Measuring direct losses to rice production from extreme flood events in Quang Nam province, Vietnam

Since the 1990s, Vietnam has made the transformation from being a net rice importer to becoming one of the world’s largest exporters of rice. In fact, Vietnamese farmers have been highly successful at increasing food production since the reformation (Doi moi) in 1986 so that by 2010, rice yields had more than doubled (General Statistics Office of Vietnam, 2012). However, Vietnam, because of its geographical location and characteristics, is highly vulnerable to natural disasters, with a World Bank report (2010) estimating that 59% of Vietnam’s total area and 71% of its population are susceptible to the impacts of tropical cyclones and floods. Furthermore, the regularity of extreme flood events during the last decade in central Vietnam has raised concern, with three flood classes, 1:10, 1:20 and 1:100-year floods occurring in Quang Nam province in 2004, 2009 and 2007, respectively (Institute of Geography, 2012; Institute of Water Resources Planning, 2011). In this study we use a three-stage approach to estimate the direct losses to rice production caused by 1:10, 1:20 and 1:100-year flood events in Quang Nam, central Vietnam. Firstly, utilising information from geo-spatial inundation maps together with the timing of the floods with respect to crop rotation, we calculate flood-depth susceptibility rates for rice crops. Secondly, we calculate the loss to rice production experienced under the three flood classes. Thirdly, using 2010 prices, cost-benefit analyses were conducted for rice production when impacted by the three flood classes. These include scenario (pessimistic, optimistic and likely) and sensitivity analyses. The estimated value of direct losses to rice production for 1:10, 1:20, and 1:100-year flood events were VND11billion, VND100 billion and VND121 billion, respectively. Benefit-cost ratios, already very low for subsistence rice farmers, are further eroded in years of extreme floods.