Flood risk in China: observed changes and variability, management, and projections

Abstract

<p>Despite massive flood protection efforts, undertaken in China for millennia, disastrous floods continue to plague the country. We discuss flood hazard and flood risk in China, starting from observed changes and variability and then dealing with flood risk management and projections. We also refer to recognized unsolved problems in hydrology.</p><p><strong>Observed changes and variability</strong></p><p>First, we review results of change detection in observed records of variables related to water abundance, such as intense precipitation, high river flow, and flood damage in China. There is a strong inter-annual and inter-decadal variability, part of which may be due to climate variability, i.e. oscillation in the ocean-atmosphere system (ENSO - <em>El Ni</em><em>ño</em>-Southern Oscillation and PDO – Pacific Decadal Oscillation). Particular large flood events (e.g. in 1998 and 2016) coincide with high values of ENSO indices.</p><p><strong>Flood risk management</strong></p><p>In its efforts to reduce flood risk, China has undertaken both structural and non-structural measures. An emergency manager's nightmare is when several serious emergencies (e.g., covid pandemic and flooding) happen at once, as in the unprecedented covid year 2020, when also record-breaking precipitation occurred in China. Yet, emergency management made it possible to constrain the flood loss.</p><p><strong>Flood risk projections</strong></p><p>In the warming climate, flood risk is likely to increase over much of China. Projections of flood loss changes for global warming scenarios from 1.5° to 4.0°C above the preindustrial temperature are presented. Projections are based on runoff simulations by a hydrological model driven by multiple downscaled general circulation models, the national GDP projected at shared socio­economic pathways, and the “intensity–loss rate” function. Flood losses in China are projected to soar in the future, particularly in lowland regions subject to rapid economic growth. There is a considerable difference between flood losses corresponding to two global climate policy target thresholds, 1.5° and 2.0°C, amounting to over US$60 billion.</p><p>Available flood projections for China are not consistent. Since the spread is large, projections have to be interpreted with caution, because of the impact on decisions related to climate change adaptation and flood risk reduction.</p>