From slopes to streams: Geospatial characterization of landslide dynamics and downstream impacts in the Western Ghats highland panchayats, Kerala, India

A. S. Amrutha; Mohan Jothika; A. Athira; G. S. Pradeep; M. R. Nandu

doi:10.64866/j.ijdscr.2026.10025

Authors

A. S. Amrutha Kerala State Disaster Management Authority, Thiruvananthapuram, Kerala 695033, India Author
Jothika Mohan Department of Geology, University of Calicut, Malappuram, Kerala 673635, India Author https://orcid.org/0009-0003-2265-5673
Athira A. Department of Geology, University of Calicut, Malappuram, Kerala 673635, India Author
G. S. Pradeep Kerala State Disaster Management Authority, Thiruvananthapuram, Kerala 695033, India Author
M. R. Nandu Department of Geology, University of Kerala, Kariavattom, Thiruvananthapuram, Kerala 695581, India Author https://orcid.org/0009-0004-3128-4322

DOI:

https://doi.org/10.64866/j.ijdscr.2026.10025

Keywords:

Landslide, frequency ratio, downstream impact, local self-governments, disaster risk reduction, Western Ghats

Abstract

The windward slopes of the Western Ghats in Kerala are increasingly experiencing frequent and catastrophic landslides, driven by intense monsoonal rainfall, complex topography, and rising human pressures. Highland Local Self Government (LSG) regions such as Mariyapuram and Vathikudy in the Idukki district, and the upper catchment area of the Manimala River, have emerged as critical areas of concern due to recurrent landslides. This study evaluates landslide susceptibility and downstream impacts in the Mariyapuram–Vathikudy Local Self Governments (LSGs) and the upper Manimala River Basin. The analysis integrates geospatial analysis with governance-focused disaster risk reduction (DRR) strategies. The methodology used includes applying frequency-ratio algorithms to generate Landslide Susceptibility Index (LSI) maps, followed by risk classification and validation using historical landslide data. Landslide susceptibility maps, generated using frequency-ratio analysis, categorize the 112.26 km² Mariyapuram–Vathikudy region into high (17.52%), moderate (65.78%), and low (16.69%) susceptibility zones. In comparison, the 189.68 km² upper Manimala catchment comprises high (25.37%), moderate (70.45%), and low (4.18%) susceptibility zones. This study identifies potential downstream impact zones that, although not located directly on steep slopes, remain considerably vulnerable to secondary hazards such as debris flows and sedimentation. The outcomes are designed to support LSG-level disaster risk reduction (DRR) initiatives and micro-level planning and mitigation strategies. This research underscores the importance of a localised, landscape-sensitive approach to managing landslide risks that accounts for both primary hazard zones and their wider impact areas.

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