Half of the Netherlands’ primary flood-protection structures need reinforcement to meet new safety standards. The Dutch Flood Protection Programme's Richard Jorissen and Erik Kraaij outline the technical details of the reinforcement projects


CLICK TO ENLARGE Figure 1 The Netherlands

The Netherlands is a small country, lying in the delta of several rivers (Rhine, Meuse, Scheldt) and bordering the North Sea (Fig 1). On the one hand, it’s a densely populated country and very vulnerable to flooding. Nearly 60% of the land, some 70% of the population (total 17 million people) and 70% of the economy (total GDP 650 billion €) are flood prone.

On the other hand, the Dutch have a long tradition of water management. Strict (legal) safety standards, dedicated forms of governance (including taxation), regular safety assessments and sound engineering have yielded a well-protected country.

The flood-prone areas are safeguarded from flooding by approximately 3,800 kilometres of primary flood-protection structures. About 90% of these structures are managed by regional water authorities (waterschappen), whereas the remaining structures are managed by the national water authority (Rijkswaterstaat, part of the Ministry of Infrastructure and Environment).

The primary flood-protection structures are found along the major rivers, large lakes, estuaries and the coast. The majority of primary flood-protection structures are typical dikes. In addition to this structures (such as locks, gates and barriers) are used. Along the coast, the dunes provide a natural protection against flooding – albeit this type of protection needs maintenance and, in some cases, reinforcement.

The total length of dikes in the Netherlands is over 22,500 kilometres, but the majority of these dikes are used for regional water-management purposes.

Safety standards and reinforcement projects

CLICK TO ENLARGE Fig 2: Floodings, 1953

After the disastrous flood of 1953 in the south-western part of the Netherlands (approximately 10% GDP), the Minister of Public Works and Water Management installed the Delta Committee. The Committee proposed safety standards based on a cost-benefit analysis. This analysis was carried out for all 94 dike-ring areas.

The result was a flood-protection standard varying from 1/10000 per year (coast) to 1/1.250 per year (river area). Every flood-protection structure surrounding this dike-ring area should be designed in order to withstand the hydraulic loads associated with the safety standard.

Based on the safety standards, large flood-protection projects were carried out during the decades after the flood of 1953. In 1996, the Flood Protection Act marked a conclusion of this period: the technical safety standards became statutory and all flood-protection structures were to be tested against these standards every five (later six) years.

However, this was proved to be otherwise quite soon. The first assessment (concluded in 2001) was a test round, but the second assessment (concluded in 2006) yielded a significant reconstruction programme of 370 kilometres (roughly 10% of the total). Most of these reconstruction projects were caused by increased hydraulic loads and new insights in technical criteria.

The reconstruction programme was initially started in the traditional way: regional water authorities conduct their projects and the reconstruction costs are fully subsidised by the Ministry. Evaluation of this programme and earlier reconstruction projects showed that considerable improvements in effectiveness and efficiency were necessary:

  • Sharing the responsibility for the programme;
  • Improving the preparation of projects (including an exploration phase); and
  • Investing in technical and project management skills by the regional water authorities.

Regional water authorities took their responsibility and, in 2011, a Governance Agreement on Water was reached. For flood protection, the regional water authorities committed themselves to co-financing (yearly maximum €181 million as the government also attributes this amount yearly) the reconstruction works and to improve effectiveness and efficiency.

With this agreement, the regional water authorities and the Ministry have laid the foundation for a joint programme, the Dutch Flood Protection Programme (DFPP). The goal of the DFPP is to improve flood-protection structures that do not meet the required safety standards.

The scope of the DFPP is 1,100km (completion in 2028). Each project will be financed for 90% of the total costs and each water authority finances 10% as an efficiency contribution in its own project.

Delta Programme

In 2008, the second Delta Committee commissioned by the Secretary of Public Works and Water Management provided recommendations on how to defend the Netherlands against the expected impacts of climate change, such as sea level rise, longer periods of drought, more intense periods of rainfall and additional land subsidence over the coming two hundred years.

The Delta Programme was announced in September 2008 based on these recommendations. The Netherlands needs to prepare for the consequences of the rising sea levels, land subsidence and rising temperatures. This means looking further ahead and making effective plans for the long term.

The Programme consists of:

  • The Delta Fund. The yearly financial volume of the Delta Programme is €1,100. This budget covers only the costs for operation, maintenance and reconstruction in (primary) flood protection, national water management and fresh water supply;
  • The Delta Commissioner, appointed by the Government and an independent position to coordinate cooperation, prepare decisions and monitor the delivery;
  • The Delta Decisions on flood-risk management, fresh water supply and spatial adaptation. The new standards on flood protection are based on the estimated probability of flooding and the expected impact of the flooding (casualties, damages, disruption). These new standards were set using a risk-based approach.

The first step in deriving the new standards is the introduction of a basic safety level of 10-5 per year for the acceptable probability (per year, on a specific place) of a fatality due to flooding. This is the so-called local individual risk.

The second step is to check whether a higher level of protection may apply for areas in which flooding could lead to large groups of casualties or significant economic losses. A higher protection level may also apply if vital functions are present, such as a nuclear power plant.

Dutch Flood Protection Programme

The Dutch Flood Protection Programme is a significant part of the Delta Programme. It is both an organisation and a methodology. The organisation is an alliance of the regional water authorities and Ministry based upon joint responsibility and financing of flood protection measures along the coast, rivers and lakes. Its main responsibilities are: programming (six years ahead), financing and sharing experience and knowledge.

The DFPP also stands for a methodology in which scientific institutes, consultancy and construction companies participate. The programme contains the (expected) projects for the next decades. The goal of the DFPP is to improve flood-protection structures that do not meet the required safety standards.

On a national level, the necessary projects are ranked based on the actual flooding risk (probability times the expected damages) and fitted within the budget constraints (€362 million yearly). The influx for the six-year programme (six-plus years ahead) is determined by the regular safety assessments.

Regional water authorities and Rijkswaterstaat assess the actual safety of the embankments against the legal standards using up-to-date information and tools (hydraulic loads and technical criteria).

Fitting the scope within the budget requires a prioritisation method. It was decided that all proposed reinforcement projects would be ranked on the actual risk due to flooding (probability*consequences). In 2013, the first programme was prepared for the period 2014-2019. After four years, the DFPP has produced its fourth programme: 60 projects, preparing 600km and €1,000 million.

The DFPP is not only aimed at realising flood-protection projects. The following comprehensive goals are relevant:

  • Increasing the production rate of flood protection projects: from 25km/y (last decades) to 50km/y;
  • Improving effectiveness and efficiency of flood management: from €10 million/km to €7 million/km;
  • Enhancing the societal value of flood-protection projects;
  • Improving the co-operation between the authorities involved;
  • Assuring the quality and control of both the programme and the projects.

Developments and discussion

CLICK TO ENLARGE Fig 3: Technical innovation screwable barrier

Now that the initial phase of the Dutch Flood Protection Programme is behind us, an evaluation of the programme will be carried out. A number of relevant developments need to be taken into account:

  • Innovations: these are essential to reach the overall programme goals (production rate, societal value and costs. The DFPP stimulates innovations on techniques, contracting, stakeholder participation and decision-making.
    In order to stimulate innovation in general, an additional incentive has been incorporated within the DFPP. For innovative projects, the remainder of 10% is paid for by DFPP, but also the risks associated to the innovation are transferred to the programme.
  • Growing need for well-trained personnel: both the size of the programme and the new technical developments, combined with the ageing of present staff of Rijkswaterstaat and the regional water authorities, require an impulse on capacity building. Strategic personnel planning based on the long-term programme shows that the public authorities need about 500 well-trained people to run all the projects.

From a long tradition in water management, the Netherlands is challenging a new perspective in flood prevention: meeting the new water-safety standards due to climate change.

Richard Jorissen and Erik Kraaij, managing directors, Dutch Flood Protection Programme

http://www.engineersjournal.ie/wp-content/uploads/2017/07/Oosterschelde-1024x580.jpghttp://www.engineersjournal.ie/wp-content/uploads/2017/07/Oosterschelde-300x300.jpgDavid O'RiordanCivilflooding,Netherlands,safety,water
  The Netherlands is a small country, lying in the delta of several rivers (Rhine, Meuse, Scheldt) and bordering the North Sea (Fig 1). On the one hand, it’s a densely populated country and very vulnerable to flooding. Nearly 60% of the land, some 70% of the population (total 17...