Flood and erosion control glossary - C
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Caisson
Concrete box-type structure.
Cap
A layer of material, such as clay or a synthetic
material, used to prevent rainwater from penetrating and spreading contaminated
materials. The surface of the cap is generally mounded or sloped so water will
drain off.
Capillary Fringe
A zone in the soil just above the water
table that remains saturated or almost saturated.
Capillary Wave
A wave whose velocity of propagation is controlled primarily by the surface tension of the liquid in which the wave is traveling. Water waves of length less than about 1 inch are considered capillary waves. Waves longer than 1 inch and shorter than 2 inches are in an indeterminate zone between capillary and gravity waves.
Carbon Adsorption
A treatment system in which contaminants
are removed from groundwater and surface water by forcing water through tanks
containing activated carbon, a specially-treated material that attracts and
hold, or retains, contaminants.
Carrying Capacity
A term most generally used to refer to
the level of use or extent of modification an environmental or man-made system
may bear without experiencing unacceptable resource deterioration or
degradation.
Catch Basin
Box-like underground concrete structure with
openings in curbs and gutters designed to collect runoff from streets and
pavement.
Catch Per Unit Effort (CPUE)
A term used in fisheries
science to standardize catch information. For example, the CPUE for blue crab
harvest might be described as the number of crabs caught per crab pot per day.
Catchline
The point where a severe slope intercepts a
different, gentler slope.
Catchment
An area confined by drainage divides usually having only one streamflow
outlet. In the UK, "catchment" refers
to what in the US is called a watershed.
Caulking
Flexible material used to fill joints in a
structure, such as around windows or doors,
which is able to resist the passage of moisture.
Caving
The collapse of a streambank by undercutting due to
wearing away of the toe or an erodible soil layer above the toe.
CBRA
Abbreviation for Coastal Barrier Resources Act. Established the John
H. Chafee Coastal Barrier Resources System (CBRS), comprised of undeveloped
coastal barriers along the Atlantic, Gulf, and Great Lakes coasts. The law
encourages the conservation of hurricane prone, biologically rich coastal
barriers by restricting Federal expenditures that encourage development, such
as Federal flood insurance through the National Flood Insurance Program. CBRA
is a free-market approach to conservation. These areas can be developed, but
Federal taxpayers do not underwrite the investments. CBRA saves taxpayer
dollars and encourages conservation at the same time. CBRA has saved over $1
billion and will save millions more in the future. Approximately 3.1 million
acres of land and associated aquatic habitat are part of the CBRS. The Fish and
Wildlife Service maintains the repository for CBRA maps enacted by Congress
that depict the CBRS. The Service also advises Federal agencies, landowners,
and Congress regarding whether properties are in or out of the CBRS, and what
kind of Federal expenditures are allowed in the CBRS.
CBRS
Abbreviation for Coastal Barrier Resources System.
CCO
Abbreviation for Consultation Coordination Officer.
CFS or
Cubic Feet Per Second
A rate of flow that would fill a container of
one cubic foot size, that is about 7-1/2 gallons, in one second. One cubic foot
of water equals about 7 1/2 gallons and weighs 62 pounds.
Channel
A natural or artificial watercourse of perceptible extent, with definite bed
and banks to confine and conduct continuously or periodically flowing water.
Channel flow thus is that water which is flowing within the limits of the defined
channel.
Channel Alterations
The improvement of the water carrying
capacity or flow characteristics of a natural or artificial channel by clearing, excavation, bank stabilization
or other means. Also referred to as channelization.
Channel Bar
An elongate deposit of sand or gravel located in the course of a stream or tidal channel.
Channel Capacity
The maximum flow which can pass through a
channel without overflowing the banks.
Channel
Erosion
Includes the processes of streambank erosion, streambed scour, and degradation.
Photo courtesy of USDA NRCS.
|
Channel erosion control structure. |
Channel Flow
Movement of surface runoff in a long narrow trough-like depression bounded by banks or valley walls that slope toward the channel.
Channel Meander
The process by which a portion of an inlet channel turns or winds along an indirect course.
Channel Scour
The erosive action of water and sediment that removes and carries away bed and bank material.
Channel Slope (or Channel Gradient)
The inclination of the channel bottom, measured as the elevation drop per unit length of channel.
Channel Stabilization
Erosion prevention and stabilization
of velocity distribution in a channel using jetties, drops, revetments,
vegetation, and other measures.
Channelization
Alteration of a stream channel by widening, deepening, straightening,
cleaning, or paving certain areas to change flow characteristics.
Check
Dam
A temporary dam across a swale or
gully to reduce gully erosion, or placed bank to bank downstream from a
headcut; often used in series. Small dam constructed in a gully or other small
watercourse to decrease the streamflow velocity, minimize channel scour, and
promote deposition of sediment.
Check Valve
A type of
valve that allows water to flow one way but automatically closes when
water attempts to flow in the opposite direction.
Chlorination
The application of chlorine to water, sewage,
or industrial wastes, generally to disinfect, oxidize, or improve settling.
Clastic Sediment
A sediment formed by the accumulation of fragments derived from preexisting rocks or minerals and transported as separate particles to their places of deposition by purely mechanical agents (such as water, wind, ice, and gravity); gravel, sand, mud, clay.
Clay
Cohesive soil whose individual particles are not
visible to the unaided human eye (less than 0.002 mm in diameter). Clay can be
molded into a ball that will not crumble.
Clay (soils)
(1) A mineral soil separate consisting of
particles less than 0.002 mm in equivalent diameter. (2) A soil textural class.
(3) A fine-grained soil that has a high plasticity index in relation to the
liquid limits.
Clay Lens
A naturally occurring, localized area of clay
which acts as an impermeable layer to runoff infiltration.
Clean Water
Act (CWA)
The Federal Water Pollution Control Act. See www.epa.gov/r5water/cwa.htm.
Climate
The average of patterns of a region or locality,
based upon long-term statistics, including extremes (such as flood and
droughts) and deviations from normals.
Clod
A compact, coherent mass of soil ranging in size from
2 to 5 inches and much larger, produced artificially, usually by the activity
by digging etc., especially when these operations are performed on soils that
are either to wet or too dry for normal soil movement.
CLOMA
Conditional Letter of Map Amendment. A Conditional
Letter of Map Amendment (CLOMA) is FEMA's comment
on whether a proposed project would be excluded from the Special Flood Hazard
Area (SFHA) shown on the effective National Flood Insurance Program (NFIP) map.
There is no appeal period. The letter becomes effective on the date sent. This
letter does not revise an effective NFIP map, it indicates whether the project,
if built as proposed, would or would not be removed from the SFHA by FEMA if
later submitted as a request for a Letter of Map Amendment.
CLOMR
Conditional Letter of Map Revision. A Conditional
Letter of Map Revision (CLOMR) is FEMA's
comment on a proposed project that would affect the hydrologic and/or hydraulic
characteristics of a flooding source and thus result in the modification of the
existing regulatory floodway or effective Base Flood Elevations. There is no
appeal period. The letter becomes effective on the date sent. This letter does
not revise an effective National Flood Insurance
Program map, it indicates whether the project, if built as proposed,
would or would not be removed from the Special Flood Hazard Area by FEMA if
later submitted as a request for a Letter of Map Revision.
CLOMR-F
Conditional Letter of Map Revision based on Fill.
A Conditional Letter of Map Revision based on Fill (CLOMR-F) is FEMA's comment
on whether a proposed project involving the placement of fill would exclude an
area from the Special Flood Hazard Area (SFHA) shown on the National Flood
Insurance Program (NFIP) map. There is no appeal period. The letter becomes
effective on the date sent. This letter does not revise an effective NFIP map,
it indicates whether the project, if built as proposed, would or would not be
removed from the SFHA by FEMA if later submitted as a request for a Letter of
Map Revision based on Fill.
Closed Depression
An area which is low-lying and either
has no, or such a limited, surface water outlet that during storm events the
area acts as a retention basin.
Closure
A shield made of strong material, such as steel,
aluminum, or wood, used to temporarily fill
gaps in floodwalls, levees,
or dry flood proofed structures and protect against water entrance
through areas that have been left open for day-to-day convenience at entrances
such as doors and driveways.
Closure Structure
All openings in levee structures are required to be equipped with sufficiently strong, stable closures, such as gates or stoplogs.
Coast
The strip of land, of indefinite width (up to
several miles), that extends from the shoreline inland to the first major
change in terrain features.
Coastal Barrier
Elongated, offshore formations of sand and
other unconsolidated sediments lying generally parallel to mainland coastlines;
including bay barriers (connected to headlands on both ends), barrier spits
(connected on one end), and barrier islands (bounded on one side by inlets
without attachment to the mainland).
Coastal High Hazard Area
The area subject to high velocity
waters, including, but not limited to, hurricane wave wash or tsunamis. The area is designated on a FlRM as Zone
V1-30.
Coastal Plain
The plain composed of horizontal or gently sloping strata of clastic materials, generally representing a strip of sea bottom that has emerged from the sea in recent geologic time. May extend inland many km.
Coastal Wetlands
Wetlands consisting mainly of tidal
marshes and mudflats that are periodically flooded by saltwater or a mix of
saltwater and freshwater.
Coastal Zone
Lands and waters adjacent to the coast that
exert an influence on the uses of the sea and its ecology, or whose uses and
ecology are affected by the sea.
Code of Federal Regulations
The compilation of federal
regulations. Each area of regulation is contained in a separate volume (e.g.,
environmental regulations are compiled in volume 40, or 40 CFR). Each volume
contains up to several hundred parts.
Cofferdam
A temporary watertight structure enclosing all or part of the construction area so that construction can proceed in the dry.
Cohesive Soil
Microscopic soil particles that have natural
resistance to being pulled apart at their point of contact.
Coir
Coconut fiber.
Coir Log or Coir Roll
Roll of coconut fiber, often used in
bioengineering systems to provide erosion control along a streambank support
the establishment of vegetation.
Column
An upright support unit for a structure that is set
in predug holes and backfilled with
compacted material. Columns are usually of concrete or masonry
construction with steel reinforcement. Columns are sometimes referred to as
posts.
Community Assistance Program (CAP)
The program established
by the Federal Insurance Administration (see www.fema.gov/about/fedins.shtm)
and intended to assure that communities participating in the NFIP are carrying
out the flood loss reduction objectives of the program. The CAP provides needed
technical assistance to NFIP communities and attempts to identity and resolve
floodplain management issues before they develop into problems requiring
enforcement action.
Community Rating System (CRS)
A program developed by the Federal Insurance Administration to encourage- by
use of flood insurance premium adjustments- community and state activities
that go beyond the basic NFIP requirements; the CRS gives communities
"credit" for certain activities to reduce flood losses, facilitate
accurate insurance rating, and promote the awareness of flood insurance.
Compaction
The process by which the soil grains are
rearranged to decrease the void space and bring the grains into closer contact
with one another, and thereby increase the weight of solid material per cubic
foot.
Comparative Assessment
An analysis of characteristics
through the evaluation of a population relative to other members.
Compound Tide
A harmonic tidal (or tidal current) constituent with a speed equal to the sum or difference of the speeds of two or more elementary constituents. The presence of compound tides is usually attributed to shallow water conditions.
Concentration
The relative amount of a substance in a
given medium.
Condensation
The cooling of water vapor until it becomes a
liquid through the release of latent heat.
Conduit
Any pipe for collecting and directing the storm
water.
Confined Aquifers
Aquifers
that are enclosed beneath the water table. Its upper, and perhaps lower, boundary
is defined by a layer of natural material that does not transmit water readily.
Confining Layer
The geological material through which
significant quantities of water cannot move; located below unconfined aquifers, above and below confined aquifers. Also
known as a confining bed.
Confluence
A meeting of two or more streams or rivers.
Core Sampling
A process by which levee strength is tested. Equipment drills deep into the levees at various points to test the stability of the soil and other materials. Core samples help determine whether levee sections meet the 100-year-standard.
Conservation Tillage
Practices that reduce cultivation of
soil, leave a protective vegetative layer on the surface, and thereby serve to
reduce or minimize soil erosion.
Corps Funding Eligibility
Eligibility determination for both federally authorized levees and some non-federal levees for U.S. Army Corps or Engineers rehabilitation assistance funding.
Consolidated Rock
See Bedrock.
Constructed Wetland
A wetland that is created on a site that previously was not a wetland.
This wetland is designed specifically to remove
pollutants from stormwater runoff.
Consumption
Water that is actually consumed, transpired,
or incorporated into new products as it is used.
Consumptive Use
The total amount of water taken up by
vegetation for transpiration or building of plant tissue, plus the unavoidable
evaporation of soil moisture, snow, and intercepted precipitation associated
with vegetal growth.
Contaminated Sediment
Soil, sand, organic matter, or
minerals that accumulate on the bottom of a water body and contain toxic or
hazardous materials at concentrations that may adversely affect human health or
the environment.
Contamination
The impairment of water, sediments, plants,
or animals by chemicals or bacteria to such a degree that it creates a hazard
to public and environmental health through poisoning, bioconcentration
(bioaccumulation), or the spread of disease. Contamination can be naturally
occurring or manmade.
Continental Margin
Edges of continents that are underwater
including the continental shelf, the continental slope and the continental
rise.
Continental Rise
An immense section of sediment located at
the bottom of the continental slope.
Continental Shelf
A gently sloping submarine plane of
varying width extending from the shoreline of a continent to the continental
slope. See Continental Slope and Continental Rise.
Continental Slope
The sloping sea bottom of the
continental margin that begins at the shelf break and ends at the top of the
continental rise. See continental shelf and continental rise.
Contingent (Partial) Flood Proofing
contingent measures
would not be effective unless, upon receipt of a warning or forecast, some
minimal action would be required to make the flood proofing measures
operational.
Continuous Berm
Temporary diversion dike or sediment barrier constructed with soil, sand,
or aggregate encased in geosynthetic fabric.
Contour
An imaginary line on the surface of the ground
connecting points of the same elevation or a line drawn on a map connecting
points of the same elevation.
Contour
Cropping
Tillage and planting of a crop across, rather than in the
direction of, a slope to reduce soil loss.
Photo courtesy of USDA NRCS.
|
Photo of contour strip cropping. |
Contour Lines
Lines on a topographic
map that determine slopes.
Control Basin
Also called a sediment basin, and used in
fields to control runoff and sediment where terraces are impractical due to
topography.
Conveyance
A mechanism for transporting water from one point to another, including pipes, ditches, and channels. A measure of the
carrying capacity of the channel section. Flow is directly proportional to the conveyance.
Conveyance Loss
Water loss in pipes, channels, conduits, ditches by leakage or
evaporation.
Conveyance System
The drainage facilities, both natural
and manmade, which collect, contain, and provide for the flow of surface and stormwater from the highest points on the land down
to a receiving water. The natural elements of the conveyance system include
swales and small drainage courses, streams, rivers, lakes and wetlands. The human-made elements of the conveyance
system include gutters, ditches, pipes, channels,
and most retention/detention facilities.
Cool Season Turfgrass
Species of turfgrass used primarily
in the northern US, such as bluegrass, fescue, bentgrass and ryegrass.
Coring
A method of aerification in which soil cores are
removed by hollow tines or spoons.
Cover
(1) Vegetation or other material providing
protection. (2) Ground and soils, any vegetation producing a protecting mat on
or just above the soil surface. (3) Stream, generally trees, large shrubs,
grasses and forbs that shade and otherwise protect the stream from erosion,
temperature elevation or sloughing of banks. (4) Vegetation, all plants of all
sizes and species found on an area, regardless of whether they have forage or
other value. (5) Wildlife, plants, or objects used by wild animals for nesting,
rearing of young, resting, escape from predators, or protection from adverse
environmental conditions.
Cover Crop
A crop that provides temporary protection for delicate seedlings and/or
provides a cover canopy for seasonal soil protection and improvement between
normal crop production periods. A close-growing crop grown primarily for the
purpose of protecting and improving soil between periods of regular crop
production.
Photo courtesy of USDA NRCS.
|
Photo of cover crops. |
CPESC
Abbreviation for Certified Professional in Erosion and Sediment
Control.
Crawl Space
The area
between the ground surface and the bottom of the first floor of an
elevated structure. The structure is elevated a minimal distance above the
ground so access under the structure is by crawling.
Created
Wetland
A wetland that is created on a
site that previously was not a wetland. This wetland is created to replace
wetlands that were unavoidably destroyed during design and construction of a
project. This wetland cannot be used for treatment of stormwater runoff.
Photo courtesy of USDA NRCS.
|
Photo of created wetland. |
Crest
The highest water level at a given location during a
flood event. Normally the crest will move downstream over time.
Crest Length, Wave
The length of a wave along its crest. Sometimes called Crest Width.
Crest Of Wave
1. The highest part of a wave. 2. That part of the wave above still-water level.
Crib Structure
A hollow structure of mutually
perpendicular interlocking beams.
Critical Area
A severely eroded sediment-producing area
that requires special management to establish and maintain vegetation in order
to stabilize soil conditions.
Critical Areas
Areas subject to erosion due to soil type
or slope including stream crossings.
Cropland
An area cultivated to provide various food products.
Photo courtesy of USDA NRCS.
|
Photo of cropland. |
Cross Section
A graph or plot of ground elevation across a
stream valley or a portion of it, usually along a line perpendicular to the
stream or direction of flow. A vertical profile of the ground surface taken
perpendicular to the direction of the flood flow. The profile is defined by
coordinates of ground elevation and horizontal distance.
Cross-Connection
Any actual or potential connection
between a drinking water system and an unapproved water supply or other source
of contamination.
Crown
The top of a levee.
Crown Wall
Concrete superstructure on a rubble mound.
CRS
Abbreviation for Community Rating System.
C-TRM
Abbreviation for composite turf reinforcement mat.
Cultural Resource Values
Floodplain values associated with
the harvest of natural products (agricultural, aquacultural and forestry uses),
as well as historical/archaeological, scientific and recreation/open space
values.
Culvert
A covered channel
or pipe or covered structure not classified as a bridge that directs water or
other substances from a conveyance system or
storage container or which conveys a waterway under a road or other paved area.
Cumulative Impacts
The impacts on the environment that
result from the incremental impact of an action when added to other past,
present and reasonably foreseeable actions. Cumulative impacts can result from
individually minor but collectively significant actions taking place over a
period of time.
Curb Inlet Sediment Barrier
Temporary barrier constructed
from concrete block and gravel or gravel-filled sandbags, designed to reduce
sediment discharged into storm drains by ponding the runoff and allowing
sediment to settle out.
Current
1. The flowing of water, or other liquid or gas. 2. That portion of a stream of water which is moving with a velocity much greater than the average or in which the progress of the water is principally concentrated. 3. Ocean currents can be classified in a number of different ways.
Some important types include the following: a: Periodic - due to the effect of the tides; such Currents may be rotating rather than having a simple back and forth motion. The currents accompanying tides are known as tidal currents. b: Temporary - due to seasonal winds. c: Permanent or ocean - constitute a part of the general ocean circulation. The term Drift Current is often applied to a slow broad movement of the oceanic water d: Nearshore - caused principally by waves breaking along a shore.
Current, Flood
The tidal current toward shore or up a tidal stream. Usually associated with the increase in the height of the tide.
Cuspate Bar
A crescent-shaped bar uniting with the shore at each end. It may be formed by a single spit growing from shore and then turning back to again meet the shore, or by two spits growing from the shore and uniting to form a bar of sharply cuspate form.
Cut
Portion of land surface or area from which soil has
been removed, or will be removed by excavation. The depth below original ground
surface to excavated surface.
Cut-And-Fill
Process of earth moving by excavating part of
an area and using the excavated material for adjacent embankments or fill
areas.
Cut Bank
The outside bank of a bend, often eroding and
across the stream from a point bar.
Cutoff
A channel cut
across the neck of a bend.
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