flood and water resources

Climate impact of changing precipitation patterns on local watercourses

Reference case City of Antwerp

Introduction to the challenge

The City of Antwerp wants to know the climate impact of changing precipitation patterns on local watercourses.

Our approach

Integrated approach with attention for combined watercourse/sewer model. Important for the urban environment

changing precipitation patterns on local watercourses
City of Antwerp
Step-by-step approach:
  • In an initial phase, the difference in impact on the local watercourses was analysed under different (local and regional) climate models by comparing the runoff flow rates per watercourse.
  • This makes it possible to determine how the local climate scenarios are situated in relation to the Flemish average climate scenarios and how the climate impact evolves over time.
  • These runoff flow rates were subsequently simulated in the watercourse models to study the impact of climate change on the flood risks. This allows flood contours to be examined and compared in relation to the return period, the time horizon and the climate scenario.
  • For the Bovenschijn (Schijn South) and the Benedenschijn (Schijn North) up to the Rode Weel pumping station, climate scenarios were extrapolated with a river model in Infoworks RS.
  • For the Benedenvliet a combined watercourse/sewer model was developed in Infoworks ICM, based on the existing VMM model. To this end, the existing model was expanded with the surface runoff over the streets and with flooding areas. In conventional sewer models, this surface runoff across the streets is not taken into account and simulations are typically based on less extreme situations. This methodology enables us to accurately simulate the flooded locations in an urban environment for a large return period and extreme climate variations.
  • The different climate scenarios were extrapolated for different time horizons, including simulations to estimate the scope of floods in the event of operational problems such as pump failure and blocking of critical pipelines.
  • For the Benedenvliet a number of structural flood protection measures were analysed in the light of the climate scenarios, i.e. the construction of controlled flooding areas (CFA). This analysis showed that during the design of CFAs, in relation to climate variations, the flow rate control at the outflow should be approached dynamically if the available buffering is to be optimally utilised at all times. The optimal utilisation of buffering and the mitigation of flood risks also requires the resolution of local bottlenecks.
  • Finally, policy recommendations were developed about the choice and use of the climate models and about potential measures for increasing multi-layered water safety.

Our solution

Policy recommendations on 3 aspects: protection, prevention and preparedness

The study resulted in specific policy recommendations about the choice and use of climate models, and potential measures. 

Another recommendation is that it is also best to use local climate scenarios and intermediate time horizons. The evolution of the impact is not always linear over time.

The measures that were developed can be classified under the 3 types of multi-layered water safety: 
  • protection (building resilience against floods by taking structural measures to prevent floods up to a certain level) 
  • prevention (taking structural measures to minimise the impact of floods as they occur) 
  • preparedness (ensuring that extreme events can be anticipated, so as to be prepared for them and know how to effectively respond to them)

The benefits

Greater accuracy in the simulation of flooded locations in an urban environment thanks to a combined watercourse/sewer model

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