Islands are almost always windier. Rapids? Not really.

Yes, islands tend to be windier than the mainland. No, rapids don’t make a significant difference on their own.

Open water means less friction. Trees, hills, and buildings on the mainland slow the wind down. On an island, especially a small one, the wind has nothing to stop it. Same reason coastal areas are breezier than inland.

As for rapids: they create noise and turbulence in the water, not the air. Unless the rapids are in a narrow canyon or gorge that funnels the wind, the wind speed right there won’t be any different than a calm stretch of the same river. If you’re feeling more wind near rapids, it’s usually because the terrain around them is more exposed.

Don’t expect extra gusts just because you hear rushing water.