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.

First step:

To begin the 3Di-modelling process a 3Di hydrological model is built using data on water channels, pumps, weirs and culverts from HHNK and public sources. This is assimilated into a 1D model that simulates water flow through the system. Spatial data on land use, elevation, ground water, friction, and infiltration are added in a separate, but integrated 2D model that simulates surface water flow.

Second step:

In the second step, the model simulates 18 different climate scenarios, based on rainfall event duration (two hours or two days), chance of occurrence (every 10, 100, or 1000 years) and initial groundwater level (low, average or high). The simulation results are aggregated to produce flood maps; input from land use maps and damage curves predict flood vulnerability and potential impacts.

Third step:

The final step involves creating a new model incorporating different potential measures. Comparing the potential damage under the old and new models allows a cost-benefit assessment to be made for each intervention.

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.

Further information:

3Di is a hydrodynamic simulation of pluvial, fluvial and coastal floods. The name 3Di refers to the integration (i) of a one-dimensional (1D) model and two-dimensional (2D) model. For more information, please visit 3diwatermanagement.com.

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Pilot information:

Through pilot studies and knowledge-sharing, the STAR2Cs partners have designed and produced innovative, transferable, and effective mechanisms to overcome the ‘implementation gap’ that currently exists in delivering local adaptation action.