ADVERSE IMPACTS: Any deleterious impact on water resources or wetlands affecting their beneficial uses including recreation, aesthetics, aquatic habitat, quality, and quantity.
APPLICANT: Any person, firm, or governmental agency who executes the necessary forms to procure official approval of a development or permit to carry out construction of a development from the county.
BASE FLOOD ELEVATION: The elevation at all locations delineating the level of flooding resulting from the 100-year frequency flood event.
BEST MANAGEMENT PRACTICE (BMP): A measure used to control the adverse stormwater related effects of development. BMPs include structural devices (e.g., swales, filter strips, infiltration trenches, and detention basins. Refer to the current acceptable standards shown in the environmental protection agency urban manual and/or the soil and water conservation district standards.) designed to remove pollutants, reduce runoff rates and volumes, and protect aquatic habitats. BMPs also include nonstructural approaches, such as public education efforts to prevent the dumping of household chemicals into storm drains.
BYPASS FLOWS: Stormwater runoff from upstream properties tributary to a property's drainage system but not under its control.
CHANNEL: Any river, stream, creek, brook, branch, natural or artificial depression, ponded area, flowage, slough, ditch, conduit, culvert, gully, ravine, wash, or natural or manmade drainageway, which has a definite bed and bank or shoreline, in or into which surface or ground water flows, either perennially or intermittently.
CHANNEL MODIFICATION: Alteration of a channel by changing the physical dimensions or materials of its bed or banks. Channel modification includes damming, riprapping (or other armoring), widening, deepening, straightening, relocating, lining, and significant removal of bottom or woody rooted vegetation. Channel modification does not include the clearing of debris or removal of trash.
COMPENSATORY STORAGE: An artificially excavated, hydraulically equivalent volume of storage within the floodplain used to balance the loss of natural flood storage capacity when fill or structures are placed within the floodplain.
CONDUIT: Any channel, pipe, sewer or culvert used for the conveyance or movement of water, whether open or closed.
DETENTION BASIN: A facility constructed or modified to provide for the temporary storage of stormwater runoff and the controlled release by gravity of this runoff at a prescribed rate during and after a flood or storm.
DETENTION TIME: The mean residence time of stormwater in a detention basin.
DEVELOPMENT: Any manmade change to real estate, including:
A. Preparation of a plat of subdivision for three (3) or more parcels;
B. Construction, reconstruction, placement of a building for business or industrial purposes or any addition to a building for business or industrial purposes or any improvement to the property or site;
C. Redevelopment of a site for commercial and/or industrial purposes;
D. Filling, dredging, grading, clearing, excavating, paving, or other nonagricultural alterations of the ground surface;
E. Storage or stockpiling of materials or deposit of nonagricultural solid or liquid waste;
F. Any other activity that might alter the magnitude, frequency, deviation, direction, or velocity of stormwater flowing from a property.
DRAINAGE PLAN: A plan, including engineering drawings and supporting calculations, which describes the existing stormwater drainage system and environmental features, as well as the drainage system and environmental features which are proposed after development of a property.
DRY BASIN: A detention basin designed to drain completely after temporary storage of stormwater flows and to normally be dry over the majority of its bottom area.
EROSION: The general process whereby earth is removed by flowing water or wave action.
EXCESS STORMWATER RUNOFF: The volume and rate of flow of stormwater discharged from a developed drainage area which is or will be in excess of that volume and rate which pertained before development.
FLOOD FRINGE: That portion of the floodplain outside of the regulatory floodway.
FLOOD PRONE AREA: Property located outside areas delineated as zone A or zone AE according to the Ogle County, Illinois, flood insurance rate maps but which are subject to occasional flooding.
FLOODPLAIN: That land adjacent to a body of water with ground surface elevations at or below the base flood or the 100-year frequency flood elevation. The floodplain is also known as the special flood hazard area (SFHA).
FLOODWAY: The channel and that portion of the floodplain adjacent to a stream or watercourse which is needed to store and convey the anticipated existing and future 100-year frequency flood discharge with no more than a 0.1 foot increase in stage due to any loss of flood conveyance or storage and no more than a ten percent (10%) increase in velocities.
HYDROGRAPH: A graph showing for a given location on a stream or conduit, the flow rate with respect to time.
INFILTRATION: The passage or movement of water into the soil surfaces.
MAJOR DRAINAGE SYSTEM: That portion of a drainage system needed to store and convey flows beyond the capacity of the minor drainage system.
MINOR DRAINAGE SYSTEM: That portion of a drainage system designed for the convenience of the public. It consists of street gutters, storm sewers, small open channels, and swales and where manmade, is usually designed to handle the 10-year runoff event or less.
MITIGATION: Includes those measures necessary to minimize the negative effects which stormwater drainage and development activities might have on the public health, safety and welfare. Examples of mitigation include compensatory storage, soil erosion and sedimentation control, and channel restoration.
NATURAL: Conditions resulting from physical, chemical, and biological processes without intervention by man.
100-YEAR EVENT: A rainfall, runoff, or flood event having a one percent (1%) chance of occurring in any given year.
PEAK FLOW: The maximum rate of flow of water at a given point in a channel or conduit.
POSITIVE DRAINAGE: Provision for overland paths for all areas of a property including depressional areas that may also be drained by storm sewer.
PROPERTY: A parcel of real estate.
REGULATORY FLOODWAY: The channel, including on stream lakes, and that portion of the floodplain adjacent to a stream or watercourse as designated by the Illinois department of natural resources, office of water resources (OWR), which is needed to store and convey the existing and anticipated future 100-year frequency flood discharge with no more than 0.1 foot increase in stage due to the loss of flood conveyance or storage, and no more than a ten percent (10%) increase in velocities. The regulatory floodways are designated for Ogle County streams on the flood insurance rate maps (FIRMs) prepared by FEMA and dated April 5, 1988, or as may be updated from time to time. To locate the regulatory floodway boundary on any site, the regulatory floodway boundary should be scaled off the FIRMs and located on a site plan, using reference marks common to both maps. Where interpretation is needed to determine the exact location of the regulatory floodway boundary, the OWR should be contacted for the interpretation.
RETENTION BASIN: A facility designed to completely retain a specified amount of stormwater runoff without release except by means of evaporation, infiltration, emergency bypass or pumping.
SEDIMENTATION: The process that deposits soils debris, and other materials either on other ground surfaces or in bodies of water or stormwater drainage systems.
STORM SEWER: A closed conduit for conveying collected stormwater.
STORMWATER DRAINAGE SYSTEM: All means, natural or manmade, used for conducting stormwater to, through or from a drainage area to the point of final outlet from a property. The stormwater drainage system includes, but is not limited to, any of the following: conduits and appurtenance features, canals, channels, ditches, streams, culverts streets, storm sewers, detention basins, swales and pumping stations.
STORMWATER RUNOFF: The waters derived from melting snow or rain falling within a tributary drainage basin which are in excess of the infiltration capacity of the soils of that basin, which flow over the surface of the ground or are collected in channels or conduits.
TIME OF CONCENTRATION: The elapsed time for stormwater to flow from the most hydraulically remote point in a drainage basin to a particular point of interest in that watershed.
TRIBUTARY WATERSHED: All of the land surface area that contributes runoff to a given point.
2-YEAR EVENT: A runoff, rainfall, or flood event having a fifty percent (50%) chance of occurring in any given year.
URBAN RUNOFF POLLUTANTS: Contaminants commonly found in urban runoff which have been shown to adversely affect uses in receiving water bodies. Pollutants of concern include sediment, heavy metals, petroleum based organic compounds, nutrients, oxygen demanding organics (BOD), pesticides, salt and pathogens.
WET BASIN: A detention basin designed to maintain a permanent pool of water after the temporary storage of stormwater runoff.
WETLAND BASIN: A detention basin designed with all or a portion of its bottom area as a wetland. (Ord., 2-22-1999)