This tool shows the extent of the potential glacial lake outburst flood (GLOF) and the water depth along the Rolwaling and Tama Koshi river. The data is from the potential GLOF hydrodynamic modeling conducted on Tsho Rolpa glacial lake, one of the potentially dangerous glacial lakes in Nepal, considering various breach scenarios based on the field survey. The lake is located at 4545 masl elevation in Rolwaling Valley in Dolakha District, close to the boarder with the Tibetan Autonomous Region. The GLOF hydrodynamic modelling utilized multiple graphics processing unit (GPU)-accelerated high-performance hydrodynamic flood model (HiPIMS) (Xia et. al., 2017) and an empirical dam breach model (Forehlich, 2008). The various dam breach scenarios were developed to consider different breach depths, breach widths and lake water levels. These parameters have been considered based on the high-resolution (0.1 m) 3D model developed from unmanned aerial vehicle (UAV) and lake bathymetry data from field survey. The time series of outflow water depth and discharge under various dam breach scenarios were used to predict GLOFs flooding processes in the downstream. High resolution (5 m) Digital Elevation Model (DEM) has been for efficient prediction of temporal and spatial flood dynamics in downstream areas. All together 12 breach scenarios have been considered for the GLOFs modelling in which only 3 prominent scenarios output were considered in this tool for visualization. The scenarios of current water level with final breach depth of 10, 20 and 30 m is visualized in this tool. The detail list of all the scenarios is given in table below.
| Scenarios |
Final breach depth (m) |
Final average breach width (m) |
Initial lake volume above the final breach bottom (x 106 m3) |
Total failure time (h) |
|
Current water level
|
10 |
60 |
7.6 |
3.1 |
| 20 |
87 |
21.4 |
1.7 |
| 30 |
102 |
33.5 |
1.3 |
| Water level rise |
1 meter |
10 |
64 |
9.2 |
2.8 |
| 20 |
89 |
23.0 |
1.7 |
| 30 |
104 |
35.1 |
1.3 |
| 3 meters |
10 |
71 |
12.4 |
2.5 |
| 20 |
93 |
26.2 |
1.6 |
| 30 |
107 |
38.3 |
1.2 |
| 5 meters |
10 |
77 |
15.7 |
2.2 |
| 20 |
97 |
29.5 |
1.5 |
| 30 |
110 |
41.6 |
1.2 |
GLOF is one of the most serious natural hazards in mountainous country like Nepal. Nepal already experienced more than 25 recorded GLOFs in last few decades. The Nepal Government has been actively seeking to reduce and mitigate the GLOF risk in the country. However, an effective early warning and risk mitigation strategies are still lacking across the country. Therefore, these kind of research and web tools is pivotal for understanding potential risk and vulnerability of peoples and infrastructures in downstream and develop a reliable early warning systems and improve preparedness as well as build resilience of the vulnerable community.
The research expedition, data analysis and development of this tools was conducted for the web-based natural Dam-Brust Assessment and ForeCasting System (WeACT) project under the SHEAR Catalyst Grant funded by the Natural Environment Research Council (NERC), UK. The project is jointly implemented by ICIMOD; Loughborough University, UK; Newcastle University, UK and Tribhuvan university, Nepal.
References:
Xia, X., Liang, Q., Ming, X., & Hou, J. (2017) An efficient and stable hydrodynamic model with novel source term discretization schemes for overland flow and flood simulations. Water Resources Research, 53, 3730-3759, https://doi.org/10.1002/2016WR020055
Froehlich, D. C. (2008). Embankment dam breach parameters and their uncertainties. Journal of Hydraulic Engineering, 134(12), 1708-1721, https://doi.org/10.1061/(ASCE)0733-9429(2008)134:12(1708)
