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1 流域区内水土流失情况及环境现状1.1 水土流失严重,洪涝灾害频繁发生近年来,老灌河流域森林过度采伐,森林覆盖率降低,水土流失严重,洪涝灾害频繁,大量“天然水库”被破坏,森林拦截洪水能力日益衰减,抗灾减灾能力逐渐降低。在相似的降雨量情况下,现在的洪峰流量较过去的大,加上泥石流不断发生,河道淤积,行洪断面日渐减少,洪灾损失也较过去严重。今年7月老灌河流域为暴雨中心,2h雨量为200mm。经调查计算,全流域雨量未超过1958年雨量,但洪峰流量却超过1958年洪峰流量,洪灾损失非常大。据统计,仅西峡县石界河、米坪、桑坪、太平镇、二郎
1 Water and Soil Loss and Its Environmental Status in the Basin 1.1 Severe Soil and Water Loss and Flood Disasters Occur Frequently Occurred In recent years, over-exploitation of forests in the old Gansu River basin has resulted in the decrease of forest coverage, serious soil erosion and flood disasters, and the large number of “natural reservoirs” Was destroyed, the capacity of the forest to intercept floods decaying day by day, and the capability of disaster prevention and reduction gradually decreased. Under similar rainfall conditions, the current flood peak flow is larger than in the past. With the continuous occurrence of debris flow, siltation of the riverway and flood reduction section, the loss of flood damage is also more serious than in the past. July this year, the old irrigation basin is heavy rain center, 2h rainfall 200mm. After investigation and calculation, the rainfall in the whole basin did not exceed the rainfall in 1958, but the flood peak flow exceeded the flood peak in 1958 and the flood loss was very large. According to statistics, only Xixia County Shijiahe, Ping, Sang Ping, Taiping town, Jiro