The Pokhara May 5th flood disaster: A last warning sign sent by nature?

Abstract

The flood disaster of May 5th, 2012 in Pokhara Valley, Nepal, taking the life of at least 72 people, is explained by a so-called sturzstrom. It developed from a huge rockfall onto a glacier in a high- mountain depression and then transformed into a subsequent debris flow/hyper-concentrated flow devastating the upper reaches of Seti Khola Valley. Apparently, the same processes have formed the smooth terrace landform of Pokhara Valley during Holocene times: two gigantic debris-flow events were identified and dated to have occurred about 12,000 and 750 years ago. Both epochs were associated with global warming processes. During these debris-flow events the whole valley was filled by 3-5 km3 of debris transported from the same huge high- mountain depression called Sabche Cirque where the recent debris flow came from. A new catastrophe of similar size would have an apocalyptic impact: about half a million people live in the valley today. A detailed investigation of the circumstances of the disaster on May 5th, especially the possible influence of global warming on the trigger of the disaster, and a reliable forecast of a potential recurrence of similar events or of even much greater scope, are urgently required. For this, the thorough understanding of the conditions, triggers and mechanisms of the huge flows in the past to compare it with the recent flood is indispensable as well.

Hydro-torrential hazard vs. anthropogenic activities along the Seti valley, Kaski, Nepal: Assessment and recommendations from a risk perspective

“…1), that drains the Pokhara valley (the second largest city of Nepal), experienced a disastrous flood (i.e., hyperconcentrated flow) on May 5, 2012 that surged downstream through the upper Seti gorges, sweeping away 72 people, obliterating dozens of homes and damaging infrastructures worth millions of dollars (Bhandary et al, 2012;Dwivedi and Neupane, 2013;Kargel et al, 2013;NASA, 2013;Kargel et al, 2014;SANDRP, 2014). Studies by Bhandary et al (2012), Petley and Stark (2012), Hanisch et al (2013), Kargel et al (2014), Oi et al (2014) and Petley (2014) have warned the Seti valley is highly prone to further flooding similar to the scale of May 5, 2012 or, even bigger. In a study, the river side settlements at Ramghat [Fig.…”

Rare flood scenarios for a rapidly growing high-mountain city: Pokhara, Nepal

“…On 5 May 2012, a hyperconcentrated flow killed 72 persons and destroyed roads, bridges, and drinking water pipelines in the northern Pokhara Valley (Gurung et al, 2015(Gurung et al, , 2021. The exact sequence of events remains debated but may have been initiated by rock-slope failures from the western flank of the Annapurna IV Massif at 7525 m a.s.l., observed by chance by a pilot (Hanisch et al, 2013;Kargel et al, 2013). Similar to the 2021 Chamoli disaster (Shugar et al, 2021), a highly mobile ice-rock avalanche may have transformed into an hyperconcentrated flow that hit the village of Kharapani (1100 m a.s.l.)…”

Hanging glacier avalanche (Raunthigad–Rishiganga) and debris flow disaster on 7 February 2021, Uttarakhand, India: a preliminary assessment

“…Closer home, the 5 May 2012 Seti River flood in Nepal initiated by the detachment of rock mass at the height of 6700 m a.s.l. from the south flank of Annapurna IV and ended up as colossal debris flow (Dwivedi and Neupane 2013;Hanisch et al 2013;Kargel et al 2014;Kim et al 2017;OI et al 2014).…”