Flood, levee, and erosion control glossary - N
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National Association of Flood & Stormwater Management
Agencies (NAFSMA)
An organization of public agencies whose function is the
protection of lives, property and economic activity from the adverse impacts of
storm and flood waters. The mission of the Association is to advocate public
policy, encourage technologies and conduct education programs which facilitate
and enhance the achievement of the public service function of its members. See http://www.nafsma.org/.
National Oceanic and Atmospheric Administration (NOAA)
A
federal agency focused on the condition of the oceans and the atmosphere. See http://www.noaa.gov/.
National
Flood Insurance Program (NFIP)
Established by the National Flood
Insurance Act of 1968 to provide relief from the impacts of flood damages in
the form of federally subsidized flood insurance that became available to
participating communities, contingent on nonstructural flood loss reduction
measures embodied in local floodplain management regulations. The NFIP is
designed to reduce future flood losses through state and local floodplain
management efforts and to transfer the costs of residual flood losses from the
general taxpayer to the floodplain occupant. As part of the Department of
Homeland Security, FEMA administers the NFIP.
National Geodetic Vertical Datum (NGVD)
A fixed reference
adopted as a standard geodetic datum for elevation in the United States. For
land-based vertical measurements, NGVD is usually given a value of 0.0 and all
other points are measured according to their distance above or below.
National
Pollutant Discharge Elimination System (NPDES)
Mandated by Congress
under the Clean Water Act, a two-phased national program to address
nonagricultural sources of stormwater discharge and prevent harmful pollutants
from being washed into local water bodies by stormwater runoff. It is the
national program for administering and regulating discharges to receiving
waters.
National Wetlands Inventory Project
Wetlands mapping on a
national basis performed by the U.S. Fish and Wildlife Service to provide
scientific information on the extent and characteristics of the Nation's
wetlands and consisting of detailed maps and status and trends reports.
Natural Channel
A watercourse without any significant
improvements or modifications and very little evidence of historical
alterations.
Natural Levee
Levees is commonly thought of as man-made, but they can also be natural. The ability of a river to carry sediments varies very strongly with its speed. When a river floods over its banks, the water spreads out, slows down, and deposits its load of sediment. Over time, the river's banks are built up above the level of the rest of the floodplain. The resulting ridges are called natural levees.
Non-federal Levees
Are defined as those levees that are not authorized by Congress or other Federal agency authority, built by other (non-USACE) Federal agencies and not incorporated into the USACE Federal System, locally built and maintained levees built by a local community, and privately built by non-public organization or individual and maintained by a local community.
Natural Location
The location of those channels, swales,
and other non-manmade conveyance systems as defined by the first documented
topographic contours existing for the subject property, either from maps or
photographs, or such other means as appropriate.
Natural Obstruction
Natural obstruction shall mean any
rock, tree, gravel, or analogous natural matter that is an obstruction and has
been located within the floodway by a nonhuman cause.
Natural Resources Conservation Service (NRCS)
Originally
called the Soil Conservation Service, the NCRS has provided leadership in a partnership
effort to help America's private land owners and managers conserve their soil,
water, and other natural resources. NRCS employees provide technical assistance
based on sound science and suited to a customer's specific needs. Provides
financial assistance for many conservation activities.
Natural Revegetation
Natural re-establishment of plants;
propagation of new plants over an area by natural processes.
Natural Stream Channel
A channel whose alignment, dimensions, crosssectional shape, and grade have not been modified.
Natural Values of Floodplains
The desirable qualities of
or functions served by floodplains including but not limited to water resources
values (e.g., moderation of floods, water quality maintenance and groundwater
recharge), living resource values (e.g., fish, wildlife and plant resources and
habitat), cultural resource values (e.g., open space, natural beauty, scientific
study, outdoor education, and recreation), and cultivated resource values
(e.g., agriculture, aquaculture and forestry).
Natural Watercourse
An unimproved natural stream of any
size. Includes rivers, creeks, branches, canyons, arroyos, gullies, washes,
etc.
NAVD
Abbreviation for North
American Vertical Datum of 1988.
Navigable Streams
Waterways of sufficient depth and width
to handle a specified traffic load.
Navigable Waters
Waters that are either tidally-influenced or navigable in fact.
Navigation Channel
A project feature with authorized project limits/dimensions, which is designed, constructed, and maintained for use by commercial and/or recreational navigation traffic. This definition includes appropriate harbors, canals, turning basins, anchorage/mooring areas and/or waterways.
Neap Tide
A tide having about 10% to 30 % less range than
the average, occurring about the time of quarter moons.
Nearshore
1. In beach terminology an indefinite zone extending seaward from the Shoreline well beyond the Breaker Zone. 2. The zone which extends from the swash zone to the position marking the start of the offshore zone, typically at water depths of the order of 20 m. 3. The region seaward of the shore (from approximately the step at the base of the surf zone) extending offshore to the toe of the shoreface. Nearshore is a general term used loosely by different authors to mean various areas of the coastal zone, ranging from the shoreline to the edge of the continental shelf.
Nearshore Berm
Artificial berm built in shallow water using dredged material. Often, the berm is intended to renourish the adjacent and downdrift shore over time under the influence of waves and currents. See berm.
Neck
1. The narrow strip of land which connects a peninsula with the mainland, or connects two ridges. 2. The narrow band (rip) of water flowing seaward through the surf.
Net Primary Productivity
A measure of carbon flux over a
given landscape unit, approximately, the actual amount of organic matter
created by green plants, whether it accumulates in plants, is eaten by animals,
or becomes dead material over a fixed time interval (Waring and Schlesinger
1985).
NFIP
Abbreviation for National Flood Insurance Program.
NFIRA
Abbreviation for National Flood Insurance Reform Act of 1994. This
act resulted in major changes to the National Flood Insurance Program (NFIP).
The law amended the Flood Disaster Protection Act of 1973. It provides tools to
make the NFIP more effective in achieving its goals of reducing the risk of
flood damage to properties and reducing Federal expenditures for uninsured
properties that are damaged by a floods.
NGVD
Abbreviation for National Geodetic Vertical Datum of 1929.
Niche
A habitat that supplies the factors necessary for
the existence of an organism or species.
Nitrate (NO3)
Inorganic form of nitrogen; chemically NO3.
An important plant nutrient and type of inorganic fertilizer (most highly
oxidized phase in the nitrogen cycle). In water, the major sources of nitrates
are septic tanks, feed lots and fertilizers.
Nitrite (NO2)
The product in the first step of the
two-step process of conversion of ammonium (NH4) to nitrate (NO3).
Nitrogen-Fixing Plant
A plant that can assimilate and fix
the free nitrogen of the atmosphere with the aid of bacteria living in the root
nodules. Legumes with the associated rhizobiumbacteria in the root nodules are
the most important nitrogen-fixing plants.
No Net Loss
A term used in wetlands protection and
restoration programs with the intent to reduce the cumulative impacts of
wetland losses; no net loss determinations may be based on acreage and/or
functional value of wetlands.
NOAA
The National Oceanic and Atmospheric Administration is a federal agency focused on the condition of the oceans and the
atmosphere.
Noncohesive Soil
Soil particles that have no natural
resistance to being pulled apart at their point of contact, such as silt, sand,
and gravel.
Nonconforming Use
A building or structure, or the use
thereof, which was lawful before the passage or amendment of the (ordinance,
resolution, act) but which is not in conformance with the provisions of these
Regulations.
Non-Native Species
See Introduced Species.
Nonnative Vegetation
Any vegetation which, under natural
conditions, does not originate within the ecosystem in which it is found.
Nonpoint Source
Refers to pollutants that enter water from numerous widespread
locations, such as agri-chemicals from leaching or runoff.
Nonpoint Source Pollution
Pollution that enters water from
dispersed and uncontrolled sources (such as surface runoff, agricultural
runoff, urban runoff, and atmospheric deposition) rather than through pipes.
Non-Potable
Water that is unsafe or unpalatable to drink
because it contains pollutants, contaminants, minerals, or infective agents.
Nonstorm Water Discharge
Means any discharge to storm
sewer systems that is not composed entirely of storm water except discharges
pursuant to a NPDES Permit and discharges resulting from fire fighting
activities.
Nonstorm Water Management
The Stormwater Pollution
Prevention Plan (SWPPP) shall include provisions which eliminate or reduce, to
the extent feasible, the discharge of materials other than storm water to the
storm sewer system and/or receiving waters. Such provisions shall ensure, to
the extent feasible, that no materials are discharged in quantities which will
have an adverse effect on receiving waters. Materials other than storm water
that are discharged shall be listed along with the estimated quantity of the
discharged material.
Nonstructural Flood Control Measures
Measures such as zoning ordinances and codes, flood forecasting, flood proofing, evacuation and channel clearing, flood fight activities, and upstream land treatment or management to control flood damages without physically restraining flood waters.
Nonstructural Measures
A term originally devised to distinguish
techniques that modify susceptibility to flooding (such as regulation,
floodplain acquisition and floodproofing techniques) from the more traditional
structural methods (such as dams, levees, and channels) used to control
flooding.
Non-Transient Non-Community (NTNC) Water System
Public
water system which serves 15 or more service connections that are used by the
same person for at least 6 months per year; or serves the same 25 or more
persons for at least 6 months per year. Examples of NTNC water systems include
schools, churches, and workplaces. The same individuals use the water from
month to month, but do not live at this facility.
Normal Depth
The depth of uniform flow. This is a unique
depth of flow for any combination of channel characteristics and flow
conditions. Normal depth is calculated using Manning's Equation.
Northeaster
An extratropical storm that occurs along the
northern part of the east coast of the United States, accompanied by strong
winds from the northeast quadrant. Northeasters are often characterized by
destructive storm surge.
Nourishment
The process of replenishing a beach, either
naturally through accretion due to the longshore transport, or artificially
through the deposition of dredged materials.
NPDES
Abbreviation for National Pollutant Discharge Elimination System. Mandated by Congress under
the Clean Water Act, a two-phased national program to address nonagricultural
sources of stormwater discharge and prevent harmful pollutants from being
washed into local water bodies by stormwater runoff.
NRCS
Abbreviation for Natural Resources Conservation Service (formerly the
Soil Conservation Service) under the US Department of Agriculture.
NRDC
Abbreviation for Natural Resources Defense Council.
Nuisance Flooding
Flooding which causes public inconvenience, but little or no property damage. Also referred to as Minor Flooding. Also see Major Flooding and Moderate Flooding.
Nurse Crop
Seeding of a short-life crop with a permanent
species to aid in erosion control until the permanent species are established.
Nutrient Enrichment
See Eutrophication.
Nutrients
Essential inorganic chemicals (e.g., nitrogen
and phosphorus) needed by plants for growth. Excessive amounts of nutrients can
lead to degradation of water quality and algal blooms by promoting excessive
growth, accumulation, and subsequent decay of plants, especially algae
(phytoplankton). Some nutrients can be toxic at high concentrations.
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