嘎龙错冰湖是西藏波曲河流域内面积最大的高危冰湖,20世纪80年代以来,其冰川面积退缩1.2 km2,冰湖面积扩张了2.78 倍,库容达到3.82×108 m3,冰湖面积增长速率达1.06 km2/10a,溃决风险不断增大。为了探明溃决洪水演化特征,基于12.5 m的地形数据和多期遥感影像,采用MASSFLOW仿真软件和MacCormack-TVD有限差分法,引入基底侵蚀模型,将二维溃坝洪水模型与泥沙输移模型进行耦合,对嘎龙错冰湖进行不同工况下溃决洪水演进过程进行模拟。分析溃决洪水在下游的传播特征,进而进行定量评价。结果表明:不同工况条件下溃决洪水在下游的演进过程中洪峰流量随距离逐渐衰减,洪峰流量随地形起伏的波动范围较小;溃决洪水凭借海拔落差对沟床及岸坡进行强烈的侵蚀,松散固体物质参与洪水的演进,逐渐演化为高含沙洪水-稀性泥石流;全溃条件下洪水将淹没聂拉木县,平均水深达45 m,流速17 m/s,除此之外流体冲刷掏蚀樟木镇潜在滑坡群坡脚,侵蚀深度达26 m,极易引发更大规模次生灾害。
Galongcuo glacial lake is the largest high-risk glacial lake in the Boqu River Basin of Tibet. Since the 1980s, its feeding glacier has retreated by 1.2 km2, resulting in a 2.78-fold expansion of the lake area. Its storage capacity has reached 3.82×108 m3, with a lake area growth rate of 1.06 km2 per decade, indicating a steadily increasing risk of outburst. To investigate the evolution characteristics of the outburst flood, this study used 12.5 m resolution topographic data and multi-temporal remote sensing imagery. Using the MASSFLOW simulation software and the MacCormack-TVD finite difference method, the flood evolution process under different storage capacity scenarios for Galongcuo was simulated. By analyzing the propagation characteristics of the outburst flood downstream, a quantitative risk assessment was conducted. The results indicate that: Under different storage scenarios, the peak discharge of the outburst flood gradually attenuates along the downstream flow path, with relatively small variations despite fluctuations in terrain. Due to the substantial elevation drop, the outburst flood intensely erodes the channel bed and banks, incorporating loose sediments into the flood. This leads to its gradual transformation into a high-sediment concentration flow—a dilute debris flow. Under a full-breach scenario, the floodwaters would inundate Nyalam County, with an average water depth of 45 m and a flow velocity reaching 17 m/s. Moreover, the fluid severely scours the toe zones of potential landslide groups in the Zhangmu Township area, with erosion depths reaching up to 26 m, thereby posing a high risk of triggering large-scale secondary disasters.
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