In 2022, Bengaluru was brought to a standstill by intense rainfall and subsequent flooding, a stark illustration of how rapidly urbanising cities are struggling to cope with increasingly severe weather events. This incident is not isolated; floods are globally the most common natural disaster, and their frequency and severity are escalating due to a complex interplay of climate change and human activities.
The UN Office for Disaster Risk Reduction reported that floods accounted for 44% of weather-related catastrophic events in the last two decades, with their number increasing by two and a half times between 1980-1999 and 2000-2019. This surge poses a significant threat to lives, property, and economic stability, with current annual river flooding damage in the EU+UK alone reaching €7.8 billion, exposing over 170,000 people yearly. Without concerted mitigation and adaptation efforts, economic losses from river flooding in the EU+UK could increase six-fold to nearly €50 billion annually by 2100, while the population exposed could almost triple. The challenge extends beyond economic costs, impacting ecosystems, critical infrastructure, and the very fabric of communities.
The Dual Drivers: Climate Change and Unplanned Urbanisation
A warmer atmosphere, a direct consequence of global warming, holds more moisture, intensifying rainfall events globally. This meteorological shift is compounded by rapid and often unplanned urbanisation. As Dr. Preeti Tewari and her co-authors noted in their study of the Bengaluru floods: "The study also emphasises the impact of climate change on the frequency and severity of extreme weather events like floods. It suggests that policymakers and urban planners must incorporate climate change predictions when devising and implementing development plans". The proliferation of impermeable surfaces like roads and buildings, coupled with the draining of wetlands and disregard for natural drainage routes, means rainwater overwhelms outdated stormwater systems, leading to pluvial or flash flooding. In Bengaluru, for instance, between 1973 and 2017, paved surfaces increased by 1028%, while vegetation cover declined by 88% and wetlands by 79%, severely reducing the city's natural water absorption capacity.
Sea Level Rise and the Exponential Increase in Coastal and Compound Flooding
Beyond riverine and urban floods, coastal regions face an escalating threat from compound flood events, characterised by the simultaneous occurrence of increased river discharge and high coastal water levels. Research highlights that sea level rise is the primary driver of these changes, even if localised climate impacts on storm surges remain less certain. Heinrich et al. (2023) found that "sea level rise will be the main contributor to those changes for most of Europe". This impact is not linear; the odds of extreme flooding double approximately every five years into the future. Projections indicate that a global warming of just 2K will result in double the amount of compound flood event days for nearly every European river estuary considered, compared to historical levels. This poses a major threat to the 50 million people living in Europe's low-elevation coastal zones and significant economic centres. For example, studies estimate up to €239 billion in annual coastal flooding costs in Europe by the end of the century under a high-emissions scenario (RCP8.5) if no countermeasures are taken.
Implementing Integrated Adaptation Strategies for Long-Term Resilience
To counteract these trends, a shift towards integrated and proactive adaptation strategies is essential. The Environmental Defense Fund advocates for incorporating natural infrastructure that absorbs and holds rainwater, such as "restored wetlands and floodplains... rebuilt oyster reefs, barrier islands and coastal dunes," and "stormwater-grabbing green roofs on buildings". The JRC PESETA IV project underscores the effectiveness of such measures, demonstrating that reducing flood peaks using retention areas has significant potential to lower impacts cost-efficiently. Implementing this strategy at the EU level could reduce economic damage and population exposure by over 70% by 2100, compared to a 'no adaptation' scenario. In addition to retention areas, building-based flood proofing measures can significantly reduce damage, often with limited investment. As Sanja V. Radovanović et al. suggest, flood risk assessment should include detailed maps, historical flood analysis, and an assessment of future flood consequences, taking into account topography, watercourses, existing defences, and the impacts of climate change.
The increasing frequency and intensity of floods demand immediate and holistic policy interventions. By prioritising integrated watershed management, smart land-use planning, and the widespread adoption of green infrastructure, policymakers can not only mitigate the devastating economic and social costs of flooding but also contribute to broader climate change adaptation goals. Investing in these resilience measures today will safeguard communities, critical infrastructure, and ecosystems for a more sustainable and secure future.
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