ADB experts named four ways to adapt roads in Central Asia to climate change
By the end of this century, the average temperature in Central Asia is expected to rise by 2-5.7°C. For about 65 million people in the region, this means a change in precipitation patterns, more frequent and severe storms, increased droughts and prolonged dry spells.
Climate change has serious consequences for the diverse landscape of the region, from vast arid and semi-arid areas to grassy steppes and mountains. The transport infrastructure in Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan, which is crucial for the movement of goods and people across the landlocked region, is becoming vulnerable to damage.
The recently released guidance from the Asian Development Bank discusses how countries in the region can strengthen existing infrastructure and ensure a secure road network. Here are four ways to make roads in Central Asia more resilient to climate change.
1. Stabilize the ground under the roads to protect against flooding.
Rain, snow, melting ice and landslides cause floods. They can soften the main material of roads, which usually consist of gravel, sand, clay. On the other hand, drought compresses and cracks these materials, and re-hydration allows them to expand. This cycle compromises the ability of the soil to withstand the stress exerted by the movement of vehicles.
To solve this problem, the soil needs to be stabilized. This increases stiffness and prevents residual deformation, increasing the stability of roads, especially in rural areas, where they are usually unpaved or lightly paved. The process is simple and involves mixing basic materials with a special binder that will be applied to the soil surface during construction.
Improving the management of the drainage system, for example, by periodically cleaning and preventing blockages or damage, also helps to reduce the effects of floods.
2. Strengthening slopes against soil erosion.
Intense rains can also lead to the erosion of large masses of soil from embankments and slopes, which jeopardizes road safety.
To strengthen embankments and slopes, it is possible to use ground nails and install gabions - steel cages filled with stones or concrete, placed at the foot of the slope.
Bioengineering solutions - planting trees and vegetation - can also protect slopes. These measures are inexpensive, but have limited ability to control erosion and stabilize slopes. When combined with other measures such as gabions, they can be a good way to promote green and sustainable adaptation.
3. Modified bitumen to protect roads from extreme heat.
Many localities in the region have long and dry summers and irregularly cold winters. On desert plains, such as in Turkmenistan and Uzbekistan, temperatures reach 45°C in summer and can drop to -25°C in winter. Roads are sensitive to the effects of this intense heat. They are made of asphalt concrete consisting of a polymer binder called bitumen, which softens when heated and hardens when the temperature decreases.
Bitumen modification can help to increase the flexibility of asphalt in the summer-winter cycle. This process involves changing the properties of natural bitumen, allowing it to maintain rigidity in summer and plasticity in winter.
4. Barriers to protect against avalanches and rockfalls.
Snow accumulating on slopes in mountainous areas, especially wet and heavy snow, can cause avalanches that can damage and block roads. To contain or reduce the amount of eroded snow and debris, slopes can be stabilized with steel or wood barriers.
The melting of the eternal snow caps, combined with an increase in temperature, also leads to rockfalls. The rapid melting of glaciers can cause rocks to break off and slopes to collapse, threatening the roads below. You can install attenuators, canopies or curtains that will serve as shock absorbers when boulders roll down the slopes.
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