Mitigating Risks Before Disasters Occur
Mass Movements: Stabilizing Slopes to Prevent Landslides
1. Vegetation Planting
- Roots as Anchors: Plants stabilize soil by anchoring it with their roots, reducing erosion and landslide risks.
- Water Absorption: Vegetation absorbs excess water, preventing soil saturation, a common trigger for landslides.
In Nepal, reforestation projects on steep slopes have significantly reduced landslide occurrences during monsoon seasons.
2. Terracing
- Creating Flat Surfaces: Terracing involves cutting slopes into a series of flat steps, reducing the steepness and slowing water runoff.
- Erosion Control: This method is particularly effective in agricultural areas, where it prevents soil erosion and limits the probability of landslides.
Terracing is most effective when combined with vegetation planting, as the roots help stabilize each terrace.
3. Retaining Walls
- Physical Barriers: Retaining walls are structures built to hold back soil and prevent it from sliding downhill.
- Materials and Design: These walls can be made from concrete, stone, or timber and are often reinforced with drainage systems to manage water pressure.
Earthquakes and Tsunamis: Engineering Solutions and Early Warnings
1. Earthquake-Resistant Building Design
Flexible Structures
- Materials: Use of steel and reinforced concrete allows buildings to sway without collapsing.
- Design: Features like cross-bracing and triangular shapes enhance stability.
The Taipei 101 skyscraper in Taiwan uses a massive tuned mass damper, a large, suspended sphere, to counteract swaying during earthquakes.
Shock Absorbers
- Base Isolation: Buildings are placed on rubber or spring-based isolators that absorb seismic energy, reducing shaking.
- Energy Dissipation: Devices like dampers convert seismic energy into heat, minimizing structural damage.
Base isolation is particularly effective for critical infrastructure like hospitals and emergency response centers.
Reinforced Foundations
- Deep Anchoring: Foundations are anchored into bedrock to prevent collapse during ground shaking.
- Soil Stabilization: Techniques like soil compaction and grouting improve the stability of the ground beneath buildings.
Avoid assuming that all buildings need the same level of reinforcement. The design should be tailored to local seismic risks.
2. Tsunami Defenses
Sea Walls
- Physical Barriers: Sea walls are designed to block or reduce the force of incoming waves.
- Height and Strength: These structures must be tall and strong enough to withstand the immense energy of a tsunami.
