As used in this chapter, the following terms
shall have the meanings indicated:
CISTERN
An underground reservoir or tank for storing rainwater.
CULVERT
A pipe, conduit or similar structure including appurtenant
works which carries surface water.
DAM
An artificial barrier, together with its appurtenant works,
constructed for the purpose of impounding or storing water or another
fluid or semifluid or a refuse bank, fill or structure for highway,
railroad or other purposes which does or may impound water or another
fluid or semifluid.
DEP
The Pennsylvania Department of Environmental Protection (formerly
the Pennsylvania Department of Environmental Resources).
DESIGN STORM
The magnitude of precipitation from a storm event measured
in probability of occurrence (e.g., fifty-year storm) and duration
(e.g., twenty-four-hour), and used in computing stormwater management
control systems.
DETENTION BASIN
A basin designed to retard stormwater runoff by temporarily
storing the runoff and releasing it at a predetermined rate.
DEVELOPER/APPLICANT
A person, partnership, association, corporation or other entity, or any responsible person therein or agent thereof, that undertakes any regulated activity as defined in §
138-4 of this chapter.
DEVELOPMENT SITE
The specific tract of land for which a regulated activity
is proposed.
DRAINAGE EASEMENT
A right granted by a land owner to a grantee, allowing the
use of private land for stormwater management purposes.
DRAINAGE PLAN
The documentation of the proposed stormwater management controls, if any, to be used for a given development site, the contents of which are established in §
138-18.
EROSION
The removal of soil particles by the action of water, wind,
ice, or other geological agents.
FREEBOARD
The incremental depth of a stormwater management structure,
provided as a safety factor of design, above that required to control
or convey the design runoff event.
HOKENDAUQUA CREEK STUDY AREA
The area comprised of the Hokendauqua Creek Watershed and
Lehigh River Sub-Basin 3 (Dry Run and four direct drainage subareas).
See map in Appendix A (provides area located within Lehigh Township only).
INFILTRATION STRUCTURE
A structure designed to direct runoff into the ground (e.g.,
French drain, seepage pit or seepage trench).
LAND DEVELOPMENT
A.
The improvement of one lot or two or more contiguous
lots, tracts or parcels of land for any purpose involving:
(1)
A group of two or more buildings; or
(2)
The division or allocation of land or space
between or among two or more existing or prospective occupants by
means of, or for the purpose of, streets, common areas, leaseholds,
condominiums, building groups or other features.
MAINSTEM (MAIN CHANNEL)
Any stream segment or other conveyance in a Single Release
Rate, Dual Release Rate or Conditional No Detention I subarea used
as a reach in any DEP approved Act 167 study area hydrologic model.
In Conditional No Detention II subareas the main channel is the Lehigh
River.
MANNING EQUATION (MANNING FORMULA)
A method for calculation of velocity of flow (e.g., feet
per second) and flow rate (e.g., cubic feet per second) in open channels
based upon channel shape, roughness, depth of flow and slope. "Open
channels" may include closed conduits so long as the flow is not under
pressure.
MUNICIPALITY
Lehigh Township, Northampton County, Pennsylvania.
PEAK DISCHARGE
The maximum rate of flow of storm runoff at a given point
and time resulting from a specified storm event.
PENN STATE RUNOFF MODEL (CALIBRATED)
The computer-based hydrologic modeling technique adapted
to the Watershed for the Act 167 Plan. The model has been "calibrated"
to reflect actual recorded flow values by adjusting key model input
parameters.
RATIONAL METHOD
A method of peak runoff calculation using a standardized
runoff coefficient (rational "c"), acreage of tract and rainfall intensity
determined by return period and by the time necessary for the entire
tract to contribute runoff. The rational formula is stated as follows:
Q = CiA, where "Q" is the calculated peak flow rate in cubic feet
per second, "C" is the dimensionless runoff coefficient (see Appendix
C), "i" is the rainfall intensity in inches per hour, and
"A" is the area of the tract in acres.
REACH
Any natural or man-made runoff conveyance channels used for
modeling purposes to connect subareas and transport flows downstream.
REGULATED ACTIVITIES
Actions or proposed actions which impact upon proper management of stormwater runoff and which are governed by this chapter as specified in §
138-4.
RELEASE RATE
The percentage of the predevelopment peak rate of runoff
for a development site to which the postdevelopment peak rate of runoff
must be controlled to protect downstream areas.
RETURN PERIOD
The average interval in years over which an event of a given
magnitude can be expected to recur. For example, the twenty-five-year
return period rainfall or runoff event would be expected to recur
on the average once every 25 years.
RUNOFF
That part of precipitation which flows over the land.
SCS
The former Soil Conservation Service, U.S. Department of
Agriculture, now known as the "NRCS."
SEEPAGE PIT/SEEPAGE METHOD
An area of excavated earth filled with loose stone or similar
material and into which surface water is directed for infiltration
into the ground.
SOIL-COVER-COMPLEX METHOD
A method of runoff computation developed by NRCS which is
based upon relating soil type and land use/cover to a runoff parameter
called a "curve number."
STORAGE INDICATION METHOD
A reservoir routing procedure based on solution of the continuity
equation (inflow minus outflow equals the change in storage for a
give time interval) and based on outflow being a unique function of
storage volume.
STORM DRAINAGE PROBLEM AREAS
Areas which lack adequate stormwater collection and/or conveyance
facilities and which present a hazard to persons or property. These
areas are either documented in the applicable Act 167 stormwater management
reports or identified by the municipality or Municipal Engineer.
STORM SEWER
A system of pipes or other conduits which carries intercepted
surface runoff, street water and other wash waters, or drainage, but
excludes domestic sewage and industrial wastes.
STORMWATER MANAGEMENT PLAN
Any plan for managing stormwater runoff adopted by Northampton
County for a watershed as required by the Act of October 4, 1978,
P.L. 864 (Act 167), and known as the "Storm Water Management Act."
SUBAREA
The smallest unit of watershed breakdown for hydrologic modeling
purposes for which the runoff control criteria have been established
in the stormwater management plan.
SUBDIVISION
The division or redivision of a lot, tract or parcel of land
by any means into two or more lots, tracts, parcels or other divisions
of land including changes in existing lot lines for the purpose, whether
immediate or future, of lease, transfer of ownership or building or
lot development.
SWALE
A low-lying stretch of land which gathers or carries surface
water runoff.
TOWNSHIP
Lehigh Township, Northampton County.
TROUT/BERTSCH CREEK STUDY AREA
The area comprised of the Trout/Bertsch Creek Watershed and
Lehigh River Sub-Basin 1 (three unnamed creeks and direct drainage
areas). See map in Appendix B (provides area located in Lehigh Township only).
WATERCOURSE
Any channel of conveyance of surface water having defined
bed and banks, whether natural or artificial, with perennial or intermittent
flow.