In Houston, yard 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.
Within those broad strokes, a well-designed yard drainage system provides proper grading, which creates positive drainage away from structures. It also takes into account adjacent properties and being careful not to drain onto them. Another aspect involves identifying and addressing existing problems such as poorly-placed downspouts, naturally-occurring low areas or an addition to the house that creates dams and changes the originally-intended water flow.
Yard Drainage: Parts and Pieces
* Catch basins, or yard drains. Catch basins can be placed under downspouts when it is undesirable or not possible to tie into the gutter. They tie into a PVC main drain line instead and carry water out through the landscape drainage system. Catch basins are usually a plastic or concrete box that uses a plastic or metal drain grate cover to filter out leaves and other waste debris.
* Channel drains. These long narrow strip drains are used between main structures and paving or at the edge of a patio or deck.
* Deck drains. Deck drains are installed in patios, decks and walkways so that water is either sloped toward drains or drained into the landscape beds. They have special drain covers, usually decorative, made of metal, brass or stone. Deck drains are smaller in size than catch basins and are only intended to drain patio surface areas.
* French drainage. Designed to take water away from saturated soil, French drains are small ditches that are filled with undersized rocks or gravel.
* Gutter downspout tie-ins. Downspout tie-ins are designed to take water from the gutters to the landscape drainage system. These tie-ins are made of plastic, metal or brass and sometimes have a side cleanout with a see-through grate so they can be easily inspected for clogs.
Yard Drainage: Affect on the Landscape
Yard drainage impacts residential landscape maintenance in several ways. Since it drains water from low-lying areas, it prevents standing water that can cause slippery surfaces, mosquito breeding grounds and drowned landscaping. A proper landscape drainage system is essential for proper lawn maintenance as it moves water off of your property in a timely manner, thus encouraging healthy grass and allowing your maintenance crew to perform their regular lawn service duties.
Drainage systems and irrigation systems can work in concert with each other. Professional landscape designers or landscape architects have the ability to develop a whole-system approach so that the nuts and bolts of both systems are hidden as much as possible. Custom decorative drain gates can be used to reduce the negative visual impact of your patio design. The design and location of the two systems should be seamless with the rest of the landscape design.
When installing a yard 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.
“If drainage contractors embark on a storm drainage project without a thorough understanding of all these demands–at the city or county level, the neighborhood level and the ground level–homeowners may find themselves in the middle of a big, expensive mess,” says Jeff Halper, landscape design specialist with Exterior Worlds.