Multimodelling approach to the assessment of climate change impacts on hydrology and river morphology in the Chindwin River Basin, Myanmar

Abstract

In the tropical region, climate change significantly affects the morphology of river channels as well as water resources. In this study, the climate change impact on hydrology and morphology is assessed in the Chindwin River Basin, Myanmar. Future climate data was developed by an ensemble of four Regional Climate Models (RCMs) using a performance-based weight method, under two Representative Concentration Pathways (RCP4.5 and RCP8.5). Two models were developed: a hydrological model (MIKE NAM) to simulate future discharge and a morphology model (MIKE 21 Flow Model) to simulate morphological changes under climate change scenarios. The results reveal that the mean annual discharge over the period from 2018 to 2040 (23 years) is projected to increase by 13.9 and 22.8%, under RCPs 4.5 and 8.5, respectively. The annual hydrograph shows a sharp rise and the recession of monsoon flood, with multiple peaks replacing the single peak observed during the baseline period (1975–2005) with a delay in peak of 8–10 days. The extreme events (floods) are expected to get more severe in the future in terms of frequency and magnitude compared to the baseline period. The study further shows that under extreme rainfall events, the left bank of the upstream areas is projected to experience severe morphological changes, accompanied by severe flood damage. As high flows become amplified due to climate change in the near future, morphological changes will exacerbate in the same period. Sediment deposition will increase the flood risk and river bank instability, constraining navigability in the river and adversely affecting riverine communities. The study reveals that mathematical modelling helps to identify the impacts of climate change on hydrology and morphology, and that knowledge coupled with an assessment of the vulnerability associated with lives and livelihoods, could help planners and policymakers to develop adaptation strategies and take meaningful action to mitigate the impact.