# A Modeling of Human Reliability Analysis on Dam Failure Caused by Extreme Weather
## 1 Introduction  
Dams are essential water infrastructures in ensuring regional socio-economic and ecological security and promoting sustainable development. By the end of 2020, China had 98,566 existing reservoirs with a total capacity of 930.6 billion m\({}^{3}\), including 774 large reservoirs, 4098 medium reservoirs and 93,694 small reservoirs (categorization is defined by the reservoir capacity). Reservoir dams produce multiple benefits, such as flood control, irrigation, power generation, navigation, and environmental protection. However, dam collapse seriously threatens human lives and property downstream and causes adverse socio-economic impacts. China has seen a significant decrease in the number of dam failures since the turn of the century [1]. According to the historical dam-break database of the Nanjing Hydraulic Research Institute, from 1954 to 1990 a total of 3260 reservoirs failed, with an annual average of about 88. Comparatively, from 1990 to 2000, 227 dams failed, giving an annual averageof about 23. From 2000 to 2014, only 72 reservoirs failed, averaging 4.8 dams per year, and the annual average rate of dam failure was only \(0.5\times 10^{-4}\). This is mainly associated with the improvement of construction and management levels and the continuous enhancement of relevant laws and regulations. Hundreds of dam failures have occurred throughout U.S. history, causing thousands of people to be killed and enormous property and environmental damage. Data records of ASDSO (The Association of State Dam Safety Officials) shows that from January 2005 through June 2013, US state dam safety programs reported 173 dam failures and 587 \"incidents\" that without intervention would have become accidents. The ASDSO believes the most likely causes of dam failure are overflow, foundation defects, cracking, inadequate maintenance and upkeep, and piping. The Chinese Ministry of Water Resources has categorized the causes of dam failures into five major groups and 16 sub-groups, i.e., height of the dam, quality problems, mismanagement, other and unknown causes. Many scholars at home and abroad have already divided the causes of dam failure into three categories: natural factors, engineering factors, and anthropogenic factors, while human factors include mismanagement, man-made destruction, and so on. In fact, dam failures caused by natural and engineering factors are also highly related to human-caused errors, such as quality problems in construction, poor decision-making by managers during the overtopping process, and ineffective rescue efforts. Advances in science and technology have led to continuous improvement in the management of dam construction, with a decreasing proportion of failure accidents during the construction period and an increasing proportion during the operational period. At the same time, as most of China's reservoirs were built in the 1950s to 1970s and are now approaching their 50-year service life, they need further assessment and maintenance [2]. In 2017, the American Society of Civil Engineers report emphasized the importance of public safety and maintenance, with measures to reduce the risk of dam failures encompassing \"better planning for mitigating the effects; increased regulatory oversight; improving coordination and communication across governing agencies; and the development of tools, training, and technology'. With the development of urbanization, the downstream of reservoirs is densely populated, making the dam safety closely related to public safety. Emphasizing the security of the utility system and reducing risks through reservoir dams are garnering consensus among decision-makers, practitioners, and researchers worldwide [3]. The Ministry of Water Resources [4] put forward the defense objectives of 'no casualties, no dam collapse, no breakage of important dykes, and no impact on major infrastructure'. Climate change has had significant adverse impacts on reservoir engineering since the turn of the new century [5].