Drainage Terms
Storm Water: The term storm water refers to rainwater. Storm water flows from properties in NRH and washes into storm drains on the curbs of roads and eventually flows to the Trinity River. Unlike wastewater, storm water is untreated and it can carry pollutants, sediments, and trash directly into our natural water resources.
Curb Inlet: A location where storm water runoff from the street enters the storm drain system. Curb inlets are part of the public drainage system and are maintained by the City.
Drop Inlet: A location where storm water runoff from an open area enters the storm drain system. Drop inlets are usually part of the public drainage system, but can sometimes be considered private (private inlets are not maintained by the City.)
Swale: A depression between slopes that carries drainage. Most homes are constructed with a swale at the property line between neighbors. Some homes also have a rear swale which directs the water around the house from the rear to the side yard. Swales tend to be relatively shallow with gentle side slopes. Swales can be almost unnoticeable as a landscape feature, but are vital for carrying storm water away from or around the home. Unfortunately, sometimes swales are mistakenly filled in by homeowners who do not realize that this lower-lying area actually serves an important drainage purpose.
Flume: An open artificial channel or chute carrying a stream of water. Typically, it is constructed of concrete, and looks like a narrow sidewalk with curbs on both sides. The benefit of a flume over an earthen or grassy swale is that it can accommodate more runoff (it carries the storm water away faster.)
French Drains and Area Drains:
Public Works discourages the use of either French Drains or Area Drains as the primary path for storm water. These types of systems are typically unable to keep up with the intense rainfall events experienced in North Texas. However, they are useful for carrying low flows and speeding up the drying process after rain.
- French Drain: A ditch filled with gravel or rock that redirects surface and ground water away from an area. They often include the use of perforated pipe in addition to gravel, to provide additional capacity. French drains are common drainage systems, primarily used to prevent ground and surface water from penetrating or damaging building foundations. French drains are also used behind retaining walls to relieve ground water pressure.
- Area Drain: An area drain system collects surface water into one or more small inlet boxes. These boxes are of variable size and usually have a grate-style opening on top. Area drains typically use small (4") diameter pipes to carry the collected storm water to the street.
Private drain outfalls (4" diameter or smaller) can be tied into the curb at the street, so long as the work is coordinated with the Public Works Street Division at (817)427-6460. While it is acceptable to discharge a French Drain or Area Drain to the street, discharging a pipe onto a neighbor is discouraged. This type of flow concentration can cause damage to this neighbor's property, and this neighbor may have grounds for legal action under Texas Water Law.
