Geology Lab
m7md98_
CoastalProcesseslecture2.pptx
Coastal Processes
Lab 7
Waves
Wave: energy in motion that results from disturbance. The energy that causes this is a disturbance force.
These disturbing forces can be landslides, calving glaciers, seafloor movements like underwater avalanches, volcanic eruptions.
Height, length, period of a wave depends on:
Wind speed
Wind duration
fetch
Types of Wave Breakers
Spilling Breakers
Break gradually over considerable distance
Form on shorelines with gentle offshore slopes
Plunging Breakers
Tend to curl over and break with a single crash
Front is concave, back is convex
Form at shorelines with steeper offshore slopes
Surging breakers
Peak up but surge onto the back without spilling or plunging
Forms when offshore slopes abruptly and wave energy becomes compressed
Wave Refraction
Bending of a wave as it propagates over different depths.
Concentrated energy on headlands causes erosion and deposition of sediments.
Tides
The periodic rising and falling of the water that results from gravitational pull of the moon and the sun’s action on the rotating earth.
Tidal Cycle includes
Flood tide
Ebb tide
Erosional Landforms
sea arch
sea stack
Coastal sediment Transport
Longshore Drift:
Net movement of sediment parallel to the shore.
Longshore current:
A current that flows parallel to the shore just inside the surf zone.
Also called littoral current
Rip current
Movement of water back into the ocean through narrow zones through the surf zone
Coastal Sediment Deposition and landforms
Beaches
accumulation of unconsolidated sediments that covers the shore
they are areas of deposition and are constantly changing
Barrier islands
long narrow accumulation of sand that is separated from the mainland by open water (lagoon, estuaries) or by salt marshes.
Emergent and Submergent Coastlines
Emergent coastlines
a coastline that has experienced a fall in sea level due to global sea level change, local uplift, or isostatic rebound.
Submergent coastline
A coastline hat has experienced a rise in sea level due to global change in sea level or local land subsidence
Coastal land loss by Erosion
Storm impacts
Dune and beach recession
Dune and beach breeching and overwash
Barrier island breeching
El Nino effects
Landslides and cliff retreat
Human activities
Mitigation of coastal erosion
Hard stabilization
jetties
groins
seawalls
breakwaters
Soft stabilization
beach nourishment
Abandonment
