The North–South Corridor serves as the main transport artery for the region, which spans quite diverse and spectacular terrains from the historic capital of Georgia, Mtskheta, up north to Stepantsminda in the Great Caucasus mountain range. The road experiences heavy traffic and is unsafe due to a design that is inadequate for the challenging geographical and climatic conditions, particularly in winter. The area is prone to avalanche, landslide, and snow load risks, which cause frequent and extended closures of the road. The two-lane highway provides a low standard alignment and is characterized by substandard open tunnels and avalanche galleries, in which modern trucks cannot pass simultaneously. An upgrade of the existing road alignment with improved geometry and avalanche galleries was considered but deemed inappropriate as it would not address the core climate-related risks.

Recognizing these challenges, the government has therefore requested ADB’s and EBRD’s assistance to improve the North–South Corridor. The climate-resilient project road will allow more traffic to travel on it safely and will remain fully operational all year. A detailed Climate Risk and Vulnerability Assessment (CRVA) report has been developed for the project road. The projected increase in extreme precipitation events is considered as the most important climate risk for the project road. This not only leads to higher extreme discharges, but can also lead to more frequent landslides, mudflows, and avalanches. The climate model analysis yields following conclusions for the project area:

• Temperature increases by about 2 °C (RCP4.5) to 2.7 °C (RCP8.5) are to be expected
• Minimum and maximum temperature are likely to change inconsistently, with maximum air temperatures increasing more than minimum air temperatures. This implies a larger diurnal temperature range for the future
• Extremes related to temperatures (e.g. warm spells, extremely warm days) are likely to increase in frequency and intensity
• Precipitation totals are likely to stay reasonable constant
• Precipitation extremes are likely to increase in frequency and intensity. Maximum 1-day precipitation volumes with return periods of 25, 50 and 100 years are expected to increase by about 10% to 20%.

Stress tests were carried out by the project road design consultant team using +10% and +20% increased precipitation input for return periods used in the engineering design. These tests revealed that bridges have sufficient capacity in the current design to cope with higher discharge levels in the future, although it would be prudent to check the bridge substructure designs for higher flow velocities and the possibility of increased debris content in the flow. The tests indicated that a small proportion of the transversal and longitudinal drainage systems might have insufficient capacity to cope with the increased precipitation extremes. These should be identified, and their dimensions increased appropriately.

Due to its geographic location, Georgia’s role as a major transit country is significant. Transport of goods into and through Georgia has increased over the past 10-15 years. Almost two-thirds of goods in Georgia are transported by road but the roads are poorly equipped to cope with the volume of traffic and the proportion of heavy vehicles, and factors such as insufficient dual carriageways, routing through inhabited areas and inadequate maintenance and repair, hinder throughputs and increase transit times. The government of Georgia has therefore launched a program to upgrade the major roads of the country, including part of the East-West (E60) Highway. This climate risk and vulnerability assessment (CRVA) has examined the proposed components for section Shorapani-Argveta (F4) of the East-West Highway Road Project. The climate model analysis yields following conclusions:

• Temperature increases by about 2.1 °C (RCP4.5) to 2.9 °C (RCP8.5) are to be expected
• Minimum and maximum temperature are likely to change inconsistently, with maximum air temperatures increasing more than minimum air temperatures. This implies a larger diurnal temperature range for the future
• Extremes related to temperatures (e.g. warm spells, extremely warm days) are likely to increase in frequency and intensity
• Precipitation totals are likely to stay reasonable constant
• Precipitation extremes are likely to increase in frequency and intensity. Maximum 1-day precipitation volumes with return periods of 25, 50 and 100 years are expected to increase by about 10% to 20%.

The increase in extreme precipitation events is considered as the most important climate risk for the project road. This may lead to higher extreme discharges that exceed the systems’ design capacity and cause flooding or inundation of road infrastructure. More extreme precipitation events can also lead to increased slope instability alongside the project road, causing more frequent and more powerful landslides, rockfalls and/or avalanches. In addition, the projected increase in diurnal temperature variability may lead to an increase in freeze–thaw conditions. This may result in deterioration of road pavement integrity, resulting in more frequent maintenance requirements. It can also further increase the risk of slope instability, making any stretch of road close to steep terrain more vulnerable to such mass movement phenomena.

According to the design team, the structures at risk of flooding (e.g. bridges, road sections) are sufficiently dimensioned to cope with return levels 10-20% higher than used in the original design calculations, which can be reasonably assumed. Retaining walls and mass movement protection structures are in place. The performance and sustainability of the pavement structure and structural joints may be adversely affected by the increase in the diurnal temperature range. To mitigate this risk, it advised to use road pavement with highest capability.