Effects of Sea Level Rise on the Stability of Retaining Structures

Abstract: Sea levels are rising at a rapid pace and taxing infrastructure at an unprecedented rate. Ports are one area that already is and will continue to face significant challenges as sea levels continue to rise, particularly during extreme weather events. Rising sea levels will have a significant effect on the geotechnical stability of seafront retaining structures. Engineers must adequately design for sea level rise, or the consequences will be catastrophic, and major weather events will potentially cause regional shutdowns of logistic systems more and more frequently. Although most port engineers and geotechnical engineers are acutely aware of the potential risks associated with sea level rise, many projects/locations are not adequately addressing these risks. The reasons for failing to address the risks are varied but include conflicting predictive models, confusion over how to use the predictive models, and lack of unified design guidance.

This paper summarizes the risks of rising sea levels, different models for predicting sea level rise, the effects of rising sea levels on the geotechnical stability of retaining structures, and how sea level rise is currently being considered in projects. It then investigates the reasons why engineers are ignoring sea level rise during design and proposes potential solutions to encourage engineers to adequately address sea level rise in their design and simplify the process. The paper also contains a case study of a sea-front retaining wall at the Portsmouth Marine Terminal looking at the direct and indirect effects of different sea level rise projections on the geotechnical stability of the wall.

How does this project / topic contribute to the advancement of the industry and profession?: This paper brings light to the importance of considering sea level rise in the design of retaining structures by looking at how it affects ports, not just from a flooding standpoint, but also how it can negatively affect the geotechnical stability of the retaining walls. Most importantly it shows how using different projections for sea level rise can have a significant effect on the stability of walls, highlighting the importance of devoting significant effort to accurately developing and using sea level rise models in projects.

Does the project / topic implement new and innovative techniques, materials, technologies, and delivery methods?: No, however, it is one of the first papers containing specific numerical data on how sea level rise affects the geotechnical stability of walls.

What was the most challenging aspect of your project / topic and how did you handle it to ensure success?: While it was tempting to choose the extreme case for all the parameters, investigated with the case study especially wave action, in a way that maximized the instability of the wall, finding a realistic balance was critical. We wanted to show parameters that accounted for the reality that sea level rise is likely to have major effects, without choosing something so extreme that the case study/paper was discredited for not representing a situation that is likely to occur. Through careful research and consultation with industry partners, a balance was able to be found.

Who is the target audience for this paper?: The target audience of this paper is anyone who has a role in evaluating sea level rise projections and/or determining the effects of sea level rise on projects. This includes port owners, master planners, coastal engineers/scientists, and civil engineers. Special focus is made on highlighting the importance of geotechnical engineers fully considering the effects of sea level rise in their design.