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(一) 过去设计洪水中存在的问题美国东部地区的洪水以暴雨为主,实测最大暴雨4个半小时曾达782毫米,24小时983毫米,三天1,148毫米。西部地区以融雪为主,暴雨较小,但往往两者遭遇,组成量大峰高的洪水。过去对于水库设计洪水,曾用历史洪水加成、经验公式和频率统计法,都是用水文资料进行推算,没有从气象方面进行研究分析。三十年代美国曾连续发生几次特大暴雨的洪水。例如1935年内布拉斯加州雷普布利根河发生的大洪水,为以前39年资料中最大纪录的10倍;1936年东北地区康涅狄格河的大洪水,超过以前135年资料中最大纪录的42％,还有些较小河流达到过去最大纪录的2～3倍,1937
(I) Problems in the Design Flood in the Past Floods in the eastern United States are dominated by heavy rain. The maximum measured rainfall reached 782 mm in 4 and a half hours, 983 mm in 24 hours and 1,148 mm in three days. In the western region, snowmelt is the mainstay with heavy rainstorms. However, it is often the case that both of them encounter floods with large peak heights. In the past, floods to the design of reservoirs, historical flood additions, empirical formulas and frequency statistics were all derived from hydrological data and were not analyzed from the meteorological aspects. In the thirties, there were several floods that hit the United States in consecutive months. For example, the floods that took place at Rembloughy River, Nebraska, in 1935, were 10 times the record in the 39 years of data; the floods of the Connecticut River in northeastern China in 1936 surpassed 42% of the record in the previous 135 years, , And some smaller rivers reached 2 to 3 times the largest record in the past, 1937