Dynamic decision making for dam-break emergency management – Part 2: Application to Tangjiashan landslide dam failure

Abstract

Abstract. Tangjiashan landslide dam, which was triggered by the Ms = 8.0 Wenchuan earthquake in 2008 in China, threatened 1.2 million people downstream of the dam. All people in Beichuan Town 3.5 km downstream of the dam and 197 thousand people in Mianyang City 85 km downstream of the dam were evacuated 10 days before the breaching of the dam. Making such an important decision under uncertainty was difficult. This paper applied a dynamic decision-making framework for dam-break emergency management (DYDEM) to help rational decision in the emergency management of the Tangjiashan landslide dam. Three stages are identified with different levels of hydrological, geological and social-economic information along the timeline of the landslide dam failure event. The probability of dam failure is taken as a time series. The dam breaching parameters are predicted with a set of empirical models in stage 1 when no soil property information is known, and a physical model in stages 2 and 3 when knowledge of soil properties has been obtained. The flood routing downstream of the dam in these three stages is analyzed to evaluate the population at risk (PAR). The flood consequences, including evacuation costs, flood damage and monetized loss of life, are evaluated as functions of warning time using a human risk analysis model based on Bayesian networks. Finally, dynamic decision analysis is conducted to find the optimal time to evacuate the population at risk with minimum total loss in each of these three stages.

Dynamic decision making for dam-break emergency management – Part 1: Theoretical framework

“…With the breaching parameters predicted, a river analysis program, HEC-RAS 4.0, developed by Hydrologic Engineering Center (2008), is used to simulate the flood routing in the river downstream of the dam. Detailed simulations in a specific case will be introduced in the companion paper (Peng and Zhang, 2013).…”

“…The decision with a different initial time (t 0 ) is defined as a stage in which the available information and the evaluated results may be different. Thus, a dynamic decision should be a multi-stage decision process, the details of which will be introduced in the companion paper (Peng and Zhang, 2013). In each stage, as the information gathered and its condition of uncertainty is different, the predicted dambreak probabilities and flood consequences could be different.…”

“…In the multi-stage decision framework, both the predicted dam-break probabilities and consequences should be updated in each new stage. This will be illustrated with a specific dam-break case study in the companion paper (Peng and Zhang, 2013).…”

“…(14) and (16). The details of the method will be demonstrated with a dam-break case study in the companion paper (Peng and Zhang, 2013).…”

“…Finally, a comparison between two existing methods and the new framework is made to show the features of this framework. A specific dam-break case study is presented in a companion paper (Peng and Zhang, 2013) of this framework to complex dam-breaching problems. HU-RAM simulates the evacuation, sheltering and loss of life in a flood event, which are closely related to the evacuation cost, flood damage and number of fatalities in this paper.…”