EM 1110-2-1100 (Change 1)
31 Jul 03
HURRICANE STAGE HYDROGRAPH
A continuous graph representing water level stages that would be recorded in a gage well located at a specified
point of interest during the passage of a particular hurricane, assuming that effects of relatively short-period waves are
eliminated from the record by damping features of the gage well. Unless specifically excluded and separately accounted for,
hurricane surge hydrographs are assumed to include effects of astronomical tides, barometric pressure differences, and all
other factors that influence water level stages within a properly designed gage well located at a specified point.
HURRICANE WIND PATTERN or ISOVEL PATTERN
An actual or graphical representation of near-surface wind velocities covering the entire area of a hurricane at a
particular instant. Isovels are lines connecting points of simultaneous equal wind velocities, usually referenced 9 meters (30
feet) above the surface, in meters per second, knots, or meters per hour; wind directions at various points are indicated by
arrows or deflection angles on the isovel charts. Isovel charts are usually prepared at each hour during a hurricane, but for
each half hour during critical periods.
HYDRAULIC DREDGE
Floating or (occasionally) truck-based plant which lifts the material through a suction pipe. It requires dilution
water for material pickup, lift, and transportation. Often used to renourish beaches when material is pumped onto the shore
from an offshore sand source.
HYDRAULIC RADIUS
Quotient of the wetted cross-sectional area and the wetted perimeter.
HYDRAULICALLY EQUIVALENT GRAINS
Sedimentary particles that settle at the same rate under the same conditions.
HYDROGRAPHY
(1) The description and study of seas, lakes, rivers and other waters. (2) The science of locating aids and dangers to
navigation. (3) The description of physical properties of the waters of a region.
HYDROGRAPHIC PRESSURE
The pressure exerted by water at any given point in a body of water at rest.
HYPOPYCNAL FLOW
Outflow from a river or coastal inlet in which a wedge of less dense water flows over the denser sea water.
HYPOTHETICAL HURRICANE ("HYPOHURRICANE")
A representation of a hurricane, with specified characteristics, that is assumed to occur in a particular study area,
following a specified path and timing sequence.
TRANSPOSED--A hypohurricane based on the storm transposition principle, assumed to have wind patterns and
other characteristics basically comparable to a specified hurricane of record, but transposed to follow a new path to
serve as a basis for computing a hurricane surge hydrograph that would be expected at a selected point. Moderate
adjustments in timing or rate of forward movement may also be made, if these are compatible with meteorological
considerations and study objectives.
HYPOHURRICANE BASED ON GENERALIZED PARAMETERS--Hypohurricane estimates based on various
logical combinations of hurricane characteristics used in estimating hurricane surge magnitudes corresponding to a
range of probabilities and potentialities. The STANDARD PROJECT HURRICANE is most commonly used for
this purpose, but estimates corresponding to more severe or less severe assumptions are important in some project
investigations.
STANDARD PROJECT HURRICANE (SPH)--A hypothetical hurricane intended to represent the most severe
combination of hurricane parameters that is reasonably characteristic of a specified region, excluding extremely rare
combinations. It is further assumed that the SPH would approach a given project site from such direction, and at
such rate of movement, to produce the highest HURRICANE SURGE HYDROGRAPH, considering pertinent
hydraulic characteristics of the area. Based on this concept, and on extensive meteorological studies and probability
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Appendix A Glossary of Coastal Terminology
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