Scientific Explanation Behind Niscemi Hill’s Landslide Movement

The recent landslide in Niscemi, Sicily, is a consequence of geological, climatic, and human factors. It exemplifies the complex dynamics of unstable slopes common in central and southern Sicily.

Scientific Explanation Behind Niscemi Hill’s Landslide Movement

Niscemi’s terrain primarily consists of Pliocene clays, formed between 5.3 and 2.6 million years ago. These clays are often misperceived as completely impermeable. However, they have a low permeability, allowing water to seep slowly. While this gives a false sense of security, these clays can absorb significant amounts of water, leading to potential instability.

Impact of Rainfall on Soil Strength

Prolonged rainfall can significantly affect soil stability in Niscemi. When water saturates the clay soils, it creates internal pressure. This pressure can weaken the soil’s mechanical strength by 50–70%. Consequently, slopes that appear stable may become hazardous over time.

• Clays: Comprised of minerals that absorb water slowly.
• Rainfall: Lengthy periods of rain can lead to soil saturation.
• Soil Stability: Saturated clays can lose structural integrity, leading to gradual deformation.

Characterization of the Niscemi Landslide

The landslide in Niscemi is likely triggered by sustained heavy rainfall, particularly from Cyclone Harry. This phenomenon demonstrated classic characteristics of a slow-moving landslide, specifically a rotational and translational slide pattern. Visual indicators included:

• Curved cracks at the upper slope.
• Ground depressions and lateral displacements.
• Deformations of roads and other infrastructure.

Approximately 4 kilometers of terrain were affected, endangering numerous homes and leading to the evacuation of about 1,500 residents.

Human Factors in Landslide Dynamics

Human activities can exacerbate landslide risks. Infrastructure such as roads, buildings, and wastewater systems alter the water balance in the area. While not direct triggers, these anthropogenic factors can accelerate landslide developments.

Recommendations for Addressing Landslide Risks

Effective measures to mitigate landslide risks in Niscemi should focus on reducing groundwater levels within the slope. Recommended strategies include:

• Continuous monitoring with GPS systems and inclinometers.
• Deep drainage solutions to lower pore pressure.
• Proper management of surface water runoff.
• Reducing loads at the slope’s summit.

Stabilizing the water regime of the slopes is crucial. Only after achieving stability should efforts for localized reinforcement be considered. In clay-rich landslides, water management remains the key to preventing further movement.