Build Resilience Against Landslides

With its unique topography, fragile geology, monsoon-driven climate, and economic challenges, Nepal is one of the most landslide-prone countries in the world. While the monsoon season is still months away, Nepal has a key window to address the expanding landslide risk year-round. Recent studies, including our research published in Environmental Earth Sciences, have highlighted a significant rise in landslide occurrences in Nepal. Irregular rainfall patterns, infrastructure development, and climate change are all factors that contribute to the increasing problem. It is essential to act well before the next monsoon season.

Our study examined landslide disaster data sourced from the Nepal Disaster Risk Reduction (DRR) catalogs spanning 2011 to 2020. These records provide insights into landslides that cause damage to life, property, or infrastructure. Landslides have quadrupled from 0.85 per 1,000 square kilometers in 2011 to 3.34 in 2020, with over 7,000 events recorded and more than 5,000 fatalities. Landslide risk varies significantly across regions, with Gandaki, Karnali, and Koshi being particularly vulnerable. The Lesser Himalayan Zone is particularly vulnerable to landslides because of its geological formations, steep slopes, high rainfall intensity, and unregulated development activities.

Earthquakes' impacts 

Damage to the landscape caused by earthquakes can result in temporary increases in landslide rates over one year to ten years. On April 25, 2015, Nepal was struck by a 7.8 magnitude earthquake that triggered over 25,000 landslides in the central and western regions. Our research highlights that the landslide rate in the 14 worst-affected districts remains significantly higher than pre-earthquake levels, even years later. While one might expect a peak immediately after the earthquake, the most significant increases occurred three years later, approximately in 2018, with landslide numbers continuing to increase. This delayed impact may be linked to the progressive weakening of slopes because monsoon rains exacerbate earthquake-induced fractures. 

After the 2005 Kashmir Earthquake in Pakistan and the 2008 Sichuan Earthquake in China, landslide events in the impacted areas notably rose for 8–10 years and, in certain instances, even longer. The destabilisation of slopes from seismic shaking weakened geological formations, making the terrain more prone to rainfall-triggered landslides. This highlights the long-term effects of earthquakes on landslide risks. The seasonal occurrence of landslides in Nepal highlights the impact of monsoonal rains. Landslides predominantly occur in summer, coinciding with torrential rains that saturate and destabilise slopes. The results revealed that landslide events were clustered in space and time, with 93.26 per cent of the landslides occurring in the rainy season.

 Climate change further compounds this issue, as monsoon rains are projected to become more intense and erratic, increasing the likelihood of landslides. In addition to monsoonal rains, glacial lake outburst floods (GLOFs), triggered by melting glaciers, are becoming a significant hazard. Recent events, such as the 2024 Thame GLOF and 2021 Melamchi debris, have caused extensive destruction, triggering landslides in downstream areas. In September 2024, central Nepal experienced a record-breaking rainfall triggering widespread landslides and debris flows, affecting over five hundred thousand households and 2.59 million people. These disasters highlight the dual threats posed by climate change: intensified rainfall and accelerated glacier melt. 

Studies have reported increased climate-induced landslides, with increasing temperatures, erratic rainfall patterns, and rapid glacier retreat being key drivers. ICIMOD reported that extreme precipitation events in the Himalayas have increased by 20 per cent over the last three decades, leading to more frequent and severe landslides. In recent years, Nepal's rapid urbanisation and infrastructure development are also significant drivers of landslides. Following the 1990s transition to a more decentralised governance model, local governments began allocating substantial budgets to road construction. Unfortunately, many projects were undertaken without adequate geological surveys or slope stability assessments. Roads built without consideration of their environmental impact have destabilised slopes, making them more prone to failure, especially during the rainy season. 

Between 2011 and 2020, Nepal’s urban population grew significantly, fueling demand for infrastructure. While roads are vital for economic development and connectivity, their haphazard construction has exacerbated landslide risk. The increasing frequency and impact of landslides in call for urgent action. Existing landslides have a lasting impact, influencing the occurrence and size of subsequent landslides, a concept known as path dependency. Landslide path dependency underscores the need for proactive measures to prevent future events. 

Comprehensive land-use policies should be implemented to regulate construction activities, particularly in landslide-prone areas. Proper planning and enforcement can minimise slope destabilisation caused by unregulated development. Engineering interventions such as retaining walls, drainage systems, and slope reinforcement can mitigate landslide risk. Additionally, advanced monitoring systems, including satellite imagery and ground-based sensors, can provide early warnings and improve disaster preparedness. Nepal is not alone in facing landslide challenges; similar trends are seen across the Himalayas. 

In Uttarakhand, India, rising landslides are linked to heavy rainfall and poor construction. Bhutan also experiences monsoon-triggered landslides that damage infrastructure. These examples emphasize the regional nature of the issue and the need for cross-border cooperation. Safe construction requires geological and environmental assessments, with a focus on reducing exposure in challenging areas. Comprehensive risk assessments, including multi-hazard analysis, are essential to address cascading risks. Furthermore, insurance and reinsurance policies must be developed to safeguard communities and assets financially, ensuring rapid recovery post-disaster. This holistic strategy mitigates the direct impacts of landslides and enhances the overall adaptive capacity of vulnerable regions.

Sustainable methods

Training local engineers and contractors on sustainable methods is equally important. Global efforts to combat climate change are crucial for mitigating its impact on monsoon intensity. Public education campaigns can help communities understand landslide risk and adopt preventative measures. Community-based disaster risk reduction programmes should be prioritised. Nepal's increasing challenge of landslides emphasises the critical equilibrium between development and environmental preservation.

 Mitigating these challenges necessitates collaborative efforts from the government, scientific community, and local stakeholders to implement effective solutions. By integrating science, policy, and community action, Nepal can build resilience against landslide disasters and ensure safer living conditions for its people. Nepal’s majestic landscapes have long inspired awe but demand respect. Let us not only marvel at the grandeur of the Himalayas but also pledge to safeguard them — and the communities that reside within their majestic embrace.

(Sharma holds a PhD and KC a Masters in Geotechnical Engineering, and both work in disaster mitigation and resilient related programmes, planning and design.)