Changes in the water level, e.g. due to heavy rain, is an important aspect to take into account in many types of construction works. The West Link is designed to manage both current and future water levels, which decreases risks such as flooding.
During construction of the West Link, we have to give consideration to the fact that the sea level will rise, and construct the tunnel so that water cannot seep into it. This to make sure that the West Link will be safe and be able to function throughout its entire lifetime. Prior to the year of 2100, the water level in Gothenburg is expected to rise by one meter, and up until year 2150 the level is estimated to rise by two meters compared to the levels today.*
Martin Malm is a soil and water/wastewater specialist, and is working with issues relating to dewatering, climate change and ground construction in the West Link Project.
– Particularly dewatering in, or in other words the collection, handling and removal of water that could damage the construction, is an important factor in being able to build a sustainable tunnel. Heavy rainfall would otherwise seep in and break down the facility, wash away work material and, in the worst case, flood the tunnel. Therefore, it is also important to protect the technical equipment from flooding, both during the construction but above all in the completed tunnel, says Martin.
The tunnel is being built for the future
The entrances to the West Link have been designed with protecting construction to avoid possible floodings. In case of extreme situations it will also be possible to close the entrances that are located below the protection level. Since it never is possible to know what the future holds, we have also made it possible to extend the protecting construction. In this way, the West Link is prepared to manage another meter of increased water level.
Thas is how the West Link will manage heavy rainfall
The West Link has been designed so that the water will not be able to flow into the tunnel in the event of heavy rainfall. We based the design of the tunnel on an extremely heavy rain that fell in Copenhagen in year 2011, which during two hours was measured to be 150 mm. To be on the safe side, we have raised this number by 20 %, which means that the West Link will be able to handle 180 mm of rain during two hours.
– We have also produced maps that show how deep the water would be along the entire tunnel route if such a heavy rain would fall. No openings where water could flow into the West Link will be located below this level, concludes Martin.
*Data taken from SMHI's (the Swedish Meteorological and Hydrological Institute) list of future sea levels published in 2012.