I do what I can on my little bit of land in CA at the bottom of a hill to slow water down and help it infiltrate. Swales, basins, plantings, ridiculous amounts of mulch. But I get the drainage from 10 other properties above me where they're doing nothing but funnel their stormwater on (to me, and then down the mountain). I really wish they'd do this stuff... it would make my life a lot easier, and there's no way I really do anything on my own about literal hundreds of thousands of gallons per inch of rain moving through...