•New

The Maritime Engineering Laboratory (LIM) of the Universitat Politècnica de Catalunya (UPC) is testing various engineering solutions to find the most efficient ones for fighting the coastal impact of climate change and for preventing current solutions from becoming ineffective in the not too distant future. These solutions are included in the first results of a European project led by the UPC: Responses to Coastal Climate Change: Innovative Strategies for High-End Scenarios – Adaptation and Mitigation (RISES-AM).

The aim of RISES-AM, led by researcher Agustín Sánchez-Arcilla, is to consider the impact of climate change in extreme and vulnerable coastal scenarios worldwide, analysing the effects of erosion and flooding. The project is now proposing the first possible solutions to improve the sustainability and preservation of the coasts. Researchers are calculating the costs of climate change in the coastal zone that may arise from damage to infrastructure, indirect damage to beaches that are eroded and lost for tourism, and loss of life. Eleven other universities and research centres in the UK, Holland, Germany, Italy and Romania also participated in this study, which will end in 2016 and will include analysis of deltas, urban beaches and all vulnerable areas of the coast.

The project studies the areas of the Catalan coast that are most vulnerable to changes in sea level and storm distribution that may cause them to lose natural or artificial assets such as those that have been built recently in the Llobregat Delta.

Within the range of responses considered, the project has begun to analyse the behaviour of traditional cost-engineering solutions based on stones and sand, and has compared them with more innovative actions that are still in the experimental stage. It has been found that the margins of uncertainty of traditional engineering are high because of climate variation.

The new options involve combining earlier solutions but aspiring to make them adapt more flexibly to climate change. One of the possible solutions considered in the RISES project is the use of vegetation to fix sandy beaches in combination with stones and sand. The LIM team is working on the design of underwater dikes and natural barriers covered with algae and plants to curb the onslaught of large waves. They are investigating the plants that best adapt and they recently analysed the possibility of cultivating banks of plants on the seafront. Alternatively, in cases such as the Maresme, the seafront infrastructure will have to be set back to leave room for the natural beach to react naturally to changes.

The climatic factors affecting the coastal zone that have been studied are essentially rising sea levels and wave storms, which could affect inland areas that are currently protected from wave action. The most optimistic scenario, RCP 4.5 (one of the Representative Concentration Pathways established by the IPCC), is that the sea level will rise half a metre compared with the present level worldwide by 2100. The most extreme forecast (RCP 8.5) is an increase in sea level of 1.8 to 2 metres. A one-metre rise in sea level is equivalent to a loss of 100 metres in the width of a gently sloping sandy beach such as some on the Costa Dorada and Maresme and many beaches of the Ebro, Ter and Llobregat deltas. Steeper, narrower beaches such as those on the Costa Brava suffer less sand loss.

Another very important factor affecting harbours is the damage caused by boat propellers. In a situation of rising sea level and stronger storm surges, boat propellers must work more intensively to manoeuver, especially when entering and leaving ports, and this leads to greater erosion of the bottom sand. These effects will have a great impact on the world’s largest ports but the ports of the Costa Brava will also be greatly affected.

The researchers have analysed the most extreme scenarios, in which infrastructure could begin to disappear in 2025 unless solutions are applied. According to preliminary results of the study, the most vulnerable coastal areas are the lowest ones, such as the Ebro Delta and the Danube Delta, crowded coastal cities such as Ho Chi Minh City, Vietnam, and some islands such as the Maldives.

In Ho Chi Minh City the problem is the high population density. If measures are not applied to deal with the disappearance of the coast, in a few years the physical substrate could be lost, leading to a mass migration of population.

The Catalan coast has also become an extremely vulnerable area, as the study showed that in the coming years demographic pressure in Catalonia will increase much faster than the world population. The Ebro Delta is an extreme area subject to erosion and flooding because the river no longer provides sediment. Given the future climate scenarios, scientists predict an accelerated loss of both horizontal and vertical volume in the Delta. It is forecast that by 2100 the Delta will be reduced to about half what it is now. The researchers believe that one solution would be to open the floodgates and let the stored sediment flow down, but the current flow of 100 m3/s is not sufficient to move the sand: it would need to be at least four times that figure.

Climate change will accelerate in the second half of this century, according to the report by the Intergovernmental Panel on Climate Change (IPCC) published in 2013. From 2025 a small change is expected, and its impact will double by 2050 and quadruple by 2100.

Waves are the main cause of the current erosion of the coast due to climate change. In some places they will increase and in others they will decrease, but in both cases the damage will be greater because of the rising sea level. Wave direction is expected to vary and will affect mainly coasts with more artificial areas, as in Catalonia, possibly involving a greater need for investment.

The beaches in the Maresme and many in Tarragona are artificial and may disappear by the year 2100 if no remedies are applied. Storm waves do not cause damage if beaches have enough space to reorient themselves and react to changes. The problem of the Maresme coast is that the beaches cannot react because they are small, the railroad is right on the seafront, and the deltas are artificial because the rivers no longer provide sediment.

The very fine sediment of the Costa Daurada also makes it highly vulnerable. The beaches of Barcelona and other urban areas will also require additional maintenance. In contrast, on the Costa Brava the beaches are natural and are able to maintain their natural resilience.

The European Union has awarded funding to the LIM to adapt its Maritime Research and Experimentation Wave Flume to allow EU and associated countries to test proposals for combating climate change based on future scenarios. This funding forms part of the HYDRALAB+ project.

The UPC’s Maritime Research and Experimentation Wave Flume, linked to the Barcelona School of Civil Engineering (ETSECCPB), is a marine engineering research facility that uses wave and current generation to perform controlled hydraulic tests on coastal, oceanographic and port engineering, and marine energy resources.