Often fragile ecosystems are threatened by increased flooding and erosion.
Finding a way to protect them in the long term is a major challenge.
Barbara Zanuttigh, Theseus project coordinator said: “One of the key things that the environment now demands of us is sustainability, so we have to develop defences that are not only useful, but also environmentally friendly.”
Scientists have now launched a European Union research programme called Theseus to investigate how our coastlines should be managed.
As they begin work the oceans continue to rise.
Fernando J Méndez, Associate Professor, University of Cantabria explains: “The sea level is going up. Recent data from satellites have confirmed for us that at the moment the mean sea level is rising at a speed of 3.3 to 3.5 milimetres per year, and this is a fundamental fact.”
Venice, the sinking city, is a classic case study in coastal protection and management.
For centuries Venetians have been digging channels, redirecting rivers and shoring up low-lying islands to keep the lagoon from either silting up, or being washed away by the sea tides.
Pierparolo Campostrini, Director of CORILA, a Venice-based group of scientific researchers:
“The Venice lagoon has many problems, the best known problem is flooding of the city. But the lagoon is a delicate geological system, almost ephemeral, so if you didn’t have specific measures it would already have disappeared.”
The full challenge of coastal protection can best be seen from the air.
From above it is possible to see the work of the MOSE project (“Moses” in Italian) to create a huge tidal barrier for Venice, due for completion in a few years’ time.
Pierpaolo’s research is on more natural ways of preserving the lagoon, including building new sandbanks and submerged breakwaters.
Pierparolo Campostrini, Director, CORILA:
“The submerged breakwaters are part of the protection system that we set up when we built the beach to limit erosion and to help the coastal defences. So the submerged dykes were built in order to protect, but in recent years we have seen how they have also become a haven for biodiversity.”
A maze of coastal waterways and islets is a vital reserve for marine and bird life.
A huge challenge is finding a way to protect the delicate sandbanks from the waves emanating from ships’ bows.
As part of the project Pierpaolo’s team is evaluating a number of systems, including these floating barriers.
Pierparolo Campostrini explained: “At this experimental site we’re testing the effectiveness of the Ondarail floating barrier to resist the fairly large volume of traffic we have in this channel with the frequent passage of quite large boats.”
Different sandbanks require different solutions.
Some use fixed barriers, many others semi-permeable bags of rocks or shells.
Scientists have developed sophisticated theoretical models to understand these sandbanks, and in so doing found that it was neccessary to leave breaks in the barriers to let oxygenated water flow into the sand.
Pierparolo Campostrini again: “Very complicated maths helps us to understand the processes. They are processes that has been studied using fractal equations. So we are recreating a natural environment to understand it better, and so help engineers to better rebuild a piece of nature that we were losing.”
A second port of call is Santander, where coastal engineer Fernando Mendez is studying how climate change could alter wave size and direction.
His role in the Theseus project is to understand how wave patterns alter our coasts.
Fernando J Méndez, Associate Professor, University of Cantabria: “To evaluate the beach platform what we need is a conceptual model in which waves approach the shore, waves break, and at the moment when the waves break they act like a hammer, smashing sediment into suspension. And in function of the longitudinal currents or rip-currents the sediment is transported, inducing areas of accumulation and erosion. If the average direction of the waves changes then we would have a change in the form of the beach, there will be a shift. This rotation will produce areas of accumulation and erosion of sediment.”
A traditional wooden sailing ship is a great way to get a clear view of Santander bay.
Alongside Fernando is Jose Juanes, another member of the Theseus team, evaluating how to handle climate change.
He will examine the impact of rising sea levels on the dunes that dominate one side of the bay.
Behind the dunes are homes – meaning the sand cannot just push back inland.
José A Juanes, Associate Professor, University of Cantabria: “Some dunes don’t have much room for movement. If the sea level rise is enough they could be broken. And apart from the sea level rise, other effects of climate change could be a modification of rain patterns or flooding and this could mean that in some areas dunes are broken or even disappear.”
Increased erosion and flooding are the two main effects of rising sea levels. The researchers embarking on this project already know that a combination of techniques and modifications will be needed to protect our coastlines.
Fernando J Méndez, Associate Professor, University of Cantabria: “For example one solution might be to raise the sea wall by a metre to avoid flooding, that could be a mitigation solution. Or another solution could be the regeneration or replenishing of a beach, that is another option for mitigation.”
Barbara Zanuttigh, Coordinator, Theseus project: “Traditional defence methods have not only shown their limits but sometimes they have had a negative impact, so of course we have to work on the coastlines but also preserve the quality of our environment, and we have to reach a consensus with the population because they need to feel safe on the one hand and on the other hand they need to see the environment in which they live preserved.”
The key is to find that balance by working with nature rather than against it.
For more information:
www. theseusproject .eu. theseusproject .eu