2B.5 Sediment Transport and Deposition Flashcards
how is sediment transported alone a coastline
long shore drift
name 4 processes of sediment transportq
saltation
solution
suspension
traction
traction
sediment rolls along, pushed by waves and currents
saltation
sediment bounces along, due to the force of water or wind
suspension
sediment is carried in the water column
solution
dissolved material is carried in the water as a solution
on what type of coast are depositional landforms most common?
drift-aligned
-wave crests break at an angle to the coast
-longshore drift occurs and features develop
swash aligned coasts
wave crests approach parallel to the coast, there is limited longshore movement of sediment
gravity settling
the energy of water transportation is too weak to move sediment so it is deposited
flocculation
depositional process for small particles, they remain suspended in water, clump together and sink due to a chemical attraction
longshore current
zigzag movement of water in the surf zone
longshore drift
movement of sediment caused by longshore current
bayhead beach
a swash aligned feature
-waves break at 90 degrees to the shoreline and move sediment into a bay where beach forms
-erosion occurs at headlands
-deposition occurs at the bay
example of a bayhead beach
Lulworth Cove in Dorset
spit
a sand or shingle beach ridge that extends beyond a tun in the coastline
-longshore drift currents spread out and lose energy leading to deposition
-length is determined by whether secondary currents cause erosion
example of a spit
Spurn Head, Holderness Coast
tombolo
a sand or shingle bar that attaches a coastline to an offshore island
-forms due to wave refraction around offshore islands, creating an area of calmness and deposition
example of a tombolo
St Ninian’s tombolo in Shetland
bar/ barrier beach
a sand or shingle connecting two areas of land, a shallow water lagoon forms behind
example of a bar/ barrier beach
Chesil Beach in Dorset
recurved/ hooked spit
a curved landward spit into a bay or inlet
-seaward end of the spit curves landward in to shallow water
-hook can be more pronouced by waves fro another direction to the prevailing wind
example of a recurved or hooked spit
Hurst Castle Spit in Hampshire
cupsate foreland
rough triangular shape feature that extends from a shoreline
-longshore drift from opposing directions converge at the boundary of two sediment cells
-sediment is deposited by both currents
example of cupsate foreland
Dungeness, Kent
why can depositional landforms often be unstable?
they are made up of unconsolidated material, dynamic environments
-loose material is transported by the waves tides, currents and wind
-can be stabilised by plant succession (binding sediment, encouraging more deposition)
what are salt marshes?
areas of flat, silty sediment that accumulates up, around estuaries or lagoons
-they develop in sheltered areas, fresh and saltwater meet, no strong tides or currents
sediment cell model
consists of sources, transfers and sinks, it shows how sediment moves along the coast in sediment cells
sediment cell
a linked system of sources, transfers and sinks along a section of coastline
each cell operates between physical barriers that prevent the sediment form moving any further along the coastline
sediment budget
the amount of sediment available within a sediment cell
what happens if the sediment budget falls?
the waves transport sediment (positive feedback)
-increasing the original change
what happens if the sediment budget increases?
more deposition occurs (negative feedback)
works against original change
dynamic equilibrium
the way in which systems attempt to balance inputs and outputs
how many sediment cells are in the UK
11
e.g. the east coast of england
source region: Flamborough Head
transfer zone: Holderness Coast
sink region: Spurn Head
how does a sediment cell operate?
as a CLOSED SYSTEM
examples of sources and inputs
sediment is generated
-cliff erosion
-onshore currents
-river transport
-wind blown sediment from land
-sub-aerial processes
-marina organisms
examples of transfers
places where sediment is moving along the shore
-longshore drift
-swash or backwash
-tidal/ sea currents
-wind
examples of sinks or outputs
deposition dominates and landforms form
backshore depositional landforms e.g. sand dunes
-foreshore depositional landforms e.g. beaches- berms, runnels and ridges
-nearshore depositional landforms e.g. bars
-offshore depositional landforms e.g. barrier islands
