Predicting wave impact to safeguard coastal communities

“Ever since childhood, I’ve been inspired by waves. I grew up by the sea and spent time in and on the sea – swimming, sailing and surfing. I’m awestruck by the beauty and force of waves, and the destruction they can cause.”

Professor Alison Raby is one of the world’s leading experts on how extreme waves and coastal flooding impact coastal structures and hence communities. Her collaborations span the globe, with UK partnerships in London, Exeter and Oxford, to as far afield as Sri Lanka, Thailand, Indonesia and Perth.

Growing up with a father in the Navy, it wasn't just his passion for the sea and love of swimming and sailing that Alison shared with him.

“He nurtured a boldness in me, giving me the confidence that there was nothing I couldn't tackle. As a result I never worried about working in challenging environments – I just followed my passions.”

Alison's research interests lie in understanding how extreme waves interact with structures. Historic lighthouses, seawalls and breakwaters are still standing after many years, having endured an incredible battering. There is no rest for them, as they are still required to warn mariners of hidden perils beneath the waves, or to protect critical infrastructure. However, even modern structures have famously failed in the face of tsunami waves of unimaginable size.

At secondary school Alison's passion for waves and engineering was already evident when she built a wave tank as a teaching tool for geography students. “Its rotating mechanism generated waves that propagated up a beach, and caused the sediment to move.”

Alison went on to study physics with mathematics at the University of Sussex, before being awarded a PhD in 'Experimental and Theoretical Analysis of Perfusion and Diffusion in MRI' at the University of Surrey – researching the motion of fluids in the human body. She then realised the role she really wanted to do was within engineering, and it would take some effort to change career track.

During a period of time off to raise her young children, Alison developed a vision to work on developing country projects where people didn’t have access to power for education or other basic necessities. Several postdoc projects at the University of Reading followed, where she worked on technologies as varied as small-scale hydro, wind turbines and solar PV concentrators.

This developing background in renewable energy led to Alison obtaining a job in industry, working on renewable energy projects including the development of the world’s first commercial scale tidal turbine. Getting increasingly interested in water waves she returned to study, to be awarded a DPhil from the University of Oxford in 'Extreme Waves, Overtopping and Flooding at Sea Defences'. Ever since, Alison has continued to follow her passion and work tirelessly within civil and coastal engineering.

Alison's dedication across 18 years at the University of Plymouth has resulted in her witnessing the devastation caused by tsunamis in several countries and being up close to the incredible engineering structures of rock lighthouses. She has been principal investigator on a number of high-profile research projects, led the REF 2021 exercise for engineering, and is leader of the University's COAST Engineering Research Group. Alison's teaching portfolio includes advanced hydraulic engineering and interdisciplinary design.

One of Alison's research passions revolves around lighthouses. Of course, with the nature of our location we are very familiar with the iconography of these structures. We only have to take a short walk to the Hoe to witness Smeaton's Tower – a memorial to civil engineer John Smeaton, designer of the third and most notable Eddystone Lighthouse, located on the dangerous Eddystone Rocks 14 km south of Rame Head in nearby Cornwall.

Historic rock-mounted lighthouses, such as Eddystone, still play a vital role in the safe navigation around perilous reefs. Virtual navigational aids such as GPS are fallible, and reliance on them can be disastrous. Mariners will therefore continue to need the physical visual aids of these strategic structures. As an island trading nation experiencing some of the world's strongest storms, the UK is particularly vulnerable to maritime navigation failure, and loss of one strategic lighthouse will have an incalculable effect on safety, trade and heritage.

“As coastal engineers we understand wave transformation on more typical coastal structures like breakwaters. But on these cylindrical structures situated on surface-piercing reefs, there is a real lack of information and knowledge. We needed to understand the wave transformation on the rocky reefs around the lighthouse and the response of the structure to that wave loading.”

Leading the national STORMLAMP project, a collaboration with UCL, Exeter University and the UK and Irish General Lighthouse Authorities, Alison has examined the resilience of lighthouses and how they might be affected in future years as a result of the climate change and its effects on sea level and storminess.

“STORMLAMP has provided a fantastic opportunity to bring together engineers of different disciplines to try and solve some of the problems associated with wave loading on rock lighthouses.”

Integral to this research has been the facilities housed in the University's Coastal, Ocean and Sediment Transport (COAST) laboratory, which allows students and staff to physically model different scenarios. In this case, the Ocean basin was transformed into the Atlantic Ocean and a scale model was created of Wolf Rock – one of the country’s most exposed rock lighthouses situated between Cornwall and the Isles of Scilly. Its light can be seen from the mainland by day and night and it was the first in the world to be fitted with a helipad – vital as all rock lighthouses are now unmanned.

Valuable data was sourced from preliminary testing in the 35 metre sediment flume – a facility that allows tidal energy and wave energy technology to be studied – and the Coastal Basin – a facility that allows sediment transport and coastal structures to be studied at scale in a controlled environment. This enabled Alison and her team to investigate simple representations of the rock and lighthouse geometry before testing a scale-model.

In the past, methods of designing more common structures in the coastal zone were empirical, with much of the understanding acquired by considering previous failures. More recently, the understanding of the nature of waves has encouraged a statistical approach. Here, physical investigations use long random wave realisations to identify worst responses. But in the ENFORCE project, which gave her the opportunity to work with her Oxford doctoral supervisors again, their investigations led to the verification of a design wave in shallow water. This represents an extreme waves in the coastal zone that can be used to identify extreme wave run up and overtopping of structures.

Alison's interests in extreme waves also extend to researching the effects of tsunamis on coastal regions and debris flow and flooding. She has played a vital role in a number of collaborative initiatives with the UK Earthquake Engineering Field Investigation Team. Following the Tōhoku earthquake and tsunami in Japan in 2011, Alison produced research findings on comparative design codes for coastal structures, and featured in a National Geographic film about the disaster. “To witness the devastation was really distressing, but the mission to see the aftermath was really significant in terms of collecting research material.”

Flooding features strongly in a couple of Alison’s newest projects C-FLOOD and SENSUM, funded by the Natural Environment Research Council (NERC). C-FLOOD is investigating how vulnerable coastal communities in Sri Lanka might be to the combined threats of severe rainfall and cyclone-induced storm surge, in so-called compound flooding. The project is seeking to link complex hydrologic models that describe the rainfall-runoff with hydrodynamic models of the storm surge.

In the SENSUM project, the motivation for the investigation is the increase in storminess under climate change and population pressure, which are resulting in an increase in landslides and floods. Traditionally, these hazards have been monitored separately, using a combination of satellite-based remote-sensing techniques and wired ground-based instruments to measure factors such as river flow level, slope displacement and soil moisture.

Technology deployed up to now is unable to cope effectively with the rapid increase in hazard frequency and intensity. So the project aims to reduce these risks related by proposing an integrated way of tracking movement and monitoring hazards taking advantage of advances in Wireless Sensor Network (WSN) and Internet of Things (IoT) technologies, microelectronics and machine learning. These devices will enable the SENSUM team, led by Alison's colleague Dr Irene Manzella, to collect unprecedented datasets and understanding of landslide and flood processes.

Alison has worked at the University for nearly 20 years and has witnessed a sea change in Plymouth's research and facilities since she first joined.

“Our facilities have drawn the attention of some of the best coastal and ocean engineering researchers in the country and have led to exciting collaborations. And our own COAST Engineering Research Group is a thriving group of academics, postdocs and PhD students who use these facilities, but also drive forward research in numerical modelling. We have stimulating discussions around climate change threats to energy security and coastal infrastructure, and how we can provide sustainable solutions to real-world challenges. We have visiting speakers from all over the world, recently made simpler through virtual presentations during the pandemic.”

Looking ahead, Alison wants to keep exploring the multidisciplinary approach to natural hazards. “I very much value the collaborations with earth scientists and geographers”. These have led to her involvement with SENSUM and a new PhD studentship led by Dr Sarah Boulton. “It was conversations with one of my sons who studied earth sciences that made me realise there were different but complementary ways of viewing natural hazards; it’s an exciting space to work in!”

Alison is also fascinated by the overlap of the secular and sacred, as a civil engineer with a Christian faith. “In the early manuscripts of Scottish lighthouse construction, written by the famous Stevenson family members, there are many religious references and a humility about their endeavours that’s rarely visible in the modern engineering world. At the top of the Eddystone Lighthouse there’s an inscription of Psalm 127: Except the Lord builds the house, they labour in vain who build it. I’d like to do some research into how religious belief affects our engineering vision.”

There doesn't seem a single day when Alison doesn't think about or experience the power of waves. Whether it is introducing her young grandson to the pleasures of the beach, or going open water swimming, to kayaking with her husband and dog, or walking along a coastal footpath, there is an ever-flowing connection to the ocean.

Alison enjoys her commute to campus via the Cremyll Ferry that connects Plymouth with South East Cornwall. It gives her another chance to see the sea in all sorts of conditions, from calm crossings to dramatic stormy conditions bringing big swells that are exhilarating and terrifying at the same time.

After 30 years of meandering down a path to find her dream profession, the message is it is never too late to change.

“I did my second doctorate when I was in my mid-30s, after having my children. I'm still thrilled that I achieved that qualification which ultimately got me to where I wanted to be; this year I achieved my ambition to become a Chartered Civil Engineer, and a Fellow of the Institution of Civil Engineers.”

With waves a constant inspiration, Alison is continuing collaborations with colleagues across the University and globe, endeavouring to understand the processes of wave impacts and flooding, in the hope that structures and communities can be made safer from these natural hazards.