The removal of dams, weirs or barriers to river flow, is frequently a contentious issue. This is because of the competing demands of flood protection and the ecological, social, economic and cultural health of the river. Many of the barriers are old or obsolete and there is an international drive to create ‘free-flowing rivers’ with no or fewer barriers, thereby increasing longitudinal connectivity. This has been most noticeable in North America and continental Europe, and less apparent in the UK. We explore the issues around weir removal with a case study of a lowland southern English river, the River Rother, West Sussex, in a predominantly agricultural catchment where weirs have been constructed for a variety of purposes over the last ~1000 years. The river is dominated by inputs of sand-sized sediment with very low organic matter content that is frequently stored upstream of structures. The multiplicity of stakeholders and the strong interests of the fishing and farming communities render decision-making about structure removal or modification to improve fish passage difficult. There is also the demand for potable water abstraction by the local water company which would be affected by dam removal and the potential release of the fine (mostly < 2mm dia.) sediments stored immediately upstream of the weirs. This paper subsequently explores selected issues around weir removal under the requirement of the European Water Framework Directive to achieve Good Ecological Status and explores guidance on best practice; including the decision which weirs to remove and in which order.

Channel banks can contribute a significant proportion of fine-grained (<63 µm) sediment to rivers, thereby also contributing to riverine total particulate phosphorus loads. Improving water quality through better agricultural practices alone can be difficult since the contributions from non-agricultural sources, including channel banks, can generate a ‘spatial mismatch’ between the efficacy of best management applied on farms and the likelihood of meeting environmental objectives. Our study undertook a reconnaissance survey (n=76 sites each with 3 profiles sampled) to determine the total phosphorus (TP) concentrations of channel banks across England and to determine if TP content can be predicted using readily accessible secondary data. TP concentrations adjacent field topsoils and local soil soil type/texture and geological parent material were examined as potential predictors of bank TP. Carbon and nitrogen content were also analysed to explore the impacts of organic matter content on measured TP concentrations. The results suggest that channel bank TP concentrations are primarily controlled by parent material rather than adjacent topsoils, but significant local variability in concentrations prevents the prediction of bank TP content using mapped soil type or geology. A median TP concentration of 873 mg kg -1 was calculated for the middle section of the sampled channel bank profiles, with a 25 th percentile of 675 mg kg -1, and 75 th percentile of 1159 mg kg -1. Using these concentrations and, in comparison with previously published estimates, the estimated number of inland WFD waterbodies in England for which channel bank erosion contributes >20% of the riverine total PP load increased from 15 to 25 (corresponding range of 17 to 35 using the 25 th and 75 th percentiles of measured TP concentrations). Collectively, these 25 waterbodies account for 0.2% of the total inland WFD waterbody area comprising England.