After floods inundated large stretches of the C&O Canal last winter, National Park Service officials closed much of the 184-mile park to visitors and set about trying to clean up an estimated $9.3 million in devastation.

The rushing waters had uprooted large trees and deposited tons of debris in the canal bed and along the towpath, making some areas unsafe for the bicyclists, joggers and campers who flock to the park each year.

"When the flood came, park staff morale was pretty low," said park Superintendent Richard Stanton. "We had worked for years getting the canal beautiful; it broke our hearts to see that kind of damage."

Stanton said his maintenance workers felt overwhelmed by the task at hand, which, at a time of federal budget cutbacks, is expected to take four years. Unable to call in the Marines, Stanton did the next best thing: He called the scouts.

Stanton said the response to his distress signal to Boy Scout and Girl Scout troops in this region far exceeded his expectations.

In less than a month, some 4,863 volunteers, most of them from Boy Scout troops in the area and some from church and community groups, have pledged to work weekend stints along the canal, which follows the Potomac River from Georgetown to the foot of the Allegheny Mountains in Cumberland, Md.

In all, about 10,000 volunteers said they would spend at least a day at one of the five cleanup campsites, at Paw Paw, Four Locks, Antietam, Falling Water and White's Ferry.

In addition to the work of the scouts, high school students from Montgomery County who were hired for the summer by the county's Conservation Corps have also been assigned to the cleanup as one of their environmental projects.

The volunteers spend at least four hours each day clearing brush and lugging tree limbs and huge logs sawed by maintenance workers. The debris is pulled from the canal bed to Park Service trucks and taken away to be dumped.

"This is a lot of fun 'cause you're seeing nature, but it's hard work -- it really is," said Spedden Walker, 14, a Boy Scout from Upper Marlboro who was working at the White's Ferry campsite Saturday under a blazing sun.

As the scouts and their scoutmasters labored in 90-degree heat and wilting humidity more than a mile away from their campsite, their hair became matted with sweat and their clothing covered with grime.

" I don't think we'll do more than two miles," Walker said, removing a glove and flicking sweat from his forehead. "I feel sorry for the guys who have to do this every day."

Both Walker and Eric Johnson, 15, a member of a Scout troop in Fairfax, were putting in community service toward a "50-Miler" scouting award for outdoor activity.

Johnson, faithful to his Boy Scout oath, was candid about the work.

"I don't like doing this stuff, but it's not so bad as long as it's for the community," he said. "Me and my dad used to come up here on the weekends and it was neat, but I usually just like to laze around on Saturdays."

York, Pa., scoutmaster Armin Mineer, who brought six scouts to camp out at White's Ferry overnight, said his boys are learning about the historical importance of the 158-year old canal. It was once a commercial link between the rich Ohio River Valley and the East Coast.

"They're working up a sweat and that's good for them," Mineer said, sitting on a fallen tree in the canal bed. "The canal is the kind of thing they read about and hear about, but they don't really care. Working out here brings it to life for them; it makes it real."

"This is the kind of work Boy Scouts are supposed to do," said Derrick Shearer 12, a member of Mineer's troop.

Park Superintendent Stanton said the volunteer effort has been so successful that the cleanup at the Falling Waters worksite has been completed well ahead of schedule. He said if that if the Park Service receives sufficient funding next year and the volunteer efforts continue, much of the towpath might be reopened to hikers by the fall of 1987.

"With our small staff this work would have taken years," he said. "But you look at some of the areas that were in really bad shape after the floods now they look like someone took a vacuum cleaner to them."

Stanton said the volunteer efforts had been scheduled to end in August, but have been extended until September to accommodate all the groups who have expressed interest in helping out. "I'm keeping my fingers crossed," he said. "It looks like we are going to be in business next fall."