ESTABLISH A CRITERIA SET FOR ASSESSING THE FLOOD RISK AT OVERFLOW BRIDGE IN CENTRAL VIETNAM

An overflow bridge is a drainage work in combination with a road, which is built across rivers and streams. In the rainy season, the flood flow over the work is both deep and fast, causing danger to the lives of people, vehicles, and even the overflow bridge itself. So far, in Vietnam there is no official statistics on the number of overflow bridges as well as tools / criteria for assessing their potential risks. This study collects 10 criteria from the three groups of hazard, vulnerability, and exposure to assess the danger level for overflow bridges which was applied in the central region of Vietnam. The weight of each factor is determined by AHP hierarchical analysis. The aggregated criteria value is classified into 3 levels as C = 1.0 - 1.66 (Low danger); C = 1.66 - 2.0 (Medium danger) and C = 2.0 - 3.0 (High danger). This set of criteria is the basis for the management agency to apply in alerting people to reduce flood risks as well as for repairing and upgrading overflow bridges.