§ 35-27. Definitions.

The definitions in this section shall apply to sections 35-26 through 35-36 of the Irving Land Development Code, as amended:

(1)

Allowable headwater. Maximum depth of flow at the upstream face, measured from the invert, minus the required freeboard.

(2)

Conduit. Any closed drainage system designed for conveying water.

(3)

Conveyance. 25-year, 24-hour storm event.

(4)

Culvert. A culvert (or box culvert) is a component of an open drainage system that conveys flow under roads, driveways, and other improvements that cross the drainage system.

(5)

Design flood. A flood having a one (1) percent chance of being equaled or exceeded in any given year based upon fully developed watershed conditions.

(6)

Detention basin. A dry or wet basin or depression constructed for the purpose of temporarily storing stormwater runoff and discharging water over time at a reduced rate.

(7)

Developer. A person, partnership, corporation, or any other legal entity engaged in development, and not excluded by exemption under state or federal law or this division.

(8)

Development. Any man-made change to improved or unimproved real estate, including, but not limited to, construction of buildings, structures, or other improvements, mining, dredging, filling, grading, paving, excavation, drilling operations, grading, or clearing.

(9)

Discharge. Rate of stormwater for flood waters flowing in a river, creek, channel, storm sewer system, conduit, culvert, or other stormwater conveyance system.

(10)

Dry detention. An excavated area installed on, or adjacent to, tributaries of rivers, streams, lakes or bays to protect against flooding and, in some cases, downstream erosion by storing water for a limited period of time.

(11)

Erosion. The wearing away of the land surface by water, wind, ice, or other geological agents, including such processes as gravitational creep.

(12)

Extended detention (ED). A facility constructed through filling and/or excavation that provides temporary storage of stormwater runoff and includes an outlet structure that detains and attenuates runoff inflows and promotes the settlement of pollutants.

(13)

Facility. Any building, structure, installation, process, or activity from which there is or may be a discharge of pollutant.

(14)

Federal Emergency Management Agency (FEMA). Federal agency which administers the National Flood Insurance Program.

(15)

Flood or flooding. A general and temporary condition of partial or complete inundation of normally dry land areas from the overflow of inland waters, or rapid accumulation or runoff of surface waters from any source.

(16)

Floodplain. Any land area susceptible to being inundated by water from any source.

(17)

Flood mitigation. 100-year, 24-hour storm event.

(18)

Flume. Any open conduit on a prepared grade, trestle, or bridge.

(19)

Freeboard. The vertical distance between the design flood elevation and the top of an open channel, dam, levee, or detention basin to allow for wave action, floating debris, or any other condition or emergency without overflowing the structure.

(20)

Hydraulic gradient or hydraulic grade line (HGL). A line representing the pressure head available at any given point within the drainage system.

(21)

Levee. A man-made structure, usually an earthen embankment, designed and constructed in accordance with sound engineering practices to contain, control, or divert the flow of water so as to provide protection from temporary flooding.

(22)

Levee system. A flood protection system which consists of a levee, or levees, and associated structures, such as closure and drainage devices, which are constructed and operated in accordance with sound engineering practices.

(23)

Manning equation or manning formula. The uniform flow equation used to relate velocity, hydraulic radius, and energy gradient slope.

(24)

Natural drainage. The dispersal of surface waters through ground absorption and by drainage channels formed by the existing surface topography or formed by man-made changes in the surface topography existing at the time of adoption of this ordinance.

(25)

NCTCOG-iSWM. The North Central Texas Council of Governments Integrated Stormwater Management design criteria and technical manuals, as amended.

(26)

Open channel. A channel in which water flows with a free surface.

(27)

Owner or property owner. The person who owns all or part of a facility or property, including any person controlling the facility or property or acting on behalf of the owner; including, but not limited to, the owner's agents, assigns, developers, and contractors. Owner or property owner does not include the City of Irving.

(28)

Person. Any individual, partnership, co-partnership, firm, company, corporation, association, joint stock company, trust, estate, governmental entity, or any other legal entity, or their legal representatives, agents, or assigns. This definition includes all federal, state, and local governmental entities, unless otherwise exempted by law or this ordinance.

(29)

Privately maintained easement area. A floodplain or flood-prone area that is not dedicated to the City of Irving as an easement.

(30)

Probable maximum flood (PMF). The flood magnitude that may be expected from the most critical combination meteorological and hydrologic conditions that are reasonably possible for a given watershed.

(31)

Rational method. The means of relating runoff with the area being drained and the intensity of the storm rainfall.

(32)

Registered professional engineer. A person who has been duly licensed and registered by the State Board of Registration for Professional Engineers to engage in the practice of engineering in the State of Texas.

(33)

Sediment. The soil particles deposited through the process of sedimentation as a product of erosion. These soil particles settle out of runoff at variable rates based on the size of the particle and soil type.

(34)

Site. The land or water area where any drainage or floodplain improvements, facility, or activity is physically located or conducted, including adjacent land used in connection with the drainage or floodplain improvements, facility, or activity.

(35)

Streambank protection. 1-year, 24-hour storm event.

(36)

Stormwater. Stormwater runoff, snow melt runoff, surface runoff, and surface drainage.

(37)

Use. Any purpose for which a building or other structure or a tract of land may be designed, arranged, intended, maintained, or occupied; or any activity, occupation, business, or operation carried on, or intended to be carried on, in a building or other structure or on a tract of land.

(38)

Watershed. The area drained by a stream or drainage system.

(39)

Water quality. Criteria based on a volume of one and a half (1.5) inches of rainfall, not a storm frequency.

(Ord. No. 2017-10008, § II, 10-26-17)