Floodplain importance in Building Resilience Against Natural Disasters

The UK’s Environment Agency is responsible for protecting the environment and promoting sustainable development. Their website provides a wealth of information on floodplains, including how they can be managed to reduce the impact of flooding. This post highlights the critical role of floodplains in natural disaster resilience and how the UK is harnessing its potential to benefit both people and the environment.

Types

In the United Kingdom, floodplains can be categorised as either functional or inactive, depending on their purpose and characteristics.

Functional Floodplains

Functional floodplains refer to tracts of land alongside rivers and serve as natural buffers that can absorb floodwater during periods of high water flow, mitigating the risk of downstream flooding. In the UK, these areas are crucial components of flood risk management, as they offer a passive approach to flood control that can help protect communities and infrastructure from the catastrophic impacts of flooding. In the UK, these areas usually store the 1 in 30 storm events or flood zone 3b. In surface water management, these areas are a very high flood risk.  

Inactive Floodplains

Those floodplains disconnected from rivers by human intervention or natural processes can no longer function as flood storage areas, called inactive floodplains. Although these areas may still have ecological significance, they are not considered part of the active floodplain system.

Floodplains Formation

The formation of floodplains in the UK is a natural process influenced by erosion, sediment movement, and deposition. River channels experience constant erosion, leading to meandering and changes in course. Over time, the riverbanks erode, and sediment deposits accumulate in bends, forming natural levees.

When the river experiences a surge in water flow, it surpasses its bank and submerges the neighbouring low-lying regions. The floodwater transports sediment and organic matter accumulated on the floodplain as the water retreats. As time passes, this alternating deposition and erosion procedure creates a rich floodplain that can effectively absorb and hold surplus water during high water flow.

Importance of Floodplains as Natural Systems

The significance of floodplains to the UK’s environment cannot be overstated. They provide a range of ecological and socio-economic benefits, including flood management, biodiversity conservation, and recreational opportunities.

Here are some of the benefits of the floodplain from the vast list of advantages:

• As natural water reservoirs, floodplains collect and retain excess water during high-flow periods, significantly reducing the likelihood of downstream flooding and protecting adjacent communities.
• The diverse ecosystems found in floodplains, including wetlands, meadows, and riparian forests, are essential for preserving biodiversity and providing wildlife with vital resources such as breeding sites, food, and shelter, supporting healthy ecosystem function.
• they act as natural filters by effectively removing harmful substances and sediment from stormwater, protecting freshwater sources and aquatic habitats while purifying water.

Ecological benefits

Wildlife habitat

Some of the wildlife habitats of the floodplain are:

• Wetlands: Floodplain wetlands, comprising marshes, swamps, and fens, offer critical ecosystems for various plant and animal species, many of which are endangered. These valuable wetlands also serve as vital breeding grounds for numerous bird species, including the elusive bittern and graceful marsh harrier.
• Riparian forests: They offer a thriving environment for riparian forests to grow, creating essential ecosystems along riverbanks. These forests provide a home to diverse fauna, including avian, mammalian, reptilian, and amphibian species. 
• Meanders and oxbows: As time passes, rivers naturally shift their course, forming distinctive U-shaped meanders and oxbows in the surrounding floodplains. These natural formations are critical in supporting diverse aquatic species, including fish, amphibians, and invertebrates, by providing essential habitats and shelter.
• Fish spawning grounds: Floodplains play a vital role in the life cycle of several fish species, including salmon and trout. These aquatic creatures choose gravel beds in water bodies to lay their eggs. They provide the perfect setting for their nourishment and maturation due to their spacious and well-flowing conditions.
• Providing sediment trapping: As floodwaters flow across the land, they decelerate and trap sediments and pollutants within the floodplain. This natural filtration process shields against hazardous contaminants, shielding watercourses from damage and protecting aquatic habitats.

Water filtration

The floodplains of the UK play a critical role in filtering water as it travels across the terrain. A range of techniques can be employed to facilitate this process, including:

• Increasing infiltration rates: They are crucial in enhancing water infiltration into the soil by maintaining high soil moisture content. This mechanism allows the soil to absorb and purify more water effectively, thereby reducing the runoff that ultimately ends up in rivers and streams.
• Groundwater recharge: As floodwater permeates the floodplains’ soil, it helps recharge the underground water resources. Groundwater reserves are essential to support ecosystems, serving as a primary drinking source for wildlife and human inhabitants.
• Providing sediment trapping: As floodwaters flow across the land, they decelerate and trap sediments and pollutants within the floodplain. This natural filtration process shields against hazardous contaminants, shielding watercourses from damage and protecting aquatic habitats.

Water filtration

The floodplains of the UK play a critical role in filtering water as it travels across the terrain. A range of techniques can be employed to facilitate this process, including:

• Increasing infiltration rates: They are crucial in enhancing water infiltration into the soil by maintaining high soil moisture content. This mechanism allows the soil to absorb and purify more water effectively, thereby reducing the runoff that ultimately ends up in rivers and streams.
• Groundwater recharge: As floodwater permeates the floodplains’ soil, it helps recharge the underground water resources. Groundwater reserves are essential to support ecosystems, serving as a primary drinking source for wildlife and human inhabitants.

Increased Frequency and Intensity of Floods

Climate change is predicted to significantly impact UK floodplains, with increased flood frequency and intensity being among the most significant.

• According to UK Climate Projections, there is a high degree of certainty that intense and frequent rainfall events will become more common, resulting in higher flood risk throughout the country.
• Floodplain ecosystems are likely to be significantly affected by these changes, with altered water quality, sediment transport, and habitat suitability being among the impacts.
• The higher frequency and severity of floods caused by climate change could exacerbate existing flood risks and potentially have far-reaching consequences for floodplain biodiversity and ecosystem services.

Erosion and Sedimentation

Climate change will significantly impact the UK’s floodplains, with erosion and sedimentation expected to increase due to rising temperatures and shifting rainfall patterns. 

Some of the impacts are:

• Soil fertility and productivity decline due to erosion and nutrient depletion, reducing crop yields and increasing land degradation.
• Infrastructure, including roads and bridges, may suffer significant harm from erosion, sedimentation, and landslides, resulting in costly repairs and maintenance.
• The increased sedimentation of downstream waterways can have severe consequences for aquatic ecosystems and water quality, including changes in the nutrient and oxygen levels, the composition of marine flora and fauna, and the overall health of the aquatic ecosystem.

Habitat Loss and Fragmentation

Climate change can trigger various impacts that contribute to habitat loss and fragmentation. These impacts include:

• More frequent and severe floods can cause river banks to erode, leading to the loss of vegetation. As a result, floodplain habitats suffer a decline in both quality and availability, impacting species that depend on them.
• Changes in precipitation patterns and water availability directly impact the timing and duration of floods. This, in turn, can affect floodplain-dependent species’ breeding and feeding activities and their ability to thrive.
• Sea-level rise poses a significant threat to coastal floodplains, making them increasingly vulnerable to saltwater intrusion and habitat loss. Additionally, it can also heighten the flood risk faced by communities living in coastal areas.

Impacts on Biodiversity

Some of the climate change effects on biodiversity are

• The escalation in flood frequency and severity caused by climate change threatens to harm floodplain habitats, disrupting natural processes vital for biodiversity. This may result in altering plant and animal communities and losing species prone to flooding.
• Moreover, climate change magnifies other stressors such as habitat loss, fragmentation, invasive species, and pollution, lowering the resilience of floodplain ecosystems and increasing their susceptibility to further disturbances.

Conflicts with Urban Development and Land Use

One of the significant challenges facing floodplains in the UK is the conflict between urban development and land use. As cities and towns expand, there is increasing pressure to develop floodplain areas for residential, commercial, and industrial purposes. However, this can lead to a range of negative impacts, including:

• Increased flood risk: Development in floodplains can increase the number of impermeable surfaces, reducing the land’s ability to absorb and store water. This can increase the risk of flooding downstream and exacerbate the impacts of extreme weather events.
• Habitat loss: They are home to various unique and valuable ecosystems, including wetlands, riparian forests, and floodplain meadows. Development in these areas can lead to habitat loss and biodiversity, affecting wildlife and ecosystem services.
• Water quality degradation: Development in floodplains can lead to increased pollution and runoff, degrading water quality and harming aquatic ecosystems downstream.

However, there are also opportunities for balancing urban development with floodplain management, such as using green infrastructure to promote sustainable development in floodplain areas. This requires a collaborative and integrated approach involving stakeholders from various sectors to ensure that floodplain areas are managed sustainably and resiliently.

Community Engagement and Social Resilience

Community engagement and social resilience are critical components of successful floodplain management in the UK. Effective engagement with local communities can help to build trust, increase awareness of flood risk, and promote the uptake of measures that can improve resilience.

However, community engagement also presents several challenges, including limited resources, competing priorities, and a need for understanding and interest in flood risk. To overcome these challenges, it is crucial to develop tailored engagement strategies that are responsive to the needs and concerns of local communities.

Engagement should also be part of a broader approach to social resilience, which involves building the capacity of individuals, communities, and institutions to cope with and adapt to the impacts of flooding. This can involve a range of measures, such as improving communication and information-sharing, enhancing social networks and community cohesion, and providing access to resources and support.

Flood and Water Management Act 2010

The Flood and Water Management Act 2010 contains provisions to bolster planning policies to protect floodplains and riparian zones in the UK. Some of the critical measures are:

• National planning policy statements: The Act mandates the issuance of national planning policy statements that outline the development policy framework for flood risk areas, including guidance on considering flood risk and designing flood-resilient developments that protect riparian land and floodplains.
• Local flood risk management strategies: Local authorities must prepare local flood risk management strategies that account for the role of riparian land and floodplains in reducing flood risk and how to design developments to avoid or mitigate flood risk.
• Sustainable drainage systems: The Act encourages using sustainable drainage systems (SuDS) in new developments to reduce the impact on flood risk and mimic natural drainage processes that protect riparian land and floodplains.

National Planning Policy Framework (NPPF)

The UK government’s National Planning Policy Framework (NPPF) sets out a comprehensive framework for planning decisions nationwide. The NPPF contains targeted policies for restoring functional floodplains, prioritising sustainable development, and mitigating flood risk.

• Policy 14 & 16: Effective planning decisions prioritise preserving and enhancing the natural environment, such as protecting and promoting biodiversity and recognising the vital role of functional floodplains in mitigating flood hazards. It is imperative to prohibit development activities in areas prone to high flood risks to prevent severe damage and losses.

Flood Risk Regulations 2009

Flood risk management plans must explore using floodplains for retention in compliance with Flood Risk Regulations 2009.

• Assessing floodplains’ potential for retention and downstream risk reduction is vital to develop a comprehensive flood risk management strategy.
• A thorough evaluation of floodplains’ benefits, drawbacks, and associated risks to people, property, and the environment is necessary.
• Collaboration with local authorities, environmental organisations, and the public is crucial to integrate local insights and concerns.
• The strategy must outline measures for managing flood risk, including using floodplains to ensure the effectiveness and sustainability of the approach.

Effective management of floodplains requires thoughtful planning, considering various factors such as climate change, and balancing competing land-use demands. A collaborative and comprehensive approach to floodplain management will guarantee that these valuable ecosystems continue to benefit future generations.