I’d be bagging all that river muck I could get if I were you.
I think limestone subsoil would be preferable to the adobe I’ve got. But I can ameliorate it all the same. I’ve been thinking about trying a clover cover crop. Or maybe buckwheat. My neighbors will wonder what the hell I’m up to now... although actually they all admire and are entertained by my gardening adventures.
I’m in a suburban area... no deer nearby but there are raccoons and coyotes and rats. I’m guessing raccoons are the thieves even though I never see them.
One trick that works well with clay soil is to plant daikon radishes, and then leave them in the ground to rot. It stinks to high heavens for a while, but you wouldn’t believe the difference!
Daikons are sometimes referred to as “nature’s rototillers”.
When I take a trip to the beach—Maryland or Virginia—I pick up as much washed up seaweed as I can. Possible to bring it home and add to compost heap, or dry and crumble over garden and rake it in. Don’t forget the value of Vetch as a cover crop. Grows vigorously and has pretty flowers.