Dutch parliament has agreed on an amendment of law that will fundamentally change the national flood defense standard.
With the amendment, the Dutch flood standard will no longer be based on the probability of a flood given a certain height of the water level that can be expected during an extreme weather event.
Instead, the new Dutch flood standard is risk-based, demanding a life protection level of 1:100.000 years of becoming a flood casualty for every citizen living behind levees or dunes.
The Netherlands is the first country in the world to implement a national flood standard based on the quantitative estimation of flood probability, including levee failure.
The new law is expected to come into force by 2017. By 2050 all concerning levees are to meet a failure probability standard that has been derived from the maximum allowed flood risk.
The costs to implement the new flood protection standard are estimated at 14 billion euros in the period up to 2028.
“In 2050 we still want to be the best protected river delta in the world“, explains Roald Lapperre, deputy director general for water and spatial planning at the Dutch ministry of Infrastructure and the Environment.
According to Lapperre the new risk-based standard will allow the Dutch government to provide additional flood protection for less money. He gives an example. “By investing in specific levee sections in the central part of the Netherlands, with its large rivers, we are able to increase the flood protection tenfold.”
Deltares has been involved in the development of the new risk-based flood protection standard. A break through has been the development by Deltares of a model and software to calculate the economic optimal dike heights.
The national Dutch government and the regional water authorities started a collaborative levee reinforcement program. This on going program started in 2014 and envisions the reinforcement over 1,900 km levee. Every year a new priority list is adopted to make sure that the most critical levee sections are handled first.