Systemic risk in interdependent infrastructure: impacts on the population and economy

Critical infrastructure systems like roads, drinking water, telecommunications, and electricity are interconnected and the failure of one system can affect another. When evaluating climate adaptation approaches, understanding this systemic risk, and the time and place-based effects on communities, yields a clearer picture of adaptation priorities. With better information, authorities can make better decisions to safeguard communities and the economy.

How would an extreme flood affect a low-lying region such as South Holland?

Satellite image of South Holland provinc — South Holland province is in a southern, flood-prone area of the Netherlands and is the most populated province in the country. Credit: Lobelia

A hypothetical flooding scenario in South Holland can be used to model systemic impacts across critical infrastructure systems and help regional planners evaluate the effectiveness of different adaptation strategies.

What does the scenario show?

For South Holland, researchers at Deltares based the flooding scenario on the devastating floods that struck Germany in July 2021 and evaluated the systemic impacts of a similar flood to the road network and the electrical substation system in the region.

The model shows shallow flooding spreading across the regional road network for a long period before receding. As a result, many service areas are affected, disrupting electrical substations and impacting around 24,000 inhabitants.

Animation showing the extent of flooding after 48 hours — Specific roads and substations impacted by different flood depths and the resulting population impact. Data: Deltares.¹ Visualisation: Lobelia.

Flooded roads prevent repair crews from reaching disrupted and flooded substations for many hours or days. As transport network failures spread across neighbouring areas, many locations become isolated.

Using a first responder model for this scenario, illustrated below, a crisis manager at the electricity company can evaluate how long substations need to wait for repair. They can explore how the numbers of flooded, operational, and disrupted substations change over time. These insights can help a region to answer important planning questions, decide how many response crews are needed, and how they should be positioned.

The above video shows how long it takes to repair flooded and disrupted substations depending on the number of repair crews. In this case the model uses ten repair crews. Over the first five days following the flood, the status of each substation is modelled hourly. Data: Deltares.¹

Mapping disruption from flood onset through flood recession

The time-based analysis of flood depth, flooded substations, and flooded roads is key to understanding the disruption to different neighbourhoods, to society, and to the economy. Analysis showed that although rainfall stops and flooding peaks after 48 hours, floodwaters recede slowly, and some substations and roads remain flooded for several days afterwards, resulting in highly uneven population and service impacts.

A deeper look at flood impact over time — Researchers compared spatially the impacts to neighbourhoods over three points in time. Data: Deltares.¹ Visualisation: Deltares and Lobelia.

Economic and population impacts across the region

Using the above information, the economic impacts of flooding across the region are analysed to prioritise future adaptation investments. The greatest impacts occur in areas with high economic activity, areas that are densely populated, and where there is a more extensive road network.

Areas of greatest economic losses — Researchers analysed areas of greatest economic losses. Data: Deltares.¹ Visualisation: Deltares and Lobelia.

The highest economic losses overlap with higher rates of population affected, but there are some areas that are particularly disruptive for the economy (above) and others that are particularly disruptive to society (below).

Areas of greatest population impacts — Researchers analysed areas with the largest societal impacts, in terms of the largest population affected. Data: Deltares.¹ Visualisation: Deltares and Lobelia.

Combined adaptation measures reduces overall impacts

The benefits of different adaptation measures can be assessed across multiple levels: hazard-level measures (improving drainage), asset-level measures (elevating infrastructure), network-level measures (prioritising repairs based on economic or service impacts), and system-level measures (providing backup power). The effectiveness of each strategy varies significantly depending on the location and type of intervention.

Depending on which areas and assets are targeted, benefits lean more towards economic impact reduction or towards improving services for local populations.

However, using a combined approach that integrates multiple adaptation measures at different levels (targeting not only drainage for roads, but also elevation for substations) creates a more balanced distribution of benefits for both the economy and local populations.

Combining two or more adaptation measures, such as drainage for roads and elevation for substations, reduces population service impacts by almost 60% and economic impacts over 75%.

Economic and social impact reduction graph — Data: Deltares.¹ Visualisation: Lobelia.

By creating an adaptation appraisal model that allows planners a view of systemic risk in the comparison of adaptation measures, the MIRACA approach can help decision-makers prioritise investments and reduce losses on multiple levels, strengthening resilience where regions need it most.

To discover more about the MIRACA approach to adaptation appraisal, visit the MIRACA book.

References

Peregrina Gonzalez, E. D., Meijer, L. G., van Marle, M. J. E., van Ginkel, K. C. H., & Koks, E. E. (2026). Time-explicit modelling of disruption, recovery and adaptation of an interdependent road-electricity system. ResearchSquare [Preprint]. https://doi.org/10.21203/rs.3.rs-10082159/v1.

Header photo: Flood in Nijmegen, Netherlands. 12th Jan, 2025. Alamy.