Pre-event strategies for managing landslides

Landslides pose significant risks to communities and infrastructure, particularly in hilly or mountainous regions. Implementing pre-event strategies can help reduce the likelihood of landslides and minimise their impact on human life and property.

Methods to reduce landslide risks

• Terracing steep slopes - Creating stepped levels on steep terrain reduces the gradient, slowing down water runoff and stabilising the soil.
• Drainage systems - Installing pipes or channels to divert water away from slopes prevents soil saturation, which can trigger landslides.
• Restraining structures - Building stone walls or gabions at the base or along slopes helps to hold soil in place and prevent movement.
• Erosion control - Protecting the base of cliffs with vegetation or barriers stops undercutting by water or wind, reducing the risk of collapse.
• Road diversion - Rerouting roads away from areas prone to landslides avoids placing infrastructure in high-risk zones.

Pre-event strategies for managing earthquakes

Earthquakes can cause devastating damage, especially in urban areas with high population densities. Designing infrastructure and planning land use carefully can significantly reduce the risks associated with seismic activity.

Earthquake-resistant building techniques

• Single-storey designs - Lower structures are less likely to sway or collapse during ground shaking compared to multi-storey buildings.
• Soft storey construction - Incorporating a collapsible lower level, such as a car park on pillars, allows upper floors to settle onto it during an earthquake, absorbing some of the impact.
• Basement isolation - Mounting building foundations on rubber pads allows the ground to move beneath the structure without transferring all the tremors to the building.
• Deep bedrock foundations - Anchoring buildings into stable bedrock provides a solid base that resists shaking.
• Steel-framed structures - Using flexible steel frames in construction enables buildings to withstand ground movement without collapsing.

Innovative designs for quake-resistant homes

• Lightweight materials - Houses with light walls and gables experience smaller forces during shaking, reducing the chance of collapse.
• Light roofs - Sheet-metal roofs on wooden trusses are more resistant to collapse compared to heavy concrete roofs.
• Small window openings - Limiting the size and spacing of windows reduces weak points in walls, enhancing structural integrity.
• Reinforced walls - Using natural materials like bamboo or eucalyptus, or plastic mesh in adobe houses, strengthens walls against tremors.
• Confined masonry - Framing brick walls with reinforced concrete corner columns and crown beams ensures the structure moves as a single unit during a quake.
• Shock-absorbing foundations - Tyres filled with sand or stones placed between the floor and foundation act as low-cost absorbers of ground motion.

Land-use planning for earthquake risk reduction

• Strategic zoning to avoid building in high-risk seismic areas minimises exposure to potential damage.
• Identifying safer locations for critical infrastructure, such as hospitals and schools, ensures essential services remain operational during and after an event.

Historical earthquake data for context

Pre-event strategies for managing volcanoes and tsunamis

Volcanic eruptions and tsunamis are challenging to predict and control, but specific pre-event measures can help mitigate their destructive effects on communities and infrastructure.

Managing volcanic hazards

• Lava flow diversion - Constructing dry channels or using explosives can redirect lava flows away from populated areas. Pumping water onto the lava front cools it, slowing its advance.
• Pyroclastic flow response - Little can be done to stop these fast-moving, deadly flows of hot gas and debris, so evacuation of at-risk areas is the primary strategy.
• Monitoring systems - Using Global Positioning System (GPS) technology to track ground swelling can provide early warnings of potential eruptions, allowing time for evacuation.

Managing tsunami risks

• Sea walls - Constructing barriers along coastlines offers some protection against smaller tsunami waves, though cost limitations often restrict their height and effectiveness against larger waves.
• Early warning systems - Deploying sensors and communication networks to detect underwater earthquakes and issue rapid alerts gives communities time to evacuate to higher ground.

Post-event disaster recovery model and strategies

After a natural hazard strikes, recovery efforts are critical to saving lives, restoring normalcy, and rebuilding communities. A structured model of disaster recovery illustrates the timeline and activities involved in coping with such events.

Disaster recovery timeline

The recovery process follows a pattern of coping activity over time, starting from the disaster event and extending over several years. Key phases and indicators include:

• Immediate aftermath (week 0-1) - Coping activity rises sharply as search and rescue operations peak.
• Early recovery (weeks 2-10) - Activity dips slightly as emergency shelter and feeding end, rubble is cleared from main roads, and major urban services are restored.
• Mid-term recovery (weeks 20-40) - Refugees begin to return, and rubble clearance is completed, marking a gradual increase in activity.
• Long-term recovery (around week 100) - Coping activity reaches a higher, sustained peak as pre-disaster levels of infrastructure and economic activity are regained.
• Final stages (up to week 500) - Major construction projects are completed, with activity slowly declining as recovery stabilises.

Key phases of post-event management

• Rescue - The immediate priority is saving lives using search and rescue teams, sniffer dogs, and thermal sensors to locate survivors. The chance of finding people alive drops significantly after 72 hours.
• Rehabilitation - Focus shifts to making homes safe for residents to return, addressing structural damage and basic needs.
• Reconstruction - For areas where rehabilitation isn’t possible, rebuilding is necessary. This long-term process, which can take up to a decade, aims to restore communities to pre-disaster levels and support ongoing development.

Case study: 2004 South Asian tsunami recovery in Indonesia

Following the catastrophic tsunami, the Indonesian government developed a master plan for recovery in affected regions like Banda Aceh. Key actions included:

• Providing immediate assistance to survivors.
• Managing the burial of the deceased to prevent health risks.
• Rebuilding essential facilities and infrastructure to support victims. With approximately $6.5 billion in international aid, homes and communities were prioritised, followed by infrastructure restoration and economic redevelopment. Within eight years, significant progress was achieved in rebuilding the region.

The role of technology in hazard management

Advancements in information and communication technology (ICT) have transformed post-event management by enabling rapid response and coordination. These tools are particularly valuable in mapping hazards and reuniting families after disasters.

Using technology for hazard mapping

• Community involvement - In initiatives like a project in Rio de Janeiro, organisations such as UNICEF train young people to map social and environmental risks using mobile devices. This data helps identify vulnerable areas and plan responses.
• Real-time data distribution - ICT allows for the quick sharing of information about a hazard’s scale and location, aiding in efficient resource allocation and emergency planning.

Technology for reuniting families

• RapidFTR app - Developed as an open-source tool by a student in New York and supported by UNICEF, Rapid Family Tracing and Reunification (RapidFTR) helps humanitarian workers register information about missing children using phones and laptops.
• Impact on child safety - Quick reunification reduces the risk of violence, exploitation, or trafficking, ensuring children are reconnected with families as soon as possible after a disaster.