目前国外大江大河的防洪,一般以实际发生过的最大洪水或百年一遇洪水作为防洪标准。各国江河的防洪标准不太高,对洪水都不能做到完全控制,还存在特大洪水灾害的威胁。近年来特别强调对洪水威胁地区的管理、控制,调整土地的利用,限制城镇和工厂的发 At present, the flood control of major rivers in foreign countries generally takes floods that have actually occurred or floods once in a hundred years as flood control standards. Flood control standards of rivers in various countries are not too high, and full control over floods can not be achieved. There is also the threat of catastrophic flood disasters. In recent years, special emphasis has been placed on the management of flood-threatening areas, the control and regulation of land use, and the restrictions on the development of towns and factories