过去300年雄安新区涝灾年表重建及特征分析

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

通过对历史文献、县志和相关期刊中雄县、安新、容城(合称"雄安新区")洪涝灾害记录的摘录整理,并与降水观测数据比对,确定了反映雄安新区1715~2016年洪涝灾害程度的年表,分析了过去300年洪涝灾害时空分布特征.主要结果为:1715~2016年间雄安新区发生洪涝灾害共计139次,平均2~3 a发生1次;其中灾情最为严重的特大洪涝灾害(文中定义为4级)发生在1738,1801,1892和1954年,3级大涝、2级偏涝、1级轻涝发生的年份数分别为14,35和86.1796~1827,1886~1898和1948~1965年3个时期,雄安地区洪涝灾害发生频繁且灾情严重;空间上,偏涝年份,区域内滨临河湖、地势低洼地段容易被淹没,占全区面积的20%~30%,而特大洪涝年份,除了容城地势较高之处,雄安新区约80%面积被淹没.鉴于历史时期本区水患频发,未来城市建设规划设计中需要考虑水灾频率及空间发生特征.

The chronology of flood grades in the Xiong＇an New Area between 1715 and 2016 is reconstructed based on Chinese historical documents,specifically the Haihe-Luanhe River Flood Historical Archives from the Qing Dynasty,local gazettes from Anxin,Xiong,and Rongcheng Counties,and peer-reviewed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 19 th 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 18 th 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 1810 s and 1820 s,the 1880 s and 1890 s,and during the 1950 s,while they occurred infrequently during the 1850 s and 1860 s.Data also show that the frequency of floods has decreased since the middle of the 20 th century;at the centennial time scale,the 18 th 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 19 th century,once every one to two years on average,while 49 flood events were recorded throughout the 20 th 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.