Guidance on variables characterising water bodies including sustainable flood retention basins.

Climate change is likely to increase the frequency of flood events, thus increasing the associated hazard. This may threaten some existing flood defences, which were designed and built prior to climate change being identified as a major issue; therefore, they may require modification to ensure their sustainability. The European Union recognises that member states may face significant challenges in implementing the Flood Directive and has responded with programs such as the Strategic Alliance for Water Management Actions, which aims to provide tools and guidance to aid the member states in implementation. Flooding is a complex spatial planning issue and therefore requires a range of tools and approaches to solve the problem. Solutions are likely to require sustainable (urban) drainage system (SUDS) solutions applied on a small scale combined with sustainable flood retention basins (SFRB) used on a large scale. This paper aims to provide guidance on 40 variables used to rapidly assess water bodies including SFRB in terms of their flood and diffuse pollution control purposes and potentials. The variables described should be the basis for the characterisation of SFRB, which are adaptive structural measures well integrated within the landscape promoting best management practice as part of a sustainable flood risk management strategy. The variables engineered, outlet arrangement, aquatic animal passage, land animal passage, basin and channel connectivity, seasonal influence, relative total pollution and flotsam cover are novel. The list includes sum parameter such as relative total pollution, which address as part of a simplified methodology several complex environmental processes.