Coastal Hazard Flashcards
Chief agents in shaping our coastline.
Waves, currents, tides and winds
True or False. Some coasts are straight, while others are rugged or contain marshes or coral reefs.
TRUE
The strip of land bordering the sea or ocean along the continent or an island.
Coast/Shore
Marks the seaward limit of the landmass that are exposed to wave action.
Coastline/Shoreline
Part of the shore between the high tide and the highest water level, which can only be reached by exceptional storm waves.
Backshore
This refers to the zone between high tide and low tide. It is underwater during high tide. It is the surf zone.
Foreshore
Between the low-tide breaker line and the low tide shoreline.
Nearshore
This part of the shore is nearest to the sea. It is underwater even at low tide.
Offshore
Zone affected by wave action
Shore
Marks the boundary between the sea and land.
Shoreline
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 shoreline
Areas with no tectonic activity, commonly resulting in a relatively straight coastline with flat-lying terrain.
Passive shoreline
The outer margins of the continents, where continental crust transition to oceanic crust.
Continental Margin
Geologically inactive regions located some distance from plate boundaries and relatively wide and are sites where large quantities of sediments are deposited.
Passive continental margin
Located along convergent plate boundaries, where oceanic lithosphere is being subducted beneath the leading edge of a continent.
Active continental margin
True or False. The process that affects the shoreline’s nature is relative movement, either seaward or landward.
TRUE
The periodic rise and fall of sea level is known as _______.
Ocean tides
_______ 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 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 the tidal effects of one another.
Neap tide
Enumerate the three tidal patterns exist worldwide.
Diurnal, Semidiurnal, Mixed tidal pattern
Characterized by a single high tide and single low tide each tidal day.
Diurnal
Exhibits single two high tides and two low tides each tidal day; common along Atlantic coast and US.
Semidiurnal
Similar to a semidiurnal pattern except that it is characterized by a large inequality in height: water heights, low water heights, or both.
Mixed tidal pattern
When the moon is in the full or new position, the tidal bulges created by the sun and moon are aligned and there is a large tidal range.
Spring Tide
When the moon is in the first or third-quarter position, the tidal bulges produced by the moon are at right angles to the bulges created by the sun and the tidal range is smaller.
Neap Tide
Strong localized currents during high tide formed by the surface of the sea sloping towards the shore which generated mechanical energy that forces water to funnel up into inlets and river channels.
Tidal currents
The physical movement of water molecules from one location to another. Ocean currents are driven by various forms of energy and like all things in motion, current flow from an area of high energy to one of low energy.
Ocean currents
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
Formed in response to differences in ocean temperature and salinity. Cooler and more saline water is relatively dense which cause it to sink and flow towards areas where water is less dense.
Density currents
Transport energy through water such that water molecules move or vibrate in a circular manner.
Water waves
The depth where water molecules are no longer affected by passing wave.
Wave base
The energy of the wind-generated waves is also affected by the amount of contract area between the wind and water.
Fetch
The faster the wind speed, the greater the _________.
wave energy
The longer the wind blows, the larger the waves.
duration of wind
The greater the _______, the more energy the wave have.
fetch
Water from a breaker washing upon a beach at whatever angle.
Swash
Swash water retreating back under the influence of gravity.
Backwash
Takes the shortest path, direct to the sea, not oblique angle as taken by swash.
Backwash
- Strongest swash and weaker backwash
- Occurs on gentle sloping coasts
- Deposits materials on the beach more than it removes.
Constructive waves
- Stronger backwash and weaker swash.
- Occurs on steep-sloping coasts.
- Removes materials on the more than it deposits.
Destructive waves
As the wave continues towards shore, this cause a progressive decrease in velocity along the length of the wave, forcing it to bend in a process called _________.
Wave refraction
A wave whose amplitude reached a critical level at which some process can suddenly start cause large amounts of wave energy.
Breaking wave
Refers to the area where the waves break.
Surf zone
Ocean current that flow parallel to the shore and is caused by a large series of wave sweeping into the shoreline at an angle.
Longshore current
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
Increase the height of the localized sea level and can travel farther inland than the normal waves during storm events.
Storm surge
Large waves caused by a sudden mid/under sea displace of a large volume of water.
Tsunamis
Coastline evolve over time due to the erosion and deposition from breaking waves.
Shoreline evolution
Interaction between waves and a landmass can cause the shoreline to slowly move landward.
Shoreline retreat
When land itself becomes lower due to subsidence.
Landward migration
Accumulations of sediments deposited by waves and longshore currents.
Beaches
4 main sources of beach sediments.
Local cliffs and promontories
Offshore zone
Calcareous sand and shell fragments
Local river bedload material
Elongated deposits of sediments parallel the shore and are separated from the main land by open water.
Barrier island
The origin of barrier island.
Sand bars
Sand eventually accumulates to where the bar stay above the high tide line, creating a _______.
True Island
Result from a complex interaction between waves, sea level change, and sediment supply.
Barrier island
Long narrow ridges of sand and shingle project from the coastline into the sea.
Spits
Beach tied to the coast at one end and free at the other.
Spits
Tombolos is also known as __________.
Sandy isthmus
Depositional landforms by which an island becomes attached to the mainland by a spit or bar.
Tombolos
Formed when sand deposited off the shore dries out and blown out to the back of the beach.
Coastal dunes
Coastal dunes usually needs:
Large tidal range
Broad intertidal zones
Large supply of sands
- Sites of mud and organic deposition
- Quiet waters
-A combination of river processes and coastal processes.
Lagoons, mudflats, marshes, and mangrove swamps
Wetlands that form as river empty their water and sediment into another body of water such as ocean.
Deltas
Two major ways of classifying deltas.
Influences/processes
Shape
Types of influence delta
Wave-dominated delta
Tide-dominated delta
Gilbert delta
Estuarine delta
Types of shape delta
Cuspate delta
Bird-foot delta
Inverted delta
Inland delta
Abandoned delta
The movement of waves controls a delta’s size and shape.
Wave-dominated delta
Form in areas with large tidal range or area between high tide and low tide.
Tide dominated delta
Formed as river deposits large, coarse sediments.
Gilbert deltas
Form as a river does not empty directly into the ocean, but forms a partly enclosed wetland that contains brackish water habitat.
Estuarine delta
Deltas with a triangular shape or fan shape are called __________.
Arcuate
Stronger waves form a __________ which is more pointed than the arcuate delta, and is toothed shaped.
Cuspate delta
Widely spaced distributaries, making it look like a birds foot.
Bird foot delta
The distributary network is inland.
Inverted delta
Empty into a plain are extremely rare.
Inland deltas
Forms as a river develops a new channel, leaving the other to dry up or stagnate.
Abandoned delta
The process of abandoned delta is also called ____________.
Avulsion
A rock, sandbar, or other feature lying beneath the surface of the water.
Reefs
Underwater structures made from calcium carbonate secreted by corals.
Coral reefs
Most coral reefs are less than ________ years old.
10,000
True or False. Most coral reefs were formed after the last glacial period when melting of ice caused the sea level to rise.
TRUE
True or False. Coral reeds are found in continental shelves and away from oceanic islands.
FALSE. Away from continental shelves and around oceanic island.
_____________ set out his theory about atoll formation in ________.
Charles Darwin; 1842
3 Stages of Atoll Formation
Fringing Reef
Barrier Reef
Atoll Reef
Directly attached to a shore, or borders it with an intervening shallow channel or lagoon.
Fringing Reef
Reef separated from a mainland or island shore by a deep channel or lagoon.
Barrier Reef
More or less circular or continuous barrier reef extends all the way around a lagoon without central island.
Atoll Reef
Observed where a more resistant portion of the rock remains in the surf, separated from a retreating cliff.
Sea stacks
Column of rock standing in the water off a beach
Chimney
Wave erosion has hollowed out a line of weakness in otherwise resistant promontory.
Sea arch
Repetitive hydraulic action slowly breaks the rocks apart and form a ____________ within the cliff face.
undercut/notch
Places where waves first make a contact with the land and with a great amount of energy; are the places where erosion is high.
Headlands
Greatly sloping platforms of rock that extends seaward in to a steep drop off.
Shore platforms
Enumerate the dominant influences of coastal landforms.
- Type of continental margin
- Relief, structure, and lithology
- Climatic influences
- Rates of erosion
- Sea level
Enumerate the type of continental margin..
Pacific type of boundary
Divergent boundaries
Atlantic-type margins
Edges of actively diverging plates; form passive margins with continental sheves.
Divergent boundaries
No continental shelves and deep offshore trenches
Pacific type boundary
Have shallow and broad continental shelves.
Atlantic-type margins
The energy available for coastal processes is controlled by wave height, windspeed direction and duration.
Climatic influences
Influenced by variations in the resistance of rock to fluvial, glacial, and coastal processes.
Relief, Structure, and Lithology
Coastal zone is a rapid zone of change; thousand tons of sands are transported throughout the day.
Rates of erosion
Coastal positions have changed almost constantly through constant cycle of glaciation and melting.
Sea level
Solid walls made resistant to materials such as concrete, rocks, or wood built parallel and on the coast.
Sea walls
Solid walls are usually made of granite built parallel to the coast, or with one end attached to the coast.
Breakwaters
Solid walls are usually made of granite or wood built on and perpendicular to the coast.
Groynes/Groins
Barriers made of a large rock are installed at the mouth of an inlet to keep sediments from longshore current.
Jetties
Wire cages filled with small rocks piled up and placed along the coast.
Gabions
Manually add sands to the beach is a process called ________.
Beach nourishment
Existing structures would either be allowed to fall into the sea or be relocated farther inland.
Natural retreat
Tools used for assessing coastal vulnerability
CIVAT
ICSEA-C-Change
TURF
CIVAT
Coastal Integrity and Vulnerability Assessment Tool
ICSEA-C-Change
Integrated Coastal Sensitivity, Exposure, and Adaptive Capacity to Climate Change
TURF
Tool for Understanding Fisheries Resilience
Related to storm events because both wind and wave energy are at their highest.
Coastal hazards
Refer to large rotating low-pressure storm systems that originate in tropical oceans
Tropical cyclone
Unusually strong winds associated with hurricanes result from the circulating air masses within the storm.
High winds
Hurricanes have winds speed at least ________.
74 miles per hour
Anything less than 74 miles per hour winds is called _____________.
Tropical storm or depression
Winds and low pressure within a hurricane produce a rise in sea level called ________.
Storm surge
Storm surges usually have _________ rise in sea level.
up tp 9 meters
________ commonly leads to ___________ far from where a storm makes landfall.
Intense precipitation;
Inland flooding
Enumerate ways to mitigate storm hazards
Avoid settlement on the coast,
Development of early warning signs,
Forecasting models,
Elevate the building above the expected storm surge level,
Use metal straps to secure the roof to the main structure.
