Jeff Halper asked: According to the U.S. Geological Survey, Houston sits only 39 feet above sea level. We have 21 major bayous in the greater metropolitan area, creating significant watershed boundaries. The dominant component of the local soil is clay, which has a particular sensitivity to moisture fluctuations. Oh, yes-and we regularly get torrential rainfall. While these conditions don’t make us, say, New Orleans, they certainly give homeowners pause when considering a functional landscape drainage system.
The advantages of a proper residential landscape drainage system are self-evident. It protects your home from flooding. It is also important for plant and tree health, which further enhances your property value. It protects the foundation of your home from cracking and uneven shrinkage and swelling. It drains water away from the roof, patio, garden landscape and lawn areas to prevent standing water that can cause slippery surfaces, mosquito breeding grounds and drowned landscaping. All of these benefits underscore the importance of a whole-system approach to a landscape drainage system so that all the appropriate functions and fixtures work together for the betterment of the entire property.
Elements of Good Residential Landscape Drainage Systems
A well-designed landscape 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. The key to solving most existing problems is to find out where the water comes from-other than the obvious cause of rain falling from the sky.
Considerations during Planning and Installation
Drainage plans. The total landscape drainage area of your property for drainage purposes is called a watershed. Watershed means the total water drainage area with its different slopes, rates of water run-off, soil porosity and the dividing line between each drainage surface area such as roof, deck and lawn areas. A property watershed analysis by a drainage expert will identify these different areas and will recommend the appropriate fixtures and pipe size for the landscape drainage system.
Permitting. Many cities require the submittal of a drainage plan with regulations concerning minimum pipe size.
Engineering plans. In addition, some jurisdictions may require an engineered landscape drainage plan with submitted runoff equations.
Tree preservation. When installing a drain 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 method exposes tree root so they are not torn. Alternately, pressurized water can be used to dig deep trenches and expose roots, which also minimizes damage.
City utilities. It is imperative to locate city utility lines so they are not cut. It can be very expensive to repair fiber optic lines, gas lines and other utilities.
Types of Landscape Drains
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.
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.
French drainage. Designed to take water away from saturated soil, a French drain is a small ditch that is filled with undersized rocks or gravel.
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.
Residential Landscape Drainage Systems: Additional Considerations
Because the Houston terrain is so flat, the use of sump pumps or sump systems are sometimes needed to move the water out of areas lower than the elevation being drained to. A sump pump basin is usually constructed of brick or concrete. Proper maintenance consists of regular inspection and cleanout of catch basins, downspout clean-outs, and inspection and replacement of power connections on sump pumps and drain covers.
Drains can be unattractive, so it is important that the landscape designer or landscape architect locate the drains so they are hidden as much as possible. Sometimes the use of custom decorative drain gates can be used to reduce the negative visual impact.
If you are having gutters, hardscapes and landscaping installed, it is best to hire a landscape contractor that uses competent subcontractors so that the design, location and installation of the entire landscape design, including the drainage system, is seamless with the overall improvements.
Rodney
