NORFOLK — At her cozy house by the river, Julie Faella spoke as though a monster lurks nearby. It rises under a tidal moon, she said, or when the winds howl, or when rains crash down.

She’s seen it with her own eyes. It crept under the front door of one house she owned when Hurricane Isabel whipped the Lafayette River into a frenzy in 2003, and invaded a second house three years later when a nor’easter churned the waters for days.

“Your home isn’t destroyed once. It’s destroyed twice,” said Faella, who tore down one house and rebuilt the other. “How are you going to get through it?”

In Norfolk, Virginia’s second-largest city, with 250,000 residents, Faella’s concerns aren’t the isolated fears of one woman living on the river’s edge. The entire city is worried. Miles of waterways that add to Norfolk’s charm are also a major threat in the era of increased global warming and relative rising sea levels, as well as its odd and unique sinking ground.

Sea-level rise isn’t expected to significantly affect most American cities for at least 30 years. But Hampton Roads — including Virginia Beach and Portsmouth on Norfolk’s borders — is already knee-deep in floodwaters because, as one activist said, the area is “as flat as a pancake” and Chesapeake Bay river tributaries slice deeply inland.

Tides rise daily, but as the climate warms, seas have risen and pushed up the Chesapeake Bay around Norfolk a few inches each year, scientists said. In the spring tidal cycle, waters sometimes rise a foot or more above normal.

Worse, the ground is sinking in Tidewater, as Hampton Roads is also known. It sits in the nation’s largest known geologic impact crater, an Ice Age formation that’s causing land to drop about seven inches every century, accounting for about one-third of the sea-level change.

On top of that, homes in pricey communities such as Larchmont, where Faella lives, are built partially on slowly sinking historic wetlands.

“Water runs downhill, but here it has nowhere to go,” said Skip Stiles, executive director of Wetlands Watch, a nonprofit group devoted to preserving wetlands. “There’s all this water in neighborhoods. It’s just something people put up with. People have had to change their car brakes because they had saltwater in them.”

Pricey real estate in Virginia Beach, Portsmouth, Hampton and other cities is also threatened, but Norfolk has so far taken stronger steps to prevent flooding than its neighbors, activists said.

Recently at the downtown Half Moone Cruise and Celebration Center, which juts into the Elizabeth River, the city hosted a nearly four-hour networking session of about 30 planners, engineers, educators and environmentalists to present the findings of flood preparation studies for which it paid tens of thousands of dollars.

A Dutch-based engineering firm, Fugro Atlantic, which studied the city’s vulnerability to high tides and storm surges, recommended floodwalls, tide gates, elevated roads and powerful water pumping stations at several areas at an estimated cost of $300 million.

A second firm, the Timmons Group, determined that major storms that once occurred every 10 years are coming more frequently, and most of the city’s aged storm water drains, built more than a century ago, could not handle runoff. Timmons recommended upgrading storm water pipes at a cost of up to $775 million.

Flooding sometimes happens when storm water flowing to rivers through inadequate pipes is pushed back by tidal surge invading land, said Liz Scheessele, a senior project manager for Timmons who gave that presentation.