Transatlantic collaboration aims to boost resilience of sea walls

Waves crashing against a sea wall (image credit: Ray-Bilcliff, available on Pexels)

A seemingly pioneering research project that aims to strengthen the resilience of sea walls to increased coastal flooding has been launched by Heriot-Watt University in Edinburgh and Virginia Tech in Blacksburg, Virginia.

The PIONEER project has been funded by the Engineering and Physical Sciences Research Council (EPSRC) and hopes to be the first step in an international collaboration to strengthen coastal sea defences globally.

Around 148 million people worldwide are exposed to coastal flooding events, which are predicted to surge in frequency and severity in the coming decades as climate change drives sea levels higher.

The research being conducted by Heriot-Watt and Virginia Tech will investigate how the soil behind sea walls is impacted by repeated wetting and drying cycles over time from waves overtopping the sea walls. It’s hoped this will highlight areas where the design and resilience of sea walls could be strengthened.

Dr Melis Sütman, an Assistant Professor in Geotechnical Engineering at Heriot-Watt’s School of Energy, Geoscience, Infrastructure and Society, said: “The sea level around the UK has already risen by around 1.5 millimetres a year on average from the start of the 20th century. And even in the best case climate change scenario, the sea level will continue to rise. So our coastal defence structures will be of paramount importance to defend our shorelines – not only for the UK, but also for the United States on the other side of the Atlantic.”

Under a low emissions scenario, by the year 2300, the sea level for London and Cardiff is predicted to rise between 0.5 metres and 2.2 metres and up to 1.7 metres for Edinburgh and Belfast. Under a high emissions scenario, this increases to between 1.4 metres and 4.3 metres for London and Cardiff, and between 0.7 metres and 3.6 metres for Edinburgh and Belfast.

In the US, the coastal sea level by 2050 is predicted to be between 0.25- 0.30 meters higher than in 2020 – and as much as the rise measured over the last 100 years before that, from 1920 to 2020.

“According to the Intergovernmental Panel on Climate Change, unavoidable sea level rise will bring cascading and compounding impacts resulting in flooding and damage to coastal infrastructure that cascades into risks to livelihoods, settlements, health, well-being, food, and water security in the near to long-term,” Dr Sütman said.

She added that rising sea level also has strong economic consequences. For example, the investment needed to protect London is expected to exceed £20 billion. And at Staten Island in New York City, $165 million is being invested to build an 8.5 km seawall along the coastline to build resilience to sea level rise and extreme events.

PIONEER stands for ‘An adaPtatIon apprOach for resilieNt coastal infrastructurE against sEa level Rise’ and is being funded through an EPSRC Early career researcher international collaboration grant. EPSRC is part of UK Research and Innovation – the UK’s national funding agency for investing in science and research.

The research will involve testing wave overtopping scenarios on interfaces that mimic the interaction between sea walls and the backfill soils. At Heriot-Watt, tests will take place in the lab on a small-scale device that the University says it has developed as a world first. This is called a thermo-hydro-mechanical direct shear interface device, and it allows numerous scenarios to be tested and measured. This includes, for example, different water contents, overtopping frequencies and lengths and different properties of the both the soil behind the wall and the wall itself.

“It means that we can create a soil and structure interface – or a concrete interface – in the lab in the size of 60 by 60 millimetres, so very small,” Dr Sütman explained. “And we can apply almost every possible temperature and water content change to this interface. Because this is a small-scale device, the setup is easier – and it’s cheaper – so we’ll be able to investigate many different parameters in a relatively short amount of time.”

Virginia Tech will then conduct its set of experiments on a full-sized wall that is 5 metres in height.

Dr Sherif Abdelaziz, Associate Professor of Geotechnical Engineering at the Charles E Via, Jr. Department of Civil and Environmental Engineering at Virginia Tech, said: “Our large-scale tests will investigate how the soil and wall are affected by different levels of temperature, suction, water pressure and other parameters. Heriot-Watt will then perform additional lab-scale tests to investigate the conditions we record at full-scale. So our investigations on each side of the Atlantic will very much go hand-in-hand.”

PIONEER’s Advisory Board features world-renowned experts from both academia and industry. These include Advisory Board Chair Professor Paul Jowitt, who is the former President of the Institute of Civil Engineers in the UK. Also on the UK Advisory Board is Professor Lindsay Beevers from the University of Edinburgh, who is an expert in hydrological extremes – extreme water-related events such as floods. Professor Beevers is developing numerical models to understand and quantify these events, their future evolution and associated impacts on society and the environment. In the US, Advisory Board members include Prof Thomas Brandon, Professor of Geotechnical Engineering at Virginia Tech. Prof Brandon works with the US Army Corps of Engineers (USACE) to investigate multiple breaches in floodwalls, as a member of the Interagency Performance Evaluation Task Force. This was set up after Hurricane Katrina devastated the southeastern coast of the United States in August 2005.

Also involved in the project is US infrastructure consulting firm AECOM, whose offices in both the UK and US will help to share the research results and apply them in practice. And in the UK, William Allsop Consulting, who are experts in seawall design, including most seawall developments in the UK, will be consulted to advise on the practical implications, and plan the next stages of PIONEER.

Dr Sütman is a Turkish civil engineer who has an MSc and a PhD degree in Geotechnical Engineering from Virginia Tech. Geotechnical Engineering is a branch of civil engineering focused on how man-made structures interact with the ground – for example, tunnels, metro lines and building foundations.

Sea walls are thought to have been first constructed in in 448 AD by the Roman Emperor Constantine I, as part of a larger defence system to safeguard the city of Constantinople (now Istanbul, Turkey) from attackers by land or sea.

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