Back to basics – Making infrastructure more robust for a long term resilience to climate change

Experts in long-term planning, HHNK is the regional water board north of Amsterdam. As a water manager, HHNK is responsible for safety against flooding, the management of surface water quantity and quality, the purification of the waste water and the management of the polders – low-lying tracts of land enclosed by dykes that form artificial hydrological entities. For expected climate change, HHNK has a dedicated water crisis management team and has close links with national organisations (such as Deltares) and local municipalities to deliver flood risk management.

The water system of tomorrow faces increasing challenges from climate change and urbanization. These require adaptive solutions in both the water system and the design of public space. Within the STAR2Cs project, HHNK has worked on a new three-step 3Di-modelling approach that provides insights into future flood vulnerability, and tests potential solutions.

Over the past three years, HHNK has used this approach to create 3Di models for 57 separate polder systems, generating 1,028 climate scenarios and evaluating over 250 potential measures. Each model can be used to run live simulations which help assess failure mechanisms or potential solutions with partners. The models are especially useful to municipalities in assessing the efficiency of blue and green infrastructure to increase urban flood resilience.

The process has been automated to such an extent that new models and simulations can be created and run rapidly from our own systems. This allows HHNK to be versatile in testing new measures, adding sewage system and other data from partners, adapting to new climate scenarios and testing for different kinds of scenarios, such as a dyke breach. It also allows HHNK to shift the focus from the management of data quality to in-depth analyses to better understand our water system.

Through stakeholder engagement with the 3Di-models, we have learned the different roles stakeholders can play in reducing the impact of climate change. We have also assessed contribution that our organisation and government policies can make to address flood risk at a local or regional scale. We have identified three universal principles or ideas we believe should be considered when reviewing local and regional flood risk policies, especially in the light of climate change.

1. Stakeholder roles change depending on the extremity of the event. To properly organise new forms of collaboration, contingency plans and planning should include clear conditions under which roles change, and in what ways.
2. In extreme events the sphere of influence of human action is reduced. There are limits to the extent to which people and infrastructure can be protected. Flood risk policy should therefore define, as accurately as possible, the accepted level of risk and how that risk is managed.
3. Managing extreme flood risk means that we need to find new ways of working together. With improved understanding of temporal and geographical dimensions of risk, it can be reduced by being managed and distributed among stakeholders. This requires new agreements/contracts, particularly between high economic value (often urban) areas and lower economic value (often rural) areas.

To learn more about HHNK’s 3Di modelling work and their strategies to build long term resilience to climate change, please visit hhnk.nl/bouwsteen-e.