基于树木年代学的冰川型泥石流灾害历史重建方法-以西藏天摩沟为例

藏东南帕隆藏布流域冰川型泥石流规模大、数量多。天摩沟是帕隆藏布左岸一级支流,最近20年多次爆发冰川型泥石流,重复堵江并形成长1.5 km左右的堰塞湖。冰川型泥石流事件爆发时间和规模的确定对山区泥石流防灾减灾意义重大。本文基于树木年代学方法,通过分析树木年轮损伤组织、生长抑制和释放动态,重建天摩沟60年来的泥石流事件的时空分布；从树木生长扰动强度等方面探讨泥石流的流动范围和沟道溯源侵蚀过程；并通过Wit指数进一步分析泥石流发生时间和日降雨及气温之间的关系。结果表明天摩沟在1965、1970、1976、2007、2010和2018年爆发过泥石流,与2007年以来的有记录的泥石流事件吻合,印证了通过年轮损伤组织、生长抑制和释放等参数重建泥石流事件的可行性；Wit指数的变化表明树木年轮的生长释放和抑制滞后于泥石流事件1-3年,并与泥石流规模成正相关。

Reconstruction of glacial debris flow disaster based on dendrochronology: A case study on Tianmo gully, Tibet

The glacial debris flows along Palong River is large and frequency. Tianmo gully is a primary tributary on the left bank of Palong River. Glacial debris flows broke out many times in history, repeatedly blocking the river and forming a 1.5 km-long barrier lake. The frequency and volume of glacial debris flows is of great significance to the disaster prevention and reduction in mountainous areas. Based on the method of dendrochronology and the analysis of damaged tissue, growth inhibition and release of tree rings, the temporal-spatial distribution of debris flow events in the past 60 years is reconstructed. From the intensity of tree growth disturbance, the inundate area of debris flow and gully erosion process are discussed. The relationship between the occurrence time of debris flow and daily rainfall and temperature is further analyzed by Wit index. The results show that debris flows broke out in 1965, 1970, 1976, 2007, 2010 and 2018; The growth release and inhibition of tree rings lag behind the debris flow event for 1-3 years, and is directly proportional to the debris flows volume.