Niscemi at risk: landslide of 80 million cubic meters, evolving slope and relocations

Imagine a slope that never stops moving, with a cliff threatening Niscemi, in the province of Caltanissetta. The landslide of January 2026, with its 80 million cubic meters of earth mobilized over 4.7 km, reignites a historical instability, but now the technical-scientific report from the professors of the University of Florence, led by Professor Nicola Casagli – president of the Civil Protection center and professor of Applied Geology – sheds new light: high and evolving risk, with shocking proposals for relocations within 50 meters from the edge. Published on the website of the Civil Protection Department, this 150-page study integrates satellite analyses and site inspections, confirming that the inhabited center remains substantially stable but the main cliff evolves dangerously.

The geological roots of a centuries-old disaster
Niscemi rests on a precarious balance: permeable Pliocene-Pleistocene sands above impermeable Pliocene marly clays, with interstitial pressures concentrated on contact planes that favor deep sliding. The monoclinal structure towards SSE, the cliffs on the western and southern margins, and the erosion of the Torrente Benefizio create a chronic instability system, echoing landslides from 1790 with sedimentary volcanism and from 1997. The Casagli report confirms this polycyclicity: relief at the foot, reorganization of sliding surfaces, and progressive retreat of the crowns, controlled by stratigraphy, hydrogeology, and channelized waters.

The three fronts of January: collapses that change the landscape
It starts on January 15-16 with the North landslide: over 12 meters to the west, hydrographic erosion causing the collapse of Sp12. Then on January 25-26 the Central landslide, main explodes: more than 50 meters southwest along the Benefizio, with a slope that nearly touches the urban area. It is followed by the Southern landslide, over 7 meters to the west and southwest, destroying part of Sp10. A retrogressive compound slide – compound slide at Hutchinson – with pseudo-rigid movements, Horst and Graben at the top, depths of up to 80 meters and a Fahrböschung of 6.5° suggesting liquefaction or minimal residual resistance. A tragedy that has isolated the town and displaced hundreds of families.

Satellites and geophysics: data that do not lie
Sentinel-1, COSMO-SkyMed, and PlanetScope track everything: pre-event, urban stability within ±2 mm, but slow creep downstream since 2011; co-event, 37 meters in 11 days to the south; post-event, calm in the center with minimal residuals outside the red zone. 3D geophysics reveals lithological contrasts at 35-40 meters; FLAC modeling confirms basal listric sliding. The Casagli report integrates these data: “The picture outlined by the inspections and satellite data indicates that the risk remains high for the landslide as a whole and that the phenomenon is destined to evolve further.”

Dangerous evolution and immediate interventions
The report from Florence, commissioned by the Department of Civil Protection, warns: “The main slope bordering the town is susceptible to an evolution that could involve additional buildings located near the unstable edge and permanently compromise sections of strategic roadways.” Yet, the center of the town “shows conditions of substantial stability.” The approach must be multi-faceted: reduce infiltrations from above, intercept water flows before they penetrate the destabilized mass, protect the foot of the slopes against river erosion – “the driving element of reactivation” – and intervene in the bed of the Benefizio with natural engineering such as planting.

Enhancing monitoring with deep inclinometers for pressures, and above all: “Predicting the relocation of buildings located within a 50-meter range from the edge of the slope.” Currently, the restricted area is 100 meters, but Casagli advocates for targeted and urgent actions, partially overturning previous more cautious estimates.

Multifactorial causes and residual risk
Erosion at the foot of the Benefizio reduces confinement, previous rains inflate residual pressures on limit planes: a geological-hydrogeological-erosive trigger, not unpredictable. The report confirms potential retreat of 50-83 meters with FS=1.5, but insists on a high evolutionary risk that requires relocations within 50 meters for immediate safety.

The roadmap for resilience: a national lesson from Niscemi
We need GNSS networks, piezometers, deep drainage systems, river protections, and dynamic satellite bands. Integrated management – Civil Protection, INGV monitoring, naturalistic mitigations, and relocations – transforms the drama into a resilient opportunity. Niscemi, with its vibrant slope, teaches Sicily: monitor, intervene, adapt. From March 9, compensation for damages will begin, but the future depends on bold choices like those of Casagli.