Floods and Landslides in Hilly Regions

The current monsoon has brought unusually intense rainfall to hilly states such as Uttarakhand and Himachal Pradesh, exacerbating the incidence of floods and landslides. Rivers are swelling to perilous levels, increasing risks to both lives and infrastructure.

Understanding the factors behind these disasters and effective mitigation strategies is crucial for SSC aspirants, as it is an important part of current affairs and disaster management topics.

Factors Increasing Vulnerability of Hilly Regions to Floods and Landslides

Steep Slopes and Gravity

• Water flows down steep slopes much faster than on flat land, preventing proper infiltration.

• This leads to rapid accumulation in streams and rivers, causing flash floods.

For example, regions like Mandi, Kullu, Dharali, Tharali, and Jammu frequently experience floods and landslides due to steep terrains.

Geology and Soil Type

• Many young mountain ranges like the Himalayas are geologically active and composed of weak, fractured, or weathered rocks.

• Mountain soils are often thin, lacking deep root systems, making them susceptible to soil erosion and landslides.

• Areas such as Darjeeling and Sikkim witness frequent landslides due to these fragile formations.

Hydrological Factors

• Valleys funnel rainfall into narrow rivers, and the steep gradient increases water’s erosive power.

• This causes river floods and worsens slope destabilization.

• Notably, the Alaknanda and Mandakini river valleys in Uttarakhand are prone to flash floods during heavy rains.

Trigger Factors

• Continuous rain or intense cloudbursts saturate soil, reduce friction, and trigger landslide risk.

• Sudden snowmelt due to temperature rise can release large water volumes, intensifying floods and landslides.

For example, the northwestern region received over 30% surplus rainfall during June–September 2025.

Human-Induced Factors

• Unregulated construction, road cutting, blocked drainage systems, and unsustainable agriculture exacerbate slope instability.

• The Joshimath land subsidence (2023) highlighted how human activities increase vulnerability to floods and landslides.

How Climate Change Increases Vulnerability

1. Increased Extreme Rainfall Events

• A warmer atmosphere holds more moisture (~7% per 1°C), leading to intense rainfall and flash floods.

• Disrupted monsoon patterns cause droughts followed by heavy rain, reducing soil absorption and increasing flood and landslide risk.

2. Glacial Lake Outburst Floods (GLOFs)

• Glacial retreat forms unstable lakes dammed by moraines.

• Their sudden breach can trigger catastrophic floods and landslides.

• The 2023 South Lhonak GLOF in Sikkim destroyed hydropower infrastructure and increased downstream flood risk.

3. Permafrost Thaw and Wildfires

• Rising temperatures destabilize slopes through permafrost thaw, causing rockfalls and debris flows.

• Increased wildfires destroy vegetation, making soil water-repellent and aggravating hill floods during rainfall.

• Uttarakhand recorded over 5,300 forest fires between November 2022 and June 2023.

NDMA Guidelines for Flood and Landslide Management

Structural Measures:

• Diversion of floodwater via channels

• Afforestation and catchment area treatment

• Embankments, levees, and walls

• Drainage restoration and channel improvement

• Reservoirs and dams for water storage

Non-Structural Measures:

• Flood Management Plans (FMPs) for all agencies

• Flood forecasting and warning systems based on CWC and IMD data

• Raised platforms and flood-proofing shelters

• Integrated Water Resources Management (IWRM)

• Floodplain zoning to regulate land use

Landslide-Specific Measures:

• Landslide Hazard Zonation (LHZ) maps using UAVs, laser scanners, and EO data

• Landslide Early Warning Systems (LEWS) with rainfall thresholds and real-time monitoring

• Capacity building for local communities

• Mountain zone regulations and updated building codes

Measures to Mitigate Floods and Landslides

1. Environmental Measures:

• Afforestation and reforestation with native trees

• Contour trenching, terrace farming, and check dams to reduce runoff and trap sediment

2. Engineering Measures:

• Rock bolts, soil nails, retaining walls, and debris flow barriers

• Channel improvement and diversion channels to increase river capacity and reduce flood risk

3. Policy and Urban Measures:

• Enforce carrying capacity studies and hazard zone identification

• Robust early warning systems integrated with rainfall and river level data

• Urban flood resilience through proper drainage, sponge city models, and rainwater harvesting

4. Economic & Financial Measures:

• Dedicated disaster risk reduction budgets

• Parametric insurance models for quick payouts based on rainfall/flood triggers

Final Thoughts

The current monsoon has caused unusually heavy rainfall in hilly states like Uttarakhand and Himachal Pradesh, leading to increased incidents of floods and landslides. Steep slopes, fragile soils, and geologically weak mountains make these regions highly vulnerable. Rivers such as the Alaknanda and Mandakini often swell rapidly, causing flash floods and severe erosion. Human activities like unregulated construction, road cutting, and overgrazing further worsen slope stability.

Climate change has amplified these risks by increasing extreme rainfall, triggering glacial lake outburst floods (GLOFs), and causing permafrost thaw, while wildfires destroy vegetation and reduce soil absorption. The NDMA guidelines recommend both structural measures, like embankments and check dams, and non-structural strategies, including early warning systems, floodplain zoning, and disaster management plans, to mitigate impacts.

Effective solutions involve afforestation, terrace farming, slope stabilization, and community-based early warning systems, combined with policy enforcement and urban planning.