Once in a thousand years: The increasing threat of mega floods in southern China
River flooding is among the most catastrophic disasters worldwide. The Pearl River, the longest watercourse in southern China, particularly its lower reach with dense population and economic activity, has been identified as one of the world’s most vulnerable regions to flood exposure. Over 400 major flood disasters have been documented in the Pearl River basin over the past 2000 years. Model simulations even suggest that future surface warming can enhance both the intensity and frequency of extreme rainfall in this region.
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The climatic background related to these great floods was found to match the period of weakening Asian summer monsoons, indicated by Chinese speleothem δ18O data and higher El Niño-Southern Oscillation (ENSO) frequency. Therefore, the authors suggest that the past great floods in the lower Pearl River area were possibly triggered by a weak summer monsoon and enhanced ENSO.
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Furthermore, the earliest FL1 flood coincided with the demise of the Dingsishan culture approximately 6000 years ago. Megafloods also play a central role in some famous tales or old legends. In the Pearl River basin, the Dragon Mother is worshipped as a water god and protector against floods. The origin of this worship culture can be traced back to the Qin Dynasty (221–207 BC), fitting chronologically with the FL5 flood. The FL7 flood coincided with the beginning of levee construction along the local West Pearl River during the Song Dynasty. The authors argue that the recurrent megafloods had noticeable impacts on the development of local civilization and human society in the Pearl River basin.