable means of linking sediment directly back to its sources.
Although to date, sediment fingerprinting has been used to provide information on generic sediment sources (e.g. grassland, arable land, chanel banks) the proposed work seeks to refine existing procedures to improve the resolution of the sediment source evidence base. As an example of the refined sourcing procedure, high resolution sediment sources will be investigated during this pilot project in a predominantly grassland catchment in Cumbria, England. The proposed work will specifically seek to apportion sediment loss from grassland between poached gateways, poached cattle tracks and wider areas of trampling and degradation across pasture fields. The proposed work will complement similar high resolution sediment sourcing currently being undertaken in an arable landscape in Norfolk, England, by the same contractor.
Whilst high resolution sediment source apportionment is needed to target mitigation options, including those offered in the Capital Grant Scheme of the England Catchment Sensitive Farming Delivery Initiative (ECSFDI), an improved evidence base is also required in relation to the efficacy of available sediment mitigation options, including those listed in the Diffuse Pollution Inventory (DPI) User Manual. Accordingly, the procedure used to provide high resolution sediment source data will also be deployed in a pilot study to assemble information on the efficacy of two sediment mitigation options: 6 m buffer strips and channel bank fencing.
It is stressed that the proposed work on high resolution sourcing and assessing mitigation method efficacy will be undertaken as a pilot study to be used as proof of concept.