Extreme high tides rose more often on Galveston Island in the last year than they have at almost any other time in the island’s recorded history, a federal agency said in a report released last week.
Galveston recorded 18 days of high-tide flooding from May 2019 to May 2020, according to the National Oceanic and Atmospheric Administration — matching a record set in 2017.
High-tide floods are a type of coastal flooding that occurs when ocean waters rise above their daily average high-tide levels. In some coastal areas, high-tide floods can spill into streets or infiltrate stormwater systems and send seawater bubbling up from storm drains. According to the administration, such floods are happening more frequently in coastal communities because of sea-level rise.
“Sea level rise flooding of U.S. coastlines is happening now, and it is becoming more frequent each year,” the report states.
The report notes in some places, including Galveston, high-tide flooding may not be noticeable because of structures like the Galveston seawall. Still, high tides can enter infrastructure below streets. They also can flood areas that are typically used as parking or recreation areas.
In Galveston, city officials have at times blamed high tides for street flooding that occurs during rainstorms. When tides block storm outlets, there is no place for rainwater to drain.
The report, published by the administration last week, describes the state of high-tide flooding across the United States last year. Galveston was not the only city to set or match records for flooding in the period measured by the administration.
Nineteen locations along the East Coast and Gulf Coast broke or tied their high-tide flooding records, including in Miami, Savannah, Georgia, Charleston, South Carolina, and Annapolis, Maryland.
The rate of high-tide floods around the country was twice as high as it was in 2000, according to the administration.
The most frequent location for high-tide flooding in the country was at Eagle Point in the northeast corner of San Leon. There were 64 high-tide floods at Eagle Point in 2019, though the report notes that the location has been an anomaly for 20 years because of land subsidence in the area contributing to increased sea-level rise.
The report also warns of more high-tide flood days this year. The administration predicted there would be between seven and 12 days of high-tide flooding during the next 12 month period.
High tide flooding “is of a growing concern to coastal residents, emergency managers, community planners and resource managers,” the administration said.
By 2030, the frequency of high-tide floods nationally is likely to increase by two- or three-fold, according to the administration. By 2050, it is likely to be five to 15 times higher, and in some locations the unusually high tides could represent a new normal high tide.