2014年-世界发展银行全球_Managing_Flood_Risk_in_Guyana___The_Conservancy_Adaptation_Project_2008-2013_24页_9mb

Managing Flood Risk in Guyana: The Conservancy Adaptation Project (2008-2013)

Core Content

The Conservancy Adaptation Project (CAP) was initiated in Guyana following the 2005 flood, which caused widespread devastation in the coastal lowlands, particularly in Region 4, home to over 40% of the population, including the capital city of Georgetown. The project aimed to reduce the risk of catastrophic flooding in the low-lying coastal areas, which are increasingly vulnerable due to climate change and sea level rise.

The East Demerara Water Conservancy (EDWC) is a key infrastructure in the region, serving as a water storage and flood control mechanism. It is bounded by a 67 km long dam and has five main drainage relief canals. The EDWC covers 571 km² and can store up to 250 million m³ of water. However, due to its age and the impact of rising sea levels, the system is under significant stress, with gravity-based drainage becoming less effective.

The CAP, funded by a Global Environmental Facility (GEF) Special Climate Change Fund grant of US$3.8 million, aimed to strengthen the government's understanding of the EDWC and its drainage systems, identify strategic interventions, and implement infrastructure improvements to increase drainage capacity and improve dam safety.

Main Objectives

• Strengthen understanding of the EDWC and coastal drainage systems through hydrological and hydraulic modeling.
• Identify strategic investments to reduce flood risk and improve resilience to climate change.
• Implement infrastructure upgrades, such as the rehabilitation of two sluices at Lama and the purchase of equipment for rapid dam repairs.
• Enhance institutional capacity for managing water levels and coordinating flood control efforts.

Key Components of the Project

1. Hydrological Data Collection

• A hydro-meteorological monitoring system was installed to provide real-time data on rainfall and water levels.
• Tipping-bucket raingauges and water-level sensors were deployed to record rainfall intensity and depth.
• Acoustic Doppler Current Profiler (ADCP) was used to measure river discharge.
• The system was integrated with a telemetry network, enabling efficient data transmission and management.

2. LiDAR and Bathymetric Surveys

• LiDAR (Light Detection and Ranging) surveys were conducted during the dry season to produce high-resolution topographic maps.
• These surveys, combined with aerial photography, created a Digital Elevation Model (DEM) for the EDWC and east coast.
• Bathymetric surveys were carried out to measure underwater relief, complementing the LiDAR data.

3. Computer Modeling

• Hydrological and hydraulic models were developed to simulate water flow under various extreme weather scenarios.
• The models were used to test the impact of proposed interventions, including the Hope-Dochfour canal, which was expected to reduce water levels significantly.
• The 2005 flood data and new monitoring data were used to calibrate and validate the models.

4. Dam Stability Analysis

• A geotechnical stability study was conducted to assess the condition of the EDWC dam.
• The northeast dam (between Annandale and Flagstaff Mahaica) was found to be the most vulnerable part, built on soft clays and peat.
• The north dam and east dam also showed marginal stability, requiring rehabilitation.
• The west dam, though not meeting international standards, was still considered stable.

Key Investments

• The project funded US$123 million in strategic investments, including:
  • Rehabilitation of key drainage channels.
  • Improvements to the EDWC dam.
  • Infrastructure upgrades in the east coast drainage system.
  • Purchase of a floating punt and pontoon and a long-boom excavator for rapid dam maintenance.
  • Hydrological instrumentation for real-time water level monitoring.

Institutional Strengthening

• Training programs were conducted for government agencies on hydrometeorological monitoring, LiDAR data use, and hydrological modeling.
• Workshops were held to bring together stakeholders, donors, and practitioners to ensure coordination and consensus on future flood management strategies.

Looking Forward

• The CAP has provided a template for future flood risk reduction initiatives in similar regions.
• Follow-up investments are expected to increase the capacity to manage water levels in the EDWC and reduce vulnerability to extreme climate events.
• The project has contributed to the revision of the national drainage and irrigation master plan.

Key Facts

• Funded by: GEF Special Climate Change Fund (US$3.8 million)
• Project Period: January 2008 to August 2013
• Flood Impact (2005): Over 1 m of rainfall, 65 cm in 5 days; damages estimated at US$465 million, or 59% of Guyana's GDP.
• EDWC Capacity: Stores up to 250 million m³ of water at maximum safe operating level.
• Project Outcomes: Improved data collection, modeling, and infrastructure to enhance flood resilience and dam safety.