2010年-世界发展银行全球_Safety_of_Small_Rural_Dams_and_Barrier_Lake_Management_8页_734kb

EAP DRM KnowledgeNotes Summary

Core Content

This document provides a comprehensive overview of disaster risk management (DRM) related to artificial dams and barrier lakes in the context of earthquakes, with a focus on lessons learned and recommendations from international experiences and the Wenchuan Earthquake in China.

Main Points

Artificial Dams

• High Risk from Small Dams: Small, rural dams in China represent a higher hazard due to their poor design, lack of maintenance, and absence of operation and maintenance systems (OMS).
• Emergency Measures: Immediate action is required to mitigate risks to human life after an earthquake. These measures include emergency repairs and the implementation of emergency preparedness plans (EPP).
• Rehabilitation and Modernization: Long-term rehabilitation and modernization should be planned and implemented to reduce the risk profile of the entire dam group.
• Risk Assessment: A uniform and consolidated risk assessment of all dams in the earthquake-affected area is essential. This should guide the prioritization of rehabilitation and modernization efforts.
• Recommendations:
  • Owners of small dams should develop OMS manuals.
  • The Chinese government should issue guidelines for EPPs for small dams, referencing international experiences.
  • Adequate technical assistance should be provided for the design, construction, operation, and modernization of small dams.
  • A census of rural dams should be completed and made available in different regions.

Barrier Lakes

• Formation and Hazards: Barrier lakes can form through various mechanisms such as landslides and glacier movements. They pose significant risks, especially if they are large or located in populated areas.
• Monitoring and Early Warning: Satellite imagery and remote sensing are essential for detecting and monitoring barrier lakes. Early warning systems and monitoring plans are necessary for long-term management.
• Risk Assessment: Risk assessment is crucial for understanding the potential impact of barrier lake failure. It should be integrated into the design and operation of monitoring and early warning systems.
• Recommendations:
  • Barrier lake occurrences should be monitored in high-risk areas.
  • Emergency preparedness plans should be developed for long-living barrier lakes.
  • Gauging stations and rainfall stations should be established upstream and downstream of the lake.
  • A monitoring system and EPP should be set up to manage the lake effectively.

Key Information

• Case Studies: The document references three case studies:
  • Gujarat Earthquake (2001): Highlighted the vulnerability of small dams and the importance of emergency measures.
  • Lake Sarez (Tajikistan): Demonstrated the need for monitoring and early warning systems for natural barrier lakes.
  • Armenia Dam Safety Program: Showcased the impact of poor maintenance and design on dam safety and the use of risk assessment methodologies.
• Technical Measures for Dams:
  • Provide ample freeboard.
  • Use wide transition zones of non-crack-prone materials.
  • Implement chimney drains and wide core zones with plastic materials.
  • Include well-graded filter zones and crest details to prevent erosion.
  • Flare embankment cores at abutment contacts.
  • Stabilize zones around the reservoir rim.
  • Address fault movement risks in the foundation.
• Risk Assessment Methodologies:
  • Semi-quantitative and empirical methods are recommended for large sets of dams.
  • Failure modes, effects, and criticality analysis (FMECA) is used to rank the risk of dams based on probability and consequences.

Conclusion

The document emphasizes the need for a proactive approach to dam safety and barrier lake management in post-earthquake scenarios. It underscores the importance of risk assessment, emergency preparedness, and the use of modern technologies such as satellite imagery and remote sensing to mitigate potential disasters. The recommendations are tailored to the specific context of China but draw on global best practices to enhance DRM strategies.