Coastal Environments

Significance of costal environments

1. Population

2. Economics (transportation, resources, tourism)

3. dynamic environment

4. relatively young (geologic time)

Littoral zone

the area where marine processes can regularly move sediment about

Components of the littoral zone

Offshore, Nearshore, Surf zone, swash zone, foreshore, backshore

offshore

deep water (not part of the littoral zone)

Nearshore

water is shallow enough the waves are able to stir sediment and move it about

Surf zone

where waves peak up and break

Swash zone

first covered with water and then exposed to air as each breaking wave rushes up and then back down the beach

Foreshore

the area between high tide and low tide zone (intertidal zone)

Backshore

the beach

tides

the increase and decrease in elevation of water at the shore line

flood tide

the time period between high tide and low tide when water is rising up the beach

ebb tide

after high tide when the water begins to recede

tidal range

the difference in elevation between high tide and low tide

Tide causation

Tides are caused by gravity and inertia

Neap tide

lowest high tide, highest low tide, and minimum range

spring tide

highest high tide, lowest low tide, and maximum range

Wave controls

1. Wind speed

2. Wind duration

3. Fetch (distance of open water that is available for the wind to blow across)

Height

the difference in elevation between the crest and the trough

period

the time that it takes for a wave to travel one wavelength

steepness

height/length

wave orbit

water does not move forward, the particles travel in circles

Wave Shoaling transformation

• speed decreases

• wave length decreases

• height increases

• wave steepness increases

• period remains constant

wave refraction

a bending of the crest line when different portions of a wave are in different water depths

longshore current

a current that flows parallel to the beach, in the direction of wave movement

Types of coasts

rocky, sandy, muddy

rocky

characterized by cliffs and cobble beaches

Sandy

characterized by beaches, barrier islands, and sand dunes

Muddy

dominated by fine grain material and salt marshes

erosional features of costal environments

wave-cut platforms, cliffs, terraces, arches, and stacks

wave-cut platform

the result of wave erosion:

1. Sea erodes cliff

2. Waves cut notch weakening cliff

3. Cliff collapses to form a wave-cut platform

costal terraces

a wave-cut bench that is the result of uplift on the coastline

longshore transport

waves that approach the shoreline at an angle

types of longshore transport

spits and tombolo

spit

an extension of the shoreline a ridges of sediment that is deposited where the shoreline suddenly changes in orientation (generally from south to north- shore- parallel)

tombolo

a ridge sediment that is perpendicular to the shoreline rather than parallel (shore- perpendicular) - forms when a sandpit connects an island to the mainland

storm-fairweather cycle profiles

normal beach, adjustment to large waves, recovery

normal beach profile

• summer profile

• calm/fair weather conditions

• beach is relatively wide and foreshore is quite steep

• carry sand from bar onshore

• characterized by dunes and beaches on the surface

Adjustment profile

• winter profile

• stormy conditions

• large waves attack the beach eroding material depositing material in the nearshore zone (creates a nearshore bar)

• narrow beach

• flatter foreshore slope

• dunes and beach release sand and the sand moves offshore

Recovery

Sediment by the nearshore bar is picked up by fair weather waves and put back on the beach to build it out wider and recreated the steep foreshore zone

barrier islands

long linear features that are separated from the shoreline by a shallow body of water (sand-dominated coast, with a water body separating the island from the mainland)

Two types of barrier islands

ocean beaches and bay side beaches

ocean beaches

• tolerant

• intensive recreation

• intolerant of construction

bay side beaches

• intolerant

• no passage, breaching, or building

• no filing

Process of barrier island rollover

1. Narrow barrier island develops peat soil

2. A major storm occurs and dunes are destroyed

3. A new dune is created and a peat outcrop is created

Spatial distribution of coral reefs

• Common between 30 degrees north and south latitude (due to needing warm waters to form)

• Close to the coastline in shallow waters

• Not located near river systems

Three stages of coral reef development

Fringing, Barrier, atoll

Fringing

new volcanic island where coral pulps come to form a fringing reef

Barrier

the island subsides and a lagoon forms

atoll

a ring of coral surrounds an empty lagoon

hard shoreline protection

building a structure along the shoreline to redirect sediment transport pathways or alters the movement of wave energy

Types of hard shoreline protection

groins, breakwaters, stable shorelines

groins

a linear structure made of concrete or stone that extends from a beach into the water that shifts erosion

breakwaters

parallel ridges that break water and reduce sediment transport (help build tombolos)

bulkheads

a wall that is build right along the shoreline used to break waves and decrease erosion and push the process further down shore

types of softline protection

beach nourishment and dune restoration

beach nourishment

the artificial replenishment of a beach with sand

dune restoration

the planting of dune grass and sand fences to help trap sand and encourage it to accumulate to help build sand dunes and satisfy the transport capacity of the waves

stack

vertical towers of rock separated from but near a rocky coastal cliff face