Flood risk management / Disaster risk reduction

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Prevention and mitigation

A thorough risk analysis provides the base for an integrated approach to flood risk management, including pre-flood prevention, risk mitigation and flood preparedness. Prevention of flood risks focuses on the design of flood management schemes taking into account economic development and climate change. Deltares develops and applies decision support systems and planning kits to support the integrated evaluation of large sets of possible measures. These measures include application of safety standards, raising and reinforcing of embankments, coastal protection works, storm surge barriers as well as making room for rivers. Mitigation of risks requires another type of measure, taking into account spatial planning: development of new urban areas, flood proofing and compartmentalisation and dedicated protection of vital infrastructure.

Coastal protection

The natural coastline of The Netherlands consists of sand and dunes and comprises the main protection against coastal floods. Beach nourishment is a popular way to strengthen this coastline and keep it at its present position. It is a soft protective and remedial measure that leaves the coast in a more natural state and preserves its recreational value. Deltares studies the functioning of sandy coastal systems to gain insight into the shape of the coast and its changes by erosion, sedimentation and other geophysical processes or human intervention. We implement this knowledge in our models and monitoring instruments and use it to advice coastal managers on appropriate management measures.

Design and operation of storm surge barriers

For decades Deltares has been active in the design and testing of storm surge barriers and closure dams. Major studies were executed during the implementation of the Delta Plan in the Netherlands after the 1953 flood disaster. Highlights of the Deltaplan included the construction of storm surge barriers in the Eastern Scheldt (1986) and the Maeslant barrier in the Nieuwe Waterweg which protects the harbour and city of Rotterdam from storm surges in the North Sea (1997). Abroad we have been involved in several large storm surge protection projects, for instance St.Petersburg, Venice Lagoon and New Orleans.

Room for Rivers

Due to climate change an increase is expected of the flood discharges in the major rivers. To accommodate such increase, rivers will need more room. Urban development in the past has created several bottlenecks in the floodplain. Careful planning should avoid losing land to the river by combining the discharge function with flood-proof land use functions.

Giving more room to rivers may substantially lower flood levels and sustain a more attractive environment, both urban and natural. Room for Rivers was officially adopted by the Dutch government to achieve the required safety level for the river systems. Later it also became the guiding principle for climate change adaptation along the major rivers. Deltares audits the designs of individual measures along the Rhine, Scheldt and Meuse rivers and makes assessments of their combined large-scale effects on the river system.

Flood-proof spatial planning

Flood risk management may also focus on restoring the resilience of natural systems. This includes a more flood-sensitive planning of new developments as well as adaptive designs (flood-proof structures). Flood risk maps, as required by the European Flood Risk Directive, are valuable instruments to promote a more sustainable spatial planning. Deltares develops and implements integrated approaches, for example in urban flood management.

Decision support

Recently, the use of decision support systems (or DSS’s) has gained importance in flood risk management. DSS’s are developed and used to assist in the integral evaluation of large sets of possible measures. The tools are valuable in communicating complex results and solutions to a wide audience of stakeholders. Deltares has been at the forefront of developing such systems. One of the successful examples in the field of flood risk management is the Room for the Rivers Planning Kit. Another example is the Expert DSS for integrated coastal zone management and vulnerability assessment, developed for Andhra Pradesh, India. This tool enables an explorative analysis of typical flood risk measures as well as land use planning and environmental management measures.