While Todd Garvis' older brothers were picking up gold medals for their victory in the two-man international slalom racing two months ago, the 13-year-old from McLean, Va., quietly slipped his green kayak into the surging waters of the deserted Aux Sable River and shot the rapids.

The result - the same that many world-class paddlers had come up with that championship weekend. He ruined a perfectly good boat.

That was August in Jonquiere, Quebec.

The event was the preworld championship canoe and kayak races, a preclude to the 1979 worlds to be run on the same course.

For the first time in the history of the world championships, the races were being held in North America instead of Europe. That delighted the Washington, D.C., contingent.

The preworld consisted of two races, the wildwater, a downriver race on a five-kilometer course, and the slalom, a 28-gate race on a much shorter stretch.

The wildwater came first on the Metabetchauan River about 30 miles from Jonquiere. Crowds clung to the steep, rocky banks of the river as the paddlers prepared for the descent.

By noon of that first day six Washington-area paddlers had taken first and second-places in their classes. David Hearn and Ron Lugbill, competing together in a C-2 (two-man decked canoe), took the gold in what was to be the beginning of a winning stretch for both.

In the two days that followed Washington-area paddlers, all members of the Canoe Cruisers Association, showed the world how a salom canoe is paddled.

At the end of the C-1 slalom competition, the second day the scoreboard showed six Washington-area men in the top eight spots. Hearn took first place, followed by Ron Lugbill in second and Kent Ford III in third. Robert Robison, ex-Washingtonian Jamie McEwan and Jon Lugbill took fifth, sixth and eighth places, respectively.

The Canadians and Europeans were flabbergasted. The French paddlers, who looked so strong a year before in Spittal, Austria, did no better than fourth and 13th.

There was more of the same the final day. Todd's brothers, Stephen and Michael Garvis, easily took first place in the C-2 slalom competition.

With whitewater competition no longer in the Olympics, several nations did not send teams to this off year prechampionship. Each time the Americans were tempted to grow boisterous in victory, Coach Bill Endicott solemnly reminded his charges that somewhere out there the East Germans were practicing, determined to copy the American boats and to shame the U.S. next summer.

One indelible image from the racing was of 4,000 cheering French-Canadians lining the banks of the Aux Sable as the young paddlers from Washington grunted, groaned and strained in victory.

The Americans left Jonquiere with 33 medals, 12 in individual events and the rest team awards. The local team members gathered here last month to watch movies and slides of themselves. Grudgingly, Robison admitted "that guy's a pretty good paddler" when his picture flashed on the screen.