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Developing the evidence base on buffer strips and other options for sediment loss from agriculture - WQ0208

Diffuse sediment pollution causes a number of negative impacts on freshwater ecology including fish and macroinvertebrates, whilst also representing a vector exerting a key control on the transfer and fate of nutrients and contaminants responsible for a wide range of off-site environmental problems in aquatic habitats. It is therefore important to understand and mitigate sediment pressures across England and Wales. Previous research by ADAS has suggested that the agricultural sector contributes ca. 76% of the current total suspended sediment loadings delivered to watercourses at national scale and as a result, attention needs to be focused on mitigating such losses. Defra therefore requires an improved evidence base on the scope for mitigating the problem. Such evidence is required in light of the recent CAP Healthcheck and concomitant need to off-set the loss of set-aside, as well as the need to support policy on agri-environment schemes (in the light of the peak of ELS renewals in 2010-11), Cross Compliance and the EU Water Framework Directive (including Catchment Sensitive Farming and Water Protection Zones).

A range of preferred mitigation options has been identified in the Defra User Manual-ALL to help combat sediment pressures. The proposed work will primarily assess the efficacy of riparian buffer strips for mitigating sediment delivery to neighbouring watercourses. A range of fixed widths, soil types, adjacent crops and buffer strip ages will be encompassed by survey and monitoring in the Demonstration Test Catchments (Hampshire Avon, Eden and Wensum).

In addition, the efficacy of a select number of alternative mitigation options for sediment (fencing off rivers and streams from livestock, re-siting gateways away from high risk areas, farm track management and establishing new hedges) will also be assessed. The outputs on efficacy will be used to improve the empirical evidence base and to augment modelling work used for extrapolation purposes across the Demonstration and ECSFDI priority catchments and at strategic scale.

Based on the empirical data gathered, the project will also provide the basis for: a) management guidance on best practice for maintaining effective buffer strips; b) advice in support of NE decision making regarding the prioritisation of management options in ES renewals (e.g. the parameters for renewing buffer strips – including the utilisation of resource protection options other than buffer strips); and c) guidance and advice on optimising the link between resource protection efficiency and biodiversity benefits.

7. (b) Objectives

1. To survey and assess the management of riparian buffer strips in agri-environment schemes for resource protection. To achieve this by:
1.1 Surveying the biodiversity value of riparian buffers.
1.2 Assessing their effectiveness for sediment mitigation including identification of reasons for any poor functioning using tracer technologies and surveying of buffer condition.
1.3 Assessing their effectiveness for phosphorus mitigation by examining P saturation status.

2. To assess the efficacy of alternative sediment mitigation options in the Demonstration Test Catchments. To achieve this by:
2.1 Using tracer technologies to estimate baseline sediment contributions from generic (arable, grass, road verges, channel banks) and high resolution sediment sources (e.g. farm tracks, poached gateways) in target areas.
2.2 Using tracer technologies for repeat sediment source apportionment in target areas to assess the efficacy of the mitigation options installed.

Project Documents
• ROAME Document : WQ01   (200k)
Time-Scale and Cost
From: 2010

To: 2014

Cost: £965,480
Contractor / Funded Organisations
Diffuse Pollution              
Environmental Protection              
Sustainable Farming and Food              
Water Pollution