COASTAL HAZARDS Flashcards
often called shorelines, are a critical component of the biosphere because a large number of species are connected in some way or another to the unique habitats found at this interface between the land and sea.
Coastlines
are areas where tectonic forces deform and uplift the land. They are usually rugged and irregular, with beaches sometimes being restricted to coves and inlets.
Active shorelines
are areas with
little to no tectonic activity,
commonly resulting in a relatively
straight coastline with flat-lying
terrain. Ex. U.S. Gulf and Atlantic
Passive shorelines
The periodic rise and fall of sea level is known as
ocean tides
This complex interaction creates a net outward force, called
tidal force,
high tides and two low tides each day (approximately __________ passes
between two high tides). Note that tides also occur on large lakes, but the rise and fall is
12 hours and 25 minutes
refers to the difference in sea level between high and low tides.
Tidal range
occurs when the Moon and Sun periodically line up such that their gravitational
effects reinforce one another.
Spring tide
occurs when the gravitational pull of the Moon and Sun are at right angles which
tend to cancel their tidal effects on one another.
Neap tide
++In addition to orbital influences, tidal range varies depending on latitude, water depth, shape
of the shoreline, and the presence of large storms.++
are strong localized currents during high tide formed by the surface of
the sea sloping towards the shore which generates mechanical energy that forces
water to funnel up into inlets and river channels.
Tidal currents
involve the physical movement of water molecules from one
location to another
Ocean currents
are large-scale currents in the open water near the surface of the
sea which are driven mainly by winds blowing consistently in the same direction.
Surface currents
are formed in response to differences in ocean temperature and salinity. Cooler and more saline water is relatively dense which causes it to sink and
flow toward areas where water is less dense.
Density currents
refer to density-driven currents that circulate enormous volumes
of water, both vertically and horizontally, in a convective manner between tropical and polar regions.
Ocean Conveyor
++Density and wind-driven currents transfer vast amounts of heat energy from the Tropics toward higher latitudes (influence the global climate system) and also transport nutrients into the ocean.+++
transport energy through water such that water molecules move or vibrate in a circular manner.
Water waves
As the wave continues toward shore, this causes a progressive decrease in velocity along the length of the wave, forcing it to bend in a process called
wave refraction
is a wave whose amplitude reaches a critical level at which some process can suddenly start causing large amounts of wave energy to be transformed into turbulent kinetic energy.
Breaking wave
refers to the area where the waves break
Surf zone
is an ocean current that flows parallel to the shore and is caused by large swells Iseries of waves) sweeping into the shoreline at an angle and pushing down the length of the beach in one direction.
Longshore current
is the process of transporting material along a coast by waves that approach at an angle to the shore but recede perpendicular from it.
Longshore drift or beach drift
interaction between waves and a landmass can cause the shoreline to slowly move landward, a process referred to as
shoreline retreat
are points of land that are just seaward and areas where waves first make contact with land
Headlands
are elongate deposits of sediment that parallel the shore and are separated from the mainland by open water, lagoons, tidal mudflats, or saltwater marshes
Barrier islands
result from the complex interaction between waves, sea level change, and sediment supply
Barrier islands
In general, most barrier islands are no
higher than _____ above sea level, but their shape varies depending on the relative
6m
are elongated sediment deposits separated from the mainland by open water or wetlands.
Barrier islands
to refer to large, rotating low-pressure storm systems that originate in tropical oceans.
Topical cyclones
Winds and low pressure within a hurricane produce a rise in sea level called a
storm surge
The unusually strong winds associated with hurricanes result from the circulating air masses within the storm.
High Winds
the lowest category has winds of at least 74 miles per hour anything less is called a
tropical storm or depression.
used to rank hurricanes based on their wind speed. Note how wind speed is related to the level of air pressure within the eye of a hurricane and its associated storm surge.
Saffir Simpson scale
rapid rise in sea level called a ________ that inundates
areas above the normal high tide line (up to ___ rise in
sea level)
storm surge
9 m
commonly leads to inland flooding far from where a storm makes landfall.
Intense precipitation
the primary source of energy for tropical cyclones
ocean
In addition to a storm’s precipitation rate, another key factor affecting the level of
flooding is a __________ as it moves over land. Slow moving storms
storm’s forward speed
Slow-moving storms less than
___________
(16 km/ hr)
Slow moving storm is particularly more dangerous since ________________
more rain will fall on a
given area compared to a storm that passes more rapidly .
Rainfall intensity will also increase
when an ocean storm moves inland and encounters____________________
rugged or mountainous terrain
The rapid elevation gain results in faster cooling rates, which, in turn, increases
the __________________
condensation and precipitation rates.
The oldest mitigation strategy goes back to ancient cultures, where they___________________
avoided locating large settlements directly on the coasts
the use of radio technology by ocean-going ships in the early 1900s to report weather conditions back to land-based stations.
Development of early warning systems
combined with aircraft data allow scientists to use computer models to predict the path of hurricanes with
impressive accuracy.
weather satellites continuously track the storms’ location
can now commonly predict out to 48 hours in advance where a hurricane
will make landfall and do so with a fairly high degree of accuracy.
Forecasting models
which allows wave energy to pass beneath the structure rather
than smashing it completely off its foundation.
elevate a building above the
expected storm surge level
These are unusually high-energy waves that form not from the wind, but rather by the transfer of energy from earthquakes, volcanic eruptions, landslides, or asteroids to a body of water.
Tsunamis
Tsunamis traveling through deep ocean waters have exceptionally long wavelengths, typically from___________, and their wave base can be rather deep.
(10 - 500 km)
Tsunamis travel at speeds of over _____________
(800 km/ hr ).
December 26, 2004, wherein a magnitude 9.1 earthquake
occurred in the subduction zone located off the Indonesian coast of Sumatra which caused the______________
seafloor to suddenly shift
passing tsunami waves are detected
based on their unusually long wavelength and high velocity.
deep ocean buoys
are strong currents that flow away from the shore, sometimes inappropriately referred to as a
rip tide.
Is a physical barrier made of concrete, steel, or large rocks built against the
shore. It is also called a bulkhead or revetment.
Seawall
Often referred to as
hard stabilization or “armoring a shoreline” because it
physically prevents waves from directly impacting the shoreline.
Seawall
made of large rocks or steel sheets and is built perpendicular to the shore.
groin
refers to a group of groins.
groin field
built-in perpendicular
to the shore in order to trap sand
moving with the longshore
current.
Groins
barriers made of large rocks and are installed at the mouth of an
inlet to keep sediment from longshore current to clog channels,
thereby reducing dredging costs.
Jetties
normally come in pairs
and are placed at the mouth
of inlets to help keep the
longshore movement of sand
from clogging navigational
channels.
Jetties
barrier placed just offshore and is used to keep waves from
directly impacting the shoreline.
breakwater
In many cases, the only real solution to beach starvation is to manually add
sand to the beach in a process called
beach nourishment.
