EM 1110-2-1100 (Change 1)
31 Jul 03
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NATIONAL TIDAL DATUM EPOCH (NTDE)
A period of 19 years adopted by the National Ocean Service as the period over which observations of tides are to be
taken and reduced to average values for tidal datums.
NATURAL TRACER
A component of a sediment deposit that is unique to a particular source and can be used to identify the source and
transport routes to a place of deposition.
NAUTICAL MILE
The length of a minute of arc, 1/21,600 of an average great circle of the Earth. Generally one minute of latitude is
considered equal to one nautical mile. The accepted United States value as of 1 July 1959 is 1,852 meters (6,076.115 feet),
approximately 1.15 times as long as the U.S. statute mile of 5,280 feet. Also GEOGRAPHICAL MILE.
NAVIGABLE WATERS
Waters that are either tidally-influenced or navigable in fact.
NAVIGATION PROJECT
A specific and fixed geographic area within a water body or series of water bodies that has been authorized for
navigation by some group or organization (often a national government).
NEAP HIGH WATER
See NEAP TIDE.
NEAP LOW WATER
See NEAP TIDE.
NEAP RANGE
See NEAP TIDE.
NEAP TIDAL CURRENT
Tidal current of decreased velocity occurring semimonthly as the result of the moon being in quadrature.
NEAP TIDE
Tide of decreased range occurring semimonthly as the result of the moon being in quadrature. The NEAP RANGE
of the tide is the average semidiurnal range occurring at the time of neap tides and is most conveniently computed from the
harmonic constants. The NEAP RANGE is typically 10 to 30 percent smaller than the mean range where the type of tide is
either semidiurnal or mixed and is of no practical significance where the type of tide is DIURNAL. The average height of the
high waters of the neap tide is called NEAP HIGH WATER or HIGH WATER NEAPS (MHWN), and the average height of
the corresponding LOW WATER is called NEAP LOW WATER or LOW WATER NEAPS (MLWN).
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.
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.
NEARSHORE CIRCULATION
The ocean circulation pattern composed of the NEARSHORE CURRENTS and the COASTAL CURRENTS.
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Appendix A Glossary of Coastal Terminology
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