2006年-世界发展银行全球_Earthquake_Vulnerability_Reduction_Program_in_Colombia___A_Probabilistic_Cost-benefit_Analysis_22页_374kb

Summary of the Earthquake Vulnerability Reduction Program in Colombia: A Probabilistic Cost-benefit Analysis

Core Content

This paper presents a probabilistic cost-benefit analysis (CBA) of the Earthquake Vulnerability Reduction Program in Colombia, specifically focusing on the Bogotá Disaster Vulnerability Reduction Project. The analysis is designed to evaluate the economic viability of disaster risk mitigation investments, which are inherently uncertain due to the unpredictable nature of natural disasters.

The study introduces a probabilistic approach to CBA, moving beyond traditional methods that rely on average values of benefits. Instead, it uses catastrophe risk models to generate risk metrics such as the loss exceedance curve (LEC) and probable maximum loss (PML), which provide a more comprehensive understanding of the project's potential net benefits and their variability over time.

The paper also emphasizes the importance of microeconomic modeling in assessing the effectiveness of specific mitigation measures, such as structural and functional investments in public infrastructure, and how these investments can significantly reduce both economic losses and human casualties.

Main Points

• Colombia's Vulnerability: Due to its geographical location, Colombia is highly exposed to natural disasters, particularly earthquakes. Major cities like Bogotá are at high risk, with potential losses from a 1-in-100-year earthquake estimated at US$5 billion.
• Disaster Risk Management: Following the 1983 Popayan earthquake, Colombia adopted a broader disaster risk management strategy, including seismic-resistant building standards (Law 400, 1997) and the establishment of a National System for Disaster Response and Prevention.
• Bogotá Project: The World Bank supports a US$160 million project in Bogotá to reduce vulnerability to natural disasters. The project includes structural and functional investments in public buildings, such as schools, hospitals, and fire stations.
• Probabilistic Risk Model: The model used in the analysis includes five modules:
  • Hazard: Defines the frequency and severity of natural events.
  • Exposure: Estimates the value of assets at risk.
  • Vulnerability: Assesses the damage to different asset classes based on event intensity.
  • Damage: Translates vulnerability into actual dollar losses.
  • Loss: Calculates losses for insurers based on insurance data.
• Key Metrics:
  • Average Annual Loss (AAL): Expected loss per year over a long period.
  • Loss Exceedance Curve (LEC): Probability that a loss of a certain amount will be exceeded in a given year.
  • Probable Maximum Loss (PML): Maximum loss expected for a given return period.
  • Pure Risk Premium (PRP): AAL divided by the replacement value of the asset.

Key Information

• Structural investments in public buildings have a significant impact on reducing earthquake risk.
• Structural investments in schools and hospitals reduce the pure risk premium from 7.4 per mill to 1.5 per mill.
• Average Annual Returns (AAR) on mitigation investments are:
  • 14.5% for retrofitted schools.
  • 19.1% for retrofitted hospitals and fire stations.
  • 7.7% for structural and functional investments in schools.
  • 32.8% for structural and functional investments in hospitals and fire stations.
• Economic Rate of Return (ERR) is calculated using a 30-year time horizon and a discount factor of 12%.
  • ERR for structural investments: 16.6%.
  • ERR for structural and functional investments: 20.2%.
• Sensitivity Analysis shows that even with a scaling factor reducing benefits by up to 40%, the ERR remains above the discount factor, confirming the project's economic viability.
• The project is financed with a combination of a World Bank loan (US$80 million) and bonds issued by the District of Bogotá (US$80 million).
• The financial structure of the project includes front-end fees (0.5%) and commitment fees (0.35%) for the World Bank loan.

Conclusion

The Bogotá Disaster Vulnerability Reduction Project is economically viable, as the probabilistic cost-benefit analysis demonstrates that the expected returns significantly exceed the discount factor. This approach provides decision-makers with a more nuanced understanding of the risks and benefits associated with disaster mitigation investments, enabling better-informed policy and investment choices.