The Western Ghats are naturally susceptible to rainfall-triggered landslides because several risk factors overlap. The region has steep, deeply dissected terrain, weathered basaltic rocks and soil-like regolith that can lose strength when saturated. Miraswadi receives approximately 1,733 millimetres of rain annually, much of it during the southwest monsoon. During prolonged or unusually intense storms, water infiltrates the slope, raises groundwater levels and increases pore-water pressure between grains. That pressure reduces the friction and effective stress holding the material together, lowering its shear strength. Surface runoff can then concentrate in channels, erode exposed soil and mobilize loose debris. The July 2021 event occurred during an extreme rainfall episode that triggered thousands of landslides across Maharashtra’s Western Ghats. The local landscape also includes agricultural terraces, settlements, drainage modifications and other human changes that can redirect runoff or alter infiltration. The researchers did not identify these activities as the primary cause of the Miraswadi failure, but they concluded that such modifications may influence local susceptibility when combined with steep slopes, weathered materials and exceptional rainfall. Seismic activity in the nearby Koyna–Varna zone may contribute to long-term fracturing, although rainfall remains the principal trigger in this setting.

To reconstruct the terrain, the team flew a DJI Phantom 4 Pro equipped with a 20-megapixel, one-inch sensor camera at roughly 200 metres above ground level. The mission collected 283 georeferenced high-resolution images, with about 80 per cent forward overlap and 30 per cent side overlap between photographs. Overlapping images allow photogrammetry software to identify the same surface points from multiple viewpoints and calculate their three-dimensional positions. The resulting dataset produced an orthomosaic, a digital elevation model, contour information and a dense point cloud containing approximately 31 million points. Its mean ground sampling distance was 5.52 centimetres, meaning that individual image-derived cells represented only a few centimetres of ground surface. Image calibration was reported as 100 per cent successful, with a mean reprojection error of approximately 0.143 pixels. Handheld GPS measurements supplied ground control points to improve positional consistency and elevation calibration. The researchers emphasize that the products were intended primarily for relative geomorphological analysis rather than survey-grade geodetic measurement. Recreational-grade GPS accuracy and the absence of a pre-failure drone survey limit the precision with which surface movement and lost volume can be interpreted. Even so, the model provided sufficient detail to identify cracks, scarps, slumps and debris pathways across a hazardous slope.

The mapped landslide began approximately 125 metres northeast of Miraswadi on 23 July 2021. Its visible failure area covered about 1.34 hectares, while the associated debris spread extended across roughly 2.95 hectares. From crown to toe, the movement reached approximately 255 metres, with widths ranging from 112 to 162 metres. The researchers estimated that between 42,050 and 46,076 cubic metres of material had been displaced, presenting the result as a range because the pre-failure surface had to be reconstructed from surrounding undisturbed terrain. Morphological evidence suggests that the event began as a debris slide, in which weathered soil and rock moved downslope as a relatively coherent mass. Once the material entered a pre-existing second-order drainage channel, it became more confined and flow-like, evolving into a channelized debris movement. The terrain model divided the slope into an initiation zone between approximately 747 and 690 metres above mean sea level, a transport zone from about 690 to 665 metres, and a deposition zone from roughly 665 to 642 metres. The upper initiation area included steep slopes exceeding 45 degrees and locally surpassing 60 degrees. Lower gradients allowed transported soil, rock fragments and uprooted vegetation to accumulate across the broader depositional area.

The most consequential discovery was not confined to the old landslide scar. Immediately upslope of the habitation, researchers identified a deformation area containing three to four major tension cracks between approximately 70 and 90 metres long and up to half a metre wide. Several cracks coincided with localized ground settlement and slumping, with vertical displacement reaching about 0.5 metres. Their roughly slope-parallel alignment and position on a hillside directly above homes indicate that the ground has continued to adjust after the 2021 failure. A second area, above the original crown, contained two or three smaller cracks approximately 10 to 15 metres long and 0.1 metres wide. These may represent instability propagating upslope, although the study does not establish a precise rate or direction of movement. Field inspections confirmed active slumping, regolith displacement, minor scarps, surface undulations and additional cracks within the weathered soil. Tilting vegetation supplied another visible sign that the ground beneath roots may be shifting. The researchers carefully distinguish these observations from pre-failure warning signs: because the survey was conducted after the landslide, the features document ongoing post-failure deformation rather than proven precursors. Their location nevertheless matters for risk assessment. A hazard map drawn only around the original scar could overlook unstable ground that threatens the settlement from above.

The team also compared land use in satellite imagery from 2011 and 2022 to examine how the surrounding landscape had changed. Settlement area increased from approximately 8,014 square metres to 15,403 square metres, an expansion of about 92 per cent. Over the same period, terrace farming declined from about 454,746 to 409,114 square metres, while barren or fallow land decreased from approximately 115,372 to 105,709 square metres. Forest cover increased from about 170,695 to 218,601 square metres, suggesting that vegetation expanded overall even as localized changes occurred near the hamlet. The researchers observed the growth of residential structures, modifications to agricultural terraces and exposed soil surfaces, particularly on slopes northeast of the settlement where active instability was detected. These changes can affect how water travels across a hillside. A building platform, track, terrace or altered drainage line may concentrate runoff in one place, increase infiltration in another or remove material that previously protected the soil. The study does not claim that settlement growth caused the landslide. Instead, it presents human landscape modification as a factor that can interact with natural controls and increase exposure. In a small rural community, even modest expansion can place more homes, fields and livestock facilities beneath an unstable slope.

The findings have immediate implications for monitoring and preparedness, but the authors caution against treating their preliminary recommendations as final engineering plans. The deformation zone above the hamlet should receive continued attention, particularly during and after periods of intense rainfall. Repeated drone surveys could compare successive digital elevation models and orthomosaics to detect crack widening, new scarps, changing vegetation tilt or accelerated ground displacement. Field observations remain essential because dense vegetation, shadows and image geometry can obscure features in aerial data. Surface drainage management may reduce water concentration and infiltration in unstable areas, while vegetation-based measures could help control erosion and reinforce shallow soil. Retaining structures might be appropriate in selected locations, but their design would require detailed geotechnical, hydrogeological and engineering investigations. The study also identifies a potential temporary refuge area chosen using topography, distance from unstable slopes, access and proximity to agricultural and livestock resources. That site is not validated as a permanent rehabilitation location; no dedicated land-suitability, geotechnical or hydrogeological assessment was performed. Because many residents depend on farming and livestock and maintain strong ties to their homes, temporary evacuation during extreme rainfall may be more realistic than immediate permanent relocation. Warning signs such as widening cracks, renewed slumping or rapidly increasing deformation could help guide such decisions.

Miraswadi illustrates both the power and the limits of high-resolution remote sensing in landslide science. Regional susceptibility maps can identify broad patterns of danger, but they cannot always show whether a particular crack runs behind a house, whether a drainage channel links a scar to a settlement or whether deformation extends beyond a mapped failure. A drone can be deployed quickly over a relatively small area and generate detailed terrain information without exposing surveyors to the most hazardous ground. Yet a single post-event flight cannot reveal how fast the slope is moving, what is happening underground or whether another failure will occur. The study therefore calls for repeated UAV acquisitions combined with rainfall records, hydrological monitoring, geotechnical testing, geophysical surveys and analysis of rainfall thresholds. Such integration could turn a detailed snapshot into an early-warning system. For communities across the Western Ghats and other tropical mountain regions, the approach offers a practical way to document landslides after extreme storms and identify danger zones that remain active after the debris has stopped moving. In Miraswadi, the central message is straightforward: the end of a landslide’s visible movement does not necessarily mean the slope has stabilized. High-resolution mapping can make that hidden continuation visible before the next monsoon tests the hillside again.

Subject of Research: UAV mapping of landslide morphology and post-failure slope instability in Miraswadi, India

Article Title: UAV based assessment of landslide morphology and slope instability in Miraswadi, Western Ghats, India

Article References: Shirke, A. V., Khandge, A., Umrikar, B. N., & Asim, M. (2026). UAV based assessment of landslide morphology and slope instability in Miraswadi, Western Ghats, India. Discover Geoscience, 4(1), Article 334. https://doi.org/10.1007/s44288-026-00707-y

Image Credits: AI Generated

DOI: 10.1007/s44288-026-00707-y

Keywords: landslides, UAV mapping, Western Ghats, slope instability, debris flows, remote sensing, monsoon rainfall, hazard mitigation, based, assessment, landslide, morphology

The Kahramanmaraş earthquake sequence was extraordinary in magnitude and complexity. Unlike more transient seismic events, this series involved multiple large shocks that generated widespread shaking, triggering extensive slope failures throughout the region. The affected terrain is characterized by steep hillslopes, which are inherently susceptible to disruption due to gravitational forces and the geological composition of the substrata. When shaken by sustained, high-intensity ground motions, these landscapes become critical zones of instability, especially where anthropogenic activities have altered natural slope conditions.

Wang et al.’s study involved an integrated approach combining remote sensing, geotechnical field surveys, and sophisticated numerical modeling to assess how the earthquake sequence altered the mechanical properties of hillslope materials supporting settlements. One key finding was that seismic loading caused progressive weakening of soil and rock cohesion, dramatically lowering the shear strength parameters of these slopes. This weakening was exacerbated by pre-existing geological discontinuities such as fractures and bedding planes, promoting the initiation and propagation of landslides in both urbanized and rural zones.

The team’s analysis also revealed that many new settlements developed in the years leading up to 2023 were constructed without adequate consideration of the underlying geotechnical hazards. Rapid urban expansion, driven by demographic pressures, often prioritized convenient access and scenic vantage points over ground stability. Consequently, these locations sat atop slopes that were already marginally stable under normal conditions, rendering them highly vulnerable when subjected to the intense shaking of the Kahramanmaraş event.

In contrast, some older settlements displayed better resilience, largely because traditional construction methods frequently adapted to local terrain features and utilized more flexible building designs. However, prolonged seismic exposure and amplified ground motions still caused serious damage in these communities, underscoring the insufficiency of purely empirical or historical hazard assessments. The study stresses the urgent need for integrating detailed geotechnical hazard mapping into urban planning frameworks to mitigate future seismic risks effectively.

Central to the research is the elucidation of the mechanisms underlying seismic slope failures. The authors describe how the dynamic stresses induced by the earthquakes increased pore water pressures in saturated zones within the hillslopes, effectively triggering temporary liquefaction in certain soil layers. This process drastically reduced frictional resistance along potential slip surfaces, enabling catastrophic slope failures that were spatially extensive and sometimes rapidly mobilized, leaving little time for evacuation or warning.

Moreover, the research highlights the role of cumulative seismic strain caused by the sequence, which progressively degraded slope integrity. Unlike a single seismic shock, multiple closely spaced events caused complex loading-unloading cycles within the slopes, severely weakening internal fabrics and precipitating delayed or secondary landslides weeks after the initial shocks. This phenomenon complicates disaster response planning by prolonging the window of geological risk and necessitates continuous monitoring.

Technological advances in high-resolution satellite imaging and drone-assisted surveys were instrumental in the study. These tools allowed precise mapping of disrupted topography, including fresh scarps, lateral spreads, and mass failures across large areas previously inaccessible for ground inspection. The remote sensing data were integrated with ground truthing to calibrate numerical models simulating slope stability under seismic loads, enabling predictions of which hillslopes remain at risk under future earthquake scenarios.

Interestingly, the research also identified human-induced factors that intensified hillslope weakening beyond seismic shaking alone. These include deforestation, improper drainage, and unregulated excavation activities that collectively reduce natural slope cohesion and increase susceptibility to failure. The authors argue for a holistic approach to hazard mitigation—one that couples seismic risk evaluations with sustainable land-use management to preserve slope integrity.

The implications of this study extend well beyond the Kahramanmaraş region. As urbanization steadily expands into hilly and mountainous terrains worldwide, understanding how earthquake sequences interact with terrain stability becomes critical. The integration of geotechnical science with earthquake engineering and urban planning can bolster societal resilience against these compounded hazards, potentially saving countless lives and infrastructure.

This research also paves the way for advances in early-warning systems specific to hillslope failures triggered by earthquakes. By identifying geophysical precursor signals and monitoring key slope stability indicators, authorities could develop tailored alert mechanisms that warn communities living in hazard-prone hillslopes before catastrophic collapse events occur. Such adaptive systems would complement conventional seismic alerts focused primarily on shaking intensity.

In sum, Wang and colleagues provide a stark and scientifically rigorous reminder that the intersection of human activities and natural seismic phenomena generates complex, heightened risks in hillslope settlements. The Kahramanmaraş earthquake sequence has exposed vulnerabilities that transcend individual buildings and pose systemic challenges to regional safety and sustainable development. Addressing these challenges necessitates a paradigm shift in how seismic hazard assessments incorporate terrain deformation dynamics and long-term landscape evolution.

Their study calls for immediate policy attention directed at enforcing stricter building codes on vulnerable slopes, integrating slope stability criteria in land-use zoning, and investing in continuous geotechnical monitoring infrastructure. The lessons learned from Kahramanmaraş are applicable to seismic hazard management globally, emphasizing that scientific insight must be translated swiftly into actionable urban safety strategies to avoid similar tragedy.

Looking ahead, further interdisciplinary research combining seismology, geomorphology, geotechnical engineering, and social sciences will be essential to develop comprehensive hazard mitigation frameworks. Such integrated studies can better anticipate how earthquake sequences might modify terrain susceptibility patterns and inform community-centered resilience planning.

In conclusion, the 2023 Kahramanmaraş earthquake sequence has not only reshaped the physical hillslopes around this historic city but also reshaped the scientific understanding of earthquake-slope interactions and their ramifications for human settlements. Wang et al.’s work stands as a seminal contribution, merging cutting-edge technical analysis with urgent societal relevance, and marking a critical advance in how we conceptualize and prepare for seismic disasters in hilly regions of the world.

Subject of Research: Seismic-induced hillslope weakening and settlement vulnerability following the 2023 Kahramanmaraş earthquake sequence.

Article Title: New and existing settlements built on hillslopes weakened by the 2023 Kahramanmaraş earthquake sequence.

Article References: Wang, Y., Dahal, A., van Westen, C.J. et al. New and existing settlements built on hillslopes weakened by the 2023 Kahramanmaraş earthquake sequence. Commun Earth Environ (2026). https://doi.org/10.1038/s43247-026-03492-1

Image Credits: AI Generated