Coastal flooding along the densely populated Eastern Seaboard of the United States has surged in recent years, a Reuters analysis has found.

During the past four decades, the number of days a year that tidal waters reached or exceeded National Oceanic and Atmospheric Administration flood thresholds more than tripled in many places, the analysis found. At flood threshold, water can begin to pool on streets.

As it rises farther, it can close roads, damage property and overwhelm drainage systems. Since 2001, water has reached flood levels an average of 20 days or more a year in Annapolis, Maryland; Wilmington, North Carolina; Washington, D.C.; Atlantic City, New Jersey; Sandy Hook, New Jersey; and Charleston, South Carolina. Before 1971, none of those locations averaged more than five days a year. Annapolis had the highest average number of days a year above flood thresholds since 2001, at 34.

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