A Manual for Integrated Urban Flood Management in China
Floods stand as the most frequent natural hazard globally, inflicting more damages than any other disaster. Between 1998 and 2018, floods impacted over 2 billion people, constituting 45 percent of all disaster-affected individuals during that period, with an estimated 142,088 fatalities. Immediate impacts include loss of life, livelihoods, property damage, crop destruction, livestock loss, service disruption, and health deterioration due to waterborne diseases. Direct economic losses from flooding in the last decade totaled US$ 656 billion, though likely underreported. When factoring in intangible impacts on human well-being, natural disasters are believed to cost the global economy over US$ 520 billion annually.
Increasing exposure to floods, coupled with changing climate conditions, is expected to exacerbate damages. This heightened exposure stems from ongoing population growth, urbanization, economic expansion, and climate change effects. Climate changes are projected to alter water regimes, precipitation patterns, runoff, and sea levels, amplifying flood frequency and severity. By 2050, approximately 1.3 billion people, or 15 percent of the global population, are expected to inhabit flood-prone areas. Acknowledging the uncertainties in climate change projections, there’s a growing call for robust approaches, evident in the rise of scenario planning and holistic flood management strategies like Integrated Urban Flood Management (IUFM), which considers various social, economic, and environmental objectives.
China ranks among the most flood-exposed nations globally, a vulnerability expected to worsen under future climate change. Over 67 percent of its population resides in flood-prone regions. Recorded flood losses in China soared from US$ 7 billion annually in the 1980s to around US$ 24 billion per year in the 2000s, peaking at US$ 51 billion in 2010. On average, floods inflict losses equivalent to 1 percent of Chinese GDP annually. China is listed as the 31st most affected country by climate-related disasters. Recent floods in southern China during 2020 incurred direct economic losses of US$ 25.87 billion, with potential secondary effects not factored in. Under different climate scenarios, China faces an 82 percent surge in direct economic losses over the next two decades without substantial adaptation measures.
Rapid urbanization and associated land use changes escalate urban flood risks in China. Urbanization leads to more impermeable surfaces, reducing infiltration and increasing runoff during storms. Urban microclimate effects and urban heat islands contribute to heightened thunderstorm occurrences. Concurrently, urban migration exposes more people and assets to flood risks. China’s urbanization rate surged from 17.9 to 59.6 percent from 1978 to 2018, with urban population expected to reach 70 percent by 2030. Flooding is already commonplace in 641 of China’s 654 largest cities, with 62 percent of cities experiencing floods from 2011 to 2014, resulting in direct economic losses of up to US$ 100 billion. Severe flooding in Hubei Province in July 2020, where the COVID-19 outbreak originated, incurred economic losses exceeding US$ 3 billion, according to preliminary estimates.
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