Illinois Administrative Code › Title 17 - CONSERVATION › Part 3700 - CONSTRUCTION IN FLOODWAYS OF RIVERS, LAKES AND STREAMS › Section 3700.20 - Definitions

Current through Register Vol. 48, No. 28, July 12, 2024
As used in this Part, the words and terms listed shall have the
				meanings ascribed to them as follows:
"Bridge or Culvert Reconstruction" - The total replacement of
				an existing bridge or culvert, including substructure and superstructure, on
				the existing road alignment or on an alignment within 100 feet upstream or
				downstream of the existing alignment in an urban area, or within 500 feet
				upstream or downstream of the existing alignment in a rural area.
"Construction" - The placement, erection or reconstruction of
				any building or structure, any filling or excavation, the installation of any
				utility, or the storage of any materials. Construction includes, but is not
				limited to, modifications to an existing building that would increase the
				building's outside dimensions, channel modifications and enclosures, roads,
				bridges, culverts, levees, bank protection, walls, fences, and any other
				man-made activity that would modify the physical features of a floodway with
				respect to the storage or conveyance of flood waters. Construction does not
				include normal maintenance and repair activities or farming operations such as
				discing and plowing.
"Department" - The Illinois Department of Natural
				Resources.
Floodplain - The land area adjacent to a stream or watercourse
				with ground surface elevations at or below the 1% annual chance of exceedence
				(100-year frequency) flood elevation.
"Floodway" The channel of a river, lake or stream and that
				portion of the floodplain that is needed to store and convey the 1% annual
				chance of exceedence flood discharge with no more than a 0.1 foot increase in
				stage due to the loss of flood conveyance and storage. Where floodways have
				been delineated for regulatory purposes, the mapped lines show the floodway
				encroachment limits and will be used. For other areas, the entire floodplain
				shall be considered to be in the floodway unless an analysis is approved by the
				Department demonstrating that a project site is outside of the floodway. The
				Department will review floodway delineation analyses provided by the applicants
				to verify that the resulting loss of flood conveyance and storage will result
				in no more than a 0.1 foot increase in stage. The Department will either
				approve or disapprove floodway delineation analyses and inform applicants of
				the reason for disapproval.
"Office of Water Resources" - The Office of Water Resources of
				the Illinois Department of Natural Resources.
"Permittee" - The entity issued a permit pursuant to this
				Part.
"Rural Areas" - All areas of the State not classified as urban
				areas.
"Urban Areas" - Areas of the State where residential,
				commercial or industrial development currently exists or, based on land use
				plans or controls, is expected to occur within 10 years after the application
				date. In determining urban areas, the Department will consider the expertise of
				local officials, regional and local planning commissions, city and county
				planners, or private development planners, as well as all available mapping.
				Areas with only isolated or widely scattered buildings will not be classified
				as urban areas.
"Worst-case Analysis" - The calculation of the maximum
				increases in flood heights, velocities and damages a project would cause due to
				conveyance and storage losses considering both the project alone and the
				combined effects of other existing construction and reasonably anticipated
				equally obstructive construction on other similarly situated properties in the
				locality. Flood events up to and including the flood which has a 1% annual
				chance of exceedence shall be used in this analysis (see Section
				3700.75
				for exception).