Germany, Belgium and the Netherlands were hit by extreme
precipitation and flooding in July 2021. This brief communication provides
an overview of the impacts to large-scale critical infrastructure systems
and how recovery has progressed. The results show that Germany and Belgium
were particularly affected, with many infrastructure assets severely damaged
or completely destroyed. Impacts range from completely destroyed bridges and
sewage systems, to severely damaged schools and hospitals. We find that
(large-scale) risk assessments, often focused on larger (river) flood
events, do not find these local, but severe, impacts due to critical
infrastructure failures. This may be the result of limited availability of
validation material. As such, this brief communication not only will help to
better understand how critical infrastructure can be affected by flooding,
but also can be used as validation material for future flood risk
assessments.
Introduction
In mid-July 2021, a persistent low-pressure system caused extreme
precipitation in parts of the Belgian, German and Dutch catchments of the
Meuse and Rhine rivers. This led to record-breaking water levels and severe
flooding (Mohr et al., 2022). Comparable heavy precipitation events in this
area have never been registered in most of the affected areas before
(Kreienkamp et al., 2021). The German states most affected include
Rhineland-Palatinate (Rheinland-Pfalz), with damage to the Ahr River valley
(Ahrtal), several regions in the Eiffel National Park, to the
city of Trier. Flooding in Belgium was concentrated in the Vesdre River
valley (districts of Pepinster, Ensival and Verviers), the Meuse River
valley (Maaseik, Liége), the Gete River valley (Herk-de-Stad and Halen) and
southeast Brussels (Wavre). The Netherlands experienced flooding, mostly
concentrated in the southern district of Limburg. In total, at least 220
casualties have been reported, with insured loss estimates of approximately
EUR 150 million–EUR 250 million in the Netherlands (Verbond voor Verzekeraars, 2022),
∼ EUR 2.2 billion in Belgium (Assuralia, 2022) and
∼ EUR 8.2 billion (GDV, 2022) in Germany. The event caused
major damages to residential and commercial structures and to many critical
infrastructure (CI) assets. Not only vital functions for first responders
were affected (e.g. hospitals, fire departments), but also railways,
bridges and utility networks (e.g. water and electricity supply) were
severely damaged, expecting to take months to years to fully rebuild.
CI is often considered to be the backbone of a well-functioning society
(Hall et al., 2016), which is particularly eminent during natural hazards
and disasters. For instance, failure of electricity or telecommunication
services immediately causes disruptions in the day-to-day functioning of
people and businesses, including those outside the directly affected area.
Despite the (academic) agreement that failure of infrastructure systems may
cause (large-scale) societal disruptions (Garschagen and Sandholz, 2018;
Hallegatte et al., 2019; Fekete and Sandholz, 2021), empirical evidence on
the impacts of extreme weather events on these systems is still limited.
This brief communication provides an overview of the observed flood impacts
to large-scale infrastructure systems during the 2021 mid-July western
European flood event and how reconstruction of these large-scale systems
has progressed. Next, we highlight how some of these observations compare to
academic modelling approaches. We conclude with suggestions on moving
forward in CI risk modelling, based on the lessons learned from this extreme
event.
In Germany, road and railway infrastructure was severely damaged as
documented exemplarily in Fig. 1. Cost estimates reach up to EURO 2 billion
Euro (MDR, 2021). More than 130 km of motorways were closed directly after
the event, of which 50 km were still closed two months later, with an
estimated repair cost of EUR 100 million (Hauser, 2021). Of the 112 bridges
in the flooded 40 km of the Ahr valley (Rhineland-Palatinate), 62 bridges were
destroyed, 13 were severely damaged and only 35 were in operation a month
after the flood event (MDR, 2021). Over 74 km of roads, paths and
bridges in the Ahr valley have been (critically) damaged. In some cases,
repairs are expected to take months to years (Zeit Online, 2021). For
example, major freeway sections, including parts of the A1 motorway, were
closed until early 2022 (24Rhein, 2022). In addition, about 50 000 cars were
damaged, causing insurance claims of some EUR 450 million (ADAC, 2021). The
German railway provider Deutsche Bahn expects asset damages of around EUR 1.3 billion. Among other things, 180 level crossings, almost 40 signal
boxes, over 1000 catenary and signal masts, and 600 km of tracks were
destroyed, as well as energy supply systems, elevators and lighting systems
(MDR, 2021). As of 11 April 2022, 14 of the affected rail stretches are fully
functional again. The less damaged stretches were functional again within 3 months, while some of the most damaged sections in the Ahr valley are
expected to be finished by the end of 2025 (DB, 2022). In Belgium,
approximately 10 km of railway tracks and 3000 sleeper tracks have to be
replaced; 50 km of catenary needs to be repaired; and 70 000 t of
railway track bed needs to be placed, with estimated costs between EUR 30 million–EUR 50 million (Rozendaal, 2021a). Most damages have been repaired within 2
weeks. The most severely damaged railway line (between the villages of Spa
and Pepinster) was reopened again on 3 October 2021 (Rozendaal, 2021b). In
the Netherlands, no large-scale damage has been reported to transport
infrastructure. A few national highways were partly flooded (e.g. the A76
in both directions) or briefly closed (< 3 d) because of the
potential of flooding. Most likely due to relative low-flow velocities,
damage to Dutch national road infrastructure was limited. Several railway
sections were closed (e.g. the railway section between Maastricht and
Liége) and some damage occurred to the railway infrastructure, in particular
to the electronic “track circuit” devices and saturated railway embankments
(Prorail, 2021).
Damage in the Ahr valley, Germany (images taken on 11 August 2021). (a) Destruction of federal highway B266 (A1) and railway (A2)
near Heimersheim. (b) Further upstream in the Ahr valley (Altenburg),
large stretches of the Ahrtalbahn railway have been destroyed (B1) and the
few remaining road and rail bridges show signs of temporary repairs (B2).
(c) Riverbed erosion uncovered and destroyed many cables supposed
to lie more than 80 cm below surface level (C1) as well as sewers (C2).
(d) Inundated electricity distribution infrastructure (D1), road
erosion and stabilization (D2), uncovered cables (D3), and collapsed
buildings in Schuld. Pictures by Margreet van Marle/Deltares/GEERassociation, distributed under Creative Commons
Attribution 4.0 license.
Electricity and gas supply
At the peak of the event, around 200 000 people experienced power outages in
Germany. Electricity infrastructure was severely damaged in North
Rhine-Westphalia and Rhineland-Palatinate. However, within 2 d around 50 %
of the power was restored through repairs and temporary fixes. Within 8
weeks, no emergency power generators were required anymore, with most of the
power infrastructure restored in Germany's affected areas. Some areas,
however, only had permanent power infrastructure after 6 months (Westnetz,
2022). The gas distribution network in the Ahr valley was severely
damaged. Approximately 133 km of natural gas pipelines, 8500 gas metres,
3400 house pressure regulators, 7220 of the approximately 8000 household
connections, and 31 systems measuring and regulating gas pressure have been
damaged or destroyed (SWR, 2021). Gas supply was almost fully restored
within 4.5 months after the flood event (Energienetze Mittelrhein, 2021). In
Belgium, approximately 41 500 people experienced power outages at the peak
of the event. This was the result of both damaged and deliberately switched-off electrical cabinets to prevent serious damages. It took around 3
weeks to fully restore power. Similar to Germany, severe damage had been
observed to the gas network. In the villages around Liége, such as
Chaudfontaine and Pepinster (Belgium), gas supply was fully recovered within
5 months (Grosjean, 2021; De Wolf, 2021). In the Netherlands, 1000–2000 households
experienced a loss of electricity supply at the peak of the event. Between
100 to 200 households had no gas supply. Within several days, electricity
supply was restored (Task Force Fact Finding Hoogwater, 2021).
Overview of observed and expected reconstruction duration of each
infrastructure sector considered in this study. It should be noted that this
figure presents reconstruction efforts of the system. No line indicates that
no impacts are observed. Solid waste is not included in the figure, as no
impacts were recorded within each country.
Drinking water supply and wastewater
In the region of Rhineland-Palatinate (Germany), most drinking water supply was
restored within 2 months (Hochwasser Ahr, 2021a). However, sewage
treatment plants in Altenahr, Mayschoss and Sinzig had been largely
destroyed (Hochwasser Ahr, 2021b), and it is expected to take at least 1.5
years to fully repair most sewage treatment plants. Emergency sewage
treatment plants have been built in the meantime (GA, 2021). In the Erft
region 7 out of 31 wastewater facilities had been destroyed. Many
facilities reported pollution of oil and diesel, forming layers up to 15 cm
thick (Kuhn, 2021). In addition, much of the groundwater (and soil) in the
flood region was mixed with oil (from destroyed residential oil tanks),
chemicals such as fertilizers (from wineries and other agriculture) and
chemicals from nearby industrial plants. In Sinzig, 3.6×106 L of
oil–water mixture was recycled, gaining 3600 m3 of oil, to be reused
for heating and industrial usage (Kuhn, 2021). In the heavily destroyed town
of Bad Münstereifel (in the state of North Rhine-Westphalia), drinking
water supply was re-established within 5 d after the flood event (most
frequently through emergency tanks), and about 50 % of the city centre was
reconnected to the fresh-water network shortly thereafter however, water
had to be boiled before consumption until about 1 month later (Bad
Münstereifel, 2021). In Belgium, several towns experienced disruptions
in water supply (in particular as a result of pollution). Directly after the
event, approximately 3400 families had no access to potable water. Within
less than a week, this was reduced to around 1650 families (Terzake, 2021).
It took, however, 6 months to rebuild the permanent water supply
infrastructure (SWDE, 2022). In the Netherlands, little to no problems have
been recorded with regards to water supply.
Solid waste
We found no information regarding direct impact on solid-waste facilities as
a result of the flood event. However, there is a large pressure on the solid-waste sector to clean the affected areas; 1 month after the event, we
observed dozens of large temporary waste fills and frequent incidences of
oil pollution in Rhineland-Palatinate during a field visit. In the Ahrweiler
district alone, the flood caused as much solid waste as normally would be
collected over 30 years. In Belgium, the amount of solid waste is
estimated around 160 000 t, stored at several places, such as the
abandoned highway track A601. This highway has been used for approximately 9
months as a temporary storage for debris (Couplez, 2022). In the
Netherlands, there have been primarily problems with waste deposits along
the river banks, which is mostly the solid waste transported by the river
from further upstream. Thousands of tonnes of tree debris (logs and deadwood)
were recycled in the Ahr valley. For instance, the towns of Höenningen and
Mayschoss, served as major recycle hubs. Per day, approximately 500 t of wood
debris was transported, cut, chipped and recycled into firewood,
which continued for at least 6 weeks after the flood (Gather, 2021).
Telecommunication
In Germany, all severely affected areas experienced disruption of mobile
network services. Within the region of Rhineland-Palatinate, it took 2 weeks to
ensure 100 % coverage again through emergency communication masts. Within
1 month, most of the network was restored to pre-disaster service
provision. After 5 months, broadband has also been restored in the most
affected areas, which started in most areas only after power infrastructure
was rebuilt (Westnetz, 2021). In Belgium, it has taken around 11 months to
restore connection to the last communities within the affected area. In the
Netherlands, approximately 7000 households were affected by disrupted telecommunication service. This was primarily due to flooded
telecommunication infrastructure in the direct vicinity of flooded houses.
However, some distribution cabinets were flooded as well, with the largest
flooded cabinet affecting around 700 households. Due to damaged bridges,
several fibre cables were damaged. Five telecommunication masts were
affected as well, but “tuning” of the network ensured that the service
disruption was kept to a minimum (Task Force Fact Finding Hoogwater, 2021).
Healthcare and education
In Germany, an estimated 180 general-practitioner practices have been
affected by the flood event. Impacts range from completely destroyed to
unable to operate due to a lack of running water and electricity (Ärzte
Zeitung, 2021). After 1.5 months, medical care was guaranteed again in the
most affected regions in Rhineland-Palatinate (Hochwasser Ahr, 2021c). In the
state of North Rhine-Westphalia, approximately 68 hospitals have been
affected, of which several have been affected severely and will take at
least 1.5 years to be rebuilt (Fig. 2). Direct damages are estimated to be
at least EUR 100 million to repair all medical facilities (Korzilius,
2021). In the town of Eschweiler (Germany), for example, the basement of the
hospital was flooded, as well as the outbuildings and the entire outdoor
area. The power supply collapsed, the entire building technology was
destroyed and some 300 patients had to be evacuated by helicopter. Property
damage is expected to be around EUR 50 million. Within 3.5 weeks, the
hospital was partly operational, and within 3 months, all hospital
operations continued normally (SAH Eschweiler, 2021). The Mutterhaus Ehrang
hospital in Trier (Germany) is now permanently closed as the hospital is too
severely damaged to rebuild. Furthermore, in the region of Rhineland-Palatinate
(Germany), 19 daycare centres and 17 schools suffered damage from the
floods, affecting more than 8000 students (Staib, 2021). Approximately 4
months after the flood event, the district of Bad Neuenahr-Ahrweiler
established emergency educational facilities using 297 containers that serve
as classrooms, offices and dining facilities for more than 800 students
(Wiesbadener Kurier, 2021). In Belgium, various rural clinics have been
affected and were unable to provide any services. Concurrently, in the most
affected areas, general-practitioner facilities have been completely
destroyed (Le Spécialiste, 2021). In the Netherlands, one nursing home
was flooded, and one hospital was evacuated as a precautionary measure.
Have research studies already “reflected” such impacts?
Most often, large-scale object-based infrastructure impact studies (e.g.
Bubeck et al., 2019) only disclose aggregated risk metrics (i.e.
country-level risk estimates), which hampers verification and validation
with observed impacts on smaller scales. Van Ginkel et al. (2021) assessed
river flood risk for all road segments in Europe. Of the eight motorway
floods incidents in Germany reported by Hauser (2021), three are
recognizable as flood hotspots in van Ginkel et al. (2021). During the event
in 2021, most damage was caused by relatively small rivers which are only
represented in the hazard data from the point that the upstream catchment is
above 500 km2. For example, the Ahr valley is partly covered (400 of
the 900 km2) by van Ginkel et al., 2021, who estimate the road repair costs
at EUR 4 million to EUR 29 million (under low- and high-flow velocities respectively.) for a
1:500 year event. The field visit showed damage caused by high-flow
velocities at multiple places, and video footage of the events suggests
these are locally more towards 2 m s-1, which van Ginkel et al. (2021) considered
“high-flow velocity”, than towards 0.2 m s-1, which they considered “low-flow
velocity”. At first sight, the spatial extent of the exposed assets has
reasonable correspondence to the model of van Ginkel et al. (2021). However,
the model ignores bridge damage, which in reality was a major source of
damage (Sect. 2.1). Also, a significant share of observed damage resulted
from pluvial flooding, flash flooding and landslides which was not captured
by van Ginkel et al. (2021).
Reconnaissance observations (August 2021) along the rivers Ahr and Erft
(Lemnitzer et al., 2022) documented severe, as well as irreparable, damage to
bridges designed and constructed within the last 2 decades and total
destruction of almost all historical bridges, typically constructed on
shallow foundations. Historical bridge designs concentrated primarily on
cross-sectional requirements for expected water volumes. Triggered by flood
events in the past four decades, bridge design research has broadened by
focusing on risk-based scour assessment, hydrodynamic pier designs,
reduction of intermediate bridge support elements, impact and collision
loading, implementation of bridge protection mechanisms such as from wood
debris, and machine learning approaches from past failures (VAW 188,
2006; Bento et al., 2020; Majtan et al., 2021; Naser, 2021). Accounting for
all these mechanisms, however, is complex (Haehnel and Daly, 2004) and no
guarantee to avoid the observed failures. Various international design codes
(e.g. American bridge standard AASHTO, Australian bridge standard AS5100,
and Japanese bridge standard SHB) provide quantitative tools to assess
impact loading from debris/tree logs; however, bridges erected prior to
recent design requirements are unable to maintain global structural
stability under the excessive multidirectional loading, such as seen in the
2021 floods. Based on field observations, the advancement of erosion
prevention practices for flood events emerged as a critical research focus,
as the interface stability between water, soil and foundation elements was
found to be compromised at almost all bridge damage locations visited.
Next to the above insights into modelling direct physical damages, we can
also use the observation from the event to further improve and validate our
assumptions on post-disaster (infrastructure) recovery. In particular, when
modelling the economic and societal impacts, the recovery process is one of
the most important drivers of losses (e.g. Koks et al., 2015). The July
2021 event has given us several insights. Firstly, there is a
prioritization between different infrastructure systems. In Germany, for
example, we found that in several affected areas the electricity network was
repaired first, which was subsequently followed by the gas and broadband
network. Secondly, there is a prioritization within infrastructure systems.
For example, more critical roads are repaired sooner than less critical
roads. While this may sound obvious, academic studies often consider a
recovery of the entire system, without considering a specific order of
importance. Finally, good recovery management practices and enough
trades(wo)men (e.g. electricians, utility workers) are one of the most
important drivers of a speedy and successful recovery. These are often not
included within the modelling assumptions.
Moving forward
Based on our findings, we highlight three aspects to move forward in the
field of infrastructure disaster risk assessments. First, merely focusing on
flood extent and depth is not sufficient to estimate the impacts of extreme
flood events to infrastructure. In particular, in Germany and Belgium, it
became evident that the high discharge and streamflow and corresponding
high-flow velocities (resulting from the local topography and the intensity
of the rainfall) are a decisive factor in explaining the degree of
destruction. Many of the observed failures such as bridge scour, road
embankment instabilities and erosion of aggregate foundations could likely
better be explained from flow velocity rather than flood depth. Future flood
impact studies, especially those focusing on transport infrastructure,
should aim to account for flow velocity in their impact modelling, in particular in areas with steep gradients.
Second, the observed impacts on CI highlight the influence of spatial scale
on the magnitude of the impacts. On a local and regional level, the
disruptions in daily lives and to the economy were enormous. Yet, zoomed out
on a national scale, the impacts were relatively small. While large-scale studies are
useful to identify potential hotspots and bottlenecks in the system,
local-scale studies are essential to better understand the real impacts (and
are also better able to do so). This is true for both the consequences to
infrastructure assets and the services and the impacts on lives and
livelihoods.
Finally, the level of destruction and disruption caused by this event
highlights the need for the development of both asset and system-level
adaptation measures, securing more resilient infrastructure systems. Extreme
weather events are expected to become more likely not only in western Europe, but
also globally in an increasingly warmer world. As such, there is an urgency
to investigate not only how service provision can be ensured in the case of
an extreme event but also how the recovery process to a minimum service
level can be as swift and smooth as possible. This calls for a further
collaboration between the different sectors of reliability and systems
engineering and disaster risk modelling and management. The limited number
of studies on impact on CI due to flooding highlights the need for more
detailed infrastructure failure impact assessments including cascading
impacts.
Data availability
No data sets were used in this article.
Author contributions
All authors collaborated and contributed to drafting, reviewing and editing the paper. EEK and KCHvG contributed equally to the initial idea of this manuscript. EEK wrote the original draft of the manuscript, with key input from KCHvG. EEK and AL collected the information for Germany and Belgium. KCHvG and MJEvM collected most of the information for the Netherlands. EEK created Fig. 2. KCHvG, MJVEvM and AL participated in a GEER field trip to visit the affected area in the disaster aftermath.
Competing interests
The contact author has declared that none of the authors has any competing interests.
Disclaimer
Publisher’s note: Copernicus Publications remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Financial support
This research has been supported by the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (grant no. VI.Veni.194.033) and funded as part of the EU Horizon 2020 project RECEIPT (grant no. 820712).
Review statement
This paper was edited by Joaquim G. Pinto and reviewed by three anonymous referees.
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