Erosion and Sediment Pollution Control Program Manual.pdf

Drainage Area -----The area above a BMP from which runoff would normally drain to that BMP.
Drainage Basin -----A geographic and hydrologic sub-unit of a watershed.
Drainage Density -----The total length of streams in a watershed divided by the drainage area.
Drainage Divide -----The boundary, along a topographic high, between one drainage basin and another.
Drainage Easement -----A legal encumbrance that is placed against a property’s title to reserve specified
privileges for the users and beneficiaries of the drainage facilities contained within the boundaries
of the easement.
Drainage Patterns -----The drainage paths stormwater runoff usually or historically takes through a given
area.
Drainage, Soil -----The frequency and duration of periods when the soil is free from saturation.
Well-drained -----Excess water drains away rapidly, and no mottling occurs within 36” of the
surface.
Moderately Well-drained -----Water is removed from the soil somewhat slowly, resulting in small
but significant periods of wetness. Mottling occurs within 18” to 36” of the surface.
Somewhat Poorly-drained -----Water is removed from the soil slowly enough to keep it wet for
significant periods, but not all the time. Mottling occurs between 8” and 18” of the surface.
Poorly Drained -----Water is removed so slowly that the soil is wet for a large part of the time.
Mottling occurs between 0 and 8” of the surface.
Very Poorly Drained -----Water is removed so slowly that the water table remains at or near the
surface most of the time. There may also be periods of surface ponding. The soil has a
black to gray surface layer with mottles up to the surface.
Drainage Course -----A natural or artificial depression that conveys surface runoff to a larger watercourse,
lake, or bay.
Drawdown -----Lowering of the water surface in an open channel, impoundment, or groundwater aquifer.
Dredge -----To remove sand, gravel, mud, or other materials from the beds of regulated water of the
Commonwealth.
Dredge Material -----Material that has been excavated or dredged from a stream channel, lake, or other
body of surface water.
Dredging -----A method for deepening streams or other water bodies by scraping and removing solid
materials from the bottom.
Drill Seeding -----Planting seed with a drill in relatively narrow rows (usually < 1 foot apart).
Drop Inlet -----In dams, it is a vertical entrance joined to a barrel section of a principal spillway system.
Drop Spillway -----An overall structure in which water drops over a vertical wall onto a protected apron at
a lower elevation.
Drop Structure -----A structure designed to drop water vertically to a lower level, dissipating its surplus
energy, without causing accelerated erosion. See Figure 9.11.
Droughty -----Exhibiting a poor moisture-holding capacity due to high permeability and low fines content.
Drumlin -----An elongated hill or ridge of glacial drift.
Dry Basin -----A basin that has an outlet structure designed so that essentially all stored water will be
drained from the impoundment by gravity.
Dry Weather Flow -----See Base Flow
Dry Well -----1. A catch basin with open bottom and perforated walls used to store rooftop or surface
runoff for infiltration into the ground. 2. A seepage pit.
Dumped Rock Protection -----Sound, durable stone or concrete rubble, insoluble in water and placed by
dumping for the purpose of protecting against erosion, scour or sloughing of a bank.
Dunes -----Ridges or mounds of loose, wind-blown material, usually sand.
Duration Curve -----A graph showing the percentage of time a given flow of a stream will be equaled or
exceeded based upon a statistical study of historic streamflow records.
E
E&S Permit -----Erosion and Sediment Control Permit—A permit required for earth disturbance activities
where the earth disturbance is associated with timber harvesting, road maintenance activities, or
oil and gas activities.
363-2134-008 / March 31, 2012 / Page 514