Question
Hi Sean. I'll start with my question and if you want to read more I blather on relentlessly about my particular situation:

The question: Is there a landscape cover material that accepts water but rejects soil particles? Landscape fabric isn't very permeable to water. Likewise, how can one reduce the amount of runoff without planting grass (ideally I would like to mulch a hillside with some low growing plant cover)

The rant: I live on the side of a mountain with sand/small boulder glacial deposits. The soil is fairly well drained, about 5 minutes per inch. I am only having runoff problems over my driveway, which is covered with compact road mix (gravel, sand, clay). The driveway cuts from the highest elevation down and across the hillside toward my house and then extends down the line of slope to intersect with a roadway downslope of my house. In spring freshet (lots snow and rain here)I have huge gouges formed in my driveway, especially the portion running downslope. Right now my drainage consists of a series of 2 x 6's bolted faceward with a 2 inch gap to direct water off the driveway. The problem with the 2 X6's is that they fill up with dirt and no longer direct water effectively. I thought about adding gravel to them and covering it somehow. Without a barrier to prevent fine soil particles from entering, however, the gravel will become clogged in short order. In the future I would like to pave the driveway with asphault or concrete and so any drainage project should be cost effective and/or be suitable for the future paved driveway.  

Answer
There are lots of types of 'Landscape Fabric' some are better suited for your needs. Consult Google and search "Filter Fabric" in quotes. You'll need to move away from the common weed barriers sold at home landscape stores and consult your local grading and erosion control supply warehouse (typically for commercial contractors and off the beaten path). They should be able to point you to the best fabric for your needs.  Also there are many types of erosion control measures on the market from 'gabions' to 'Excelsior Blankets', 'Straw Wattles', 'Excelsior Logs', Erosion Netting, Special Mulches, Seed nets and many more options that you may find useful.

It is difficult for me to tell you exactly what will work for your extreme conditions without visiting your site and doing extensive data gathering. I would suggest you contact a Landscape Architect in your area who is knowledgeable about your specific type of problem (not all LA's are experts or comfortable dealing in extensive drainage problems so ask before you have them come out).
When ever you have water moving down slope it is going to carry sediment and anything you do with a commercial erosion control device is eventually going to fill with the filtered material. Your best bet is to control erosion with vegetation or if you must, diversion. By diversion I mean you can create some sort of trap for the water up slope and then divert the water through pipes under your driveway or using swales around it (if that is even an option). This can get complicated so that is why it is best to hire an expert.
Good Luck.


Sean J Murphy, LA,ISA, LEED AP
Please check out my blogs and articles on landscape topics like this on my websites.
http://www.seanjmurphy.com
http://amenityarchitects.com