Designing new climate-resilient roads in the Kyrgyz Republic
ADB is piloting the use of vulnerability assessments to help build roads that withstand the impacts of climate change.
Roads are critical to transport across the vast lands of Central Asia, so we must make sure they can withstand the effects of climate change. Here is how we addressed adaptation in a new way for a project underway in the Kyrgyz Republic, where roads carry approximately 95% of passenger traffic and over 50% of freight.
ADB has committed to upgrade a 52-km road between Bishkek and Kara-Balta. The road is part of the Central Asia Regional Economic Cooperation Corridor 3 that runs from southwestern Siberia in the Russian Federation through Afghanistan, Kazakhstan, the Kyrgyz Republic, Tajikistan, Turkmenistan and Uzbekistan to the Middle East and South Asia. The road is also the only direct land link between the southern and northern parts of the Kyrgyz Republic.
The road segment is situated in in the central Chui Valley in the northern part of the country, where the climate is changing with both temperatures and precipitation increasing. Given that and with the government keen to avoid the cost overruns caused by climate change in other road projects, ADB is taking a new approach.
ADB’s project detailed design team conducted an assessment on the project’s vulnerability to climate change and identified relevant climate change parameters, their values, and adaptation measures. This is the first time such an assessment was done on a transport project in the Kyrgyz Republic.
The initial climate risk and vulnerability analysis identified several projected impacts, most importantly more extreme peak precipitation and temperatures. Climate events projected through 2050 were:
- 60% decrease in the number of very cold days (at or below -20°C) per year, with minimum temperature rising from -34°C to -24°C.
- 20% decrease in the number of yearly freezing days.
- 8-14% increase in the number of yearly freezing-thawing days.
- 36-100% increase in days with temperatures over 32°C, with 6 days per year predicted to exceed 38°C.
- Peak precipitation intensity reaching 30 mm/day in the rainiest month of August.
- Up to a 6 mm increase in snowfall in winter.
Knowing all this, we incorporated engineering and non-engineering options to design an upgraded road that will last longer and cost less to maintain. Among the engineering options for the road design are:
- Road surface. Higher peak temperatures require asphalt better able to withstand softening or melting, which we propose can be achieved through adjusting the binder composition of the asphalt.
- Subsurface. Higher winter temperatures are reducing the frost depth by 20%. However, since traffic volume—not frost depth—is the factor determining the thickness of the road’s base and sub-base, it is not necessary to engineer a thicker subsurface. There is no permafrost in the project area.
- Side drainage. There will be greater rainfall intensity per thunderstorm (up to 30 mm/day) so the drainage used in the project follows a 50 mm/day standard and is expected to be able to accommodate the increased volume and intensity of discharge.
- Bridges and culverts. Peak river water discharge primarily depends on mudflows, and is largely buffered upstream by wide flood beds. Though it could not be rigorously proved, glacier retreat is expected to reduce the number of mudflows. Still, a number of engineering options were advised upstream of road crossings to mitigate further risk. These include creating retention dams (though cost, procedural and ownership issues should first be clarified), widening rivers where possible to reduce the maximum water level under the bridges and installation of acoustic water level sensors for early warning. Additionally, concrete used in bridges should be adapted to a higher frost standard to withstand the increasing number of freezing/thawing days per year.
The assessment found that groundwater flooding, landslides and avalanches won’t affect this road.
Non-engineering options in the road design include offsetting climate change impacts, management measures, and capacity building. For example, trees offset reduce the heat island effect, absorb carbon dioxide, and trap fine dust, so as many as feasible should be planted. This issue was also raised in the initial environmental report with binding implementation by the government through the contractor. Stakeholders concerned about land degradation in the foothills and having water for irrigation could conduct regular cleaning of rivers and channels upstream and downstream of road crossings to reduce sediment and maintain water discharge capacity during mudflows. Finally, training on climate change adaptation and development of guidelines for the transport and environmental sectors is also recommended.
Climate change is an undeniable fact, and our projects need to account for that. We need climate change assessments, to incorporate those findings in the detailed design and initial environmental examination report, and develop a capacity building program. In doing so, we can build climate-resilient roads that will contribute to the country’s development for many generations.
The tenders for the Bishkek and Kara-Balta road project are now being conducted and the project is expected to be finished in 2020.