The study is built on the sixth phase of the Coupled Model Intercomparison Project, known as CMIP6, using statistically downscaled daily precipitation data at a resolution of 0.25 degrees, roughly 25 kilometers. Rather than simply counting days above a rainfall threshold, the team employed a percentile-based spatiotemporal event-identification approach, which treats extreme precipitation as coherent events unfolding across both space and time. This matters because flood damage is driven not by isolated wet grid cells but by large, persistent storm systems that dump rain over wide areas for consecutive days. By identifying events in this three-dimensional way, the researchers captured the kinds of organized, basin-scale rainstorms that have historically caused the Huai River’s most destructive floods.

The projections cover the period from 2021 to 2100 under four Shared Socioeconomic Pathways, the standard scenario framework used in the most recent Intergovernmental Panel on Climate Change assessments. These pathways span futures ranging from relatively sustainable development with low greenhouse gas emissions to a fragmented world with high emissions and slower economic growth. Against a baseline period of 1995 to 2014, the results show that basin-wide annual frequency of extreme precipitation events increases under every scenario. By the late century, from 2081 to 2100, event frequency climbs by roughly 44 percent to 99 percent depending on the pathway, a near doubling of the storm frequency that the basin’s 180 million residents and vast farmland would have to contend with.

The spatial fingerprint of this change is also revealing. In the baseline era, increases in event frequency are concentrated in the northern and eastern portions of the basin. As the century progresses, however, the areas experiencing more frequent extreme rainfall expand outward into the central and southern parts of the basin. The Huai River Basin occupies a climatic transition zone between China’s humid south and semi-arid north, and it has long been a battleground between cold northern air masses and warm, moisture-laden monsoon flow from the south. The projected expansion of extreme-rainfall territory into the basin’s core suggests that this transition zone is becoming an increasingly active arena for severe rainstorms, with consequences for regions and infrastructure that have not historically faced the most intense flood threats.

Translating hazard into risk requires overlaying it with what scientists call exposure: the people and economic assets located where hazards strike. The researchers drew on gridded population and gross domestic product datasets developed under the shared socioeconomic pathways to project exposure to the year 2100. In the baseline period, about 71.5 million people in the basin were exposed to extreme precipitation events. By 2081 to 2100, that figure rises to between 81.4 million and 160.2 million depending on the scenario, an increase of roughly 14 percent to 124 percent. The upper end of that range, associated with the higher-emission SSP3-7.0 pathway, implies that more than a doubling of population exposure is possible if both emissions and population pressures remain high.

The economic numbers are even more dramatic. Baseline GDP exposure to extreme precipitation in the basin stands at approximately 0.48 trillion constant 2010 US dollars. Late-century projections place it between 7.40 and 19.65 trillion dollars, a more than fifteenfold to fortyfold increase over the baseline. Even accounting for inflation adjustments and the general growth of the Chinese economy embedded in the scenarios, the scale of wealth potentially in the path of extreme rainfall is transformative. It underscores a pattern increasingly recognized in the climate-risk literature: as economies grow and concentrate, the same physical hazard can inflict vastly larger losses, making economic exposure a fast-moving target for adaptation planners.

Crucially, the study goes beyond projecting totals to ask which forces drive the changes. By decomposing exposure changes into climate, socioeconomic, and interaction effects, the researchers found a striking asymmetry between people and money. For population exposure, the climate effect, meaning the increased frequency and extent of extreme precipitation events, is the dominant contributor under all four scenarios, although population growth adds a positive contribution under SSP3-7.0. In other words, where and how often it rains hardest matters most for how many people are affected. For GDP exposure, the picture inverts: socioeconomic development and its interaction with climate together account for 92.8 percent to 95.5 percent of the projected increase, while the direct climate effect plays a comparatively small role. The economic toll of future floods, in short, is chiefly a story about where wealth accumulates, not merely about how the storms change.

One further finding carries particular weight for urban planners. Events that overlap with urban areas account for 55.2 percent to 57.5 percent of all basin-wide extreme precipitation events during 2021 to 2100, and these urban-intersecting storms become more frequent toward the late century. This is significant because cities concentrate both people and impervious surfaces; when intense rain falls on asphalt and concrete rather than absorbent soil, runoff surges quickly into streets and drainage systems, producing flash flooding even from storms of moderate duration. Previous research has shown that urbanization modifies local rainfall patterns and that expanding impervious cover amplifies urban flood responses to climate variability. The Huai River Basin contains some of China’s most rapidly urbanizing provinces, and the study’s results suggest that the coincidence of urban growth and intensifying storms will be a defining flood-risk challenge for the region.

The authors, who also include Fushuang Jiang of Anhui Normal University, Jianqing Zhai of the National Climate Center of the China Meteorological Administration, and Ziyan Chen of the Anhui Climate Center, emphasize that their results clarify how extreme precipitation frequency and socioeconomic exposure are expected to change in the basin and provide actionable information for flood-risk reduction. The Huai River has a long and painful flood history; the basin has been engineered for centuries with levees, channels, and detention areas, yet disasters continue to test those defenses. This study adds a forward-looking dimension to that engineering tradition, identifying not only that risk will grow but where it will grow and which levers, emissions trajectories, population policy, and especially the spatial planning of economic development, will determine its ultimate size. With late-century GDP exposure potentially two orders of magnitude above baseline, the message for the Huai River Basin is unambiguous: the coming decades will demand flood defenses and land-use planning commensurate with a hazard landscape that is expanding in frequency, in territory, and in the value of what lies in harm’s way.

Subject of Research: Projected changes in population and economic exposure to extreme precipitation events in the Huai River Basin under CMIP6 climate and shared socioeconomic pathway scenarios

Article Title: Future changes and drivers of socioeconomic exposure to extreme precipitation in the Huai River Basin

Article References: Future changes and drivers of socioeconomic exposure to extreme precipitation in the Huai River Basin. (n.d.). https://doi.org/10.1007/s11069-026-08417-x

Image Credits: AI Generated

DOI: 10.1007/s11069-026-08417-x

Keywords: extreme precipitation, socioeconomic exposure, Huai River Basin, CMIP6, shared socioeconomic pathways, flood risk, population exposure, GDP exposure, climate change, urban flooding, climate projections, disaster risk