Reconstruction of the chronology and characteristics of flood disasters in the Xiong'an New Area over the last 300 years

Abstract

The chronology of flood grades in the Xiong'an New Area between 1715 and 2016 is reconstructed based on Chinese historical documents, specifically the Haihe-Luanhe River Flood Historical Archives from the Qing Dynasty, local gazettes from Anxin, Xiong, and Rongcheng Counties, and peer-reviewed papers published in scientific journals that covered flood disasters and water resources in Hebei Province, and observed precipitation data. Flooded areas at each grade were plotted to analyze the spatial characteristics of flood disasters. The chronology of flood disaster grades between 1951 and 1985 was initially reconstructed using both county-level event descriptions (intensity and flooded area) and precipitation data. Thus, because the highest level of precipitation (1261 mm, more than twice the average, as reported by records in local gazettes) was experienced in 1954, the disaster was categorized as a grade 4 mega-flood. Similarly, records show that precipitation levels in 1956, 1959, 1964, and 1977 were more than 1.5 times the average, and these were categorized as grade 3 severe floods. Using this method, grade 2 medium floods and grade 1 light floods were defined and recognized. While the grades of floods between 1715 and 1950 were reconstructed based on the literal historical descriptions of the flood disasters, the primary index for floods during the period from 1986 to 2016 was observation data, accompanied by literal records from journals. In this way, a complete reconstruction of flood grade chronology for the period between 1715 and 2016 in the Xiong'an New Area is presented in this study. The results suggest that 139 flood events have occurred over the past 300 years within the Xiong'an region, at an average rate of approximately once every two to three years. Mega-flood events occurred in 1738, 1801, 1892, and 1954, at a rate of approximately one every 76 years. Fourteen severe floods occurred, in 1775, 1816, 1819, 1822, 1823, 1890, 1893, 1894, 1950, 1956, 1959, 1964, 1977, and 1988, at a rate of approximately once every 22 years, and grade 2 medium floods and grade 1 light floods have occurred 35 and 86 times, respectively. The periods between 1796 and 1827, between 1886 and 1898, and between 1948 and 1965 were characterized by the occurrence of severe flood events, while the periods between 1845 and 1875 and between 1989 and 2016 were characterized by less severe disasters. At the centennial scale, reconstructions show that flood disasters during the 19th century were the most serious, as mega- and severe floods have occurred twice and seven times, respectively, while just one mega- and one severe flood are thought to have occurred during the 18th century. The impact of flood disasters over the last 50 years (between 1967 and 2016) has been relatively weak, however, because no mega-flood has occurred. In contrast, a temporal comparison of the frequency of flood disasters at the decadal scale reveals that these events occurred frequently during the 1810s and 1820s, the 1880s and 1890s, and during the 1950s, while they occurred infrequently during the 1850s and 1860s. Data also show that the frequency of floods has decreased since the middle of the 20th century; at the centennial time scale, the 18th century (between 1715 and 1800) experienced the least flood disasters because events occurred 29 times over this period, which was once every three to four years on average. A total of 58 events occurred during the 19th century, once every one to two years on average, while 49 flood events were recorded throughout the 20th century, once every two years on average. Spatially, grade 2 medium flood disasters have tended to inundate between 20% and 30% of the whole region, especially low-lying areas around rivers and lakes. However, during grade 4 mega-flood disasters, 80% of the Xiong'an region was inundated because these events covered both low-lying and higher areas. Although the frequency and intensity of flood events have decreased over the last 50 years compared to the historical record, policy makers may nevertheless take into account the spatial and temporal features highlighted in this study for future urban construction planning.