DSS for operation of the lateral reservoirs during flood period

Abstract

On the lower Danube (downstream Iron Gates) the river banks on the Romanian side are protected by dykes on a length of 1100 km. Different towns along the Danube River, like Giurgiu, Oltenita, Calarasi, Braila and Galati are still threatened by floods close to or higher than 1% probability of exceedance. The floodplain is divided by transverse dykes into enclosures, which could be used as lateral reservoirs (polders) for storing water and decreasing downstream water level during high floods.A Decision Support System (DSS) was developed by UTCB in order to evaluate the hydraulic consequences (water level, maximum discharge) for different scenarios of accidental or deliberate flooding of enclosures. A special sub-model for breach development (breach elevation and length evolution) was set up. Since the hydraulic simulations are time and other resources consuming, a hydrological model for flood propagation was used. After parameters calibration and validation based on registered exceptional floods in 2006 and 2010, different scenarios of enclosures inundation were tested. FLOOD RISK MANAGEMENT STRATEGIESDue to the increasing severity of the floods across Europe, the European Union issued the Flood Directive 2007/60/EC on the assessment and management of flood risk [15], which came into force on November 2007. According to the Flood Directive 'flood risk' means the combination of the probability of a flood event and of the potential adverse consequences for human health, the environment, cultural heritage and economic activity associated with a flood event.The strategies for flood risk management are based on structural and non-structural measures [6]. A basic degree of security against floods is obtained with hydraulic works (dams, dikes, diversion, etc.), which represent structural measures, while higher degrees of security are the result of the complementary use of structural and non-structural measures.Structural measures represent the expression of the "culture of reaction" against catastrophic events. Their purpose is the maximum reduction of flooding probability through hydraulic works. Non-structural measures can be divided into: a) preparedness measures that aim to reduce the flood vulnerability of socio-economic and environmental objectives; b) response measures, which are applied during flood genesis and after water withdrawal in the riverbed.The preparedness measures consist among others in planning and management of land use within the flood plain area, which is considered the most effective method for reducing vulnerability and increasing resilience to natural hazards [3], setting up or improving real-time information systems of data acquisition, hydrological warning and forecasting, as well as decision / alert systems, reconsidering the operational rules of the hydraulic works [12].A large number of mathematical models were elaborated for the operation of single reservoirs or for a cascade or reservoirs, from the use of linear programming, dynamic programming [1] and graph theory [11], to optimal tree-b...