Nature-based flood and drought resilience

DOI: https://doi.org/10.58248/PN768

Climate change is projected to lead to more high‑intensity rainfall and extended dry periods across the UK, increasing risks of flooding and droughts.

The Environment Agency describe nature‑based solutions as actions that work with nature to address societal and environmental challenges. Actions can re-establish natural processes that increase resilience to flood and drought, such as tree planting, wooden leaky dams, and/or flood storage areas. These aim to temporarily store overland run-off and slow flows through the river system, while also providing other benefits including to nature.

The government has identified flood and drought resilience as a strategic priority.

How can nature-based solutions help flood and drought resilience?

The International Union for the Conservation of Nature have defined and set standards for nature‑based solutions: “actions to protect, sustainably manage and restore natural and modified ecosystems in ways that address societal challenges effectively and adaptively, to provide both human well-being and biodiversity benefits”. Contributors noted that defining nature‑based solutions more holistically may help align environmental and societal outcomes.

Nature-based solutions for water management set out in studies include:

• peatland restoration

• wetland restoration

• tree planting

• land and soil management

• flood storage areas (field corner bunds)

• floodplain reconnection

The studies suggest these can slow surface runoff, enhance water absorption by the soil, and increase natural water storage. During rainfall, these measures may help reduce peak river flows. In dry periods, they may help retain moisture in the soil and help groundwater stores recharge faster.

Natural flood management measures such as wooden leaky dams are considered a subset of nature‑based solutions that focus specifically on reducing flood risk, by temporarily storing overland run-off and slowing flows to alter the timing and movement of water through the catchment.

Contributors to this POSTnote said that the effect of these interventions depends on their scale (whether they apply to just one part of a water catchment or whether they are designed across the whole catchment) and placement. Whether an intervention reduces total flood volume or just slows the movement of water can depend on soil type, land management practices, and existing drainage systems.

Examples from UK projects illustrate these dynamics. The Wendling Beck project in Norfolk restored around 800 hectares of arable land to biodiverse habitat, resulting in slower runoff, improved water retention, and reduced nutrient and sediment inputs to watercourses.

Most projects have been implemented on an ad hoc site by site basis to provide benefits, but more holistic approaches could increase the capacity to retain water at the catchment scale to support both flood and drought management outcomes. Catchment‑scale programmes in the Scottish Borders, the Severn Valley, Holnicote, and Eden catchments combine multiple nature‑based solutions to increase storage across uplands, floodplains, and river channels.

Nature‑based solutions may include interventions that support wider ecological functions which in turn may improve biodiversity and water quality. However, studies have described how nature‑based solutions can have negative effects for human wellbeing. Contributors stated most such effects would arise from how nature-based solutions interact with existing land uses, such as farming and infrastructure (for example, roads and bridges), as well as community priorities.

What are the difficulties in implementing nature-based interventions?

Funding

Contributors to this POSTnote said funding was a persistent barrier to implementing nature‑based solutions at the scale and time needed to properly mitigate flooding and droughts. They described current arrangements as short term and fragmented across organisations, making it difficult to maintain interventions over the extended periods required under changing climate conditions. This also made it difficult to assess how well they were working.

Monitoring performance

They said that monitoring the performance of interventions was essential but challenging. This could be because interventions are dispersed, because they are on private land (which can make it more difficult to access), or because there was no baseline data before the intervention to determine the effectiveness.

Without long‑term monitoring, contributors argued it can be difficult to assess whether an intervention is working or to adjust it in response to changes in the climate or in land‑use. Some contributors stated this represented a contradiction since more and larger projects are needed to generate evidence, but without that, evidence funders may not be confident enough to begin large projects.

Effects on inequalities

They also discussed the need to consider effects on social and environmental inequalities. Urban areas may be at greater risk of flooding, but they have less available land for nature‑based solutions.

Most projects are established in less deprived urban and rural areas, and not necessarily in the best place across a catchment for these solutions. This may potentially reinforce existing social and environmental inequalities.

Public opinion

Contributors suggested that there could be public opposition to these interventions if the benefits and uncertainties of them are not clearly communicated. They said ensuring all parties can feed in to how a project is delivered, may better capture diverse perspectives and concerns than top-down communication alone, which could increase public acceptance.

They indicated communication strategies may need to acknowledge that, in some cases, communities trust engineered (grey) infrastructure (such as flood walls) to address flood and drought risks more than nature-based interventions. Better communication could encourage more people and organisations to participate in nature-based solutions, such as by volunteering to collect local data, and improve public understanding of the effects of nature‑based solutions.

Geographic scope and policy context

This POSTnote summarises the challenges and opportunities for using nature-based solutions to address flood and drought in England, but many of the challenges, the opportunities, the science, and the evidence pertain to the whole UK. Environment policy is devolved, with differences in how nature-based solutions are governed and implemented between UK nations.

Acknowledgements

This briefing was produced in consultation with experts and stakeholders, who are listed at the end of the briefing. POST would like to thank everyone who contributed their expertise to this briefing.