Abstract. Flooding is an imminent natural hazard threatening most river deltas, e.g. the Mekong Delta. An appropriate flood management is thus required for a
sustainable development of the often densely populated regions. Recently, the
traditional event-based hazard control shifted towards a risk management
approach in many regions, driven by intensive research leading to new legal
regulation on flood management. However, a large-scale flood risk assessment
does not exist for the Mekong Delta. Particularly, flood risk to paddy rice
cultivation, the most important economic activity in the delta, has not been
performed yet. Therefore, the present study was developed to provide the very
first insight into delta-scale flood damages and risks to rice cultivation.
The flood hazard was quantified by probabilistic flood hazard maps of the
whole delta using a bivariate extreme value statistics, synthetic flood
hydrographs, and a large-scale hydraulic model. The flood risk to paddy rice
was then quantified considering cropping calendars, rice phenology, and
harvest times based on a time series of enhanced vegetation index (EVI)
derived from MODIS satellite data, and a published rice flood damage
function. The proposed concept provided flood risk maps to paddy rice for the
Mekong Delta in terms of expected annual damage. The presented concept can be
used as a blueprint for regions facing similar problems due to its generic
approach. Furthermore, the changes in flood risk to paddy rice caused by
changes in land use currently under discussion in the Mekong Delta were
estimated. Two land-use scenarios either intensifying or reducing rice
cropping were considered, and the changes in risk were presented in spatially
explicit flood risk maps. The basic risk maps could serve as guidance for the
authorities to develop spatially explicit flood management and mitigation
plans for the delta. The land-use change risk maps could further be used for
adaptive risk management plans and as a basis for a cost–benefit of the
discussed land-use change scenarios. Additionally, the damage and risks maps
may support the recently initiated agricultural insurance programme in
Vietnam.
Towards risk-based flood management in highly productive paddy rice cultivation – concept development and application to the Mekong Delta
