Abstract

We observed the surge velocity, terminus advance, lake formation and outburst, as well as its downstream impacts at Shisper Glacier in the Karakoram, Pakistan and suggest potential nature-based risk-reduction solutions. A recent surge started in late 2017 with increased velocity since April 2018 and a resulting terminus advance from June 2018. Bi-modal peak velocity of 19.2 ± 0.16 m/day was observed in April-May 2018 and May-June 2019. Also, the terminus advance blocked the river from the adjacent Muchuhar Glacier repeatedly since November 2018. Lake outbursts were observed in June 2019 and April 2020. Relying on observations of the lake area and peak discharge of 142 m³ s⁻¹ in 2019 and 85 m³ s⁻¹ April 2020, outburst were simulated using the BASEMENT software. Simulations and field observations show that even at high discharge, damages were mainly observed along the main river channel, causing strong bank erosion rather than widespread inundation of land. The ice-dammed lake is potentially hazardous until the blocked stream completely disappears in future. Our results suggest that the biggest lake outburst hazard lies in its erosion potential with damages to infrastructure closest to the river and large sediments transport to the downstream Hunza River.

摘要

我们在巴基斯坦喀喇昆仑山的 Shisper 冰川观察了浪涌速度、终点前进、湖泊形成和爆发，以及对下游的影响，并提出了潜在的基于自然的风险降低解决方案。最近的激增始于 2017 年末，自 2018 年 4 月以来速度增加，最终从 2018 年 6 月开始前进。在 2018 年 4 月至 5 月和 2019 年 5 月至 6 月观察到双峰峰值速度为 19.2 ± 0.16 m/天。此外，自2018年11月以来，终点前进多次阻断邻近穆楚哈尔冰川的河流。2019年6月和2020年4月观测到湖泊溃决。依靠对湖区和2019年142 m ³ s ^-1和85 m ³ s峰值流量的观测⁻¹2020 年 4 月，使用 BASEMENT 软件模拟了爆发。模拟和实地观察表明，即使在高流量下，主要沿主要河道观察到破坏，造成强烈的河岸侵蚀，而不是大面积的土地淹没。在未来阻塞的溪流完全消失之前，冰坝湖具有潜在的危险。我们的研究结果表明，最大的湖泊溃决危险在于其侵蚀潜力，对最靠近河流的基础设施造成破坏，以及向下游罕萨河输送大量沉积物。