1969, in excess of 20 feet MSL over many miles of the open Gulf Coast,
with a peak value of 24 feet MSL near Pas-s Christian, Mississippi. High
water levels in excess of 12 feet MSL on the open coast and 20 feet within
bays were recorded along the Texas coast as the resuit of Hurricane Caria,
September, 1961. Water levels above 13 feet MSL were recorded in the
Florida Keys during Hurricane Donna, 1960.
Accumulation of data over many years in some areas, such as régions
near the North Sea, has led to relatively accurate empirical techniques
of storm surge prédiction for some locations. However, these empirical
methods are not applicable to other locations. In general, not enough
storm surge observations are available in the United States to make accurate prédictions of storm surge. Therefore, it has been general practice
to use hypothetical design storms, and to estimate the storm-induced surge
by physical or mathematical models. Mathematical models are usually used
for predicting storm surge, since it is difficult to represent some of the
storm surge generating processes (such as the direct wind effects and
Coriolis effects) in physical laboratory models.
a. Hydrodynamic Equations. Equations that describe the storm surge
génération processes are the continuity équation expressing conservation
of mass and the équations of motion expressing Newton’s second law. The
dérivations are not presented here; references are cited below. The équations of motion and continuity given here represent a simplification of
the more complété équations. A more simplified form is obtained by vertical ly integrating ail goveming équations and then expressing everything
in terms of either the mean horizontal current velocity or volume transport. Vertically intégrâted équations are generally preferred in stormsurge calculations since interest is centered in the free surface motion
and mean horizontal flow. Intégration of the équations for the storm
surge problem are given by Haurwitz (1951), Welander (1961). Fortak (1962),
Platzman (1963), Reid (1964), and Harris (1967).
The équations given here are obtained by assuming:
(1) vertical accélérations are negligible,
(2) curvature of the earth and effects of surface
waves can be ignored,
(3) the fluid is inviscid, and
(4) the bottom is fixed and imperméable.
schematicand is
and S is
The notation and the coordinate scheme employed are shown
ally in Figure 3-43. D is the total water depth at time t,
given by D = d ♦ S, where d is the undisturbed water depth
the height of the free surface above or below the undisturbed depth resulting from the surge. The Cartesian coordinate axes, x and y, are in
the horizontal plane at the undisturbed water level and the z axis is
directed positively upward. The x axis is taken normal to the shoreline^
(positive in the shoreward direction), and the y axis is taken alongs or
(positive to the left when facing the shoreline from the sea).
3-92
with a peak value of 24 feet MSL near Pas-s Christian, Mississippi. High
water levels in excess of 12 feet MSL on the open coast and 20 feet within
bays were recorded along the Texas coast as the resuit of Hurricane Caria,
September, 1961. Water levels above 13 feet MSL were recorded in the
Florida Keys during Hurricane Donna, 1960.
Accumulation of data over many years in some areas, such as régions
near the North Sea, has led to relatively accurate empirical techniques
of storm surge prédiction for some locations. However, these empirical
methods are not applicable to other locations. In general, not enough
storm surge observations are available in the United States to make accurate prédictions of storm surge. Therefore, it has been general practice
to use hypothetical design storms, and to estimate the storm-induced surge
by physical or mathematical models. Mathematical models are usually used
for predicting storm surge, since it is difficult to represent some of the
storm surge generating processes (such as the direct wind effects and
Coriolis effects) in physical laboratory models.
a. Hydrodynamic Equations. Equations that describe the storm surge
génération processes are the continuity équation expressing conservation
of mass and the équations of motion expressing Newton’s second law. The
dérivations are not presented here; references are cited below. The équations of motion and continuity given here represent a simplification of
the more complété équations. A more simplified form is obtained by vertical ly integrating ail goveming équations and then expressing everything
in terms of either the mean horizontal current velocity or volume transport. Vertically intégrâted équations are generally preferred in stormsurge calculations since interest is centered in the free surface motion
and mean horizontal flow. Intégration of the équations for the storm
surge problem are given by Haurwitz (1951), Welander (1961). Fortak (1962),
Platzman (1963), Reid (1964), and Harris (1967).
The équations given here are obtained by assuming:
(1) vertical accélérations are negligible,
(2) curvature of the earth and effects of surface
waves can be ignored,
(3) the fluid is inviscid, and
(4) the bottom is fixed and imperméable.
schematicand is
and S is
The notation and the coordinate scheme employed are shown
ally in Figure 3-43. D is the total water depth at time t,
given by D = d ♦ S, where d is the undisturbed water depth
the height of the free surface above or below the undisturbed depth resulting from the surge. The Cartesian coordinate axes, x and y, are in
the horizontal plane at the undisturbed water level and the z axis is
directed positively upward. The x axis is taken normal to the shoreline^
(positive in the shoreward direction), and the y axis is taken alongs or
(positive to the left when facing the shoreline from the sea).
3-92