French Drainage Systems

While we already have a drainage system in our landscape, we need to expand it. We’ve been reading about French drains and were wondering what Exterior Worlds thought about them?
French drains are trenches or ditches filled with gravel or other small rocks that move water parallel to the ground. Water flows much easier through loose gravel or rocks, especially as compared to Houston’s infamous thick and gumbo-like clay soil which is always a challenge for any local landscaper. A well-designed drainage system using this type of drain will often have pipes buried in the gravel to further ease the flow of water from the wet area to the dry one.

For those homeowners who are interested in a “green” green garden—that is, one that is ecologically-correct and sustainable—French drains add a “green” element to your landscape drainage system. By the way, French drains were not invented in France. Rather, Henry French of Concord, Massachusetts came up with the idea in the mid-1800s and popularized it with his book.
Why do people install such drains? What are their advantages?
This type of drain fits into almost any landscape design. Their rewards are many, including:
• These drains make residential landscape maintenance easier since they prevent standing water that can cause soggy roots or drowned-out plants. They also help prevent slippery surfaces and breeding grounds for mosquitoes.
• Your overall lawn service is improved because these drains pull standing water out of the landscape while at the same time storing rain water in the subsoil. Your grass ends up looking healthier and more vibrant.
• These drains can work in conjunction with your irrigation system. Both systems can be designed by landscape designers or landscape architects so that water collects in and nurtures garden beds, thus conserving water. Your designer can also work to hide the hardware to lessen any negative visual impact.
What do we need to know, in general, about drainage systems?
It goes without saying that storm drainage issues are very serious in the Gulf Coast region due to our flat topography, dense clay soils, and increased impervious surfaces on heavy forested lots due to years of construction. These three major factors have caused flooding problems for streets and homes during our seasonally heavy rainfalls. Therefore, many local ordinances have begun to follow the standard set by the Memorial Villages that require minimum pipe sizes, temporary drainage systems, topographic maps, engineered drainage plans, calculations, flow rates, and as/built plans.

Homeowners may find themselves swimming in the middle of a big mess that can cost thousands to rectify if their drainage contractors takes on a drainage project without a thorough understanding of these demands.

Also, we always recommend to our clients that, when installing any drainage system, you hand-dig trenches around trees to minimize damage to them. Alternately, pressurized water can be used to dig deep trenches or you can tunnel under tree roots by using compressed air. Any of these tree preservation methods expose tree roots so they are not abruptly torn, thus endangering the life of the tree.