For the purpose of this subchapter, the following definitions shall apply unless the context clearly indicates or requires a different meaning.
BOARD. The County Drainage Board, and any subordinate employee to whom it shall specifically delegate a responsibility authorized by this subchapter.
CAPACITY OF A STORM DRAINAGE FACILITY. The maximum flow that can be conveyed or stored by a storm drainage facility without causing damage to public or private property.
CHANNEL. A natural or artificial watercourse which periodically or continuously contains moving water, or which forms a connecting link between two bodies of water. It has a defined bed and banks which serve to confine the water.
COMPENSATORY STORAGE. An artificial volume of storage within a floodplain used to balance the loss of natural flood storage capacity when artificial fill or structures are placed within the floodplain.
CONTIGUOUS. Adjoining, or in actual contact with.
CULVERT. A closed conduit used for the passage of surface drainage water under a roadway, railroad, canal, or other impediment.
DETENTION BASIN. A facility constructed or modified to restrict the flow of stormwater to a prescribed maximum rate, and to detain concurrently the excess waters that accumulate behind the outlet.
DETENTION STORAGE. The temporary detaining or storage of stormwater in storage (detention) basins, on rooftops, in streets, parking lots, school yards, parks, open spaces, or other areas under predetermined and controlled conditions, with the rate of drainage therefrom regulated by appropriately-installed devices.
DRAINAGE AREA. The area from which water is carried off by a drainage system; a watershed or catchment area.
DROP MANHOLE. A manhole having a vertical drop pipe connecting the inlet pipe to the outlet pipe. The vertical drop pipe shall be located immediately outside the MANHOLE.
DRY BOTTOM DETENTION BASIN. A basin designed to be completely dewatered after having provided its planned detention of runoff during a storm event.
DURATION. The time period of a rainfall event.
EROSION. Wearing away of the land by running water, waves, temperature changes, ice, or wind.
FLOOD ELEVATION. The elevation, at all locations, delineating the maximum level of high waters for a flood of given return period and rainfall duration.
FLOOD OR FLOODWATERS. The water of any watercourse which is above the banks of the watercourse. It also means the water of any lake which is above and outside the banks thereof.
FLOOD HAZARD AREA. Any floodplain, floodway, floodway fringe, or any combination thereof which is subject to inundation by the regulatory flood; or any floodplain as delineated by Zone A on a flood hazard boundary map.
FLOODPLAIN. The area adjoining the river and stream which has been, or may hereafter be, covered by floodwaters.
FLOOD PROTECTION GRADE. The elevation of the lowest floor of a building. If a basement is included, the basement floor is considered the lowest floor.
FLOODWAY. See REGULATORY FLOODWAY.
FLOODWAY FRINGE. The portion of the floodplain lying outside the floodway, which is inundated by the regulatory flood.
FOOTING DRAIN. A drain pipe installed around the exterior of a basement wall foundation to relieve water pressure caused by high groundwater elevation.
GRADE. The inclination or slope of a channel, canal, conduit, and the like, or natural ground surface usually expressed in terms of the percentage the vertical rise (or fall) bears to the corresponding horizontal distance.
IMPACT AREAS. Areas defined and mapped by the Board which are unlikely to be easily drained because of one or more factors, including, but not limited to, any of the following: soil type; topography; land where there is not an adequate outlet; a floodway or floodplain; land within 75 feet of each bank of any regulated drain; or land within 75 feet from the centerline of any regulated tile ditch.
IMPERVIOUS. A term applied to material through which water cannot pass, or through which water passes with difficulty.
INLET. An opening into a storm sewer system for the entrance of surface stormwater runoff, more completely described as a storm sewer inlet.
JUNCTION CHAMBER. A converging section of conduit, usually large enough for a person to enter, used to facilitate the flow from one or more conduits into a main conduit.
LATERAL STORM SEWER. A sewer that has inlets connected to it, but has no other storm sewer connected.
MAJOR DRAINAGE SYSTEM. Drainage systems carrying runoff from an area of one or more square miles.
MANHOLE. Storm sewer structure through which a person may enter to gain access to an underground storm sewer or enclosed structure.
MINOR DRAINAGE SYSTEMS. Drainage systems having an area of less than one square mile.
OFF-SITE. Everything not on-site.
ON-SITE. Located within the controlled area where runoff originates.
OUTFALL. The point or location where storm runoff discharges from a sewer or drain. Also applies to the outfall sewer or channel which carries the storm runoff to the point of OUTFALL.
PEAK FLOW. The maximum rate of flow of water at a given point in a channel or conduit resulting from a particular storm or flood.
RADIUS OF CURVATURE. Length of radius of a circle used to define a curve.
RAINFALL INTENSITY. The cumulative depth of rainfall occurring over a given duration, normally expressed in inches per hour.
REACH. Any length of river, channel, or storm sewer.
REGULATED AREA. All of the land in the county that is not located within a municipality.
REGULATORY FLOOD. The flood having a peak discharge which can be equaled or exceeded on the average of once in a 25-year period, as calculated by a method and procedure which is acceptable to the Board. If a permit from the National Resources Commission for construction in the floodway is required (see § 153.04), then the regulatory flood peak discharge should be calculated by a method acceptable to the Board and the Natural Resources Commission. This REGULATORY FLOOD is equivalent to a flood having a probability of occurrence of 4% in any given year.
REGULATORY FLOODWAY. The channel of a river or stream, and those portions of the floodplains adjoining the channel which are reasonably required to carry and discharge the peak flow of the regulatory flood of any river or stream.
RELEASE RATE. The amount of stormwater released from a stormwater control facility per unit of time.
RETURN PERIOD. The average interval of time within which a given rainfall event will be equaled or exceeded once. A flood having a RETURN PERIOD of 25 years has a 4% probability of being equaled or exceeded in any one year.
RUNOFF COEFFICIENT. A decimal fraction relating the amount of rain which appears as runoff and reaches the storm drainage system to the total amount of rain falling. A COEFFICIENT of one-half implies that 50% of the rain falling on a given surface appears as stormwater runoff.
SEDIMENT. Material of soil and rock origin, transported, carried, or deposited by water.
SEMI-IMPERVIOUS. Land surfaces which partially restrict the penetration of water; included as examples are porous concrete and asphalt pavements, limerock, and certain compacted soils.
SIPHON. A closed conduit, or portion of, which lies above the hydraulic grade line, resulting in a pressure less than atmospheric and requiring a vacuum within the conduit to start the flow. A SIPHON utilizes atmospheric pressure to effect or increase the flow of water through a conduit. An inverted SIPHON is used to carry stormwater flow under an obstruction, such as a sanitary sewer.
SPILLWAY. A waterway in or about a hydraulic structure for the escape of excess water.
STILLING BASIN. A basin used to slow water down or dissipate its energy.
STORAGE DURATION. The length of time that water may be stored in any stormwater control facility, computed from the time water first begins to be stored.
STORM SEWER. A closed conduit for conveying collected stormwater.
STORMWATER DRAINAGE SYSTEM. All means, natural or human-made, used for conducting stormwater to, through, or from a drainage area to any of the following: conduits and appurtenant features; canals; channels; ditches; streams; culverts; streets; and pumping stations.
STORMWATER RUNOFF. The water derived from rains falling within a tributary basin, flowing over the surface of the ground, or collected in channels or conduits.
TRIBUTARY. Contributing stormwater from upstream land areas.
URBANIZATION. The development, change, or improvement of any parcel of land consisting of one or more lots for residential, commercial, industrial, institutional, recreational, or public utility purposes.
WATERCOURSE. Any river, stream, creek, brook, branch, natural, or human-made drainage way in, or into which, stormwater runoff or floodwaters flow either regularly or intermittently.
WATERSHED. See DRAINAGE AREA.
WET BOTTOM DETENTION BASIN (RETENTION BASIN). A basin designed to retain a permanent pool of water after having provided its planned detention of runoff during a storm event.
(Ord. 2007-10, passed - -)