Effective and ecologically-correct features of a landscape drainage system, French drains are trenches or ditches filled with gravel (usually) that move water parallel to the ground. Water flows much easier through loose gravel, especially as compared to the thick, gumbo-like clay soil found here in Houston. To further ease the flow of water from the wet area to the dry one, a French drainage system will often have pipes buried in the gravel.

The Positives

French drains can have a positive impact on your overall landscape. Advantages include:

• By draining standing water out of the landscape while at the same time storing rain water in the subsoil, this type of drain helps your grass look healthy and vibrant. Thus your overall lawn service is improved.

• French drains can be a de facto part of your irrigation systems. They can be developed by landscape designers or landscape architects so that water collects in and nurtures garden beds, thus conserving water. French drains turn your landscape into a green garden—in both senses of the word “green.”

• Residential landscape maintenance is made easier with French drains since they prevent standing water that can cause slippery surfaces and mosquito breeding grounds. They also help prevent drowned plants and help reducing fungus growth, which is the main killer of plants in tropical climates.

Drainage Systems: An Overview

In Houston, storm drainage issues are very serious due to our flat topography, dense clay soils, and heavy forested lots compacted by years of construction that have increased impervious surfaces. These factors have caused more streets and homes to become flooded during the heaviest rainfalls. Consequently, local ordinances are beginning to follow the model used by the Memorial Villages that require minimum pipe sizes, flow rates, temporary drainage systems, engineered drainage plans, calculations, topographic maps, and as/built plans.

“If drainage contractors embark on a drainage project without a thorough understanding of these demands, homeowners may find themselves drowning in a big mess that can cost thousands to rectify,” says Jeff Halper, landscape design specialist with Exterior Worlds.

Tree Preservation and Tree projection

When installing any drainage system, it is recommended to hand-dig trenches around trees to minimize damage to them. It is best to tunnel under tree roots by using compressed air. This tree preservation method exposes tree roots so they are not torn. Alternately, pressurized water can be used to dig deep trenches and expose roots, which also minimizes damage. Tree preservation is one of the most important aspects of proper drain installation procedures.

Fun to Know

French drains were not invented in France. Rather Henry French of Concord, Massachusetts came up with the idea in the mid-1800s. A judge and farmer, he published a book on the subject with the memorable title—“Farm Drainage-The Principles, Processes, and Effects of Draining Land with Stones, Wood, Plows, and Open Ditches and Especially with Tiles, Including Tables of Rain-Fall, Evaporation, Filtration, Excavation, Capacity of Pipes, Cost and Number to the Acre of Tiles, Etc, Etc.