The death toll from three days of heavy flooding in Virginia, Maryland and West Virginia rose to 34 yesterday as the rain-swollen James and Potomac rivers crested at record levels and wreaked unprecedented destruction in dozens of towns along their banks.

As the debris-laden rivers roared toward the Chesapeake Bay, officials in Richmond and Washington prepared for what was expected to be the worst flooding since Hurricane Agnes in 1972.

The James is expected to crest near downtown Richmond by 1 p.m. today at nearly 23 feet above flood stage, and the Potomac is expected to begin cresting at Georgetown nearly seven feet above flood stage about 3 p.m. The Potomac is expected to stay at that level here for about six hours before receding.

By early today, the James River was more than 19 feet above flood stage in Richmond and rising at more than six inches an hour. A 40-block area of downtown was flooded, with water in many places at least three feet deep and lapping near the top of a 28-foot-high wall of sandbags that had been placed around the city's municipal water plant.

At Harpers Ferry, W.Va., white-capped waves rose high above the confluence of the Potomac and Shenandoah rivers, and the torrent roared like a waterfall as it rushed through Harpers Ferry National Historical Park, flooding the visitors center and the main street into the town.

Park officials estimated the crest on the Potomac of 16 feet above flood stage at the park was reached about midnight, but National Weather Service officials said they expected the river to remain at about that level until after 2 a.m.

Downstream on the Potomac at Point of Rocks, Md., the river was already 19 feet above flood stage by 11:30 p.m., officials said, and about 150 people were evacuated as the water level was expected to rise four more feet before reaching its peak at 1 a.m. today.

By 2 this morning, water was about eight inches deep along lower K at 31st street NW, and was beginning to slosh over the sidewalks and against buildings on the north side of the street. Police blocked off the area, near the new Washington Harbour development.

In Old Town Alexandria, waters from the Potomac flooded portions of Prince, King and Duke streets below Union street, officials said.

The heavy flooding, which began Monday along the Roanoke River near Roanoke and in Lynchburg on the James and spread along the upper reaches of the Potomac in West Virginia on Tuesday, has left dozens of roads and bridges closed in the three-state area and forced thousands of residents from their homes.

More bridges were being closed last night -- three across the James River in Richmond and U.S. 15 across the Potomac at Point of Rocks.

National Guard troops were called out in Virginia and in West Virginia, where water supplies were contaminated in some areas, and states of emergency were declared in at least 36 counties in the two states.

Several towns along the upper Potomac were isolated because of the flood waters and officials said destruction there was massive.

In Paw Paw, W.Va., where the Potomac crested at 54 feet, 29 feet above flood stage late Tuesday, Mayor Dave Clark said, 'It is a total disaster. We have just about lost everything."

Portions of Paw Paw had to be evacuated again last night after leaks were discovered in large propane tanks that had been damaged by the flood waters. Officials said described the situation as "fairly serious" and had called in experts from Pittsburgh.

Virginia Gov. Charles S. Robb, who toured flood-ravaged areas of the state by helicopter yesterday, said, "It's a very sobering picture to see what kind of devastation there is: mobile homes on top of cars, and homes that are filled with nothing but mud and goo."

Damage in the Roanoke-Lynchburg area of Virginia was put at more than $250 million and the damage estimate in West Virginia, where Gov. Arch Moore has asked for federal assistance, was more than $100 million.

Sandbagging operations were under way yesterday around Great Falls Tavern on the C&O Canal, as the 184-mile towpath remained closed along its entire length for the second day.

National Park Service spokesman Earl Kittleman said that most of the canal north of Point of Rocks, Md., was under water yesterday.

The National Weather Service said lower K Street at the foot of Wisconsin Avenue in Georgetown is expected to be under four to five feet of water by this afternoon, with parts of Rock Creek Parkway near the Kennedy Center, the Maine Avenue waterfront and Old Town Alexandria also submerged.

The National Park Service said the Jefferson and Lincoln memorials and the Washington Monument will be closed today.

Along the Georgetown waterfront yesterday, the normally green and slow-moving Potomac was transformed into a murky brown, turbulent waterway. Large logs, tree trunks and barrels shot down the river or lodged in several of the small marinas that dot the shoreline.

Owners of businesses along K Street hurried to secure their buildings and belongings against the rising water, which had already invaded the first floor of the century-old Potomac Boat Club just north of Key Bridge.

Great Falls National Park on the Maryland side of the Potomac was jammed with gawkers who came to look at the churning river, and U.S. park police said they had turned back one carload of kayakers.

Police in Alexandria began at 6 last night to distribute fliers warning merchants and residents near the Potomac, in Old Town and in the Arlandria section of Alexandria, that by 10 p.m. the river would begin to overflow the banks.

The Park Service announced that the George Washington Parkway would be closed on the route into Alexandria and it would be necessary to take Rte. 1 to travel between the District and Alexandria.

Still, officials said they were concerned that some people were ignoring their warnings.

"What we are most afraid of is that people will not recognize the seriousness of the situation," said Rose Boyd, Alexandria assistant city manager.

Today's near-record flooding here comes after three days of less serious tidal flooding, which was caused by high winds that prevented the runoff from this week's rains from flowing into the Atlantic, according to the National Weather Service.

The river flooding has been caused by large amounts of rainfall in the mountainous areas of Virginia and West Virginia

National Weather Service hydrologist Leo Harrison said lighter rains here -- 1.09 inches at Washington National Airport between Nov. 1 and 5 compared with up to 18 inches that soaked parts of eastern West Virginia -- would mean less severe flooding here.

With flood waters covering tracks in some spots, Amtrak canceled or curtailed train service west of Washington, according to spokesman R. Clifford Black.

The Blue Ridge commuter train from Martinsburg to Washington was canceled yesterday morning. About 30 passengers took a chartered bus arranged by Amtrak, but no service was offered back to Martinsburg yesterday evening, Black said. "They were told they would come in at their own risk," he said.

Service in the heavily traveled Northeast corridor and south of Washington was not affected.

In western Montgomery County, rising water from Seneca Creek forced about four families to leave their homes, and 17 residents of Seneca House, a facility for those dependent on alcohol or drugs, were moved to a Gaithersburg motel, according to Maryland National Capital Park Police Officer Tim Boyle.

Fairfax County officials warned that residents in the low-lying area bounded by the George Washington Parkway and Fort Hunt, Belle Haven and Belle View roads might be asked to evacuate.

In West Virginia, authorities said that at least 17 persons were confirmed drowned and as many as 38 persons were unaccounted for in the northeast half of the state, where rains and heavy flooding hit the hardest.

State police said one man died in Pocahontas County when the hospital in which he was being treated lost power, and the life-support systems that were keeping him alive failed.

The West Virginia National Guard also was being used to combat minor looting in Petersburg, Granville and Marlinton, according to a spokesman for Gov. Moore.

In Clarksburg, one of the state's largest cities with a population of about 50,000, flood waters knocked out the municipal water system and the city was virtually closed down.

In Maryland, one death was attributed to the flooding.

The death toll in Virginia stood at 16, officials said.

Virginia's Robb said repairing roads, bridges and the transportation system would cost at least $28 million and Moore said repairs to West Virginia bridges alone would cost $26 million to $30 million.

Many of the deaths occurred when people fleeing their homes were trapped in their cars on flooded roads, or when residents refused to heed authorities' warnings to evacuate.

In the areas in which the river had already crested, the scene yesterdy was one of total devastation.

River towns from Hancock, Md., near the Pennsylvania border, to Point of Rocks, Md., south of Harpers Ferry, were under Potomac flood waters yesterday. Hundreds of homes and business were submerged, some to their rooftops, as the river swelled in some places to four times its normal width.

At Harpers Ferry, where the Potomac and Shenandoah rivers converge, churning flood waters inundated the low-lying downtown historic district yesterday. A freight train was abandoned downtown, the tracks both ahead and behind it submerged.

Coal trains were placed on two trestles spanning the Potomac from Harpers Ferry to Virginia to weigh the trestles down and prevent their supporting piers from washing away. Just a few feet below, swift-moving Potomac waters roiled.

Flooding was severe in Front Royal, Va., as well, with the Shenandoah River swelling to five to 10 times its normal size in some places. Dozens of houses were swamped by high water, many up to their rooftops.

Closer to Washington, several homes at Whites Ferry, Md., near Poolesville, were flooded, and islands up and downriver were covered over. At Great Falls, the falls disappeared beneath churning acres of a river that was capped with muddy whitewater foam.