Realising the potential of natural water retention measures in catchment flood management: trade‐offs and matching interests

Abstract

Natural water retention measures (NWRM) are a multifunctional form of green infrastructure that can play an important role in catchment‐scale flood risk management. While green infrastructure based on natural processes is increasingly recognised as being complementary to traditional flood control strategies based on grey infrastructure in urban areas, there are a number of outstanding challenges with their widespread uptake. At a catchment scale, it is widely accepted that NWRM in upstream areas based on the concept of ‘keeping the rain where it falls’ can help reduce the risk of downstream flooding by enhancing or restoring natural hydrological processes including interception, evapotranspiration, infiltration, and ponding. However, both the magnitude of flood risk reduction and the institutional structures needed for widespread uptake of NWRM are inadequately understood. Implementing NWRM can involve trade‐offs, especially in agricultural areas. Measures based on drainage management and short rotation forestry may help ‘keep the rain where it falls’ but can result in foregone farm income. To identify situations where the implementation of NWRM may be warranted, an improved understanding of the likely reductions in downstream urban flood risk, the required institutional structures for risk management and transfer, and mutually acceptable farm compensation schemes are all needed.

Natural Flood Management: Beyond the evidence debate

“…As illustrated, cross-sectoral scope does not fit neatly into existing working patterns and governance mechanisms (Rouillard et al, 2013). Accordingly, NFM and the WFD are identical (Collentine & Futter, 2016) and require coordinated action of the same sectors to manage water and land as one system.…”

“…Annual flood losses in the European Union are projected to be c .€23.5 billion by 2050, increased from €4.9 billion between 2000 and 2012 (Jongman et al., ). Traditional flood protection methods of large engineered structures are costly to construct, expensive to maintain and linked to poor water and ecological quality (Collentine & Futter, ; Thorne, ). Policy makers and scientists are increasingly interested in natural landscape retention and storage capacity as a complementary flood risk technique (Ran & Nedovic‐Budic, ) used alongside traditional hard‐engineering flood defence approaches (Pitt, ; Rouillard et al., ; Waylen et al., ).…”

Land for flood risk management: A catchment‐wide and cross‐disciplinary perspective

“…Recently, so‐called natural water retention measures (NWRMs) and nature‐based solutions (NBSs; cf. Schanze, ) are put in the fore, such as reforestation or adapted agricultural land management (see Collentine & Futter, this issue). These measures can also support other ecosystem services, such as groundwater recharge, biodiversity conservation, or aspects supporting recreation.…”

“…Optimisation and implementation of the three options of risk reduction related to land, risk management, and land governance necessitates respecting site‐specific interests and property rights at the plot scale while ensuring consistency on the catchment scale. Collentine and Futter (this issue) explore NWRMs as decentralised flood retention. Inventing proper compensation schemes is one of the key items that comes to the fore from their analysis, next to the conclusion that this involves multiple trade‐offs.…”

Assessment of the flood hazard arising from land use change in a forested catchment in northern Iran

“…However, the flood risk is perceived to be sufficiently high that the potential economic gains from increased tourism may not be fully realised if appropriate (e.g., catchment specific) flood reduction strategies are not implemented and seen to be effective. Such strategies may include so‐called grey infrastructure (i.e., traditionally engineered structures such as dams or bypass channels) or green infrastructure (i.e., “natural” flood risk management) including “natural water retention measures” (NWRMs) (Collentine & Futter, ; Hartmann, Jílková, & Schanze, ). Furthermore, the general context of natural population growth, climate change and—historically at least—significant deforestation, together mean that assessments of potential flood magnitudes and probabilities need to be easily made and updated so as to inform local flood risk management strategies.…”