Meteorological factors driving glacial till variation and the associated periglacial debris flows in Tianmo Valley, south-eastern Tibetan Plateau

Abstract

Abstract. Meteorological studies have indicated that high alpine environments are strongly affected by climate warming, and periglacial debris flows are frequent in deglaciated regions. The combination of rainfall and air temperature controls the initiation of periglacial debris flows, and the addition of meltwater due to higher air temperatures enhances the complexity of the triggering mechanism compared to that of storm-induced debris flows. On the south-eastern Tibetan Plateau, where temperate glaciers are widely distributed, numerous periglacial debris flows have occurred over the past 100 years, but none occurred in the Tianmo watershed until 2007. In 2007 and 2010, three large-scale debris flows occurred in the Tianmo Valley. In this study, these three debris flow events were chosen to analyse the impacts of the annual meteorological conditions, including the antecedent air temperature and meteorological triggers. The remote sensing images and field measurements of the adjacent glacier suggested that sharp glacier retreats occurred in the 1 to 2 years preceding the events, which coincided with spikes in the mean annual air temperature. Glacial till changes providing enough active sediment driven by a prolonged increase in the air temperature are a prerequisite of periglacial debris flows. Different factors can trigger periglacial debris flows, and they may include high-intensity rainfall, as in the first and third debris flows, or continuous, long-term increases in air temperature, as in the second debris flow event.

Debris flows originating in the mountain cryosphere under a changing climate: A review

“…High mountain ranges worldwide (e.g. European Alps, Qinghai-Tibet Plateau, Caucasus Mountains, Tianshan Mountains, Rocky Mountains, and Andes Mountains) are subject to frequent occurrences of DFMC (Deng et al, 2017; Du and Zhang, 1981; Evans and Delaney, 2015; Evans et al, 2009; Guthrie et al, 2012; Mergili et al, 2018; Wei and Gao, 1992; Wei et al, 2018) (Figure 1). Although mainly initiated in remote high mountains, many DFMC events have reached downstream temperate inhabited areas, thus causing enormous damage to settlements, infrastructures, landscapes, and ecology (e.g.…”

“…DFMCs have been quite active since 2007, when a catastrophic event with magnitude of ∼1 million m 3 was triggered in early September by a glacier/rock landslide that was considered to be induced by antecedent rainfall and high temperature. Several large and numerous small-scale ones, mainly triggered by rainfall and rising temperature, have occurred in the last decade, in particular in 2010 and 2018, causing large hazards to downstream Tibetan villages and infrastructures (Deng et al, 2017; Wei et al, 2018; Yu et al, 2020).…”

A catastrophic landslide triggered debris flow in China’s Yigong: factors, dynamic processes, and tendency

“…However, the following issues in the above studies need to be researched: (a) CLDFs led by rainfall are generally smallscale (Wang and Sassa, 2003, Guzzetti et al, 2009, Chen et al, 2010. Previous studies show that freeze-thaw cycles, dry-wet cycles, and seismic linkages are extremely conducive to the development of CLDFs (Chen et al, 2014, Zhou et al, 2016, Huang et al, 2016 and that rainfall is a decisive factor for the occurrence of a CLDF , Deng et al, 2017. Additionally, a M s 4.3 earthquake might influence the occurrence of a landslide (Delgado et al, 2011).…”

Case Study: Effects of a Partial-Debris Dam on Riverbank Erosion in the Parlung Tsangpo River, China

“…Aside from the higher-than-usual temperatures, rainfall was another pertinent factor in triggering the debris flows. There was continuous rainfall from 15 to 25 July 2010; the rainfall on the initiation day of this debris flow was 33.3 mm, and the total amount of rainfall in those 10 days was recorded as 102.7 mm [22,28]. During this time, two intense rainfalls with intensities of 12 mm/day and 8 mm/day were recorded on 15 July 2010 and 25 July 2010, respectively.…”

“…The deposits partially blocked the river and formed a partial-debris dam. The width of the river channel was reduced from 180 m to 100 m [22,28]. The location where the debris flow entered the river is shown in Figure 1b.…”