landmass such as Southern Florida and moves offshore. High offshore winds
in this case can cause the water level to drop several feet.
Setdown in semienclosed basins (bays and estuaries) also may be substantial, but the fall in water level is influenced by the coupling to the
sea. There are some detrimental effects as a resuit of setdown, such as
making water-pumping facilities inopérable due to exposure of the intake,
increasing the pumping heads of such facilities, and causing navigational
hazards because of decreased depths.
However, rises in water levels (setup rather than setdown) are of
most concern. Abnormal rises in water level in nearshore régions will not
only flood low-lying terrain, but provide a base on which high waves can
attack the upper part of a beach and penetrate farther inland. Flooding
of this type combined with the action of surface waves can cause severe
damage to low-lying land and backshore improvements.
Wind-induced surge, accompanied by wave action, accounts for most of
the damage to Coastal engineering works and beach areas. Displacement of
stone armor units of jetties, groins and breakwaters, scouring around
structures, accretion and érosion of beach materials, cutting of new inlets through barrier beaches, and shoaling of navigational channels can
often be attributed to storm surge and surface waves. Moreover, surge can
increase hazards to navigation, impede vessel traffic, and hamper harbor
operations. A knowledge of the increase and decrease in water levels
that can be expected during the life of a Coastal structure or project is
necessary to design structures that will remain functional.
3.862 Storms. A storm is an atmospheric disturbance characterized by
high winds which may or may not be accompanied by précipitation. Two
distinctions are made in classifying storms: a storm originating in the
tropics is called a tropical storm', a storm resuiting from a cold and
warm front is called an extratropical storm. Both of these storms can
produce abnormal rises in water level in shallow water near the edge of
water bodies. The highest water levels produced along the entire gulf
coast and from Cape Cod to the south tip of Florida on the east coast
generally resuit from tropical storms. High water levels are rarely
caused by tropical storms on the lower coast of California. Extrême
water levels in some enclosed bodies, such as Lake Okeechobee, Flori a
can also be caused by a tropical storm. Highest water levels at other
Coastal locations and most enclosed bodies of water resuit from extratropical storms.
A severe tropical storm is called a i^urric^the ^ximum
sustained wind speeds reach 75 miles per hour (65 knots). Hurricane
winds may reach sustained speeds of more than
mi es pe
knots). Hurricanes, unlike less severe tropical storms generallyare
well organized and hâve a circular wind pattern wi
wi
around a center or eye (not necessarily the geome ri
Atmnçnheric
is an area of low atmospheric pressure and light
* u^P^^Cthe
pressure and wind speed increase rapidly wit
is
£rom
t0 60
eye to a zone of maximum wind speed which may e anyw
3-83
in this case can cause the water level to drop several feet.
Setdown in semienclosed basins (bays and estuaries) also may be substantial, but the fall in water level is influenced by the coupling to the
sea. There are some detrimental effects as a resuit of setdown, such as
making water-pumping facilities inopérable due to exposure of the intake,
increasing the pumping heads of such facilities, and causing navigational
hazards because of decreased depths.
However, rises in water levels (setup rather than setdown) are of
most concern. Abnormal rises in water level in nearshore régions will not
only flood low-lying terrain, but provide a base on which high waves can
attack the upper part of a beach and penetrate farther inland. Flooding
of this type combined with the action of surface waves can cause severe
damage to low-lying land and backshore improvements.
Wind-induced surge, accompanied by wave action, accounts for most of
the damage to Coastal engineering works and beach areas. Displacement of
stone armor units of jetties, groins and breakwaters, scouring around
structures, accretion and érosion of beach materials, cutting of new inlets through barrier beaches, and shoaling of navigational channels can
often be attributed to storm surge and surface waves. Moreover, surge can
increase hazards to navigation, impede vessel traffic, and hamper harbor
operations. A knowledge of the increase and decrease in water levels
that can be expected during the life of a Coastal structure or project is
necessary to design structures that will remain functional.
3.862 Storms. A storm is an atmospheric disturbance characterized by
high winds which may or may not be accompanied by précipitation. Two
distinctions are made in classifying storms: a storm originating in the
tropics is called a tropical storm', a storm resuiting from a cold and
warm front is called an extratropical storm. Both of these storms can
produce abnormal rises in water level in shallow water near the edge of
water bodies. The highest water levels produced along the entire gulf
coast and from Cape Cod to the south tip of Florida on the east coast
generally resuit from tropical storms. High water levels are rarely
caused by tropical storms on the lower coast of California. Extrême
water levels in some enclosed bodies, such as Lake Okeechobee, Flori a
can also be caused by a tropical storm. Highest water levels at other
Coastal locations and most enclosed bodies of water resuit from extratropical storms.
A severe tropical storm is called a i^urric^the ^ximum
sustained wind speeds reach 75 miles per hour (65 knots). Hurricane
winds may reach sustained speeds of more than
mi es pe
knots). Hurricanes, unlike less severe tropical storms generallyare
well organized and hâve a circular wind pattern wi
wi
around a center or eye (not necessarily the geome ri
Atmnçnheric
is an area of low atmospheric pressure and light
* u^P^^Cthe
pressure and wind speed increase rapidly wit
is
£rom
t0 60
eye to a zone of maximum wind speed which may e anyw
3-83