DRR (Rockfalls)

Causes of Rockfalls

The primary causes of rockfalls in Mauritius include natural weathering processes, seismic activities (rare), and heavy rainfall, which can destabilize rock masses on cliff faces and slopes. Human activities such as construction, quarrying, and land clearing also exacerbate the risk by destabilizing already fragile slopes.

Consequences of Rockfalls

Rockfalls can lead to loss of life, injury, and damage to property. They can block major roads, isolating communities and disrupting traffic and economic activities. Additionally, rockfalls can damage power lines, water pipes, and other critical infrastructure.

Mitigation Measures

The Mauritian government and local authorities have implemented several measures to mitigate the impact of rockfalls. These include:

Geotechnical Assessments: Regular assessments of rock stability in vulnerable areas to monitor risk.
Engineering Solutions: Construction of barriers and nets to catch falling rocks, and stabilization of rock faces with bolts and mesh.
Public Awareness Campaigns: Educating the public, especially those in high-risk areas, about the dangers of rockfalls and the importance of vigilance during heavy rains and after earthquakes.
Land Use Planning: Regulating construction and development in areas prone to rockfalls to minimize potential damage and loss of life.
Future Challenges: As Mauritius continues to develop, managing the risk of rockfalls becomes increasingly complex. Climate change, which brings about more intense rainfall events, poses additional challenges by potentially increasing the frequency and severity of rockfalls. Ongoing monitoring, research, and investment in mitigation strategies are essential to address these challenges effectively.

Rockfall Prone Areas

Rockfalls in Mauritius typically occur in the more mountainous regions, including coastal cliffs.  Areas with steep topography near populated regions or critical infrastructure are particularly vulnerable.  Rockfalls occurs mostly during and after rainfall in rockfall-prone areas. 

Reported cases include Signal Mountain, Maconde, Corps de Garde, and many others.

Rockfall Conditions and Warning System

The following criteria for the issue of warnings of rockfall to the public apply:
1. Rainfall recorded
2. Strong winds
3. Cyclone warnings
4. Tree roots causing loosening of rocks, and
5. Observations from public.

The Rockfall Warning System

The rockfall warning system consists of three warning stages namely the Watch, Warning and the Termination. 

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Rockfall susceptibility map (source:  Marsala et al, 2019)

Landslide Susceptibility Assessment of Mauritius Island (Indian Ocean)
by Vincenzo Marsala, Alberto Galli, Giorgio Paglia and Enrico Miccadei, Geosciences 2019, 9(12), 493; https://doi.org/10.3390/geosciences9120493

Signal Mountain

Standing at approximately 323 meters, this mountain is one of the most frequented destinations on the island, attracting hundreds of visitors weekly who use its popular health track for physical exercise.

Maconde

(courtesy: Soonil Rughooputh)