By Molly Daly

PHILADELPHIA (CBS) — A new report by a nonprofit science advocacy group says high-tide floods will spike over the next thirty years in East Coast cities.

The report by the Union of Concerned Scientists projects that in the next three decades years, Philadelphia could go from about 19 tidal flooding events per year to more than 200.

Flooding incidents due only to high tides used to be rare and minor. But the UCS report says that by 2045, the situation will be chronic and devastating.

Erika Spanger-Siegfried, a senior analyst with UCS, says climate change is driving sea-level rise, but melting glaciers are only part of the equation.

“The ocean has warmed, and warmer water actually expands, and takes up more space,” she says.  “That has been the primary reason — the largest contributor to sea level rise to date.”

Philadelphia is already planning for a wetter future, adding wetlands to the riverfront areas to help protect the city from flooding.

Although such measures are prudent, Spanger-Siegfried says, tackling the cause is imperative.

“We really do not want to have to contend with the level of sea-level rise that may be in store if we don’t start to mitigate climate change,” she notes.