Bobby Madison, a construction supervisor at Washington Harbour, yesterday surveyed the Potomac River, its waters churning and swollen from days of rain and easterly winds, and hurried his crews to finish work on the floodgates of the massive complex now under construction in Georgetown at 31st and K streets NW.

"Those gates will be operating by tomorrow," said Madison, pointing to the gray metal walls. But he was still worried.

The floodgates for the huge retail-office-condominium project were not supposed to be operable for another month, but today the gates are expected to get a real test -- and at stake is the complex's newly installed electrical system.

"If we get anything higher than 10 feet, we are in real trouble. Water would blow the whole electrical system up," Madison said.

The river is expected to peak at seven feet above flood level this afternoon, and the National Weather Service predicted that K Street in Georgetown would be under four to five feet of water.

All along the Georgetown riverfront, business owners braced for possible flash floods. Some merchants placed sandbags around their stores to prevent water damage, while others carried expensive merchandise to higher ground.

At Washington Harbour, a crew of 25, supplied with cots and boats, was staying overnight in case flooding came earlier than predicted. Some Georgetown residents had cited frequent flooding along the river's edge in their battle to prevent construction of the $200 million complex.

Across the street at the Thrifty Rent-A-Car of Georgetown, rental agent Lydia Ewing was holding a "high water special" -- offering, she said, $5 off the usual rate "so we can get the cars off our lot and out of the basement." She added, "If we don't get them rented tonight, we'll start asking our customers tomorrow what they are willing to pay for a car so we can get them out of here. We have no place safe to park them."

At the posh Paper Mill office building at 3299 K Street NW, sandbags were neatly stacked against three glass entrance doors.

And at the Potomac Boat Club, just north of the Key Bridge, the river had already invaded the first floor as 20 Arlington high school students rushed to move 60 sculls to the second-floor ballroom of the 116-year-old club.

Outside, rowing coach Charlie Butt directed the removal of seven of the 10 wooden ramps that connect the building to the dock in hopes of giving the structure enough flexibility to prevent it from breaking up.

"Be careful! Watch your toes!" he yelled at the teen-agers and older club members as they struggled to pull the ramps into the building. "If we lose the dock, we've lost everything. We won't be able to row this spring." By midafternoon, the group had moved everything from the first floor of the clubhouse and the water was 10 feet inside the building.

The river's edge also attracted a steady stream of people curious to see the rushing water and the bobbing tree trunks.

Max Elsman of Arlington, stood at the edge of the Harbour parking lot at Wisconisn Avenue and K Street NW and gazed at the murky, fast-moving water. "It's a lot more impressive close up," he said. "When I first saw it from the bridge, it didn't look like much."

However, his companion, Sandy Alpert, voiced a skepticism shared by others that the predictions of Georgetown flooding would not prove true. She wondered if this would be "just another Hurricane Gloria scare."

On a wall inside Chadwick's restaurant at 3205 K Street NW hang three large photographs of the high water on K Street caused by Hurricane Agnes in 1972. They show the water covering K Street and lapping against the building that houses Chadwick's.

But manager Joe McGuinness said restaurant personnel would take no precautions against flooding.

"With Hurricane Agnes, we moved all the furniture upstairs and we sandbagged the place," he said. "And we didn't get a drop of water inside. This time around, we are doing nothing but staying open for business."