藏东南尼都藏布流域冰湖水量变化及潜在溃决诱因评估——以塔弄错为例

Water volume changes and assessment of potential outburst triggers for glacial lakes in the Nidu Zangbo basin,southeastern Tibet:a case study of Tanong Co

藏东南尼都藏布流域冰雪崩、滑坡和泥石流等山地灾害频发,研究团队于2021年10月对流域内的塔弄错进行了水深测量和周边地貌环境调查。同时,利用短基线合成孔径雷达干涉测量(SBASInSAR)技术监测了尼都藏布流域的地表形变速率,以识别冰湖周边的潜在滑坡体、崩塌体等诱灾因素。最后,基于数值模型RAMMS和波浪传播模型,评估了不同情景下崩塌体入湖和水量变化对冰湖溃决风险的影响。结果表明,塔弄错的最大水深为29.45 m,平均水深为15.21 m,水量为1820842 m^(3)。塔弄错周边5个不稳定区域的平均形变速率远高于其他区域,将来可能会成为触发塔弄错溃坝的外界诱因。模型模拟显示,塔弄错在入湖崩塌体质量增加或水量增加情况下,产生的洪峰流量、溃口深度和坝顶承受的压力均显著增加。因此,建议在冰湖溃决风险评估工作中重点关注周边有崩塌隐患点且水量持续增长的冰湖,并实时观测崩塌区的动态变化,为下游及时做好冰湖溃决洪水的避险提供预警信息。

The Nidu Zangbo basin is prone to mountain hazards,such as snow avalanches,landslides,and de⁃bris flows.In October 2021,we conducted a water depth measurement and a survey of the surrounding terrain in Tanong Co located in the basin.Using the short baseline synthetic aperture radar interferometry(SBAS-InSAR)technique,we also monitored the surface deformation rate of the Nidu Zangbu basin to identify potential trigger factors for disasters,such as landslides and collapses,around the glacial lake.Finally,we evaluated the risk of glacier lake outburst floods(GLOFs)using the numerical models RAMMS and wave propagation model under different scenarios,taking into account the impact of landslide entry into the lake and water volume changes.The results show that the maximum depth of Tanong Co is 29.45 m,with an average depth of 15.21 m and wa⁃ter volume of 1820842 m^(3).The average deformation rate of the five unstable slopes around Tanong Co is signif⁃icantly higher than that of other regions,which may become an external trigger for dam failure.The model simu⁃lations indicate that increasing landslide mass or water volume will result in a significant increase in the peak dis⁃charge,breach depth,and pressure on the dam crest of Tanong Co.Therefore,we recommend giving special at⁃tention to glacial lakes with potential collapsing points in their surroundings and continuously increasing water volume during the risk assessment of GLOFs.We also suggest monitoring the dynamic changes in the collapsing area and providing early warning information about GLOFs to downstream villages.