Coastal Systems Flashcards
Coastal landforms evolve in response to…
Sea level history
geology
climate
waves & tides
What are the 3 dominating factors of coasts?
Waves, Tides and Rivers
What are the 3 main divisions of the coastal area?
Foreshore
Backshore
Offshore
What is the foreshore?
Wet part of the coastline - not offshore
What is the backshore?
Usually dry - only wet under storm conditions
How is sediment carried in / through coastal areas?
-Orbital motion of water particles
-Breaking of waves
-Swash processes (rush of seawater on the beach after breaking of a wave)
What are the 3 general phases of nearshore bar evolution?
Generation and initial growth of bar
Migration or consolidation of bar
merging or erosion of bar
How has global sea level changed in modern times?
Risen 21-24cm since 1880s
What are the 2 components of sea-level rise?
Main: Input of water from greenland ice sheets
Secondary: Thermal expansion as ocean warms
Explain isostatic sea level changes?
Isostatic sea-level changes are local changes caused by subsidence or uplift of the
crust related either to changes in the amount of ice on the land, or to growth or
erosion of mountains.
What does the nearshore zone represent?
Where waves start to ‘feel’ or morphologically influence the bottom of the littoral zone.
What are the 3 types of nearshore currents
Longshore - dominant, often unidirectional current
Return Flow (undertow) - flow away from shore through gaps in intertidal bars.
Rip currents - short return (circulation cell)
What are the 3 types of breaking waves?
Spilling - gradual breaking over distance - flat terrain.
Plunging - crest curls over nearly vertical wall of water
Surging - base advances at same time as top, usually on steep beaches.
What is wave swash?
When water rushes up the beach. Limited by slope of beach
Maximum swash is the run-up level.
Provide an example of coastline evolution on very small time scale
formation of coastal bars (constantly moving hour to hour)
What deposition formation characterizes wave-dominated coastal landforms?
Spits - long narrow accumulation of sand with one end jointed to mainland and the other projecting out to sea or across an estuary
What is a barrier island?
Spit that has detached from the coast. Depositional coastal landform
What are 3 factors that influence the formation of barrier islands and spits?
Constant flow of sediment
Wave energy
Direction of wave motion
Name some characterizing factors of estuaries
-Somewhat enclosed
-Mixing of salt and freshwater
-Tidal
How do salt marshes and mangroves protect from coastal erosion?
-Trap sediment
-Act as buffer
What is the main factor controlling costal cliff erosion?
Rock hardness
What are the critical processes involved in coastal cliff evolution?
-Mass movement
-Weathering
-Rock-removal processes (marine processes)
How is climate change affecting high latitude coastal zones (in the arctic)?
-Arctic is warming 4x faster than the global base rate
-glacial retreat
-increased meltwater discharge
-increased landform erosion
-glacial ice, sea ice, permafrost & beach ice
Which processes contribute to the formation of beach ridges?
Wave swash
What is a beach ridge berm? What does it indicate?
Active ridge parallel to shoreline formed by swash processes
Indicates maximum sea-level run-up.
How does a beach ridge plain form?
They are older sea berms. When a new berm forms and the beach ridge remains, then this will indicate the old sea level.
What are the 2 ideas at the essence of integrated coastal zone management?
minimize disruption
maximize benefits
employ soft engineering (nature-based solutions)
What are some examples of coastal geomorphological evolution at different chronological and spatial scales?
Smallest to largest:
sand ripples & runnels at the cm/m scale
sandbar m/100m
beach km
peninsula, coastal bar, spit etc
entire coastline
Provide some examples of small-scale and large-scale geomorph. evolution in river systems
Provide some examples of small-scale and large-scale geomorph. evolution in glacial systems
What are the 4 processes affecting Coastal Morphodynamics?
Sea level history
Geology
Climate
Waves & Tides
Explain the process of a wave as it moves from deep water to the shore (5 steps)
Shoaling
Breaking
Bores
Breaking
Swash
The _____ is the maximum level the waves can reach on the beach
Run up level
Wave _____ erodes and smooths coastlines
refraction
explain the coastal classification triangle
Dominated by fluvial/wave/tide power/frequency/direction.
Explain this picture
Spit formed by sediment deposit from fluvial forces when rounding the point from the stream. Reinforced by sediment deposit from ocean side and forced into triangular shape. Water slowing below transport velocity is caused by meeting of stream with ocean - opposing directions = slowing.
Why do spits continuously curve inward?
Dependent on direction of longshore drift - recurved tip occurs by pushing sediment off the edge of the existing spit
What is a common formation found in wave-dominated coastal landforms?
Barrier Islands
What is a common formation found in tide-dominated coastal landforms?
Estuaries and wetlands/marshlands/mangroves
Explain wtf going on here
Parallel lines on beach are beach riges - lowest one is the beach berm (formed by current swash processes). beach ridges are previous water levels/swash levels.
2 green lines are old fluvial streams worn down to the bedrock? green because of nutrient rich sediment?
