Sea-level rise exponentially increases coastal flood frequency

Area of Science:

• * Climate Science
• * Coastal Geomorphology
• * Extreme Event Analysis

Background:

• * Global sea-level rise (SLR) is redefining coastlines, with projected 2100 levels comparable to storm surges.
• * Coastal flooding regimes are shifting, increasing risks to communities worldwide.
• * Current projections often focus on end-point scenarios (e.g., 2050, 2100) rather than continuous change.

Purpose of the Study:

• * To quantify the continuous increase in extreme water-level events driven by SLR.
• * To analyze the exponential relationship between SLR and the odds of exceeding critical water levels.
• * To project future frequencies of extreme coastal flooding events.

Main Methods:

• * Analysis of historical water-level data to establish present-day extreme event frequencies.
• * Calculation of rates of increase in the odds of exceeding water-level thresholds with incremental SLR.
• * Integration of calculated growth rates with established SLR projections.

Main Results:

• * Exponential increase in the odds of exceeding critical water levels with SLR; 1-10 cm SLR can double flooding odds.
• * Extreme flooding odds are projected to double approximately every 5 years.
• * The present-day 50-year extreme water level will be exceeded annually by 2050 for 70% of U.S. coasts.
• * By 2100, the present-day 50-year extreme water level will be a near-daily event for 90% of the U.S. coast.

Conclusions:

• * Findings highlight the urgent need for coastal planning and adaptation measures.
• * Continuous monitoring and updated projections are crucial for effective risk management.
• * Societal impacts of escalating coastal flooding require immediate mitigation efforts.