Retention walls
Explanation
Landslide mitigation strategies involve engineering and environmental measures designed to stabilize slopes and reduce the impact of mass movements. These strategies are generally classified into structural measures (engineering works) and non-structural measures (vegetation and planning).
Analysis of Options
- Deforestation is incorrect: Deforestation removes vegetation cover. Roots play a critical role in binding the soil and maintaining slope stability. Removing trees loosens the soil and increases the risk of landslides.
- Retention walls is correct: Retention walls (or retaining walls) are structural barriers constructed at the base or along the slope of a hill. Their primary function is to mechanically hold back the earth and prevent the land from slipping, making them a recognized and effective mitigation strategy.
- Increased drainage is incorrect: While drainage control works are used to restrict the movement of water into landslide-prone areas, the term "increased drainage" is ambiguous. Uncontrolled or increased water flow can saturate the soil and increase pore water pressure, triggering landslides. The correct terminology is "surface drainage control."
- Blasting is incorrect: Blasting generates ground vibrations and destabilizes geological formations. It is a human activity that often triggers landslides rather than mitigating them.
Key Takeaway
Retention walls are a structural mitigation measure used to physically stop land from slipping, while afforestation is a biological measure used to bind soil.