It's entirely reasonable that people would camp and live water-side.

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Oceans and lakes would erode and wash away (scatter) the stones. Springs wouldn't erode much, so those sites get buried with the lithic scatter still thick around the original site.

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Creeks and rivers wash away the light dirt, (sand, mud) and that leaves stones of equal weight cluttered together. (gravel bars) The artifacts will move downstream making the entire creek (river) a possibility. The sites will be upstream. It's almost impossible that artifacts will move upstream. But every time it rains, they enjoy scooting downstream. With the sand and mud carried away, they are exposed and able to congregate with like-sized rocks. It's the opposite of "social distancing".