Temporal Analysis for Multi-hazard Risk Assessment of Rice Cultivation in Coastal Areas: A Case Study of Soc Trang, Vietnam

Abstract

Rice is an important human crop and rice cultivation is threatened due to natural disasters, leading to negative effects on national and global food security. The natural disasters, such as tropical cyclones and saline intrusion, have dramatic influences in coastal regions. To investigate possible impacts of these disasters on rice cultivation, it needs an efficient tool to assess potential disasters impacts and a risk index is highly applicable. Therefore, this study aims at establishing a risk assessment of rice production in coastal areas under effects of tropical cyclones and saline intrusion. We adopted risk definition introduced by IPCC (2014) in which risk is a function of hazard, exposure and vulnerability. Multiple hazards of tropical cyclones and saline intrusion were indicated by their frequency and severity at some critical levels of 25%, 50% and >50% rice yield reduction. Each hazard was weighted by its damage on rice yield. Exposure and vulnerability of rice crops are evaluated at different growing phases. Tropical cyclone hazard index was ranked high and very high in the wet season while salinity hazard index was ranked very high in the dry season. Due to the combined effects of tropical cyclones and salinity, rice crop is highly susceptible during the reproduction phase and at the panicle initiation stage particularly. Based on the cropping calendar of My Xuyen, the period of October-November was the very high vulnerability period since it had the largest rice cultivable area and rice crops were at the reproduction phase. This result shows that rice crops are at high risk in October and November. Noticeably, saline intrusion reaches the highest level in April and May, but no risk is at this period because of no rice crop cultivated. This can reflect a measure to reduce risk by adjusting the cropping calendar.