Solving Landscape Drainage Issues

Drainage is a creative arena. There is only one rule and a thousand ways to apply it. The rule: Since water always goes downhill your job is to make it easier for water to go down the hill you want it to than any other hill available to it.

Ways of doing this include:

Putting a mound in its natural path, such that it is easier for the surface water to flow somewhere else. Digging a trench or ditch in its natural path and running that downhill to a desired location. Digging a trench and filling that trench with gravel and perforated pipe and running that to a desired location. Directing water to an open or enclosed pit and from there pumping it with a sump pump. Grading the soil so that it slopes away from things you wish to keep dry. Raising something so that it is above the natural water-table. Adding a slope to an area that is too wet so that water can easily run off. Minimizing the use of artificial irrigation to keep an area dry. Planting evergreen trees. Trees can absorb up to 2,000 gallons of water a day from the soil and disperse them into the atmosphere. When filling in a hole or raising the soil level put a layer of sand, gravel or waste bricks/concrete and cover this with drainage fabric before adding the soil. This will increase drainage significantly but may not be necessary.

I encourage you to be creative. As long as you make it slightly easier for water to flow the way you want it to, it will. Water is lazy and will always take the path of least resistance. For more visual ideas search you-tube under such topics as: Building a French Drain Installing Drainage Installing catch basins.

It is ideal to collect all gutter run-off in in 4" drainage pipes well away from any area it might cause a problem – preferably to the street. If it cannot be run to the street there are other options, such as running it to a gravel-filled trench where it can be dispersed. PVC straight pipe (usually white) is far preferable to the corrugated black pipe that is often used. The latter gets clogged easily, is not as strong and can be damaged when clearing out a block.

Plumbing for drainage using PVC is similar to plumbing irrigation pipes, with the main difference being that everything is much bigger, from the glue cans to the pipe. By the time you have mastered basic irrigation you will probably feel fairly comfortable with drainage. Jackson's Hardware in San Rafael and Goodman's Ace Hardware in Mill Valley have an unusually good selection of drainage fittings, as well as the normal pipes that are common at most hardware stores and building supply stores.Mill Valley Landscape Architect