7.3.4

Consequences of urban flooding

Low probability, high consequences

The probability of urban flooding from the sea, major rivers, or major lakes is very low in the Netherlands, yet if such a flood occurs, it will have a major impact. The probability of urban flooding from regional waters is higher, but the impact will be less devastating (with the exception of the deep polders that are protected by regional flood defence systems: here, the risks will be quite high, especially if protection is provided by peaty dykes). In the past, floods used to be taken into account in spatial planning, for example, by choosing or constructing elevated sites. In flood risk management, attention has gradually shifted to raising and improving dykes, and creating more room for rivers. However, despite the strong dykes and wider rivers, factoring in the impact of a flood continues to be important, by limiting the damage, fatalities, and social disruption if a flood occurs nonetheless, and improving the water resilience of urban and rural areas. In the long run, this may even reduce the need for dyke improvements and river widening. 

First steps

The evaluation of the Delta Decision on Spatial Adaptation shows that few parties feel the urgency to limit the impact of urban flooding through spatial adaptations. This is because the probability of a flood is small, and ownership of the problem is not acknowledged. In the Climate Adaptation City Deal, the cities of Zwolle, Amsterdam, Rotterdam, and Dordrecht are sharing experience with the planning of water-resilient areas. The Marken project has generated designs for a water-resilient planning of the island. Obstacles related to the sense of urgency and funding are hampering their implementation.

Limiting consequences for national vital and vulnerable functions 

In recent years, steps have been taken to improve the flood protection of national vital and vulnerable functions, particularly in the fields of “Analysis” and “Ambition”. Vital and vulnerable functions include, e.g., energy supply (including electricity), communication (telecom/IT), transport, health, the chemical industry, and the water chain. The “water-resilient design” is geared to each individual function. The Ministries responsible set down a strategy in collaboration with the sector concerned, and determine which measures are essential and proportionate to the function. The Delta Programme coordinates the joint approach in order to ensure that the Ministries largely follow the same methods and time frames. In addition, the parties are working with the same flood scenarios wherever possible, and they acknowledge the mutual dependencies between the individual vital and vulnerable functions. 

Demarcation: only where flood depth remains limited

Whether adaptations hold promise depends, inter alia, on the features of an area. In collaboration with the district water boards and provinces, the municipalities will conduct stress tests to visualise the consequences of a dyke failure. In deep polders, impact-limiting measures are often expensive. In such cases, focusing on evacuation will be more effective. Measures to limit the impact of deep floods are often closely interrelated with the flood defence system tasking. For that reason, options for linking the Delta Plan on Spatial Adaptation and the Delta Plan on Flood Risk Management will be elaborated in 2018. Spatial adaptations are particularly (cost) effective for flood depths of no more than 20 to 30 cm. Furthermore, in many cases, this enables concurrent limitation of the impact of waterlogging: although waterlogging occurs much more frequently compared to flooding, the adaptation solutions are similar.Because the impact of flooding is highly dependent on the location, a national standard or nationwide goal for flood impact limitation (multi-layer flood risk management, second layer) would not serve its purpose. It would be appropriate to develop a collective ambition at the local or regional level, in collaboration with the stakeholders.

  1. Cover letter and Delta Programme Commissioner’s recommendations
  2. Introductory summary
    1. Continuing the work on a sustainable and safe delta
  3. Part I National level
  4. Progress of the Delta Programme
    1. Progress based on Monitoring, Analysing, Acting
    2. General picture of the progress
      1. On schedule
      2. On track
      3. Integrated approach
      4. Participation
      5. Effectiveness of the regions
    3. Progress in flood risk management
    4. Progress in spatial adaptation
    5. Progress in freshwater supply
    6. Embedding, knowledge and innovation, international collaboration
      1. Embedding
      2. Knowledge
      3. Innovation
      4. International efforts
  5. Delta Fund
    1. Developments in the Delta Fund
    2. Resources from other partners
    3. The financial taskings of the Delta Programme
    4. Financial security of the Delta Programme
  6. Part II Regions
  7. Progress per region
    1. IJsselmeer Region/freshwater supply region IJsselmeer Region
    2. Rhine Estuary-Drechtsteden/West-Netherlands freshwater supply region
    3. Rhine/ Area around the major rivers freshwater supply region
    4. Meuse
    5. Southwest Delta/Southwest Delta freshwater supply region
    6. The Coast
    7. Wadden Region
    8. Elevated Sandy Soils South and East
  8. Part III Delta Plans
  9. Delta Plan on Flood Risk Management
    1. Implementation programmes
      1. Flood Protection Programme
      2. Second Flood Protection Programme
      3. Room for the River
      4. Meuse Projects
      5. WaalWeelde
      6. IJsselmeer Closure Dam
      7. Repair of Oosterschelde and Westerschelde stone claddings - Zeeland foreland deposits
    2. River widening in interconnection with dyke improvement
    3. Studies ensuing from knowledge agenda and in regions
  10. Map Flood risk management measures
  11. Delta Plan on Freshwater Supply
    1. Measures to ensure the availability of freshwater in the Netherlands
  12. Map Freshwater supply measures
  13. Delta Plan on Spatial Adaptation
    1. Introduction
      1. Justification
      2. Aim and state of affairs of the Delta Plan
      3. Collective realisation
    2. Context
    3. “Analysis, Ambition, Action” – state of affairs
      1. Waterlogging
      2. Heat stress
      3. Drought
      4. Consequences of urban flooding
      5. Current approach
    4. Our intentions: expediting and intensifying
      1. Vision: from the present to 2050
      2. Ambition and strategy
      3. Interim goals
      4. Nationwide governance framework regarding spatial adaptation
      5. Funding
    5. Appendix 1. Action programme
    6. Appendix 2. Outcomes of regional meetings and round table discussions
  14. List of Background Documents
    1. Background documents
  15. Colophon
    1. Colophon content Delta Programme 2018
  16. How to use Delta Programme 2018