Flood risk assessment and coping capacity of floods in central Vietnam

• Economic and human losses from flooding can push households into poverty.
• Damage to people, building structure, contents, paddy rice, road networks is assessed.
• The average annual damage for tangible costs is determined as about 3.5% of the GDP.
• Functions for estimating the number of deaths and injured people were developed.
• Flood risk maps increase the awareness about the areas to be avoided in urban planning.

In the perspective of improving and disseminating risk assessment methodologies and rise preparedness of people to flood hazard this paper presents flood hazard maps estimated in the Quang Ngai province, in central Vietnam, for different return periods in terms of depth, duration and velocity using the FLO-2D, hydrodynamic model with a 90 m × 90 m resolution grid. Then, based on the vulnerability functions determined from field surveys and the feedback to 400 questionnaires distributed to people regarding residential areas, paddy rice, road networks and the number of deaths and injuries, the total amount of tangible and intangible damage at each point in the study area is estimated and mapped, indicating risk levels and expected annual damage in case of flooding. The resulting damage functions are quite different from others available in the literature, as a result of the adaptive capacity and the resilience of the population to floods in the investigated area. Damage functions to buildings, agricultural areas, road infrastructures and people are normalised with respect to mean flooding depth and flooding hazard so that they can be generalized to areas with similar geographical conditions. In this way, a more comprehensive knowledge on the negative effects of floods is carried out, providing an important input to flood management plans in order to mitigate flood damage in tropical areas similar to the Quang Ngai province.