Assessment of future flood intensification in Central Vietnam using a super-high-resolution climate model output

Abstract

This paper presents an assessment of the changes in future floods. The ranked area-average heavy daily rainfall amounts simulated by a super-high-resolution (20 km mesh) global climate model output are corrected with consideration of the effects of the topography on heavy rainfall patterns and used as a basis to model design storm hyetographs. The rainfall data are then used as the input for a nearly calibration-free parameter rainfall–runoff model to simulate floods in the future climate (2075–2099) at the Upper Thu Bon River basin in Central Vietnam. The results show that although the future mean annual rainfall will not be considerably different compared to the present-day climate (1979–2003), extreme rainfall is projected to increase vigorously, leading to a similar order of intensification of future floods. It is very likely that the flood peak with a 25-year recurrence will increase approximately 42% relative to the present-day climate. The occurrence of floods with a 10-year recurrence may exceed those with a 25-year recurrence in the present-day climate. The projection results also exhibit insignificant uncertainties caused by an artificial neural network-based bias correction model. Additionally, the presented bias correction model shows advantages over a simple climatology scaling method.

Assessment of Flood Extremes Using Downscaled CMIP5 High-Resolution Ensemble Projections of Near-Term Climate for the Upper Thu Bon Catchment in Vietnam

“…Conventional bias correction techniques include simple scaling methods (e.g., [6,32,33]), complicated multiple regression-base models (e.g., [16,34]) and comprehensively reviewed in the literature [35]. Another work [6] of this research series presented a regression-based bias correction model to correct extreme rainfall simulated by a MRI super-high resolution model (Expt-1).…”

“…To date, most studies on climate change impacts showed attempts to project changes in runoff regime, especially the flood extremes, for mid-century, and end of century when the extreme events are expected to be intensified along with larger increases in surface temperature (e.g., [1,3,13,15,16]). These studies showed a consistent increase in rainfall and flood runoff in most river basins across the globe.…”

“…These studies showed a consistent increase in rainfall and flood runoff in most river basins across the globe. Especially, tropical regions have future projections of increasing heavy rainfall associated with tropical storms [17], leading to a significant increase in flood runoff in wet seasons ( [16,18]).…”

Future fluvial flood risks in Central Vietnam assessed using global super‐high‐resolution climate model output

“…In this study, AGCM20 is run once; therefore, the assessment can focuses on the performance of the downscaling model. Nam et al (2013b) attempted to quantify the uncertainties in the rainfall estimate caused by the downscaling model. The portion of data selected for the testing set was randomly chosen from the available data set.…”

“…Disregarding the effects of nonclimate variability factors on future flood intensification, especially large‐scale floods (Milly et al ., ), this study attempts to explore the future fluvial flood risks in terms of potential inundation extent and depth in the lower Vu Gia–Thu Bon River basin in Central Vietnam based on a state‐of‐the‐art global super‐high‐resolution (20‐km mesh) climate model output simulated under emission scenario A1B for determining the future climate (2075–2099) at which most extreme phenomena would occur because of greater increases in surface temperature. Following the principles presented previously as a part of this research series (Nam et al ., 2013b), the downscaled heavy rainfall from the model output for individual sites in the river basin (Nam et al ., 2013a) will be analysed further to construct design storm hyetographs. The hyetographs are subsequently used as input for the coupled, nearly calibration‐free parameters of a hydrological–hydraulic model to simulate the river stages and potential inundation extent in the floodplain while considering a scenario with a rising sea level (the ensemble mean), which is expected to diminish the drainage capacity at the estuaries.…”