PIONEER: An Adaptation Approach for Resilient Coastal Infrastructure Against Sea Level Rise

Mean sea level around the UK has risen by approximately 1.5 mm per year on average from the start of the 20th century. This rate has increased to levels exceeding 3 mm per year for the period 1993-2019. The projections of sea level rise show that UK sea level will continue to rise well beyond 2100, even under scenarios where future temperature rise is stopped. For instance, under a low emissions scenario, the approximate projected ranges at 2300 are 0.5 - 2.2 m for London and Cardiff, and 0.0 - 1.7 m for Edinburgh and Belfast. Under a high emissions scenario, this increases to 1.4 - 4.3 m for London and Cardiff, and 0.7 - 3.6 m for Edinburgh and Belfast. Extreme sea level events are also expected to become more frequent in the future and occurring about 20 to 30 times more frequently by the year 2050.
Around 148 million people are exposed to coastal flooding events worldwide, which will surge in the coming decades. Rising sea level will also have strong economic consequences. For instance, the investment required to protect London is expected to exceed 20 billion GBP. According to IPCC, unavoidable sea level rise will bring cascading and compounding impacts resulting in flooding and damages to coastal infrastructure that cascade into risks to livelihoods, settlements, health, well-being, food, and water security in the near to long-term.
There are several known approaches to adapt to sea level rise (e.g., realignment, nature-based solutions, soft/hard defences). Although realignment, nature-based solutions and soft defences provide lower cost, sustainable and resilient solutions, there are cases where hard defence is unavoidable to: hold the line. Yet, they have the risk of increased exposure to climate risks in the long-term unless they are integrated into an adaptive plan, which strongly relies on understanding their response to future sea level rise and extreme events.
The sea level rise, along with the increase of the extreme sea level events, will lead to increased frequency of wave overtopping at the seawalls. Wave overtopping will have significant impact on the interaction of the wall with the backfill soil, affecting the stability of the seawalls in the long-term. The extent to which the seawalls can be integrated as a part of the long-term climate change adaptation plans will depend substantially on their response to future sea level rise and extreme sea level events.
To adapt the seawall design accordingly, the impact of wave overtopping on the overall stability of seawalls need to be evaluated in terms of modified backfill soil-seawall interaction due to (i) wetting-drying cycles and (ii) erosion. This first project will focus on the first aspect, unlocking the fundamental behaviour of backfill soil-seawall interaction to wetting-drying cycles due to wave overtopping.
Considering the global nature of the problem, an international collaboration is of paramount importance to find a mutual solution with academics, stakeholders and industry partners. Thus, this project will be a first step to initiate international collaboration between Heriot Watt University (HWU) and Virginia Tech (VT), USA.
The main benefits of this research work will be on (i) coastal population, (ii) UK economy and (iii) agricultural land and cultural values.