Civil Engineering January/February 2021 | Vol 29 No 1

24 January/February 2021 Civil Engineering A few decades ago, engineering codes did not even mention sea level rise. Or, if it was stated, there was great uncertainty as to how much to allow for. ‘How much’ is still a topic of debate, but these days we do have more references to rely on. The ‘1:100 design storm condition’ from a few decades ago has changed. While it is unfair to expect sea defences to protect us against any storm that comes our way, we do still expect sufficient protection against the ‘design’ storm. NATURE-BASED SOLUTIONS Along with the climate change problem comes potential ‘green’ solutions. Research is being conducted into using a range of nature-based solutions to protect our coastlines. One such example is the use of mangrove forests, which naturally trap sediments, helping stabilise the coastline and preventing erosion from waves. The difficulty for engineers at this stage is to put numbers to these solutions. Another potential solution is the con- struction of offshore artificial reefs. Hard surfaces are created to which algae and invertebrates can attach. These structures can be constructed using, for example, sub- merged rock berms, concrete units, or even sunken ships. The raised level of the ‘seabed’ induces some of the incoming waves to break, providing protection to the coastline. However, there is no one-size-fits-all solution for sea defence structures. Each project and location is different. Whatever the future holds, we will still need to as- sess the suitability of a range of structures as possible solutions before focusing on the optimal solution. Different roleplayers have different requirements, and legisla- tion will continue to change. Marisa Ackhurst Pr Tech Eng Associate: Marine Structures Zutari marisa.ackhurst@zutari.com Protecting our coastlines with vertical seawall structures Climate change, global sea level rise, increased storminess – these ‘predictions’ by scientists are fast becoming a reality. More than 35% of the global population lives in a coastal region, and the impact of ocean forces will become an increasing concern in terms of sea defences failing to provide the expected level of protection to the public and infrastructure. Marisa Ackhurst has published a compre­ hensive guide on the design of vertical gravity concrete sea and quay wall structures for practitioners in the field. The book is available from the SAICE bookstore: bit.ly/3paeMob A vertical seawall structure