posted 8 years ago
In my front yard next to the street slopes towards the center. When heavy rain falls it pools in middle of the yard, right up to the lowest edge of the garden beds on these sloped sections. These last two springs, while most gardeners in my area have had wide spread drowning of their plants, mine have remained healthy because the water was able to drain fast enough. So there are some very sound benefits to slope in a garden.
My inclination in your circumstance would be to take advantage of the earth moving equipment. There's a reason why so many ancient cultures put the years of hand labor into building terraces for farming. If you don't do it now, will you have ready access to the earth moving equipment, and will the equipment be able to access the land to shape it without destroying other projects?
If you really don't feel these kinds of earthworks are for you, I think if you just lay out your garden in rows on contour you would get similar effects, though much smaller. If you add amendments that raise the soil level (tilled in or top dressed) the garden bed itself would be a small berm creating a micro-swale upslope. Simply keeping thick vegetation in the beds with shorter (or no) vegetation in paths between would cause water to slow and pool a little right above the garden bed.
The more texture you add to your slope, through earth works that change the shape like terracing or swales or through planting strategies that cover the ground in dense vegetation, the more opportunities you have to slow and capture water. In all but the wettest of circumstances, keeping water on your property, and in your soil is one of the best things you can do to support healthy soil life. If you have healthy soil you can hold more water in the ground itself than any rainwater catchment system.