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清至民国的306年是陕西自然灾害频发的一个时期,其中危害最为严重的是旱灾和水灾,总计旱灾发生年193年,水灾发生年242年。根据资料分析,平均1.55年有一个旱灾年,1.26年有一个水灾年,频繁性是水旱灾害发生的一个显著特点;水旱灾害的发生还呈现出比较明显的增长趋势,其高发期也与“明清小冰期”的气候冷暖波动或冷暖交替时期基本对应;从灾害影响的范围来看,旱灾具有广泛性的特点,较大面积以上的旱灾年可占旱灾年总数的51.3%,水灾则具有局部性的特点,较大面积以上的水灾年仅占水灾年总数的29.34%;就水旱灾害发生的地区而言,旱灾主要集中于关中和陕北,水灾则主要集中于关中和陕南,地域性是水旱灾害的一个共同特点;水旱灾害的发生都具有比较明显的季节性,关中和陕北地区的旱灾主要集中于夏、秋二季,陕南的旱灾则主要集中于夏、春两季;陕西各地的水灾则以秋季为最多,夏季次之;水旱灾害在年际发生特点上具有各自的周期,陕北旱灾变化的周期是40、80年,关中是80年,陕南是20、50年,陕北水灾变化表现出35、90年的变化周期,关中和陕南为30、80年的变化周期。
The 306 years from the Qing Dynasty to the Republic of China were a period of frequent natural disasters in Shaanxi. The most serious of these were the droughts and floods, totaling 193 years of drought and 242 years of floods. According to the data analysis, there is an average annual drought year of 1.55 years and a flood year of 1.26 years. The frequency is a prominent feature of floods and droughts. Floods and droughts also show a rather obvious growth trend, and their high incidence period is also related to From the scope of the disaster impact, the drought has a wide range of characteristics, a large area of drought years can account for 51.3% of the total number of years of drought-related disasters, Floods have the characteristics of locality. Floods of large area and above account for only 29.34% of the total number of floods in a year. For flood and drought disasters, the drought is mainly concentrated in Guanzhong and northern Shaanxi. Floods are mainly concentrated in Guanzhong and The characteristics of floods and droughts are common in South Shaanxi and the region. The occurrence of floods and droughts has obvious seasonal changes. The drought in Guanzhong and northern Shaanxi mainly concentrates in the summer and autumn, while the drought in southern Shaanxi mainly concentrates in Summer and spring; floods in Shaanxi are the most in autumn and summer; flood and drought disasters have their own cycles in the interannual occurrence. The period of drought change in Shanbei is 40 and 80 years, and the period of Guanzhong is 80 years , Southern Shaanxi In 20 and 50 years, the change of floods in northern Shaanxi shows a 35-90 year cycle of change, with 30- and 80-year cycles of change in Guanzhong and Southern Shaanxi.