Coastal Hazards - Hazards and Mitigation Flashcards
Most coastal hazards are related to ________ because this is when both _______ and _______ energy are at their highest.
storm events; wind and wave
refer to large, rotating low pressure storm systems that originate in tropical oceans
tropical cyclones
Exceptionally strong tropical storms are called ________, ________, or _______ depending on where they form in the Tropics
typhoons, hurricanes, or cyclones
Tropical cyclone develop over the __________
parts of oceans where a low pressure disturbance can become amplified into a gigantic, rotating storm composed of __________ and ___________
warm tropical ; high winds and intense precipitation
Winds and low pressure within a
hurricane produce a rise in sea level
called a __________ and will also produce
heavy rains that commonly lead to _________
storm surge ; river flooding
what causes storm surges?
winds and low pressure within a hurricane
cyclones, hurricane, or typhoons can produce winds with speed of:
> 150 miles/hr
How are hurricanes formed?
Hurricanes form around low pressure disturbances as evaporation removes heat energy and water from tropical waters. The resulting convection combined with Earth’s spinning motion produces a rotating system centered about the low pressure
area of the eye.
Hurricanes form around ____________ as evaporation removes_______ and _______ from tropical waters.
low pressure disturbances ; heat energy and water
________, _______, and ________cause major damage to coastal areas
Intense winds, rains, and wind action
The unusually strong winds associated with
hurricanes result from the circulating air
masses within the storm.
high winds
The unusually strong winds associated with
hurricanes result from
circulating air masses within the storm
Different hurricanes are ranked based on
their__________, with the lowest
category having winds of at least ____________ anything less is called a ___________.
sustained winds ; 74 miles/hr ; tropical depression/storm
used to rank hurricanes based on their wind speed
Saffir-Simpson scale
t or f: the area of low pressure
beneath a hurricane exerts less weight
on the ocean surface, allowing it to rise
t
The rotating eye of a hurricane is an
area of ____________
abnormally low pressure
This dome shaped water will literally
move or surge up onto land as the
hurricane makes landfall, producing a
rapid rise in sea level called a __________
storm surge
storm surges can go up to ___________ rise in seal level
9 meter
This rapid rise in sea level, called a __________, is greatest on the __________ side of the eye as the ___________ rotating system pushes water up against the shoreline.
storm surge; northeastern ; counterclockwise
explain how storm surges are formed
The decrease in air pressure toward the eye of a
hurricane allows the sea surface to rise, creating a dome of water that follows the storm inland. This rapid rise in sea level is called a storm surge
explain how storm surges are formed
The decrease in air pressure toward the eye of a
hurricane allows the sea surface to rise, creating a dome of water that follows the storm inland. This rapid rise in sea level is called a storm surge
t or f: tropical depression is stronger than tropical storm
F
what category of hurricane swept over Galveston Island, Texas, in 1900?
hurricane 4
__________ commonly leads to inland flooding far from
where a storm makes landfall.
intense precipitation
In addition to a storm’s precipitation rate, another key factor affecting the level of flooding is a storm’s _____________ as it moves over land.
forward speed
what are considered a “slow moving storm”?
less than 10 miles/hr (16 km/hr)
t or f: slow moving storm are particularly more dangerous since more rain will fall on a given area compared to a storm that passes more rapidly
t
t or f: Rainfall intensity will increase when an ocean storm moves inland and encounters rugged or mountainous terrain
t
explain how an ocean storm increases intensity when encountering mountainous terrain
the humid air masses within the storm will rapidly gain elevation, thereby resulting in faster cooling rates which in turn increase the condensation and precipitation rates
what is the oldest form of mitigation strategy for storm hazards?
avoiding locating large settlements directly on the coasts
ways to mitigate storm hazards
- avoiding locating large settlements directly on the coasts
- Development of early warning systems such
- weather satellites continuously tracking the storms’ location
- forecasting models
- elevate a building above the expected storm surge level
- Metal straps to secure the roof to the main structure
t or f: tsunamis are formed by wind
F (it is formed by earthquakes, volcanic eruptions, landslides, and meteorite impact)
typical wavelengths of a tsunami
6-300 miles (10-500km)
height of tsunami waves in deep water
less than a meter
typical speed of tsunami waves
over 500 miles per hour (800 km/ hr )
One of the most effective mitigation strategies relies of mitigating tsunami hazards
early warning system and public education
early warning system involves utilizing a network of ________________ for detecting subduction zone earthquakes that have a potential for generating a
tsunami
seismograph stations
this instrument detect passing tsunami waves based on their unusually long wave length and high velocity.
deep ocean buoys
japan tsunami engineering controls
large gates and walls
are strong currents that flow away from shore
rip currents
how does rip currents form?
when backwash from the surf zone funnels through a break in underwater sand bars
create a narrow, but powerful current that flows
toward deeper waters
rip current
what to do if you get caught in a rip current
stay calm and swim parallel to shore
Solid walls made of resistant materials such as concrete, rocks, or wood built parallel and on the coast.
sea walls
what is the downside of a sea wall?
as waves break against the sea wall, the energy is directed to the bottom of the sea wall creating a strong backwash that erodes the base of the sea wall, making it unstable and eventually collapse
Solid walls usually made of granite built of and
parallel to the coast, or with one end attached to
the coast
Breakwaters
breakwaters are usually made of________
granite
breakwater creates a zone of _______ behind them which encourages ___________ and ________ of beaches
calm waters ; deposition and formation
downside of breakwaters?
only the zones behind them are protected while those otherwise are not
Solid walls usually made of granite or wood built on and perpendicular to the coast.
groynes / groins
groins are usually made of
granite or wood
Absorbs or reduces wave energy and encourages deposition on the side of the groyne facing _____________
longshore drift
this term refers to a series of groins
Groin field
what is the downside of groins?
down drift beaches (other side of the groin) become starved, causing shoreline retreat to accelerate.
barriers made of large rocks and are installed at
the mouth of an inlet to keep sediment from longshore current to clog channels, and thereby reducing dredging costs
Jetties
t or f: longshore currents will periodically reverse from their dominant direction
t
why do jetties come in pair?
because longshore currents will periodically reverse from their dominant direction
what is the downside of using jetties?
causes down drift areas to experience rapid shoreline retreat as beaches there are starved of sand.
Wire cages filled with small rocks piled up and placed
along the coast.
Gabions
downside of gabions
only offer short term protection
as the rocks are easily eroded away and the cages
corrodes easily.
the only real solution to beach starvation is to
manually add sand to the beach in a process called
beach nourishment
The most cost effective way of nourishing a
beach is usually by
pumping sand up onto the beach from
offshore sand deposit
t or f: beach nourishment disrupt the longshore current
F (does not)
