Definitions Flashcards
Abrasion
Wearing away by friction
Alignment
The course along which the centerline of a roadway or channel is located
Angle of Repose
The angle that the sloping face of a bank of loose earth or gravel or other material makes with the horizontal
Antecedent Precipitation
Rainfall that has recently preceded the storm event being analyzed
Area Drain
A structure for collecting runoff from relatively small, paved areas
Backfill
Earth or other material used to replace material removed during construction, such as in pipeline and culvert trenches and behind retaining walls.
Base (Course)
A layer of specified or selected material of planned thickness, constructed on the subbase or on the natural subgrade to distribute the load and provide drainage, or on which a wearing surface or a drainage structure is placed
Bearing Capacity (Soil)
The load-supporting capacity of a soil
Bench
A horizontal or sloping step in a slope
Bioretention
A technique that uses parking lot islands, planting strips, or swales to collect and filter storm water
Blading
Planning or smoothing the ground surface
Borrow
Fill material imported to a site
Borrow Area
A source of earth fill materials used in the construction of embankments or other earth fill structures
Brushlayering
Live branch cuttings laid in crisscross fashion on benches between successive lifts of soil
Caisson
Similar to pile; however, rather than driven, holes are drilled into the ground and filled with concrete
Catch Basin
A receptacle, with a sediment bowl or sump, for diverting surface water to a subsurface pipe
Centerline
The survey line in the center of a road, ditch, or similar project
Channel
A natural stream, or a ditch or swale constructed to convey water
Cluster Development
A land planning technique to concentrate buildings on a portion of a site in order to preserve open space and environmentally sensitive areas
Compaction
The densification of a soil by a mechanical process
Constructed Wetland
Artificially created wetland primarily to treat point and non-point sources of water pollution
Continuity Equation
A formula expressing the principle of conservation of mass as applied to the flow of water (or other fluids of constant density.) It states that the product of cross section of flow and velocity at any point in a channel is a constant
Contour Line
An imaginary line, or its representation on a map, following all points at the same elevation above or below a given datum
Critical Depth
The depth of flow in an open channel at which critical flow occurs. For a given flow rate, depths greater than critical result in subcritical, or tranquil flow. Those smaller than critical result in supercritical, or rapid, flow
Critical Flow
An unstable flow condition in an open channel that occurs at critical depth
Critical Velocity
The velocity at which unstable flow conditions begin to occur
Crown
The rise or difference in elevation between the edge and the centerline of a roadway
Culvert
Any structure, not classified as a bridge, that provides a waterway or other opening under a road
Cut Section (Or Cut)
The part of the ground surface that, when graded, is lower than the original ground
Datum
A horizontal reference plane used as a basis for computing elevations
Detention Basin (Dry Pond)
An impoundment, normally dry, for temporarily storing storm runoff from a drainage area to reduce the peak rate of flow.
Field Dimension
Dimension that must be measured on site, usually after site elements have been constructed
Fixed Dimension
Dimension that locates site elements with a high level of accuracy
Flexible Dimension
Dimension that has a greater tolerance with regard to acceptable levels of accuracy
Semifixed Dimension
Dimension located in reference to a fixed dimension
Discharge (q)
Flow rate in a culvert, pipe, or channel
Diversion
A channel, with or without a supporting ridge on the lower side, constructed across a slope to intercept surface runoff
Drainage
Interception and removal of groundwater or surface water by artificial or natural streams
Drainage Area
The area drained by a channel or subsurface water by artificial or natural means
Edaphology
The study of the soil from the standpoint of higher plants and crop production
Elevation
(a) The altitude relative to a given datum
(b) A scale drawing of the facade of a structure
Embankment
A bank of earth, rock, or other material constructed above the natural ground surface
Emergency Spillway
A channel for safely conveying flood discharges exceeding the capacity of the principal spillway of a detention or retention pond
Erodibility
Susceptibility of soil material to detachment and transportation by running water or wind
Erosion
Detachment and movement of soil or rock fragments by water wind, ice, and gravity
Excavation
(a) The act of taking out materials
(b) The hollow or depression after the materials have been removed
Fiber Rolls
Prefabricated tubes consisting of biodegradable materials such as coconut fiber or rice and wheat straw
Fill Section (or Fill)
The part of the ground surface that, when graded, is higher than the original ground
Filter Strip
A vegetated buffer zone for removing sediments and pollutants before runoff reaches ponds, waterways, or other drainage facilities
Fine Grade
Preparation of the subgrade preceding placement of surfacing materials
Foundation
The portion of a structure (usually below ground level) that distributes the pressure to the soil or to artificial supports
Free Water
Soil water that moves by gravity, in contrast to capillary and hydroscopic water
French Drain
A trench filled with coarse aggregate (with or without a pipe) for intercepting and conveying groundwater
Gabion
A compartmented rectangular container made of steel wire mesh and filled with stone. Gabions are used for erosion control and retaining wall purposes
Geosynthetics
Degradable and nondegradable products used for a variety of purposes including soil and slope stabilization, erosion and sediment control, soil reinforcement, and subsurface drainage
Geotextiles
Woven and nonwoven permeable fabrics and grids used for soil-related construction projects
Finished Grade
The completed surfaces of lawns, walks, and roads brought to grades as designed
Natural Grade
The undisturbed natural surface of the ground
Subgrade
The grade established in preparation for top surfacing of roads, lawns, etc.
Gradient
The degree of inclination of a surface, road, or pipe, usually expressed as a percentage
Grading
Modification of the ground surface by cuts and/or fills. Fine or finish grading is light or thin grading to finish a prepared earth surface
Grassed Waterway
A natural or constructed channel, usually broad and shallow, covered with erosion-resistant vegetation, used to conduct surface runoff
Gravel
Aggregate composed of hard, durable stones or pebbles, crushed or uncrushed, often mixed with sand
Groundwater
Free subsurface water, the top of which is the water table
Gutter
An artificially surfaced and generally shallow waterway, usually provided at the sides of a roadway for carrying surface drainage
Headwall
A vertical wall at the end of a culvert to support the pipe and prevent earth from spilling into the channel
Hydraulic Radius
The cross-sectional area of flow of a pipe or channel divided by the wetted perimeter
Hydrograph
A graph showing, for a given point on a channel, the discharge, stage, velocity, or other property of water with respect to time
Hydrologic Condition
A term describing the vegetative cover, residue, and surface roughness of a soil as they may affect potential runoff
Hydrologic Cycle
The concept of a closed system, involving the transformation of water from the vapor phase to the liquid (and solid) phase and back to the vapor phase, and the movement of that water
Hydrologic Soil Group (HSG)
A soil classification system based on infiltration and potential runoff characteristics
Imperviousness
The property of a material through which water will not flow under ordinary hydrostatic pressure
Infiltratoin
The downward entry of water into the immediate surface of a soil or other material, as contrasted with percolation, which is movement of water through soil layers or material
Infiltration Basin
An open-surface storage area with no outlet, except an emergency spillway, that permits runoff to infiltrate the soil
Initial Abstraction (Ia)
Losses before runoff begins, including infiltration, evaporation, interception by vegetation, and water retained in surface depressions
Inlet
An arrangement for conveying surface water to an underdrain
Intercepting Ditch
An open drain to prevent surface water from flowing down a slope by conducting it around the slope
Interpolation (topographic)
The process of determining the location of elevations from the plotted locations of known elevations
Invert
The lowest point of the internal cross section of a pipe or channel
Layout Plan
Drawing that dimensionally located site elements to be constructed
Lift
Fill or base course material placed in successive layers. Each layer is properly compacted prior to the placement of the next layer.
Live Fascines
Bound, elongated, sausage-like bundles of live cut branches that are placed in shallow trenches, partly covered with soil, and staked in place to arrest erosion and soil slippage
Live Stake
Cuttings from living branches tamped or inserted into the earth that will eventually root and leaf out
Low-Flow Channel
A small ditch constructed in flat bottoms of larger ditches or detention basins to facilitate their drainage during periods of low flow.
Manhole
A structure, covered with a lid, that allows a person to enter a space below ground level
Manning’s Equation
A formula for calculating the velocity of flow in a channel as a function of relative roughness, cross-sectional configuration, and gradient
Maximum Potential Retention (S)
The greatest proportion of precipitation that could possibly be retained by a specific soil and land use combination
Modified Rational Method (MRM)
An extension of the Rational method for calculating the rate of runoff from a drainage area. It includes provisions for antecedent precipitation and for developing hydrographs
Moisture Content
The percentage, by weight, of water contained in soil or other material, usually based on dry weight
Monument
A boundary stone or other permanent marker location a property line or corner
NRCS
Natural Resources Conservation Service (formerly Soil Conservation Service), a federal agency in the Department of Agriculture, dealing with erosion and flood control
Outlet
Point of water disposal from a stream, river, lake, tidewater, or artificial drain
Peak Discharge
The maximum instantaneous flow rate resulting from a given storm condition at a specific location
Pedology
The study of the soil as a natural body, including its origin, characteristics, classification, and description
Percolation
Movement of soil water toward the water table
Perron
An exterior platform at a building entrance, usually with steps leading up to it
Pervious
The property of a material that permits movement of water through it under ordinary hydrostatic pressure
pH
A measure of alkalinity or acidity, with pH 7 being neutral and pH 6.5 being a desirable degree of soil acidity
Pile
Vertical structural member made of concrete or steel that is driven into the ground by a pile driver until there is significant resistance or bedrock is reached to support the intended load
Point of Beginning (POB)
Establishes a reference point that serves as the origin for site dimensioning
Porous
Having many small openings through which liquids may pass
Porous Pavement
A pavement constructed from a material that permits percolation of storm water to the subgrade
Principal Spillway
A component of retention or detention ponds, generally constructed of permanent materials. It is designed to regulate the normal water level, provide flood protection, and/or reduce the frequency of operation of the emergency spillway
Rainfall Intensity (i)
The rate at which rain falls, measured in inches per hours (iph) or millimeters per hour (mm/h)
Ramp
An inclined plane serving as a way between two different levels
Rational Method
A formula for calculating the peak runoff rate from a drainage area based on land use, soils, land slope, rainfall intensity, and drainage area
Recession, or Receding Limb (of a Hydrograph)
The portion of a hydrograph that occurs after the peak when the flow rate decreases
Retaining Wall
A wall built to support a bank of earth
Retention Basin (Wet Pond)
A reservoir; containing a permanent pool, for temporarily storing storm runoff and reducing the storm runoff rate from a drainage area
Right of Way
The entire strip of land dedicated for highway purposes
Riprap
Stones or other material placed on a slope to prevent erosion by water
Rising Limb (of a hydrograph)
The portion of a hydrograph preceding the peak when the flow rate increases
Rough Grade
Stage of grading operation in which the desired landform is approximately attained
Roughness Coefficient (n)
A factor in the Manning formula representing the effect of channel or conduit roughness on energy losses in the flowing water
Runoff
That part of precipitation carried off from the area on which it falls. Also, the rate of surface discharge of the above. (The ratio of runoff to precipitation is a coefficient, expressed as a decimal.)
Runoff Curve Number (CN)
A parameter used in NRCS (SCS) hydrological techniques, based on soil characteristics and land use
SCS
Formerly the Soil Conservation Service, now known as the Natural Resources Conservation Service (NRCS), a federal agency in the Department of Agriculture, dealing with erosion and flood control.
Sediment
Solid material, both mineral and organic, in suspension, being transported, or having been moved from its original site by air, water, gravity, or ice
Sediment Basin
A reservoir formed by the construction of a barrier or dam built at a suitable location to permit the settling out of sediments (e.g., rock, sand, gravel, silt, or other material) before releasing the water.
Shallow Concentrated Flow
Flow in shallow rills
Shear Stress (Channel)
Force per unit area exerted on the wetted area of a channel, acting in the direction of flow
Sheet Flow
Flow over plane, sloped surfaces on a thin layer
Shoulder
The portion of roadway between the edge of the hardened wearing course and the ditch or embankment
Sight Distance
The distance between approaching vehicles when first visible to one another on a horizontal or vertical curve
Slide
Movement of soil on a slope resulting in a reduced angle of repose, usually occurring as a result or rainfall, high water, or thaw
Slope
The face of an embankment or a cut section. Any ground whose surface makes an angle with the horizontal plane
Soil Bioengineering
Use of live, woody vegetative cuttings to repair slope failures and increase slope stability
Splash Block
A masonry block with its top close to the ground surface, which receives roof drainage and prevents erosion below the spout
Storage (Runoff)
Runoff that is temporarily impounded to permit control of the runoff rate and/or to improve water quality
Storm Sewer
A conduit used for conveyance of rainwater
Structure
Anything constructed that requires a permanent location on the ground or is attached to something having a permanent location on the ground
Subdrain
A pervious backfilled trench containing a pipe with perforations or open joints for the purpose of intercepting groundwater or seepage
Superelevation
The rise of the outer edge of the pavement relative to the inner edge at a curve in the highway, expressed in feet per foot, intended to overcome the tendency of speeding vehicles to overturn when rounding a curve
Swale
A constructed or natural grassed or vegetated waterway
Tangent
A straight road segment connecting two curves
Terrace
An essentially level and defined area, usually raised, either paved or planted, forming part of a garden or building setting
Time of Concentration (Tc)
The time for water to flow from the hydraulically most remote point in a drainage area to the point of interest
Time of Recession (Trec)
The period of time from the peak of a hydrograph until it reaches the beginning flow rate
Time of Rise (of a Hydrograph) (Trise)
The period of time from the beginning flow rate until the peak flow rate is reached
Travel Time (Tt)
The time for runoff to flow from one point in a drainage area to another
Trench Drain
A linear structure that collects runoff from a paved area
Vegetated Structures
A retaining wall system in which living plants or cuttings have been integrated into the structure
Vegetative Cuttings
Live, cut stems and branches of plants that will root when embedded or inserted in the ground
Water Quality Basin
A reservoir that has a provision for removing pollutants from storm runoff by retaining the runoff from high-frequency storms (i.e., those with 1- or 2-year frequencies) for prolonged periods (i.e., from 18 to 36 hours)
Watershed
Region or area contributing to the supply of a stream or lake. (Also, a drainage basin or catchment area.)
Water Table
The level below which the ground is saturated.
Waterway
A natural course, or a constructed channel, for the flow of water
Weephole
A small hole, as in retaining wall, to drain water to the outside
Weir
An opening in the crest of a dam or an embankment to discharge excess water; also used for measuring the rate of discharge
Lumen
A quantitative unit of measurement referring to the total amount of light energy emitted by a light source, without regard to the direction of its distribution
Footcandle (fc)
A U.S. unit of measurement referring to incident light.
Footcandles can be derived from lumens (1 fc = 1 lumen/sq ft) or candelas (fc = candelas/distance^2)
Lux (lx)
The International Standard (SI) measure of incident light.
It is equal to one lumen uniformly distributed over an area of one square meter (10.7 lx = 1 fc)
Candlepower
The unit of intensity of a light source in a specific direction, often referred to as Candela. One candela directed perpendicularly to a surface one foot away generates one footcandle of light.
Illuminance
Incident light, or light striking a surface
Luminance
Light leaving a surface, whether due to the surface’s reflectance, or because it is the surface of a light-emitting object (like a light bulb). Luminance is the measurable form of brightness, which is a subjective sensation.
Efficacy
A measure of how efficiently a lamp converts electric power (watts) into light energy (lumens) without regard to the effectiveness of its illumination.
It should not be assumed that a lamp which has high efficacy will give better illumination than a less efficient lamp
Light depreciation
Lamp output (lumens) will depreciate over its effective life. Illumination will be reduced further due to an accumulation of dirt and grime on the lamp and fixture. Adjustments should be made to compensate for this depreciation when determining the average values of illumination maintained over time. A maintenance factor of 50 to 70 percent is common for outdoor applications. New installations are routinely designed to deliver 1- 1/2 to 2 times as much illumination as needed, to sustain this maintained output over the anticipated life of the lamp
Color
Two measures used to describe the color characteristics of lamps are (1) the apparent color and (2) the color rendering index
Container Trees
Young trees in plastic or metal cans. Containers typically come in sizes of 1, 3, 5, and 7 gallons.
Advantages
- Younger trees establish themselves faster and have more flexibility to adapt to the conditions of their new homes
- Container trees can be healthier in the long run than older stock
Disadvantages
- Do not provide “mature” appearance for many years
- May develop circling roots if left in container too long
Balled and Burlapped Trees
The most common medium sized specimens. Field-grown and dug for the planting season, with a ball of field soil retained around the roots. The ball is then wrapped with burlap, or less frequently with plastic cloth or wire cages.
Advantages
- No circling roots
- Can be more hardy than other forms and wrapping the root ball
- More care must be taken at planting time to ensure that the wrapping materials are adequately removed to avoid future root and trunk girdling
Disadvantages
- Some roots may have been damaged or severed in the process of digging
Boxed Trees
Commonly older, larger trees that have been moved to large wooden containers.
Advantages
- Provides instant effect
Disadvantages
- More expensive to purchase and install
- Harder to handle in the field
- Can be slower to recover from transplant
Bare-Root Plants
Sold in a dormant stage. Tops and roots are pruned back, and most of the soil is washed away from the roots.
Advantages
- Cheaper than container plants
- Often establish themselves faster than container plants and can be healthier in the long-run
Disadvantages
- Must be bought and planted in the proper season
- Characteristics like flower and leaf color are not visible at time of purchase
Container Plants
Sold with upper branches and root systems intact and are available year-round
Advantages
- Flower and leaf color are easy to verify
- A wider variety of plant material is available in container form
- Can be planted year-round
Disadvantages
- Can be root-bound, leading to poor root development later
- More expensive than bare-root
Smaller Perennials
Can be found in four-inch pots, either plastic or peat. Plastic pots are handled as container plants and share the same advantages and disadvantages. Peat pots are not as common but have some advantages over plastic pots.
Advantages
- Peat pots can be set directly in the soil and left in place, where they will biodegrade, minimizing root disturbance
Disadvantages
- Peat pots can slow the initial root growth as roots attempt to push through peat walls
Groundcover Containers
Used for large prostrate shrubs that function as groundcovers
Advantages
- Better for large areas of groundcover
- Sturdier at outset
Disadvantages
- Planting grid must be worked out carefully to avoid bare patches
- Take longer to fill in than more closely planted flats
Groundcover Flats
Trays of small, quick-spreading plants that have been started from cuttings or seed. Plants are grown to form a mat of stem and root growth that must be cut into plugs or separated by hand for planting.
Advantages
- Economical, can be planted quickly and easily
Disadvantages
- Smaller root balls are more susceptible to drying out during and immediately after planting
Groundcover Seeds
Are not commonly used in commercial landscaping, although they are popular for home gardeners. Exceptions to this include hydroseeding, regenerative planting techniques, and popular mixtures of wildflower seed that can be scattered to form a “natural” looking meadow within a season
Advantages
- Seed is the cheapest way to plant
- Plants grown from local seed are well-adapted to the site, a necessity for restoration
- It is easier to achieve a random pattern
- If “wildflower mixtures” or “native mixtures” are to be used, the composition of the mix must be checked carefully
Disadvantages
- Patterning of plants is harder to control
- Long growing period before plants begin to bloom, usually much later than greenhouse grown annuals
Groundcover Hydroseeding
Used for vegetative stabilization of slopes that are difficult to access by other means. A chosen seed mixture is sprayed directly onto the slope in a solution of fertilizer and water.
Advantages
- Large areas can be planted quickly and cheaply
- Areas can be planted which are otherwise difficult or impossible
- Choice of seed may be limited
Disadvantages
- Initial appearance is unattractive (the solution is dyed to aid in the application process)
Annuals Multi-Pack
Annuals are sold with each plant in a separate plug of soil
Advantages:
- Economical
- Wide range of plants available in this form
Disadvantages
- Take longer to fill in than larger plants
Annuals Container
Annuals are larger
Advantages
- Mature and fill in faster
Disadvantages
- More expensive than multi-pack
Annual Seeds
Are not commonly used in commercial or residential applications.
Turf Sod
Is grown in a field. Upon ordering, the sod is peeled up, rolled or stacked, and delivered to the site. Sod is the most common way to install lawn turf.
Advantages
- Instant effect
- Good, even coverage
- Has to be installed very soon after delivery
Disadvantages
- Not appropriate for steep slopes or very large areas
Turf Seed
Sown directly into a prepared plot
Advantages
- Economical
- Wide variety available via mail order
Disadvantages
- Slower to grow to finished appearance
- Can require touch-up seeding if initial application was uneven
Turf Sprigged Lawns
Started from plugs of grass planted at set intervals.
Advantages
- Economical
- Faster to establish than seed
Disadvantages
- Take several weeks to fill in
- Requires care to keep weeds from growing between plugs of grass
