'The Dutch are proud of our feats of hydraulic engineering’
Closure of 5 storm surge barriers
The high water level along the Dutch coast was caused by a storm that occurred during the night and early morning of 2 and 3 January as a front crossed the North Sea towards the north of Germany. A storm developed on the southern edge of the front. 'The wind picked up strongly in the early hours of the morning and only died down again towards the end of the evening. This caused water levels to rise,' Van Waveren explains. The higher water levels ultimately forced the closure of all 5 storm surge barriers. 'The storm surge barriers are designed to prevent water from reaching dangerous levels. The Maeslant storm surge barrier, for example, was closed when water reached 2.60 m above the Normal Amsterdam Level (NAP), in order to prevent the higher water from penetrating to Rotterdam. Of course the storm surge barrier could have been closed sooner, but we preferred not to because it would have had serious consequences for shipping and the port of Rotterdam and in terms of flood protection it was not necessary.'
Closure of storm surge barriers was essential
The question arose whether the storm surge barriers actually had to be closed. 'The barriers only close when the predetermined water levels (closure levels) are reached. These levels differ from one barrier to another and depend on factors such as the strength and direction of the wind and the length of time the wind persists. For the barriers in estuaries, the water level in the river can also be a factor. It was absolutely essential to close the Oosterschelde and Hollandse IJssel storm surge barriers and the inflatable dam, the Balgstuw Ramspol, because of the risk of flooding', says Van Waveren. 'A reduced closing level applied for the Maeslant and Hartel storm surge barriers. It is impossible to ascertain with certainty during a test how the barriers will work when they are closed during a storm. To discover that, they have to be closed during a storm once every seven to 10 years. This storm was therefore an important and successful test for the barriers, but was also a training opportunity for the team that closes them.'
'The Oosterschelde and Hollandse Ijssel storm surge barriers and the Balgstuw Ramspol had to be closed because of the risk of flooding.'Harold van Waveren, senior adviser in Rijkswaterstaat's Water division
Close cooperation in the event of high water
'Rijkswaterstaat collaborates closely with the water boards when water levels are high. Together we protect the Netherlands against flooding', Van Waveren explains. 'During the storm we also communicated intensively with the port authorities of Rotterdam and Amsterdam and other stakeholders, including people living in areas outside the dykes.' The communication was not confined to the Netherlands: 'The locks at Terneuzen were shut on several occasions to allow excess water to be discharged so as to prevent flooding in Belgium.'
High water in the rivers
Although a lot of excess water is being discharged into the sea, there is still a huge volume of water arriving in the country from elsewhere in Europe via the rivers, which then have to discharge it. Can this cause problems? 'The water level in the Rhine and the Meuse is rising rapidly at the moment, but the rivers can handle it easily.' The floodplains of the rivers will be inundated, but that is what they are for. 'But even if the volume of water were to double – which is certainly not going to happen – there would be no flooding.'