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一 北京山区是泥石流多发地区之一。因此,对其发生的时间、空间规律进行分析研究,将为山区农业区划和泥石流防治规划提供某些依据。 北京地处季风气候半干旱地区,本区发生泥石流的必要条件之一,就是需要一定的降雨方式,或者说需要有一种特殊的降雨过程。 一般情况下,暴雨接踵于连阴雨之尾,常会发生泥石流。譬如,1950年8月4日房山县大石河地区发生的泥石流,据幸存的杨家两兄弟介绍:连阴雨至第三日早饭前,骤然暴雨倾盆,只见从大西沟而下的泥石流,裹携着几十株核桃树,直立、倒卧或揉折其中,凶涌而下,至谷地拐点涌上山坡,扫过半坡上的杨家宅院。结果使其全家九口仅幸存他兄弟二人。同日,清水河在“室外白茫茫一片,数步之外不辨人物”的暴雨中,
One of Beijing’s mountainous areas is one of the debris flow-prone areas. Therefore, the analysis of time and space rules will provide some basis for the planning of mountainous area agriculture and debris flow prevention and control. Beijing is located in a semi-arid climate in the monsoon climate. One of the necessary conditions for debris flow in this area is the need for a certain rainfall pattern, or the need for a special rainfall process. Under normal circumstances, heavy rain followed the end of the rainy season, mudslides often occur. For example, on August 4, 1950, the mudslides that occurred in the Dashihe area of Fangshan County reportedly survived the two brothers in the Yang Family. Before the rainy day, before the breakfast on the third day, they saw heavy rain and mud and saw the mudslides flowing down from the Daxigou. Dozens of strains of walnut trees, upright, lying down or rub them, fierce down, to the influx of valleys on the hillside, sweep the Banpo Yang House. As a result, his family of nine survived only his brother. On the same day, Qingshui River in the “outdoor vast expanse of white, a few steps away from the character does not distinguish” heavy rain,