GLACIAL LAKE OUTBURST FLOODS IN THE CONTEXT OF HIGH MOUNTAINOUS ENVIRONMENT OF ARUN VALLEY, CENTRAL HIMALAYA
文献类型：学位论文
| 作者 | RANA MUHAMMAD ALI WASHAKH |
| 答辩日期 | 2020 |
| 授予单位 | 中国科学院大学 |
| 授予地点 | 北京 |
| 导师 | 陈宁生 |
| 关键词 | GLOF模拟 冰川湖泊 流量趋势 喜马拉雅中部 风险评估 |
| 学位名称 | 博士 |
| 学位专业 | 岩土工程 |
| 其他题名 | 喜马拉雅中部阿润河谷高山环境下的冰湖溃决洪水研究 |
| 英文摘要 | A glacial lake outburst flood (GLOF) is a phenomenon that is widely known by researchers because such an event can wreak havoc on the natural environment as well as on manmade infrastructure. Therefore, a GLOF risk assessment is necessary, especially within river basins with hydropower plants, and may lead to a tremendous amount of socioeconomic loss if not done. Additionally, a comprehensive compilation of hydrological, geological, geomorphological and climatological data is required to conduct feasibility and design study of high priority projects such as hydropower plants. It should be noted that a wide range of methods are available in the literature to assess GLOFs. These methods distinguish themselves by type of method construction, number and selection of assessed characteristics, required input data and rate of subjectivity in assessment procedures. Some of them are regionally focused and some are designed to be adaptable. The demands on the input data and the rate of subjectivity of assessment procedures are generally considered as the fundamental obstructions to their repeated use. A recent study examined the suitability of these methods for use in high mountains context. It was shown that none of the applied methods meet all of the specified criteria and requires an intensive man power, time and cost; therefore, a new method is desirable. Furthermore, due to the subjective and objective limitations of the available GLOF risk assessment methods, we have proposed a novel and easily applied 4-step screening method based on volume and affected lengths of historical GLOF events with a wider application and without the need for adaptation changes in accordance with the subject area, which also allows cost-effective and time-effective repeated use of this model as it does not warrant a big team, months of analysis, expensive equipment and onsite travel and collection of samples.In this study, we focused our efforts on the Upper Arun Hydroelectric Project (UAHEP) in the Arun River Basin and followed a novel and more holistic approach for the safety of the Hydropower Plant in addition to the formation of hydrological, geological, geomorphological and climatological database to assist the designing and construction of this project.At the first stage, 49 glacial lakes with areas greater than 0.1 km2 were identified for further analysis. Following geographically representation and geomorphological analysis of these 49 glacial lakes for the period of 1990–2018 to better understand the nature and demographics of the glacial lakes at a preliminary stage before rigorous screening could be done based on the new model proposed in this study; At the second stage, it was important to eliminate or add the factor of climate change and its effect on the detailed risk assessment of glacial lakes in the studied area so we analyzed the correlation between the temperature and precipitation trends and the occurrence of recorded GLOF events in the region and found out that the scale of GLOFs may increase due to the increasing precipitation and temperature. However, the climatological analysis from 1960 to 2018 indicated that the relationship between climate change and frequency of GLOFs is yet unclear; At the third stage, additional compilation of hydrological, geological, geomorphological and climatological data information to assist the design and construction of infrastructure are as follows:The annual average discharge, at the dam site of UAHEP, has accordingly been calculated to be approximately 217 m³/s. The 100-years return period floods, at the dam and the powerhouse sites, are foreseen to be 2,620 m³/s and 2,980 m³/s, respectively. A SWAT model has been prepared and used to simulate the Probable Maximum Flood (PMF) at the dam and powerhouse sites. The PMF flood peak, at the dam site of UAHEP, is estimated to be 4,990 m³/s. The PMF flood peak, at the powerhouse site of UAHEP, is estimated to be 6,060 m³/s.Regional geology study indicated that study area is located in the Lower Himalayan Midland Units. There are thrusts, such as, the MCT, the STDS, the MBT, the MFT and the MHT, in the region. Among these, the MCT strikes northwards, both on the eastern and the western side of the proposed dam site. The shortest distance between the MCT and the Project dam site is 3 to 5 km. According to the updated Seismic Hazard Assessment, the Peak Ground Acceleration (PGA) of OBE, at the Dam site and the Powerhouse site, both are 0.12 and 0.11g, respectively. The PGA of SEE, at dam site, is 0.74g.Reservoir geology analysis shows that bedrock in the reservoir basin is mostly gneiss. The reservoir area, with slightly weathered and fresh rock mass, is expected to be with a low permeability and the Arun river valley is the lowest drainage point in the regional area. The bedrock at dam site is primarily zone ZG1 (class II), which is slightly weathered and fresh gneiss. Due to the high strength of the rock mass in this zone, this is considered to be suitable as the foundation of the dam.Landslide distribution from 1960-2019 indicates that out of the 273 landslides 15 landslides may be prone to cause landslide dam along the main channel of UAHEP. Further scrutiny based on time of their occurrence identifies 5 of them are new landslides relative to the year 2010 therefore, these 5 landslides may require further studies for their impact on the UAHEP.At the fourth stage, a novel method based on the documented affected lengths and volumes derived from historical GLOF events was used to identify 4 potentially critical lakes; and worst case scenario simulations, based on the historical GLOF events, were run and the lakes were screened on the basis of affected lengths assuming each lake has the probability to outburst because at the preliminary stage of assessment, if the multi-criteria assessment eliminates some lakes, the results may still be questionable due to the uncertainties within these methods. On the other hand, if the multi-criteria assessment identifies some lakes as individually potentially hazardous, it is not necessary that the lakes should also be hazardous to the site in focus. This may be due to the fact that these are at a safe distance from the dam/power plant site or the outburst paths go in a different direction;At the fifth stage, outburst probabilities were identified to further scrutinize the lakes based on multi-criterion assessments, triggering factors and failure mechanisms and resulted in two critical lakes out of four namely Lower Barun and Qiangzongke Tsho glacial lake. Once lakes susceptible to outburst floods were identified, flood modelling and delimitation of endangered areas were the next steps in the risk management procedure;At the sixth stage, numerical simulations were conducted to estimate the probable discharges at the dam/power plant cross-sections using MIKE 11 software because it is more appropriate for application in Himalayan region according to the experts in this field and then we examined and compared the results with widely used empirical methods and observed historical lake outburst events, further discussed the physical properties, triggering factors, and outburst probability of the identified critical lakes to be recommended for the design of the hydropower plant in focus;The results of the GLOF modeling of the Lower Barun glacial lake indicates that the outburst of the lake may cause the outflow flood with a peak as high as 10,144 m3/s. The flood peak will be attenuated to about 8,478 m3/s when it reaches the power house site after 1 hour and 1 minute after the occurrence of the breach. The results of the GLOF modeling of the Qiangzongke Tsho glacial lake indicates that the outburst of the lake may cause the outflow flood with a peak as high as 8,983 m3/s. The flood peak will be attenuated to about 7,576 m3/s when it reaches the dam site after about 1 hour and 14 minutes after the occurrence of the breach. The outflow flood will be further attenuated to about 6,935 m³/s when it reaches to the powerhouse site after about 1 hour and 30 minutes after the occurrence of the breach. The estimated peak outflow from both glacial lake compares well with the historic outburst floods peak discharges.A comparison, of the estimated outburst flood peak from the identified two critical lakes with the results from different available empirical models and the observed historical lake outburst events, shows that the estimate fits quite well with these and is, in fact, slightly on the conservative or safer side within an acceptable range. Therefore, the identification of critical lakes and their outburst flood, modeled using the proposed method, can be considered as plausible and reasonable. In addition, although the approach and the methods used in this analysis are new, the results of this research are consistent with World Bank (WB), Nepal Electric Authority (NEA), Claque and Connor and ICIMOD. In October, 2019, we visited the local water resources bureau of Shigatse, Tibet, China, and found that the Qizangzongke Tsho lake was determined as a potential dangerous glacier lake which is also consistent with the results of this study. Further comparison with existing methods for assessing susceptibility of glacial lakes to outburst floods, we feel that the potentials of the presented method are as follows: the new model based on the affected lengths and volumes of historical GLOFs is more suitable for engineering based products as the prerequisite of studying individual lakes is minimized which are suggested by the conventional methods available in the literature; repeatability, which allows both retrograde, present and also near-future assessment of the susceptibility of glacial lakes to outburst floods and their evolution in time; the principle of multiple results, which allows the most likely GLOF scenario for each lake to be identified and allows characteristics which do not play a role in a specific case to be omitted (scenarios, decision trees). Last but not the least cost-effective and time-effective, as the research introduced in this thesis does not warrant millions of dollars of budget, big team, years of analysis, expensive equipment and onsite travel to glacial lakes as does the conventional GLOF analysis require when done in cases of dealing mega hydropower projects.To achieve these objectives, a series of intensive and integrated desk studies, data collections, and GLOF simulations and analyses were performed. |
| 语种 | 英语 |
| 页码 | 222 |
| 源URL | [http://ir.imde.ac.cn/handle/131551/55025]  |
| 专题 | 成都山地灾害与环境研究所_山地灾害与地表过程重点实验室 |
| 作者单位 | 中国科学院成都山地灾害与环境研究所 |
| 推荐引用方式 GB/T 7714 | RANA MUHAMMAD ALI WASHAKH. GLACIAL LAKE OUTBURST FLOODS IN THE CONTEXT OF HIGH MOUNTAINOUS ENVIRONMENT OF ARUN VALLEY, CENTRAL HIMALAYA[D]. 北京. 中国科学院大学. 2020. |
入库方式： OAI收割
来源：成都山地灾害与环境研究所
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