The walls either side (rock walls) are quite high they affect the wind majorly and the river mouth itself isn't that wide. Its actually considered a pretty treacherous boat crossing by many.
The estuary inside North Wall Is totally sheltered by North Wall (the land between the estuary and the beach.... Sorry to disappoint. I'm about 30 min from Brunz and would be happy to kite the beach some time (especially Friday avo's as i'm in brunz anyway) if you want to kite with someone.