The sea level rises due to climate change. The sea level rise is caused by melting ice sheets and glaciers, the change in volume of the sea water as a consequence of rising temperature (dilatation) and the change in water storage on the land. Sea level rise can lead to more floods, coastal erosion and intake of lower land areas by the sea. The sea water can also affect shallow (fresh)water layers and threaten the watersupply of local ecosystems.
The annual average of the sea level was in 2017 almost 13 cm higher then at the start of the measurements a few decades ago.
Evolution of the annual average of the sea level in Oostende between 1951 and 2017 (Milieurapport Vlaanderen 2018)
Projections towards the timeframe 2100 for the middle impact scenario show us a possible sea level rise around 80 cm compared to the actual level. Nevertheless other existing scenario’s predict an ever higher rise of sea level. This middle impact scenario expects a sea level rise of 30 cm towards 2050, 50 cm (or 7,5 m for the 1000 yearly storm) towards 2075 and 100 cm (or 8,0 for the 1000 yearly storm) towards 2115. If the seawall would be inadequately resistant to the high water level of a storm surge, there could be massive flooding.
The expected sea level rise and the higher storm surge will increase the risk of floods at the coastal area, which will affect the coastal cities, port facilities and other infrastructure. Increased flooding will also occur at the riversides of rivers connected to the sea like the river Scheldt. An extreme storm surge can occur when there is a strong northwestern wind in combination with heavy rain at the mainland. This could lead to an even stronger increase of water levels and flow rates. Increased water levels do not only result in floodings but can also affect the drainage of polders and watercourses.
One third of the 67 km long coastal area is insufficiently protected against so called superstorms. This came out form a study executed by the coastal department on how the coast could be brought to a minimal safety level against a very heavy storm.
Every meter of our relatively short coastal area is been used intensively. Amongst the ten coastal cities and municipalities there are not only important seaside resorts but also two important trading ports Zeebrugge and Oostende with each their underlaying industrial areas. Nieuwpoort, Oostende, Blankenberge and Zeebrugge have a marina. And there are some valuable nature areas like the Westhoek, Ijzermonding, De Fonteintjes and the Zwin.
Besides the changing flood risks, the changing water levels and flows at the coast will lead to changes in coastal erosion, turbidity of the water and so the available light, and the inflow of fresh water (salinization). Together with changes in sea temperature this could lead to changes of habitat and physiological effects in certain animal and plant groups, which will affect the food chains in ecosystems. Low amounts of precipitation and increased evapotranspiration strengthen the salinization process. If no measures are taken to prevent the salinization, the extraction of fresh water should be reduced and possibly relocated.
The increased fresh water flux leads to a stronger salty seepage in the polders and salinization of the agricultural area and the ecosystems which depend on groundwater. The reinforced seepage causes an increase of the groundwater level in the polders which means a decrease in storage capacity and a bigger need for drainage.
The sea level rise also changes the tidal regime which will affect specific ecosystems like mud flats and salt marshes and sand dune ecosystems and their protective capacities.
In 2007 a study was executed to find out how the coastal area could be protected by a severe storm. This resulted in 2011 in the masterplan coastal security “Masterplan Kustveiligheid met tijdhorizon 2050”. This plan contains different measures at municipal level in order to protect the coast and the hinterland from flooding by the sea. This plan took into account the predicted sea level rise at that time. The masterplan on coastal security should guarantee the security of the housing in de coastal area and the hinterland until 2050. An estimated sea level rise of 30 cm towards 2050 was taken int account and the proposed measures are flexible in the long term so that they can be adapted to higher security levels and a rising sea level.
Many research and experiences show us that sand dunes and wide high located beaches form the best natural protection against storm and floods.
The Flemish government is looking at the coastal protection in the long term, towards 2100, in the Complex Project Kustvisie, taking into account the more extreme climate scenario’ s. This might also lead to an adaptation of the actual policy towards 2050.
The CREST-project (Climate Resilient Coast) (2014-2018) focusses on knowledge building on coastal processes and the impact of climate change on this processes.
The Coastbusters project (2017 – 2020 ) tests different innovating techniques of natural coastal protection at our westcoast.
The INTERREG ENDURE project (ENsuring DUne REsilience against Climate Change) (2014-2020) looks at the construction of sand dunes as adaptive, living sea walls.
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