"...just recently bought his own kayak..."
Probably not a journey to get beginning practice with. You might want to play on the Shenandoah for awhile first.
Having typed that, however, I thought Great Falls was simply some white water mostly, with the Virginia side being the danger zone. That is, a thriller perhaps but not impassable.
But the REAL danger zone, The Place That Kills, is well WITHIN the Beltway and is THE place you must be aware of and fear:
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