Ocean Zone Magnt

Coastal Geology
refers to the origin, structure, and characteristics of the
sediments that make up the coastal region, from the uplands to the
nearshore
Coastal Processes
refers to those physical processes that act upon and shape the coastline
• tides
• waves
• currents
• winds
Coastal Sediment Budget
refers to the identification of sediment sources and sinks, and the quantification of the amounts and rates of sediment transport, erosion, and deposition within a defined region.
Flood shoals
are sediment deposits
formed just inside a tidal
inlet by flood tidal currents (also
called flood tidal delta).
Ebb shoals
are sediment deposits
formed by ebb tidal currents
just offshore of a tidal inlet
(also called ebb tidal delta)
Longshore sand transport is
wave- and/or tide-generated
movement of shallow-water
coastal sediments parallel to
the shoreline.
Cross-shore sand transport
is
wave- and/or tide-generated
movement of shallow-water
coastal sediments toward or
away from the shoreline.
Cheniers
are Mississippi Delta
sediments transported westward
to form sandy ridges atop
mud plains.
The South Atlantic coast consists of three regions:
(1) the North Carolina and northern South Carolina shoreline, composed of long barrier and mainland beaches (including the Outer Banks and the South Carolina Grand Strand region)
(2) The region extending from Charleston, South Carolina, to the St. Johns River entrance at Jacksonville, Florida (a tide- dominated coast composed of numerous short barrier islands, separated by large tidal inlets and backed by wide expanses of tidal marsh)
(3) the east coast of Florida(composed of barrier and mainland beaches backed by narrow bays and rivers).
The entire Gulf coast is vulnerable to high storm surges from hurricanes.
Why?
Some areas (e.g., the Big Bend area of Florida) are especially vulnerable
because of a wide, shallow continental shelf and low-lying upland areas.
Coastal flood hazards at a site will depend upon several factors:
• the elevation and topography of the site
• the erodibility of the site
• the nature and intensity of coastal flood events affecting the site
The map changes are attributable to two factors:
(1) pre-storm FIRMs did not show the effects of erosion that had occurred since the FIRMs were published and did not meet technical standards currently in place
(2) Hurricane Fran caused significant changes to the topography of the barrier island. Not all coastal FIRMs would be expected to undergo such
drastic revisions after a flood restudy; however, many FIRMs may be in need of updating.
The map changes are attributable to two factors:
(1) pre-storm FIRMs did not show the effects of erosion that had occurred since the FIRMs were published and did not meet technical standards currently in place
(2) Hurricane Fran caused significant changes to the topography of the barrier island. Not all coastal FIRMs would be expected to undergo such
drastic revisions after a flood restudy; however, many FIRMs may be in need of updating.
shear waves
on sediment suspension and transport on the seaward side of an intertidal bar.
What kind of energy do you need for bar switching to occur
High energy, but antecedent morphology and other hydrodynamic factors may
also be important
neap tide
a less than average tide occurring at the first and third quarters of the moon.
spring tide
A tide just after a new or full moon
Various degrees of wave idenitified three:
-exposed
-semi-exposed
-sheltered
longshore transport
means erosion at one end but not a long-term loss of sediment
coastal rock weathering and documented the phenomenon of rock _______ where surfaces are observed to rise up over ______ rather than wear down as
might be expected.
They argued that this behaviour results from salt growth and wetting and drying, and speculated that it may be an important part of the weathering of coastal rocks
Stephenson and Kirk (2001)
swelling, months
point at which ocean meets land
(for example: sandy beach)
Shore:
larger zone affected by processes occurring in this boundary
(includes marshes, dunes, cliffs inland; sand bars, troughs offshore)
Coast:
Active
West Coast
Passive
East coast
“young” coasts dominated by terrestrial influences
Primary
older coasts significantly altered by wave and other ocean processes
Secondary
Erosional
with sea cliffs, sea stacks,etc.
Depositional
Usually more sediment rich than erosional coasts
lagoons,baymouths, Spits Barrier Islands
Exs; Long Island, NC, SC, VA
longshore drift
*water moves on the shore at an angle
*returns straigt down the beach
*so the sand moves down coast in a zigzag path
What are the 3 types of Deltas?
-River dominated deltas (Mississippi)
-Tide dominated deltas (Ganges-Brahmaputra)
-Wave dominated deltas (Niger)
What kinds of estuaries are there? (5)
1)Salt wedge (Mississippi)
2)Well-mixed (Columbia)
3)Partially-mixed(puget sound)
4)Fjord (puget sound)
5)Reverse (Baja)
What are some techniques are used to help “prevent” erosion.
Groins and Jetties
Breakwaters
Seawalls
Beach Nourishment
-Feed the beach.
-Expensive and not permanent.
-Typically creates an environmental mess just offshore.
How do we minimize risk?
– built well above high tide line
– establish vegetation
– what have prior storms/floods done?
surf zone model
which they claim enables understanding of morphodynamic evolution of coasts.
Who created the surf zone model?
Malvarez and Cooper
_____________ is strictly defined as the wave height at maximum inundation.
Runup