Dam-Break Flood Risk Assessment on Laiyang City

Laiyang, one of the most important cities in east Shandong province, has experiencing a rapid urbanization and economic development in the last decade. It means a great deal to the flood security for this city to practice integrated flood management at river basin level, moreover, flood risk assessment is the baseline for flood management. Muyu Reservoir, located 9 km northeast of the urban area of Laiyang City, is the most important structural measure for flood management and has significant impact on the flood features at this city. The focus of this study was on the risk assessment of dam-break flood from Muyu Reservoir to Laiyang City. The dam-break flood is one of the catastrophic disasters to the urban area of Laiyang City. The dam-break analysis was performed by numeric simulation according to the following four steps. First, it was analyzed on the reasons for possible dam-break flood's occurrence. Simply speaking, extreme flood, earthquake, and terrorist attack are likely to result in dam-break flood. Second, a simulation on the typical reason, namely the extreme hydrological event, of dam-break flood was implemented. The key information considered in this simulation includes the water level at the dam (the check flood water level), the inflow to the reservoir (the check flood hydrograph), and two typical structural scenarios (with/without-levees) in the lower reach of the reservoir. Third, based on flood simulations, flood hazard analysis was conducted and the results indicated that the peak discharge would be over 40,000 m(3)/s at the breach and over 22,000m(3)/s near Laiyang City area; most of the urban area would be flooded; the duration from the beginning of dam-break to the arrival of peak discharge at Laiyang City is less than half an hour. Finally, a plan for integrated dam-break flood management was presented for the purpose of dam-break flood disaster mitigation, both available structural and nonstructural measures were proposed according to the situations in the river basin, the main strategic advises include flood emergency planning, flood risk mapping, flood monitoring and early warning system construction, reservoir regulation, and flood risk public awareness.