ADB publication describing a study assessing potential climate change impacts on a large transport infrastructure project in Viet Nam.
Facing threats from sea-level rise, storm surges, floods, and the intensification of extreme weather events, Viet Nam is projected to be among those countries most impacted by climate change. Due to it’s low altitude, the Mekong Delta is a region at particularly high risk to these projected changes, as evidenced by the numerous severe flood events in recent decades. Against such challenges, careful assessment is required by engineers and decision-makers when determining risk and project viability. This Asian Development Bank publication describes a study of an infrastructure project consisting of two bridges and an interconnecting road which assessed its vulnerability to future climate-related impacts, in particular the incremental effects of more intense storm surges. The study in question aimed to test a climate change threat and vulnerability assessment methodology for use in transport infrastructure projects; improve understanding of climate change risks among key stakeholders; quantify impacts on infrastructure, performance, maintenance, and legal compliance of bridges and roads; and prioritise specific adaptation options that are robust, realistic and economically viable. Regarding methodology, the assessment process utilised a multi-model ensemble of six general circulation models, two global emissions scenarios, statistical downscaling techniques, and a suite of modelling tools developed for the Mekong over the past 15 years. The study found that the 1-in-100 years floodplain water level may increase by 0.6m over the 100 year design life of the project. This estimate places the projected peak water level as 3.1-3.6m above sea level at the project site, higher than the initial feasibility study for the project allowed. Without adaptation, water levels were estimated to rise 0.1m over the embankment freeboard, presenting a situation of risk. These embankments were therefore raised, at an additional cost of $4.5 million. Additionally, the left bank of the Cao Lanh bridge will experience significant increase in bed scour and bank erosion during large flood events. Navigation clearance should not be significantly affected by climate change however. The paper concludes that the study provided a deeper understanding of the climate change threats in the Mekong basin to infrastructure, an appreciation of the need to incorporate climate change risk assessments, and a consensus-building tool for project financiers and the government of Viet Nam to adapt a better strategy for climate change response.