We examine the debris flow activity in Trans-Ili Alatau since 1900 till the present. Characteristics of the debris flow formation conditions and data on the largest debris flows are presented. A study is made of the interannual and intra-annual variability of debris flow activity. The debris flow activity was characterized by the number of debris flows in a year, and by the total volume of debris transported. For the period from 1900 to 2017 we recorded 481 debris flows. It was found that the genetic types of debris flows are dominated by rain-induced and glacial flows (87 % of the total number of debris flows). The other genetic types (snow-caused, seismogenic and anthropogenic) account for 13%. Most of the debris flows have a rain genesis (71% of the total number of rain-induced and glacial debris flows). Glacial debris flows account for 79% of the volume of debris transported. The volumes of the largest debris flows, both glacial and rain-induced, exceed one million cubic meters. They make up 3% of the total number of debris flows but they transported 70 % of debris. Small debris flows with a volume of less than 10 thousand cubic meters, in terms of their number, constitute 74%; however, they account for a mere 3% of the volume of debris flow deposits. Observations indicate that the earliest debris flows occurred in the second ten-day period of March, and the latest occurred in the first ten-day period of September. The distribution of the number of debris flows according to the dates of their occurrence clearly shows two maxima: one maximum in the second ten-day period of June, and the other maximum in the second ten-day period of July. The June maximum is due to rain precipitation, and the July maximum is associated with glacial debris flows. From 1950 to 2017 there were only 5 (7%) years without any debris flows. Four of them corresponded to the 2010s. The number of years with rain-induced and glacial debris flows was 55 (81%) and 39 (57%), respectively.

中文翻译：

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20 世纪至 21 世纪初跨伊犁阿拉套的泥石流活动

我们研究了从 1900 年至今的 Trans-Ili Alatau 泥石流活动。介绍了泥石流形成条件的特征和最大泥石流的数据。对泥石流活动的年际和年内变化进行了研究。泥石流活动以一年内发生的泥石流数量和运送的泥石流总量为特征。在 1900 年至 2017 年期间，我们记录了 481 次泥石流。结果表明，泥石流的成因类型以降雨和冰川流为主（占泥石流总数的87%）。其他遗传类型（雪引起的、地震引起的和人为的）占 13%。大多数泥石流都有降雨成因（占降雨和冰川泥石流总数的 71%）。冰川泥石流占运移的泥石流总量的 79%。最大的泥石流，包括冰川和雨水引起的，都超过了 100 万立方米。它们占泥石流总数的 3%，但运送了 70% 的泥石流。1万立方米以下的小泥石流占74%；然而，它们仅占泥石流沉积量的 3%。观测表明，泥石流最早发生在3月的后十天，最晚发生在9月的前十天。根据泥石流发生日期的分布，清楚地显示出两个最大值：一个在 6 月的第二个十天期间最大，另一个在 7 月的第二个十天期间最大。6 月的最大值是由于降雨，而 7 月的最大值与冰川泥石流有关。从 1950 年到 2017 年，只有 5 (7%) 年没有任何泥石流。其中四个对应于 2010 年代。降雨和冰川泥石流的年数分别为 55 (81%) 和 39 (5​​7%)。