First look at changes in flood hazard in the Inter-Sectoral Impact Model Intercomparison Project ensemble

Area of Science:

• Environmental science
• Climate science
• Hydrology

Background:

• Anthropogenic greenhouse gas emissions drive climate change, altering precipitation patterns.
• Increased precipitation intensity and frequency are expected, potentially raising future flood probabilities.
• Global flood hazard assessments are crucial for understanding climate change impacts.

Purpose of the Study:

• To explore uncertainties in global flood hazard projections under climate change.
• To analyze changes in the 30-year return level of 5-day average peak river flows.
• To assess impacts using the Representative Concentration Pathway RCP8.5 scenario for the end of the century.

Main Methods:

• Utilized river flow simulations from nine global hydrology and land surface models.
• Analyzed changes in the 30-year return level of 5-day average peak flows.
• Evaluated flood hazard under the RCP8.5 climate change scenario.

Main Results:

• Climate change is projected to increase flood hazard frequency at over half of global land grid points.
• Decreased flood hazard magnitude and frequency are predicted for approximately 20-45% of land grid points, particularly snowmelt-dominated regions.
• The current 30-year flood peak is projected to occur more frequently (more than once every 5 years) across 5-30% of land grid points.

Conclusions:

• Large-scale patterns of flood hazard change are consistent across models, but local-scale projections show significant uncertainty.
• Model uncertainty, even on the sign of change, is substantial at the river basin scale.
• Acknowledging and incorporating modeling uncertainties is vital for local flood adaptation studies.