COASTS Bk4 - Depositional Landforms Flashcards
What are the inputs and outputs of sediment within a beach?
INPUTS
- LSD
- cliff and dune erosion
- beach nourishment
- fluvial sediment
- onshore transport (swash)
OUTPUTS
- LSD
- offshore transport (backwash)
- sand mining
- offshore wind transport
- storm events (quarrying)
What % of beaches have net erosion, no change and net deposition?
Erosion - 70%
No change - 10%
Deposition - 20%
What are ridges and runnels and how are they formed?
Ridges and troughs running parallel to the coast near the LWM
- deposition during backwash (can be broken by drainage channels)
What are ripples and how are they formed?
Relatively small elongated ridges that form on the beach
- wave and currents slow across loose sand (dragged along and piled up)
What are cusps and how are they formed?
Semicircled shaped depressions with coarser material around the edge and finer material in the middle
- backward sourcing the finer material
What are berms and how are they formed?
Small ridges that form near the high tide mark
- deposited by the swash of constructive waves
What are storm beaches and how are they formed?
Ridge found near the back of the beach composed of larger sediment
- deposited by waves during storm events
What is the definition of a spit?
A long narrow beach of sand and shingle with one end attached to the shore and the other extending into the sea esturary
Conditions needed for a spit?
- huge volumes of sediment
- sharp change of direction of the coastline
- low energy coastline
- prevailing wind to allow LSD (drift aligned)
What are the steps of formation for a spit?
- Prevailing winds + max fetch from SW (LSD)
- Coastline direction change (sediment build up in sheltered area)
- Projects eastwards (material above HWM)
- Builds out and curves (2nd most dominant wind pushes the spit parallel to the mainland)
- Several curved ends develop (sand dunes + salt marsh)
- Finer material carried eastwards (deeper water of estuary)
What is the proximal point?
Where the spit joins the mainland
What is the distal point?
Furthest point of the spit that extends from the headland
What is a simple spit?
Either straight or recurved, do not have minor spits or recurved ridges along their landward edge
What is a compound spit?
Occurs where transport processes vary more - barbs form
What are tombolos?
Where a spit extends to a small offshore island and connects it to the mainland
What are offshore barbs? and what are their two reasons for formation?
Sandbars are submerged (only appear at low tide) ridges of sand or course sediment
- can act as sediment sinks (reduce impacts of waves by absorbing energy)
FORMATION
- destructive waves (strong backwash) erode sand from the beach and deposit it offshore
- shallow areas where the waves break a distance offshore
What are bars (barrier beaches)?
When a spit develops and there is no opposing force
What are barrier islands?
Depositional islands running parallel to the coastline
Definitions of sand dunes?
Accumulation of sand behind an active beach zone that is mounded by the wind and can become fixed in location by vegetation
Conditions needed for sand dunes?
- Large supply of sediment
- Dominant offshore wind
- Flatter gradient > aeolian processes are more effective
- Large tidal range
- Obstacle for deposition
What is plant succession?
Directional change in the types of plant species that occupy a given area through time (colonisation, establishment and extinction)
What is psammosere?
Ecological succession that began life on newly exposed coastal sand
What is climax vegetation?
Dominant mix of vegetation species that characterise an environment given time for colonisation to occur and reach stability
What is an ecosystem?
A collection of plants and animals that adapt and adjust to biotic and abiotic factors in a particular location
