Managing the Impacts of Natural Hazards » Land Use Zoning and Building Design

What you'll learn this session

Study time: 30 minutes

How land use zoning reduces vulnerability to natural hazards
Different types of zoning strategies and their implementation
Building design techniques that mitigate hazard impacts
Case studies of successful zoning and building design approaches
How to evaluate the effectiveness of these management strategies

Introduction to Land Use Zoning and Building Design

Natural hazards like earthquakes, floods and hurricanes can cause devastating damage to communities. However, we can reduce their impacts through careful planning of where and how we build. This is where land use zoning and building design come in as essential management strategies.

Key Definitions:

Land Use Zoning: The process of dividing land into zones where certain land uses are permitted or prohibited.
Building Design: The specific structural and architectural features of buildings that make them resistant to natural hazards.
Vulnerability: The degree to which a system is susceptible to damage from hazards.
Resilience: The ability of a system to absorb disturbances and reorganise while maintaining its function.

★ Land Use Zoning

Land use zoning divides areas into different risk categories based on their vulnerability to natural hazards. High-risk zones might be designated for parks or agriculture, while residential and commercial developments are restricted to safer areas.

☆ Building Design

Building design focuses on making structures more resistant to specific hazards through techniques like elevated foundations in flood-prone areas or flexible frames in earthquake zones.

Land Use Zoning Strategies

Effective land use zoning requires understanding the local hazards and implementing appropriate restrictions. Here are the main approaches:

Types of Zoning Approaches

§ Risk-Based Zoning

Areas are categorised by hazard risk level (high, medium, low). Different building restrictions apply to each zone.

§ Exclusionary Zoning

Completely prohibits development in extremely high-risk areas, such as active fault lines or frequent flood zones.

§ Conditional Zoning

Allows development in moderate-risk areas only if specific building standards and safety measures are implemented.

Zoning regulations typically include:

Setback requirements (distance from hazard sources like rivers or coastlines)
Density restrictions (limiting the number of buildings in hazard-prone areas)
Land use restrictions (determining what activities are allowed in different zones)
Building code requirements specific to each zone

Building Design for Hazard Mitigation

Different hazards require different building design solutions. Engineers and architects have developed specific techniques to make buildings more resilient to various natural disasters.

⊕ Earthquake-Resistant Design

Base isolation: Using flexible bearings to separate the building from ground movement
Shear walls: Reinforced walls that resist lateral forces
Moment-resisting frames: Flexible connections that allow buildings to sway without collapsing
Cross-bracing: Diagonal supports that provide additional stability

⊕ Flood-Resistant Design

Elevated structures: Building on stilts or raised foundations
Wet floodproofing: Allowing water to enter and exit with minimal damage
Dry floodproofing: Making lower levels watertight
Flood barriers: Temporary or permanent walls to keep water out

⊕ Hurricane/Cyclone-Resistant Design

Impact-resistant windows: Specially designed to withstand flying debris
Reinforced roofing: Straps and clips that secure the roof to the structure
Aerodynamic shapes: Designs that reduce wind pressure
Storm shutters: Protective coverings for windows and doors

⊕ Landslide-Resistant Design

Retaining walls: Structures that hold back soil and rock
Drainage systems: Channels that direct water away from slopes
Deep foundations: Piles or caissons that reach stable ground
Flexible utility connections: Allowing movement without breakage

Implementation Challenges

While land use zoning and building design are effective strategies, they face several challenges:

Economic pressures: Development interests often push for building in hazardous but desirable locations
Existing development: Retrofitting existing buildings is expensive and sometimes impractical
Enforcement difficulties: Ensuring compliance with zoning and building codes requires resources
Social equity concerns: Zoning can sometimes disproportionately affect lower-income communities
Changing hazard patterns: Climate change is altering the frequency and intensity of many hazards

Case Study Focus: Christchurch, New Zealand

Following the devastating 2010-2011 earthquakes, Christchurch implemented a comprehensive land zoning system:

Red Zone: Areas with severe damage where rebuilding was prohibited. The government bought out properties and the land was converted to open space.
Technical Categories (TC1, TC2, TC3): Different zones based on the likelihood of land damage from liquefaction, with specific foundation requirements for each zone.

Results: The zoning system prevented rebuilding in the most vulnerable areas, potentially saving lives and property in future earthquakes. However, it also displaced communities and created significant social challenges.

Evaluating Effectiveness

How do we know if land use zoning and building design strategies are working? Here are some key indicators:

✓ Success Indicators

Reduced damage and casualties during hazard events
Lower insurance claims and recovery costs
Faster community recovery after disasters
Maintained property values in appropriately zoned areas
Sustainable development patterns that respect natural hazards

✗ Failure Indicators

Continued development in high-risk areas
Building damage consistent with poor design
High costs of emergency response and recovery
Repeated damage to the same areas
Community resistance or non-compliance with regulations

Case Study Focus: Japan's Building Codes

Japan has some of the strictest building codes in the world due to its high earthquake risk:

After the 1995 Kobe earthquake (which killed 6,400 people), Japan significantly strengthened its building codes.
When the much stronger 2011 Tohoku earthquake struck, very few buildings collapsed from the shaking itself (though many were destroyed by the tsunami).
Modern buildings in Tokyo are designed to sway during earthquakes, with flexible structures and damping systems.

Results: The improved building codes have saved countless lives. During the 2011 earthquake, most casualties were caused by the tsunami rather than building collapse, demonstrating the effectiveness of earthquake-resistant design.

Integrated Approaches

The most effective hazard management strategies combine land use zoning and building design with other approaches:

Early warning systems that alert people to imminent hazards
Community education about hazard risks and preparedness
Insurance schemes that reflect actual risk levels
Ecosystem-based protection like mangrove forests for coastal protection
Emergency response planning tailored to local hazards

Summary

Land use zoning and building design are powerful tools for reducing the impacts of natural hazards. By controlling where and how we build, communities can significantly reduce their vulnerability to disasters. While these approaches face challenges, their effectiveness has been demonstrated in numerous case studies worldwide.

Remember that successful hazard management requires a combination of strategies, with zoning and building design forming the foundation of a resilient community. As climate change alters hazard patterns, these approaches will become even more important for protecting lives and property.

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