Summary
Due to climate change, extreme weather events such as flooding are expected to increase in Germany in the future. This poses hidden risks to the healthcare system that have hardly been the focus of resilience planning to date: restrictions on access to hospitals and the supply of medical products due to flood-related traffic disruptions. This has been revealed by Germany-wide modelling carried out by Dr. Seth Bryant from the GFZ Helmholtz Centre for Geosciences and partners, which thus closes a significant gap in flood prevention. They used the GFZ's regional flood model and expanded it with algorithms that take into account flood spread at the level of transport routes and can simulate realistic detours and travel time delays. This also allows the impact on hospitals that are not directly affected by flooding to be determined. The study has been published in the journal Nature Communications Earth and Environment .
Background: Hidden risks to the healthcare system from flooding
The frequency and intensity of extreme weather events are increasing due to ongoing climate change. This places specific burdens on the healthcare system – with far-reaching human, economic, and political consequences. For example, hospitals may be directly affected by flooding or overwhelmed by additional sick or injured people. This can lead to increased morbidity and mortality and, for example, promote the spread of infectious diseases or the worsening of chronic conditions.
However, there are also indirect effects that have received little attention to date – such as disruptions to the transport network, which is crucial for the rapid transport of patients and medical resources. Making health infrastructure resilient to such crises requires effective disaster planning, coordination, and training based on the most accurate and reliable information possible.
New simulation approach: Link between traffic disruption and health infrastructure
Existing assessments of flood situations show where the water flows, but not how this changes access to medical care. This gap is closed by the study conducted by researchers led by Dr Seth Bryant, postdoctoral scientist in GFZ Section 4.4 “Hydrology,” and Jonas Wassmer, doctoral student at the Potsdam Institute for Climate Impact Research (PIK). Both were members of the NatRiskChange Graduate School , which was funded by the German Research Foundation (DFG) until the end of 2024, and both were supervised by Prof. Dr Bruno Merz, former head of the GFZ Hydrology section, Professor at University of Potsdam and co-author of this study.
The team linked two complementary modelling frameworks. First, they drew on previously published simulations from the GFZ Regional Flood Model for Germany ( RFM ), a system developed and refined over more than a decade. To better resolve impacts on transportation infrastructure, these flood outputs were downscaled using a computationally efficient algorithm, increasing spatial detail to roughly five meters and enabling street-level representation of flood propagation.
Second, the researchers implemented a gravity-based traffic model using open-source transportation and demographic data. In this framework, population centers exert a stronger “pull” on travel flows — much like gravitational mass. The novelty lies in integrating this scalable flow model with flood-induced road failures to simulate nationwide detours and congestion effects that simpler routing methods cannot capture.
Results: The vulnerability of hospitals is a nationwide problem in Germany, with 75 priority cases identified
With their combined approach, the researchers highlight previously unconsidered risks posed by flooding events in Germany for hospitals: Hospitals are inaccessible due to traffic jams or road closures, some of which last for months, resulting in the loss or alteration of transport routes for patients and medical products, and the patient load shifting to surrounding hospitals that are not designed for this.
The study, which divided Germany into seven catchment areas of major rivers, shows: Such effects are a challenge for hospitals throughout Germany.
In particular, the study identified 75 hospitals in Germany at risk of patient surges beyond their regular capacity due to an increase in demand by more than 30 percent, driven solely by flood-related traffic disruptions. Alarmingly, one-third of them are located more than ten kilometres away from potential flood areas, so there may be little awareness of this type of hazard.
Although these 75 hospitals represent only a relatively small proportion of the 2,475 facilities in Germany, the scale and severity of the potential disruptions can lead to an increase in morbidity and mortality, underscoring the urgency of addressing such hidden risks with preventive measures.
According to the researchers, the situation is particularly alarming for 29 hospitals, where demand could increase by more than 50 percent, and for nine clinics with a possible increase of 85 to 400 percent.
To better understand the risk situation, the study examines the latter nine most severe scenarios in more detail. They are located in the catchment areas of the Weser (3), lower Rhine (5), and Danube (1) rivers.
The overall analysis also shows that infrastructure close to the border in neighbouring European countries is also under pressure in the event of a disaster. This underscores the need for cross-border disaster management: only through coordinated efforts and the sharing of resources between neighbouring countries can the increased demand for health services after such drastic events be effectively managed.
Conclusion
“Unlike earlier studies, our approach can pinpoint these hidden vulnerabilities and show how their effects ripple far beyond the floodwaters. We identify hospitals that are rarely flooded themselves but could still face major strain because nearby road disruptions redirect patients. Our findings and interactive maps give planners clear, practical information to strengthen key transport links, plan detours in advance, and factor healthcare access into preparedness and early warning systems,” summarizes Dr Bryant.
The identification of hidden risks—facilities that are vulnerable to indirect disruptions despite their distance from flooding—underscores the need for comprehensive, system-wide resilience planning.
To help decision-makers better incorporate the results and align their scenario planning, the researchers provide interactive maps.
Outlook
According to the authors, a major strength of the simulation framework presented here is its adaptability to other contexts and scenarios, such as other geographic regions or other infrastructure networks.
Next, the team plans to extend the framework to an EU-wide model and improve the downscaling algorithm with machine learning.
Communications Earth & Environment
Computational simulation/modeling
Not applicable
Unveiling hidden risks in healthcare from flood-induced transportation disruption in Germany.
19-Aug-2025