This report is an annex to the Natural England commissioned report Enhanced Drainage Ditch Management: A framework approach for nutrient neutrality. The annex details a literature review that was used to set the evidence base for the Enhanced Drainage Ditch Management Framework.
The literature review used a literature search using an academic literature search engine. Search terms were refined to capture all available literature on drainage ditch management using ‘Best Management Practices’ (BMPs), resulting in a set of studies for analysis that detailed results from studies of two-stage ditches, vegetated ditches and low-grade weirs. The studies were reviewed to determine the key mechanisms that can result in nutrient reductions due to the use of BMPs within a drainage ditch or small watercourse.
Data on the nutrient reduction potential of these BMPs were extracted from each study and analysed to determine precautionary nutrient reduction efficiency for a ditch managed with a combination of the three BMPs listed above. This reduction efficiency is suggested for use in the Framework to support the deployment of Enhanced Drainage Ditch Management schemes for nutrient neutrality.
The review also assessed key design factors for drainage ditch management nutrient mitigation schemes and used this assessment to recommend a process for designing ditch management schemes in manner that should increase the probability of achieving nutrient reductions.