Adapting the Built Environment to Sea Level Rise

Homepage
News
News article

Comment & Analysis

Adapting the Built Environment to Sea Level Rise

With a high-level roundtable on turning ambition into action and achieving the global goal on adaptation, forming part of this year’s COP29 discussion agenda, IMechE policy advisor Chandni Gondria examines the impact of rising sea levels to communities living in at risk areas, and the role of engineers in helping to create equitable solutions.

The IMechE has created a new committee to address the pressing issue of rising seas. If you are interested, please get in touch. Read the IMechEs report on Rising Seas: The Engineering Challenge, written by Dr Tim Fox, for more on this topic.

The year 2023 was characterised by record breaking temperatures, becoming the hottest year on record with global mean surface temperature reaching 1.45°C above preindustrial levels ^[1]. Early data shows the highest on record loss in glacier mass for September 2022 – August 2023, with an average balance of -1.2m of water equivalent ^[2]. This severe loss was primarily due to extreme melting in both western North America and the European Alps, with Switzerland’s glaciers having lost about 10% of their remaining volume over the previous 2 years ^[2]. The loss of glacier mass contributes to sea level rise because when glaciers melt, the melt water flows into the ocean.

Increasing global surface temperatures also plays a role in global mean sea level (GMSL) rise through increasing sea surface temperatures (thermal expansion). When the temperature of water increases, so does its volume, hence sustained periods of thermal expansion can result in accelerated levels of GMSL rise. Over the course of the northern hemisphere summer of 2023, global sea surface temperatures reached a record high of over 21°C^[3]. This period saw the arrival of El Niño conditions, characterised by the warming of the tropical eastern Pacific Oceans surface waters, alongside extreme marine heatwaves in the Mediterranean and record-breaking sea surface temperatures in the North Atlantic.

The rate of GMSL in the past 10 years (2014-2023) has more than doubled since the first decade of satellite records (1993-2002) ^[1]. This rate will continue to accelerate in response to further warming, which alongside changes in storm activity affecting the probability of storm surges, compounds the risk of coastal flooding. Local weather conditions strongly effect how these two factors combine.

UK sea levels have risen by 16cm since the start of the 20th century ^[4]. They are currently estimated to be rising at around 3.6cm per decade ^[5]. In October 2023, when Storm Babet swept through the UK, the Met Office issued two red warnings for rain and multiple severe flood warnings were issued by England’s Environment Agency (EA) and the Scottish Environment Protection Agency ^[6]. Babet left behind thousands of flooded homes and businesses across Scotland, Northern England and the Midlands; 30,000 homes lost power in northern Scotland and seven people were reported to have died as a result of the storm ^[6].

The risk to vital infrastructure

Coastal communities globally are increasingly at risk due to sea level rise and storm surges. Without direct intervention and investment into adaptation, up to 2.6 million people in the UK may be left vulnerable to flooding by 2050 under a 2°C warming scenario ^[7]. As GMSL accelerates, the risk of coastal flood and in some instances physical erosion of infrastructure, including for example energy, transport, and water and wastewater services, will increase ^[8]. Despite recent improvements in flood defences, forecasting, warning and emergency response, many assets in low-lying coastal areas remain vulnerable to damage in the event of a defence failure ^[9]. Across the UK 22 clean water facilities, 34 electric substations, 35 power stations and 91 sewage treatment works have been identified as being located in coastal areas at significant risk of flooding ^[8]. At even greater risk is coastal transport infrastructure, including 25 rail stations and 511km of track line, as it is a more difficult asset to protect in its entirety ^[8].

Infrastructure is increasingly interconnected, meaning failures to one asset can spread both within and across sectors. For every household impacted by a major flood, about 16 people suffer knock on effects from utility service disruption^[10]. Calls to protect vital infrastructure from coastal flooding and erosion by the UK’s Climate Change Committee (CCC) and the IMechE in 2019 remain a priority ^[11][12]. The CCC urged that the design and location of new infrastructure account for increased risk of flooding ^[11], which IMechE echoed, adding that it made good economic sense to also ensure that worst-case projections of GMSL are taken into account at the infrastructure design stage^[12]. Given the often long lifetimes of infrastructure assets (in excess of 100 years), adaptation that considers long term changes in the context of the most extreme future emissions pathways, resulting in a 2-4°C global temperature increase, are particularly important for infrastructure planning ^[11].

The engineering solutions

Coastal management strategies across the UK to adapt to sea level rise date as far back as the late 20^th century. Sections of the Poole Quay Sea Wall for example were reinforced in the early 1980s, whilst other sections of the quay remain a much older masonry construction^[13]. Alongside seawalls, other common physically engineered adaptation methods include levees and flood barriers, protecting people and vital infrastructure from coastal flooding. The UK, alongside EU counterparts, have also started to integrate sea level rise margins into infrastructure standards and building codes. The UK specifically has allowances for climate safety margins for sea level rise contained in planning regulation and guidance for engineers ^[14]. It must be stressed though that hard engineering solutions such as sea walls often lead to increased urban development resulting in potential increased flood damage if a defence is being breached, a phenomenon referred to as the Safe Development Paradox ^[15].

The electricity sector has a well-developed understanding of risks faced by coastal flooding, with planned actions by electricity supply, transmission and distribution companies expected to see over 90% of substations deemed at risk of flooding become resilient to 1 in 1000-year flood events ^[8]. The majority of the UKs nuclear power generation plants are located on the coast and are therefore required to meet 1 in 10,000-year flood protection standards ^[8]. Coastal rail infrastructure is also being adapted, with projects such as the reengineering of the Dawlish Sea Wall on the London-Penzance line ^[16]. Flood risks are also being managed through policies like Shoreline Management Plans developed by the EA for the coasts of England, and Flood and Coastal Erosion Risk Management (FCERM) strategies, also developed by the EA with a focus on both English coastal and inland areas. Similar policies have also been set up for the devolved nations by The Scottish Environment Protection Agency, Natural Resources Wales and The Department for Infrastructure in Northern Ireland, each tailoring its approach to suit local conditions and needs. However, more work is needed to ensure the effective delivery of all. While infrastructure owners are taking action, it remains unclear if current investments are enough to maintain today's risk levels ^[8].

Nature-based solutions should not be overlooked, with many countries turning to nature to help hold back sea water. Cities across China, Vietnam and India are adopting a ‘sponge city’ strategy, ensuring urban land can absorb or reuse flood water ^[17]. Nature positive solutions must also become more widely used. These are solutions that go beyond simply using natural processes and ecosystems as an adaptation to sea level rise, as with nature-based solutions, and instead actively lead to a net gain in biodiversity and ecosystem health. In September 2023, the Nature Positive Initiative was launched ^[18], a global societal goal to halt and reverse nature loss by 2030 on a 2020 baseline and achieve full recovery by 2050. Some nations have already started to adopt nature positive solutions. In the Netherlands, saltwater marshes are being created to help break storm waves, and tidal marshes are being restored around San Fransisco Bay in the US ^[17]. Restoring coastal wetlands, such as marshes and mangroves, can reduce impacts of storm surges and enhance costal resilience whilst also supporting marine biodiversity through providing habitats for wildlife and improving water quality.

It’s important that solutions developed by engineers are both inclusive and equitable for vulnerable communities. The FCERM strategies developed by the EA have built in requirements that encourage all Risk Management Authorities in England involved in flood and coastal risk management to ensure a greater focus is put into providing timely and quality planning advice ^[19]. This will help better manage infrastructure development in areas at risk of coastal flooding. They also aim to ensure that spending on coastal resilience contributes to job creation and sustainable growth in local places ^[16].

The engineers themselves

The question arises of how we can prepare engineers to develop these solutions along with other new innovative approaches. The IMechE ^[12] stressed the importance of ensuring that basic working knowledge of rising seas, climate change impacts, future coastal flooding risks, adaptation measures and resilient sustainable design is provided across all engineering disciplines. The Institution encouraged The UK’s Engineering Council and our sister professional engineering institutions to ensure these topics are embedded in engineering courses. In early 2024, The Engineering Professors Councils, a UK wide body, launched a sustainability toolkit ^[20]. The toolkit is designed to help engineering educators integrate sustainability into teaching, including a local scale flood warning system project ^[21]. Beyond this, engineering needs to attract more diverse talent and make education and training more accessible and responsive. Part-time and e-learning options, like those offered by Brunel University's Centre for Flood Risk and Resilience, can help develop the diverse skills needed for effective flood risk research ^[22].

Collaboration is key

Global temperatures are rising and whilst the risk of coastal flooding is a growing global issue, it is most often a risk that is addressed locally. The UK has, and will continue to, experience an accelerated rate of sea level rise. To best increase capacity for people and infrastructure to be flood resilient, integrated thinking and a broad range of cross-sector and cross-discipline collaboration within and beyond the engineering community is required.

Panellists part of this year’s COP29 high-level roundtable on adaptation will discuss the obstacles and opportunities in advancing the progress towards achieving the Global Goal on Adaptation, and in ensuring an effective implementation of National Adaptation Plans. Effective adaptation solutions to sea level rise must consider the needs and views of industry, government, communities and other stakeholders. Solutions should also combine local case studies and problem-solving with social, scientific and engineering approaches to reduce and mitigate coastal flood risk, in turn enhancing societal resilience to the impacts and hazards associated with global sea level rise

Don’t miss the opportunity to be part of the conversation at our 2nd International Conference on Climate Change Adaptation and Resilience, held at One Birdcage Walk on October 14-15, 2025. Stay tuned for more details, and mark your calendar to join leaders and experts in shaping a resilient future.