Integrated lowland catchment management: working with natural processes to meet the needs of multiple stakeholders

Natural Flood Management (NFM) interventions include a multitude of measures that mitigate flooding by restoring or enhancing natural processes. Processes include slowing flows, storing water; increasing floodplain roughness and increasing soil infiltration. In addition to mitigating flooding they are likely to have important impacts on water quality. For example, increasing soil infiltration may reduce pesticide and nutrient runoff, slowing river flows may increase instream algal growth and nutrient processing, increasing floodplain roughness (with trees) may result in more river shading (reducing algal growth and cooling rivers), and increasing floodplain connectivity may enhance the deposition of sediments. Thames Water have a strong interest in catchment based interventions which bring together key stakeholders to maintain and seek to improve natural catchment functions of flow attenuation (securing water supply; mitigating low flow issues) and pollution amelioration (reducing treatment costs and mitigating environmental impacts). They are promoting this approach through catchment trials and future investment is dependent on robust cost-benefit evidence. Given that the effectiveness of such measures on both mitigating floods and their impacts on water quality are poorly understood there is an urgent need for this research.