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In this paper, nature‐based solutions (NBS) include: (1) natural flood management (NFM) interventions with a primary function of flood risk reduction but with additional multiple benefits for water quality improvements through the mitigation of diffuse pollution; and (2) ponds with a primary function of water quality improvement. This study assesses the ability of these NBS to trap pollutants in run‐off within two small (3.4 km2) agricultural catchments (Upper Thames, UK). The masses of sediment, phosphorus, and organic carbon trapped by 14 features (since construction 2–3 years previously) were quantified through sediment surveying and sampling. Streamflow and suspended sediment monitoring downstream of features enabled catchment yields to be calculated. The features trapped a total of 83 t sediment, 122 kg phosphorus, and 4.3 t organic carbon. Although the footprint of the features was <1% of the catchment area, they drained 44% of the total land area and captured the equivalent of 15% of the total suspended sediment yield, 10% of the total phosphorus yield, and 8% of the particulate organic carbon yield as monitored at the catchment outlet over the monitoring period. Results reveal that accumulation rates were influenced by hydrological connectivity, with greater accumulation in features constructed directly on streams (online ponds), and those offline features that filled from overbank flows. The low to moderate accumulation rates observed in offline features suggests that their floodwater storage potential is only likely to significantly reduce in the medium term, necessitating maintenance after ~10 years. Compared with topsoil in each contributing area, trapped sediment was enriched in phosphorus and carbon in the majority of features, having on average 50% higher phosphorus and 17% higher organic carbon concentrations than surrounding arable soils, highlighting its potential value for redistribution on farmland. Monitoring results demonstrate the potential of NBS, including NFM, to mitigate diffuse pollution in lowland catchments. [ABSTRACT FROM AUTHOR]

Adapting to climate change and its impacts on water resources is one of the major challenges facing the UK. In the first scheme of its kind in the Thames basin, this paper describes how natural flood management (NFM) is being piloted in the Littlestock Brook tributary of the Evenlode catchment. This 5-year scheme (2016–2021) explores the delivery mechanisms and assesses the effectiveness of NFM measures to reduce flood risk in Milton-under-Wychwood, improve water quality and create habitat. It has secured £640 000 from Environment Agency programmes, the Thames Regional Flood and Coastal Committee, other partners and landowners. In 2018, ten field corner bunds were created with a combined storage capacity of 26 000 m3. Woody dams in the brook divert high flows into these flood storage areas. Critical to success is integrated delivery through the Evenlode Catchment Partnership and engagement of the local community. Catchment partnerships deliver a range of environmental, social and economic benefits, and directly support many of the ambitions under the government's 25-Year Environment Plan and the Water Framework Directive. Collaborative working with Thames Water, the Department for Environment, Food and Rural Affairs, consultants and academics has enabled the project to utilise existing delivery mechanisms and to model and monitor the effectiveness of NFM. [ABSTRACT FROM AUTHOR]