Page 8 - Identifying cascading effects on vital objects during flooding

Identifying cascading effects on vital objects during flooding is a case study under the Adaptive
Circular Cities project. Increasingly we see flood-related events and these will intensify in the
future due to climate change and social-eco development, especially in coastal cities (high-tides,
storms, hurricanes, tsunamis) as well as pluvial flooding (heavy rain or long rainy periods) and fluvial
flooding (in river deltas).

1.2. Challenge and response

Identifying cascading effects on vital objects during flooding

Flood related events can cause enormous damage to cities if not controlled. The first stage is the
flood itself and the second stage is the cascading effect on the city infrastructure that can potentially
paralyze the entirety of a city.

It is essential to understand the short-term and long-term effects of flooding in order to be able to
improve the resilience of the impacted cities and control the cascading effect.

Different challenges and measures for urban areas are to be considered, which include:
implementing climate change mitigation and adaptation actions, rising sea level, sustainable use
of natural resources and ecosystems, finding alternatives for valuable resources, and transition to
circular economies.

In response, a tool has been developed to build a model (3Di) that allows a detailed analysis
of cascading effect, called Circle knowledge. It is performed on critical infrastructure where
information can be gathered from different stakeholders in an area. In combination with the high-
resolution hydraulic model, 3Di is capable of stimulating a flooding scenario by making use of a
variable-size computational grid combined with high-resolution underlying input data. The results
are based on a combination of information from the stakeholders and the high spatial and temporal
resolution of the model.

3Di is a state-of-the-art computational model to simulate flooding, both fluvial and pluvial (see
reference 2 and 5 for details). The 3Di instrument is based on detailed hydraulic computations.
The computations are extremely fast and therefore allow for interactive modelling, with multiple
stakeholders, on a touch-table.

3Di is a process-based, hydrodynamic model for flooding, drainage and other water management
studies. It can be used for the computation of water flow in 1D and 2D. The software is developed
by a consortium of Stelling Hydraulics, Deltares, TU Delft and Nelen & Schuurmans. With 3Di it is
possible to make fast simulations while using a high level of detail. 3Di allows the user to interact
with the model during a simulation. One can interactively influence the simulation by changing
the rainfall, wind force and model components like cross-sections, breaches and pump capacities.
Deltares also has developed a fully open source model to complement 3Di, called Delft3D Flexible
Mesh. More information about that model can be found here .
3
The first analysis has been conducted in North Rotterdam followed by several cities around the
world.

2 Identifying the cascading effects on vital objects during flooding | October 2019