Geoff Lawton's locale typically has high rainfall, but can have droughts. Swales are the basis for all his designs, even in wet climates. Ponds and other water features are far more productive than land features. Sepp Holzer also makes water the central focus of all his designs, even in places where droughts are rare or non-existent.
I think swells would still be the way to go, I have some wet land even in summer not swampy but heavy clay soil and always wet and sticky. I built swells for a few of reasons first is water control to prevent flooding and best use of water. The second is I wanted a large berm, with a berm you get wicking which allows for controlled watering just the right amount of moisture not sopping wet like I normally have there. lastly this configuration allows me to cover the berm and swell with old hay, as it breaks down it is healing the soil turning sticky clay into rich soil. I have a YouTube video on it if you want to see it
Where only swamp grass would grow I now have 30,000 garlic cloves planted and they are growing well, I soon will be adding trees and in the flats grow alfalfa and grasses. You never can count on the weather to be in your favor but if you set things up correctly nature will take over and regulate herself.
Yeah. What he said. Totally. Wait. What? Sorry, I was looking at this tiny ad: