2015年-世界发展银行全球_Water_and_Climate_Adaptation_Plan_for_the_Sava_River_Basin___Annex_2_Guidance_Note_on_Adaptation_to_Climate_Change_for_Flooding_18页_1mb

Water & Climate Adaptation Plan for the Sava River Basin - Annex 2: Guidance Note on Adaptation to Climate Change for - Flooding

Core Content

This document is part of the Water and Climate Adaptation Plan (WATCAP) for the Sava River Basin (SRB), prepared under the World Bank's Water Partnership Program (WPP) and the Trust Fund for Environmentally & Socially Sustainable Development (TFESSD). It provides a guidance note on adapting to climate change, specifically focusing on flooding in the SRB. The report draws on previous studies and data from the University of Ljubljana, as well as other key documents such as the University of Split Vulnerability Analysis and the ICPDR Danube Study.

Main Points

• Objective: To guide decision-making on adaptation needs related to flooding in the Sava River Basin.
• Climate Scenarios: The report uses the IPCC SRES A1B emission scenario for all 21st-century simulations, as it is considered representative for the middle of the century.
• Climate Projections: Climate projections are based on 16 different GCM/RCM model runs and are used to estimate future flood risks.
• Data Sources:
  • E-OBS Data: Provides reference data for daily precipitation and is used to derive transfer functions for comparison with climate model outputs.
  • Hydrological Data: Includes precipitation, temperature, evapotranspiration, and discharge data from 32, 8, and 12 measurement stations, respectively.
• Hydrological Model: The HBV model is used to simulate flood discharge and assess the impact of climate change on flood events. It is based on the water balance equation.
• Sub-basins: The SRB is divided into 10 sub-basins for analysis, with detailed information on each sub-basin's area and location provided in Table 1.
• Precipitation Trends:
  • Temperature is expected to increase across all seasons, with the most pronounced increases in summer and winter.
  • Precipitation is expected to decrease in spring, summer, and autumn, with the most significant decrease in summer.
  • Winter precipitation is expected to increase, particularly in the north-western part of the basin.
• Model Calibration and Verification:
  • Calibration was based on data from 1974, which corresponds to the last major flood event before flood protection measures were implemented.
  • The verification period was from September 1978 to November 1978, showing relatively lower peak discharges compared to the 1974 event.
• Flood Risk Assessment:
  • The report includes a flood vulnerability assessment and identifies possible adaptation measures.
  • It emphasizes the need for further studies to improve the understanding of uncertainties in climate model outputs, particularly in areas with complex orography.
• Statistical Bias Correction: Applied to raw model outputs to improve accuracy, especially in precipitation and temperature simulations.
• Sensitivity Analysis: Suggests that future studies should focus on convective parameterization schemes and model resolution changes to better understand flood risks under climate change.

Key Information

• Climate Impact on Precipitation:
  • Autumn precipitation is expected to increase for some stations, while others show a decline.
  • The 100-year return period precipitation is projected to decrease in the 2041-2100 period.
• Model Performance:
  • Calibration results vary by sub-basin, with some showing significant discrepancies (e.g., -31.3% for Bosna).
  • The model was calibrated to reproduce flood peaks rather than water balance.
• Uncertainties:
  • High model spread is observed in areas with complex topography, such as the Julian Alps and Dinaric Mountains.
  • The E-OBS dataset may not fully capture precipitation in Montenegro, leading to discrepancies.
• Recommendations:
  • Future climate model simulations should focus on large-scale circulation patterns affecting the SRB.
  • Further analysis of convective parameterization schemes and model resolution changes is recommended to reduce uncertainty in flood predictions.
  • The use of more detailed and localized data is encouraged to improve the accuracy of climate change impact assessments on flood events.

Conclusion

This guidance note outlines the climate change impact on flooding in the Sava River Basin, emphasizing the need for improved climate models and adaptation strategies. It highlights the importance of integrating climate projections with hydrological models to better understand and manage flood risks in the future. The report also points out the necessity of addressing data gaps and uncertainties to ensure effective flood risk management planning.