Climate Change Impact on Flooding and Inundation

Projecting changes in the frequency and intensity of future precipitation and flooding is critical for the development of social infrastructure under climate change. The Mekong River is among the world's large‐scale rivers severely affected by climate change. This study aims to define the duration of precipitation contributing to peak floods based on its correlation with peak discharge and inundation volume in the Lower Mekong Basin (LMB). We assessed the changes in precipitation and flood frequency using a large ensemble Database for Policy Decision‐Making for Future Climate Change (d4PDF). River discharge in the Mekong River Basin (MRB) and flood inundation in the LMB were simulated by a coupled rainfall‐runoff and inundation (RRI) model. Results indicated that 90‐day precipitation counting backward from the day of peak flooding had the highest correlation with peak discharge (R² = 0.81) and inundation volume (R² = 0.81). The ensemble mean of present simulation of d4PDF (1951–2010) showed good agreement with observed extreme flood events in the LMB. The probability density of 90‐day precipitation shifted from the present to future climate experiments with a large variation of mean (from 777 mm to 900 mm) and standard deviation (from 57 mm to 96 mm). Different patterns of sea surface temperature (SST) significantly influence the variation of precipitation and flood inundation in the LMB in the future (2051–2,110). Extreme flood events (50‐year, 100‐year, and 1,000‐year return periods) showed increases in discharge, inundation area, and inundation volume by 25–40%, 19–36%, and 23–37%, respectively. This article is protected by copyright. All rights reserved.

Full article: Try et al., (2020a): Projection of extreme flood inundation in the Mekong River Basin under 4 K increasing scenario using large ensemble climate data

Fig. Changes of extreme flood events in the Lower Mekong Basin in the future projection (Try et al. 2020a)

Climate change currently affects the resilience and aquatic ecosystem. Climate change alters rainfall patterns which have a great impact on river flow. Annual flooding is an important hydrological characteristic of the Mekong River Basin (MRB) and it drives the high productivity of the ecosystem and biodiversity in the Tonle Sap floodplain and the Mekong Delta. This study aims to assess the impacts of climate change on river flow in the MRB and flood inundation in the Lower Mekong Basin (LMB). The changing impacts were assessed by a two-dimensional rainfall-runoff and inundation model (RRI model). The present climate (1979-2003) and future projected climate (2075-2099) datasets from MRI-AGCM3.2H and MRI-AGCM3.2S models were applied with a linear scaling bias correction method before input into the RRI model. The results of climate change suggested that flood magnitude in the LMB will be severer than the present climate by the end of the twenty-first century. The increment of precipitation between 6.6 and 14.2% could lead to increase extreme flow (Q 5) 13-30%, peak inundation area 19-43%, and peak inundation volume 24-55% in the LMB for ranging of Representative Concentration Pathways (RCP) and sea surface temperature (SST) scenarios while there is no significant change on peak flood timing. 

Full article: Try et al., (2020b): Assessing the effects of climate change on flood inundation in the lower Mekong Basin using high-resolution AGCM outputs

  

Fig. Changes of inundation probability and inundation duration in the Lower Mekong Basin under future climate change (Try et al. 2020b)