JTT, Around here some of the non-commercial organic folks now frown on that permeable stuff and recommend just a thick layer of mulch. There's a method some are beginning to use called no-till gardening. Here's a bit from the Dirt Doctor site:

There are several modern no-till gardening methods today. There are several books on the subject too. One of the most famous is Patricia Lanza's books, "Lasagne Gardening" parts one and two.

My version of no-till is fairly simple. I have a 3 acre home/farm. About 3/4 acre is all no-till borderless raised beds. Most of my beds are about 3-4' long, all around the house and backyard.

I start by mowing down any existing weeds or grass on a virgin spot of land. Then I smother the weeds and green manure mulch with about 6-12" of unfinished compost or horse manure/sawdust that I get weekly from the local equine clinic. Then I put about 1-2" of rich garden dirt, or mature compost on top to guarantee good seed germination of my plants.

If any new weeds pop up through the organic matter, I smother them again with more unfinished compost or an organic mulch like straw or leaves.

I weekly feed my plants and new beds' soil, with lots of aerated teas to maximize aerobic bacteria and fungi in the soil. I also like to make and use lots of fish/seaweed products for my plants' health and growth.

In the fall/winter, I grow lots of legume/grain cover crops like hairy vetch, crimson clover, winter peas, mustard, turnips, whole grain cattle feeds loaded with oats and wheat, and radishes, to get lots of new organic matter and nitrogen-fixation in these borderless raised beds.

I mow and smother these green manures down in early spring or late winter with my scythe, swing blade, hoe, and lots of more unfinished compost. After several days of decomposing, then I'll start planting again.

During the spring/summer months like to grow lots of cover crops like buckwheat, birdseed sunflower seeds, beans, and peas around my crops as great border plants to draw in beneficial insects, and for beauty.

The same fellow, on a different thread, posted this link to show people what his garden looks like. He's in the American South so will have a longer growing season and a moister climate than many parts of the U.S. and I dare say all of the U.K. But the priniciples would work in other areas.

SRS