Micro Landslide Hazard Zonation Mapping of Aizawl City

The project “Micro Landslide Hazard Zonation Mapping of Aizawl City using Remote Sensing and GIS” was undertaken by the Mizoram Remote Sensing Application Centre to produce a detailed spatial assessment of landslide susceptibility within Aizawl City. The study was initiated in response to recurrent slope failures, rapid urban expansion and increasing development pressure on the city’s narrow ridges and steep hill slopes. Its principal objective was to identify areas of varying landslide hazard, analyse the major causative factors influencing slope instability and provide a scientific basis for safer land-use planning, infrastructure development and disaster-risk mitigation.

The study covered the entire Aizawl urban area of 128.98 sq. km. High-resolution QuickBird imagery with 0.8 m spatial resolution was used as the primary dataset, supplemented by IRS-P5 Cartosat-I stereo data at 2.5 m resolution, Survey of India topographic maps, field observations and GPS-based ground verification. Five principal thematic parameters—land use/land cover, slope, geomorphology, lithology and geological structure—were generated and integrated in ARC/INFO GIS using a weighted heuristic approach. Additional consideration was given to active and old landslides, fault proximity, road cutting, drainage conditions and dip-slope relationships. The final hazard maps were prepared at 1:5,000 scale, with grid-wise reference maps also produced at 1:20,000.

The results demonstrate the inherent fragility of Aizawl’s terrain. About 64.22% of the city lies on slopes exceeding 40°, including 63.95% within the 40–60° class, indicating that steep terrain is the dominant physical constraint. Scrubland forms the largest land-use category, occupying 52.51 sq. km or 40.71%, while built-up areas already cover 18.23 sq. km or 14.13%. Geomorphologically, medium and low structural hills together account for more than 96% of the study area, whereas valley fills occupy only 0.28%, confirming the scarcity of naturally stable flat land. Lithological analysis shows that sandstone covers 39.41%, while crumpled shale and shale-sandstone units together occupy over 45%, creating extensive zones of relatively weak and weathering-prone material.

The hazard zonation classified the city into five categories. Very High and High Hazard Zones together cover 37.77 sq. km, or 29.28% of the city, representing areas where construction and major development require avoidance or stringent geotechnical scrutiny. The Moderate Hazard Zone is the largest class at 56.66 sq. km (43.93%), while Low and Very Low Hazard Zones account for 20.61% and 6.18%, respectively. High-risk locations were associated with active landslides, faults, crumpled shale, steep road cuts, quarrying, poor drainage and dense settlement.

The project’s principal outcome is a detailed GIS-based hazard database for Aizawl City. It provides planners, engineers, municipal authorities and disaster-management agencies with an operational tool for site selection, building regulation, road and drainage design, slope stabilization, emergency planning and hazard-sensitive urban development.

Summarized Metadata

Mapping Scale: 1:5,000 

Satellite data & Year: IRS P5 Cartosat-I & Quickbird (2006)

Thematic sub-category: Forestry, Administrative boundary

Collaborating/Funding Agency: Science, Technology & Environment Wing, Planning Department, Government of Mizoram

Report Publication Month/Year: March, 2008