2016年-世界发展银行全球_Flood_Risk_Assessment_for_the_Ganges_Basin_in_South_Asia_264页_19mb

Flood Risk Assessment for the Ganges Basin in South Asia

Core Content

This document presents the Final Report Volume I of a Flood Risk Assessment for the Ganges Basin in South Asia, submitted by RMSI Private Limited to Dr. Bill Young, Lead Water Resources Specialist at the World Bank. The report is part of the South Asia Water Initiative (SAWI), a collaborative program involving the World Bank, the governments of the United Kingdom, Australia, and Norway, aimed at improving transboundary water management and supporting sustainable development of the Himalayan Rivers.

Main Objectives

The primary objectives of the study include:

• Data Collection and Management: Gathering and processing exposure data across the Ganges Basin.
• Flood Hazard Assessment: Evaluating flood risks using meteorological, hydrological, and topographical data.
• Risk Assessment: Estimating potential losses based on exposure, vulnerability, and hazard analysis.

Key Components

1. Exposure Data Collection and Management

• Methodology: The report outlines the methodology for developing exposure data, including data collection, processing, quality checks, and GIS data layer generation.
• Exposure Elements Analyzed:
  • Demographic Analysis: Includes population distribution, gender ratio, and literacy rates across India, Nepal, and Bangladesh.
  • Housing Data: Categorizes housing by type (residential, commercial, industrial, educational, health facilities, and others), along with structural types and occupancy data.
  • Infrastructure Data: Focuses on road and rail networks, with their respective exposure values.
  • Agricultural Data: Analyzes rice, wheat, and maize cultivation and production across the basin.

2. Flood Hazard Assessment

• Methodology Overview: Describes the framework and tools used for flood hazard assessment, including HEC-RAS hydraulic modeling.
• Data Sources:
  • Meteorological Data: Rainfall stations and historical records.
  • Hydrological Data: Flow gauge stations and discharge data.
  • Topographical Information: Elevation maps.
  • Land Use Land Cover (LULC): Data on land use patterns.
  • Soil Map: Information on soil types and characteristics.
  • Flood History: Historical flood events used for calibration and validation.
• Basin and River Delineation: Identifies the major sub-basins within the Ganges Basin.
• Hydraulic Modeling: The model was calibrated and validated using historical flood events (e.g., 1978, 1981, 1988, 1996, 1998, 2004, 2008).
• Flood Hazard Mapping: Generates maps for return periods ranging from 2 to 100 years to visualize flood risk zones.

3. Risk Assessment

• Vulnerability Functions: Developed using data from the Asian Institute of Technology (AIT) and the U.S. Army Corps of Engineers (USACE), which provide depth-damage relationships for different asset types.
• Risk Analysis: Includes the loss module, which calculates Annual Exceedance Loss (AEL) and Annual Exceedance Probability (AEP) for various exposure types (buildings, infrastructure, agriculture).
• Key Metrics:
  • Affected Population: Analyzed by district, sub-basin, and demographic group (children, SCs, STs).
  • Asset Loss: Quantified in Indian Rupees (INR) for different exposure classes.
  • Validation: Cross-checked with real-world data and reports from institutions like GFCC and Dartmouth Flood Observatory.

Findings

Basin Level Findings

• Demography: The Ganges Basin is home to a significant population, with varying distribution across states, provinces, and districts.
• Economic Losses:
  • Buildings: Residential, commercial, industrial, educational, health, and other buildings were analyzed for their exposure and vulnerability.
  • Infrastructure: Road and rail networks were assessed for flood damage potential.
  • Agriculture: Rice, wheat, and maize were evaluated for their economic exposure to flood events.

Sub-basin Level Findings

• The report provides detailed analysis for 15 sub-basins, including:
  • Lower Ganges Sub-basin
  • Bagmati Sub-basin
  • Kosi Sub-basin
  • Gandak Sub-basin
  • Mahananda Sub-basin
  • Middle Ganges Sub-basin
  • Ghagra Sub-basin
  • Kamla-Balan Sub-basin
  • Yamuna Sub-basin
  • Ramganga Sub-basin
  • Gomti Sub-basin
  • Sone Sub-basin
  • Upper Ganges Sub-basin
  • Tons Sub-basin
  • Sind Sub-basin
  • Ken Sub-basin
  • Betwa Sub-basin
  • Chambal Sub-basin

Each sub-basin analysis includes:

• Exceedance Probability Curves
• Asset Loss (AAL) in million INR
• Population Affected in thousands

Key Information

• Data Sources: Utilized datasets from India-WRIS, Central Water Commission, Dartmouth Flood Observatory, Department of Hydrology and Meteorology (Nepal), and India Meteorological Department.
• Modeling Tools: HEC-RAS was used for hydraulic modeling, and flood hazard maps were generated for different return periods.
• Validation: The results were validated against historical flood data and field reports, ensuring accuracy and reliability.
• Supporting Organizations: The project was supported by the World Bank and SAWI, with contributions from RMSI and several consultants.

Conclusions and Recommendations

The report concludes with Recommendations for improving flood risk management in the Ganges Basin, focusing on:

• Enhancing transboundary cooperation
• Strengthening water institutions
• Supporting sustainable development of the Himalayan Rivers
• Implementing targeted investments to reduce flood losses

The study emphasizes the importance of data integration, risk modeling, and policy support in mitigating the impact of floods on human populations and infrastructure.