Cities and Climate Change: Water-related challenges
In the 'Cities and Climate Change' series we are exploring how cities and urban areas are affected by climate change. Besides introducing the challenges cities are facing, our aim is also to discover how cities can be the drivers of change. Therefore, we will also introduce solutions and best practices of enhancing cities’ resilience, too.
As the first article explained, cities are becoming centres of people, consumption and economic activities. Hence, urban areas are also responsible for the vast majority of greenhouse-gas emissions. However, cities also have significant responsibility in tackling these challenges. Ideally, well-thought-out urban development plans consider all environmental, social and economic aspects. Cities aim to provide appropriate services and a decent level of quality of life to their citizens, but this endeavour is often disrupted by the effects of climate change. Water-related challenges associated with climate change are expected to take form in extreme rainfall events, urban flooding, and disturbances of stormwater management, while at the same time, droughts and water scarcity are also challenging cities and settlements (IPCC, 2022).
Figure 1 - Rainy city - Source: Pixabay - StockSnap
In Europe, cities are already experiencing seasonal differences in precipitation. Northern Europe is facing an increase in annual average precipitation, while in the southern parts, a decrease is expected. Typically, dryer summer periods will become more frequent, and increased precipitation during winter is foreseen. Extreme events such as rainfalls, heavy precipitation events and changes in snow mass are becoming more common, often leading to pluvial and fluvial flooding. Urban areas will face intense flooding due to heavy rainfalls and water runoff management are already challenging for several cities. Furthermore, extreme rainfall events might also result in landslides causing disturbances in infrastructure systems, such as transportation. The increase in flood risks is further exacerbated by the growth in land imperviousness. In Denmark, for example, the impervious land cover was elevated by 19% from 1984 to 2014, resulting in a projected increase in the overall extent of flooding between 6% to 26% during heavy precipitation (in projections with present climatic conditions). The capacity and state of urban drainage systems can also influence the emergence of urban pluvial floods, as many urban drainage systems are unable to manage higher levels of rainwater during intense precipitation. Urban pluvial floods are becoming more common. Budapest, for example, was heavily flooded several times (Figure 2.), causing interruptions in urban transport systems and damage to houses. Rainfall events and flooding caused severe damages in the case of Münster, Germany too, where pluvial flooding resulted in damages worth of 72 million EUR in 2014. In 2021, a rainfall of 135 mm caused losses of over 800 million EUR.
Figure 2. Flooding due to heavy precipitation, Budapest, 2020 - Source: hvg.hu
Further economic impacts are associated with damages to buildings and infrastructure, indirect expenses of flooding (e.g. lost business activities), interruption of urban services (e.g. transportation) and health impacts (spreading of infectious diseases and water-borne diseases).
At the same time as extreme rainfall and flooding events, cities are also expected to face water scarcity and drought-related issues. According to a high-impact (high consequence, but low likelihood to define extremes) scenario, droughts could be 14 times more intense than droughts experienced from 1951 to 2000. Water scarcity is becoming more common among European cities, which is worsened by the estimated increase in water demand due to population growth. Reduced public water supply is affecting the well-being of the population, also the functioning of water-dependent economic activities and infrastructure. In the case of Barcelona, water scarcity caused a loss of 1,6 billion EUR, including the expenses of interruptions in industrial production, indirect costs of decreased regional economic productivity and implementation of emergency measures (EEA, 2020). Many European cities faced difficulties due to the severe droughts and other impacts of climate change in 2022. France had to decrease its energy production of nuclear reactors due to high water temperatures. Cities like Spain and the Netherlands had to restrict water consumption in some areas, while Germany faced shipping issues due to low water levels on the Rhine (The Guardian).
Figure 3. - The partially dried-up riverbed of the Rhine near Düsseldorf - source: Guardian
Adaptation – the process of adjusting to the adverse effects of climate change to reduce cities' vulnerability, aiming to preserve the functioning of urban systems – is essential in tackling the aforementioned extremes. The goal of adaptation is to decrease the extent of and prepare for the unavoidable impacts of climate change (Climate Adapt). There are several examples of adaptation measures for water-related impacts. Early warning systems for river flooding have the potential to halve flood-related damages, while long-term solutions of land-use planning can support the development of floodplains and removal of sensitive land uses such as housing, industry or transport. The upgrade of water drainage systems and the separation of rainwater and sanitary sewage systems can support the management of urban water runoff. Extreme rainfall events can also be handled by rainwater harvesting in either surface or underground storage systems. As an example, cities like Glasgow, Copenhagen and Malmö had already implemented such measures. Investments in flood protection infrastructure – such as mobile barriers, floodgates, and strengthened and raised dikes - proved to be a cost-efficient solution for flood management. Drought and water scarcity can be eased by rainwater management methods, such as wastewater re-usage, water demand management or freshwater production through desalination (EEA, 2020).
Water-related issues are strongly interconnected, and overlaps of implemented adaptation measures are seen among European cities. In the case of Rotterdam, the city has been preparing for climate change adaptation for many years. Several resiliency and adaptation strategies were created, focusing also on urban water management among others. The Water Sensitive programme includes the implementation of water storage measures, removing paving, and increasing the city’s water-absorbing capacity through the improvement of green roofs and outdoor public spaces, both aiming to enhance the ‘sponge function’ of the city. Another interesting example is Rotterdam’s Benthemplein water square for rainwater storage. To prepare for extreme weather events, such as heavy rainfalls, storm surges and floodings due to sea-level increases, the Copenhagen metro company developed an adaptation strategy. The lines are now protected against flooding, critical metro elements were elevated, water runoff was diverted from the entrances, drainage grates and floodgates were established and some stations’ pumping capacity was increased as well. The French city, Rouen adopted a water management system formed by small water canals, combined with green infrastructure elements to manage heavy rainfalls and river flooding.
Just as mentioned in the previous article, further examples and best practices are to be found on the main climate adaptation websites for urban areas, such as the Network Nature, Climate Adapt or C40 Cities database.
IPCC, 2022: Dodman, D., B. Hayward, M. Pelling, V. Castan Broto, W. Chow, E. Chu, R. Dawson, L. Khirfan, T. McPhearson, A. Prakash,Y. Zheng, and G. Ziervogel, 2022: Cities, Settlements and Key Infrastructure. In: Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA, pp. 907–1040, doi:10.1017/9781009325844.008.
EEA, 2020: European Environment Agency, Kaźmierczak, A., Urban adaptation in Europe: How cities and towns respond to climate change, Publications Office, 2020, https://data.europa.eu/doi/10.2800/324620
The Guardian: ‘The new normal’: how Europe is being hit by a climate-driven drought crisis https://www.theguardian.com/environment/2022/aug/08/the-new-normal-how-europe-is-being-hit-by-a-climate-driven-drought-crisis
HVG: Törvényszerű, hogy felhőszakadás után elúszik a főváros? https://hvg.hu/itthon/20200616_budapesti_felhoszakadas_extrem_idojaras_klimavaltozas
Climate Adapt: Urban Adaptation Support Tool
Network Nature - Database of EU research and innovation projects on nature-based solutions: https://networknature.eu/ridb?field_ridb_societal_challenges_tid=3495&field_ridb_approach_tid=All&field_ridb_environment_tid=3497&field_ridb_programme_tid=All&field_ridb_nbs_type_tid=All&combine=
C40 Cities: https://www.c40.org/cities/