Understanding Landslide Mitigation Methods

The question asks to identify the disaster associated with specific risk mitigation methods: constructing retaining walls and implementing surface drainage control works.

Analyzing Mitigation Techniques

Let's break down the purpose of these mitigation methods:

• Retaining Walls: These are structures built to hold back or support masses of soil or rock. Their primary function is to prevent the lateral movement or collapse of unstable slopes, which is the defining characteristic of a landslide. They provide support and resist the forces pushing the soil/rock mass downslope.
• Surface Drainage Control Works: These involve managing water flow on the surface. Excess water can saturate soil, increasing its weight and reducing its internal strength, which often acts as a trigger for slope failures like landslides. Controlling surface drainage helps divert water away from vulnerable slopes, reducing the risk of saturation and subsequent movement.

Connecting Methods to Disasters

Based on the functions described above, both retaining walls and surface drainage control are specifically designed to address the causes and effects of soil or rock movement on slopes. This directly points towards landslides as the associated disaster.

Evaluating Other Disaster Options

• Avalanche: Avalanches involve the rapid flow of snow down a slope. While slope stability is a factor, the primary mitigation methods involve snow management, avalanche sheds, or zoning, not typically retaining walls designed for soil.
• Floods: Floods are caused by excessive water inundation. Mitigation involves levees, floodwalls, and managing river flows. While drainage control is related, retaining walls are not the primary method for flood mitigation in the same way they are for landslides.
• Cloudburst: A cloudburst is an extreme weather event involving sudden, heavy rainfall. While the heavy rain can *cause* secondary disasters like flash floods or landslides, the cloudburst itself isn't directly mitigated by retaining walls or surface drainage in the same manner as a landslide. These methods help manage the *consequences* (like landslides) triggered by such events.

Conclusion on Mitigation

The specific methods mentioned, retaining walls and surface drainage control, are most directly and commonly employed as risk reduction strategies for landslides, aiming to stabilize slopes and manage water infiltration that can trigger instability.