The climate trouble on India’s roads

Bengaluru-based writer and educationist Chandrika R. Krishnan has made five visits to the mountains in North India in the last decade. And each time, her road journeys have gotten delayed because of landslides.

“I remember waiting it out in Kashmir, Ladakh and Uttarakhand because rainfall-triggered landslides had temporarily blocked the road,” Krishnan told ISignal.

Some of these visits were outside the monsoon window. Krishnan visited Leh and Ladakh in August 2019, Char Dham (the four sacred Hindu Himalayan shrines) in May 2022, Amarnath and Kashmir in May 2024, Adi Kailash in June 2025, and Vaishno Devi in October 2025.

While hilly roads are known to be prone to landslides, studies show that road construction—which the Himalayan region (and India as a whole) has seen a lot of in the last decade—can contribute to both their frequency and magnitude.

In March 2025, researchers published a landslide susceptibility map for an 80-km stretch from Karnaprayag to Joshimath in Uttarakhand along National Highway 7, a mountainous corridor connecting Punjab, Haryana, Himachal Pradesh and Uttarakhand. The study demarcated areas into five categories of susceptibility: very low, low, moderate, high, and very high. Both the high and very high zones majorly lay alongside the road, a sign that “road widening, construction works, etc. are significantly causing the slopes to be more prone to landslides”, they concluded.

In the Himalayan region, road construction frequently involves cutting into steep slopes with complex geological and hydrological conditions, explained Satish Pandey, scientist F & head, Flexible Pavement Division, CSIR-Central Road Research Institute, under the Ministry of Science and Technology.

Geological surveys, drainage characteristics, groundwater conditions and landslide susceptibility must be considered at the planning stage, Pandey said. If not, road construction can increase slope instability. Without adequate stabilisation and drainage, and given the concentration of surface runoff, it can further increase the risk of landslides, erosion and road damage during intense rainfall, he explained.

“Even in flood-prone areas that aren’t hilly, roads and bridges can become vulnerable when the design does not adequately account for catchment hydrology, changing runoff conditions, floodplain behaviour and river morphology,” added Pandey, who is also a professor at the Academy of Scientific & Innovative Research.

For example, inadequate assessment of the highest potential overflows, or inadequate provision for those overflows to drain, or insufficient consideration of the washing away of the riverbed material around the base of structures can increase the likelihood of damage or structural distress to embankments during major flood events.

New lessons, even as old ones are ignored

With climate change, particularly heavy rainfall, increasing the hazards facing infrastructure and habitations, experts said road design needs to be revisited.

“Climate change is necessitating the analysis of multiple variables to design infrastructure that can withstand potential disasters,” said Dikshu Kukreja, Principal Architect, CP Kukreja Architects.

For instance, during the February 2021 Rishiganga valley disaster, a road bridge constructed by the Border Roads Organisation near Raini village in Uttarakhand’s Chamoli was destroyed, along with other bridges and sections of road infrastructure. The National Disaster Management Authority’s detailed assessment of the disaster found that the exceptionally complex combination of rock-fall, ice break-off, debris flow and extreme sediment transport was of a scale that exceeded previously observed flood conditions and caused enormous sediment deposition and changes to the river channel.

Essentially, bridge and road planning in vulnerable valleys cannot look only at conventional data impacting road longevity such as river discharge data. “It has to account for cascading hazards, including debris flows, sudden channel blockage and avulsion [switch of a river course], and changes in the river’s morphology,” said Kukreja, who is also co-author of The Future of the Himalayas, a whitepaper on rethinking development and resilience in that region. “Different datasets must be brought together at the point where an infrastructure decision is made.”

While India has considerable technical expertise and a growing body of information on rainfall, floods, geology, terrain, landslides and climate variability, Pandey said, the extent to which these datasets are integrated into project planning, design, construction and maintenance can vary considerably across projects and agencies.

Manmohan Singh Deol, technical director, Rodic Consultants, said that hazard findings mapped by studies sit largely in academic literature and internal project reports. He suggested that they should feed into a live, updated risk register, and that project engineers and Detailed Project Report consultants should be required to refer to it before finalising alignments.

For instance, Deol pointed out, slope stability studies across Himalayan highways on NH-44 in Kashmir, NH-10 in Sikkim, and NH-37 in Manipur, among others, have repeatedly flagged specific cut slopes as unstable using established geotechnical methods.

“Mainstreaming research findings should allow known risks to be designed around in advance, not rediscovered only after failure,” said Deol. “Existing data must be systematically built into decision-making before ground is broken.”

Integrating climate risk key to sustainability

Road and bridge design in India is largely informed by Indian Roads Congress guidelines, specifically, a “return period”, which is an estimate of the average time between extreme weather or flood events of a specific magnitude that could damage the constructed asset.

Rural road drains are designed for a return period of 10 years, and urban road drains are designed for a 25-year return period. Highways and major drains are designed for 50- to 100-year return periods based on the traffic risk and surroundings, and bridges for a return period of not less than 100 years.

A highway designed for a, say, 60-year return period, would have a 1.67% chance of seeing that worst case scenario in any given year. But climate change is exacerbating the magnitude of the worst case scenario as well as their frequency.

“Return-period models rely on stationarity, the assumption that past rainfall patterns are a reliable guide to future risk,” Deol pointed out. This assumption is breaking down. “In today’s times, a road designed to meet a 1-in-100-year flood standard today may be facing that intensity of event far more often within its service life,” he said.

Consider an access-controlled highway. Some of these have continuous 6- to 10-metre-tall embankments for kilometres, which block the flow of water. In heavy rain, they act as linear dams, explained Atasi Das, assistant vice president, GR Infraprojects, a road construction company. “When openings are sized on a nominal return period rather than on catchment behaviour, flood history and changing rainfall, water ponds on both sides, and culverts at intervals cannot restore the original drainage.”

The solution, according to Pandey, “is not to abandon return-period-based design altogether, but to supplement it with climate-informed, risk-based and adaptive engineering approaches.”

In practice, Pandey explained this means moving beyond designing for a single design event towards assessing performance across a range of possible hazards. “Infrastructure should also be designed to facilitate inspection, maintenance, repair and, wherever feasible, future upgrades as climate risks evolve,” he said.

For roads and bridges specifically, Kukreja said, a revised approach means asking not just what magnitude of flood the structure can withstand, but also what happens if that threshold is exceeded. “Can the road fail without triggering a larger slope failure? Can a bridge be overtopped or damaged without isolating an entire valley? Is there redundancy in the network? Can a section be repaired quickly?,” he explained.

Treating climate risk as a design input from the outset rather than a check applied later also means weighing the consequences of failure alongside capital cost, explained Aashish Kapur, chief commercial officer, egis India.

Building flexibility into infrastructure decisions

If the data show that a full double-lane standard is not advisable, decision-makers must turn to a solution that is more responsive to the terrain. A blanket application of plains-derived road standards can be counterproductive in fragile mountain terrains, Kukreja pointed out.

Analysing the function, traffic demand, strategic requirement, terrain, geology, ecological sensitivity and the consequences of failure may show that in some locations, a properly designed single-lane road with a few widened sections may be more appropriate than forcing a uniform two-lane formation through a vulnerable slope. Particularly on strategic routes, a wider road may be justified, he explained.

Also, infrastructure planners may need to move away from the idea of linear progression from narrow road to intermediate road to double-lane road. “A mountain does not become more suitable for infrastructure simply because we have the engineering capacity to cut a wider road through it,” said Kukreja. “A wider road necessitates additional cutting, blasting and slope exposure that the traffic requirement may justify but the terrain may not.”

An instructive example, according to Kukreja, is the Char Dham road project. On the one hand, the August 2019 Supreme Court-appointed High Powered Committee noted the adoption of a uniform double-lane-with-paved-shoulder standard did not sufficiently account for the geological fragility, slope instability, recurring landslides and environmental conditions of different stretches. On the other, the committee also noted deficiencies in traffic data, including the reliance on limited seasonal traffic counts and the absence of traffic surveys for the higher Himalayas.

The Supreme Court subsequently upheld a narrower carriageway standard for the project, recognising the need to account for the terrain and environmental consequences of widening.

“Recognising limits is not a constraint on development; it is a condition for its long-term viability,” said Kukreja.

While the Supreme Court in December 2021 permitted the construction of double lane paved shoulder roads, under-construction stretches of the project witnessed a higher frequency of landslides, and 81% of these instances occurred within 100 metres of the road, according to a paper published in the journal of Geotechnical and Geological Engineering in July 2025.

“Better alignment, tunnels or viaducts where geologically appropriate, strategically located passing places, improved public transport, and in some corridors a shift towards rail may all be better alternatives,” said Kukreja. “In many Himalayan locations, designing for resilience may mean accepting lower speeds, narrower formations, greater redundancy, more frequent maintenance and, in some cases, choosing an entirely different alignment or mode of connectivity.”

The challenge with implementation

Making note of the challenge in developing climate-resilient roads in the geologically fragile Himalayan region, Union Minister of Road Transport & Highways Nitin Gadkari, in April 2026, announced a policy shift to prioritise slope stabilisation before starting the construction of roads in addition to existing initiatives for specialised landslide treatment, geo-hazard mitigation and geological investigations and data sharing.

Sanjay Nirmal, former director general of the Ministry of Road Transport and Highways (MoRTH), told ISignal that MoRTH’s intensifying focus on slope stabilisation comes as steeper hill cutting is creating slopes of increasing heights, and the treatment options are expanding to modern methods such as geo cells (cellular structure to bind and strengthen loose soil) and geo grids (a grid used to bind loose hillside soil). “Modern methods used to be very expensive but as they become more competitively priced, their deployment is poised to increase,” he said.

It’s not as if India lacks technical guidance for addressing slope instability and erosion in road construction. Detailed hill road guidelines exist as do recommendations to strengthen embankments and roadside slopes, and design road drainage.

Besides, Deol pointed out, the Indian Roads Congress has begun moving in a new direction. For instance, it has laid out retrofitting guidelines specifically for protecting road systems from rainfall, waterlogging, and flooding, which is itself an admission that older designs need revisiting.

Practically, he said, this should translate into asset management systems that flag risk exposure rather than just design compliance at the time of construction.

But translating this foundation into consistent implementation remains a key challenge.

Decades-old codes and standards explain slope stabilisation methods such as stone pitching, turfing, benching, etc., Nirmal explained. And these used to be included in tenders and were made compulsory (stone pitching) for embankments taller than six metres. But, “their implementation remained a concern and their maintenance wasn’t prioritised”, he added.

“Road engineering essentials are sometimes dropped under pressure of access, deadlines and milestone payments,” said Das. “Stabilisation is deferred to the end, and slopes are sometimes left to ‘settle naturally’ over two monsoons only to necessitate the raw face to meet the monsoon unprotected. Field decisions are also made without thinking through consequences.”

A common example she cited was dumping excavated material against an existing retaining wall for want of a dumping yard. In the monsoon, the saturated dump imposes heavy, unplanned pressure on a wall designed for another condition, and the wall fails.

In particular, Das said, “Unprecedented construction rates compress investigation, and agencies new to complex terrain miss early warning signs.”

In the Himalayas alone, the Border Roads Organisation has constructed about 4,595 km of mountainous roads between 2020-21 and 2024-25, at a cost of approximately Rs 23,625 crore.

While the Border Roads Organisation’s 2022 Technical Instruction on road classification and geometric standards explicitly recognises hazards associated with Himalayan terrain and requires its technical officers to follow prescribed standards for slope stabilisation, drainage, erosion control and landslide protection, Kukreja questioned “whether the stabilisation philosophy is being applied sufficiently early and comprehensively across the entire road network.”

“In a Himalayan road, slope stability cannot be treated as a remedial engineering package after the road has been cut,” he said. “Alignment, drainage, excavation geometry, retaining structures, vegetation, muck disposal and slope treatment need to be conceived as one system.”

The need for continuous monitoring

Slope stabilisation isn’t a one-time task, it needs to be monitored, said Nirmal.

Where bioengineering and other slope stabilisation methods have been used in both national and state projects supported by the World Bank Group, such as Green National Highways Corridor Project and Himachal Pradesh State Roads Transformation Project, project monitoring and field observations indicate that these interventions have performed effectively, with upgraded road sections remaining stable through successive monsoon seasons, without major slope failures or significant damage on the treated stretches.

For instance, both the civil engineering structures (retaining and breast walls) and bio-engineering (including brush layers, slip plantation, bamboo crib walls, hydroseeding and jute netting) on a 33.1-km stretch of the Baddi – Sai – Ramshahar road and a 27-km stretch of the Mandi – Rewalsar – Kalkhar road, both roads that were severely disrupted during the 2025 monsoon, showed no signs of distress after the season, the World Bank in India told ISignal.

World Bank-supported hill road projects such as the Mizoram State Roads Project and the Himachal Pradesh State Roads Project explicitly used bioengineering measures for slope stabilisation and promoted them as a cost-effective and environmentally sound component of hill-road development, noted Kapur. “What matters is that those projects recognised slope stability as a core engineering requirement rather than a post-construction maintenance issue.”

“Data-driven planning should continue beyond the design stage, with monitoring and periodic reassessment throughout the infrastructure's service life,” said Pandey.

Technology is now adding another important layer to monitoring by picking up essential data as AI-enabled predictive models, remote sensing, GIS, IoT-based sensors and real-time monitoring can help identify vulnerable slopes and detect changes in ground movement, rainfall, soil moisture and other risk parameters before they translate into a major failure, explained Deol.

For example, an AI-enabled landslide early-warning system developed by the Indian Institute of Technology, Mandi has been deployed at high-risk sites in Himachal Pradesh, while MoRTH has also moved towards InSAR-based monitoring to detect subtle ground movements along vulnerable stretches of the Char Dham route.

Solutions for climate-resilient roads

Going forward, Das proposed making hazard and hydrological evidence a mandatory design gate, and plugging design-to-site gaps by drafting more realistic guidelines.

Evidence-led alignment using geological mapping, geophysics, LiDAR and InSAR, with drone and remote-sensing surveys where access is difficult would ensure better design, she said. “So would mandating structures instead of deep cuts—viaducts, cantilever and half-bridge sections—tunnels where geology justifies them, and narrower formations in sensitive stretches.”

Pandey said measures should be based on local geological and hydrological conditions, rather than relying on a uniform treatment for all slopes.

Typically, those who execute rarely write the codes, Das observed, and those who write them rarely face site constraints. So, getting code writers and field engineers to draft guidelines together, supported by hands-on workshops would also help new methods reaching team supervisors.

She said construction could be made more secure with progressive stabilisation, cutting in a series of gentle slopes (called benches) and stabilising each before the next. Controlled excavations would also be gentler on the geology.

Mandating engineered stabilisation would ensure this critical procedure isn’t bypassed. Planning designated muck disposal yards before excavation would help ensure it is never dumped against retaining structures. Enforcing monitoring-based construction using measuring devices would help identify weaknesses. Tying payment to stabilisation and drainage would ensure speed does not reward skipped steps.

In the instance of failures, the industry needs independent geotechnical reviews and third-party audits with real consequences, according to Das. “Publicly releasing failure investigation reports would help agencies learn from each other; otherwise the lessons stay in a closed circle, the mistake recurs, and another investigation begins,” she said.

This report is republished with permission from ISignal, formerly IndiaSpend, a data-driven, public-interest journalism non-profit. It has been lightly edited for style and clarity.