[R.O. 1992 § 420.015; Ord. No. 16-11557, 8-15-2016, effective 3-1-2017]
For the purposes of this Chapter,
the following terms shall be deemed to have the meaning indicated
below:
BEST MANAGEMENT PRACTICES or BMPs
Practices, procedures or a schedule of activities to reduce
the amount of sediment and other pollutants in stormwater discharges
associated with construction and grading activities.
DESIGN STORM EVENT
A storm of a specified duration expected to occur having
a given probability of occurrence in any given year, generally described
in frequency intervals.
1.
A 100-year storm event will have
a one (1) in one hundred (100) [one percent (1%)] chance of occurring
in any given year.
2.
A twenty-year storm event: five percent
(5%).
3.
A ten-year storm event: ten percent
(10%).
DETENTION FACILITY
A surface water runoff storage facility that is normally
dry but is designed to hold (detain) surface water temporarily during
and immediately after a runoff event.
DIFFERENTIAL RUNOFF
The difference between the calculated volume and rate of
runoff discharged from a site after development versus the calculated
volume and rate of runoff discharged from the predeveloped site.
DITCH or DRAIN
Any watercourse or conduit, whether open or enclosed, natural
or artificial, by which waters coming or falling upon lands are carried
away.
DRAINAGE STRUCTURES
Those structure other than ditch, drain or pumping plants
which are intended to promote or aid drainage. Such structures may
be independent from other drainage work or may be part of or incidental
to such work. The term includes, but is not restricted to, dams, catch
basins, bulkheads, walls, spillways, flumes, drop boxes, pipe outlets,
junction boxes and structures, the primary purpose of which is to
prevent the erosion of soil into a drain.
FILTER STRIP
A belt of vegetation preserved to protect the stream bank,
provide infiltration, intercept sediment and other pollutants and
reduce stormwater flow and velocity.
FREEBOARD
The difference in elevation between the top of the detention
basin dam and the design surface water elevation.
MAJOR STORM EVENT
A storm of a specific duration expected to occur with a frequency
of once every one hundred (100) years.
RATIONAL METHOD
An empirical formula for calculating peak rates of runoff
resulting from rainfall.
RETENTION FACILITY
A surface water runoff storage facility always contains (retains)
a substantial volume of water to serve recreational, aesthetic, water
supply or other functions. Surface water is temporarily stored above
the normal stage during and immediately after runoff events.
SCS TR-55
Soil Conservation Service Technical Release 55, Urban Hydrology
for Small Watersheds, from the Natural Resources Conservation Service.
STORMWATER MANAGEMENT PLAN
The drawings, computations, data, proposed contours, reports,
etc., that identify how stormwater runoff is to be handled.
STORMWATER MANAGEMENT SYSTEM
All means, natural or man-made, used for conducting stormwater
runoff to, through or from a drainage area to the point of outlet.
STORMWATER RUNOFF
Water that results from precipitation which is not absorbed
by soil, evaporated into the atmosphere or entrapped by ground surface
depressions and vegetation.
STREAMBANK
Top of existing: The top of the natural incline bordering
a stream.
TIME OF CONCENTRATION
An estimate of the time of surface water flow from the hydraulically
most remote part of the drainage area to the point in question.
TRIBUTARY AREA
All of the area that contributes stormwater runoff to a given
point.