coastal environments

A2 geography

upper beach/backshore

area of the beach closest to land (includes cliffs, dunes and berms)

foreshore

area between high tide and low tide; can be a topic of debate for land ownership

offshore

the area of deeper water beyond the point at which waves begin to break

wave orbit

the circular movement in which water moves as energy goes by in waves

wave base

the depth where the circular/orbital motion of water particles no longer exerts impact on the seabed (usually half the wavelength)

wave frequency

the number of waves per minute

wave height

how tall the wave is… the distance between the trough and the crest

wave length

how long the wave is—distance between two successive troughs or crests

crest

highest point of a wave

trough

lowest point of a wave

swash

remnants of a wave that already broke; gets to the beach at a 45 degree angle due to longshore drift and releases energy

backwash

the water an energy washed back down to the sea from the beach; returns at a 90 degree angle due to gravity

fetch

how far the wave has travelled—the longer it is, the more energy in the wave

tidal range

the vertical distance between the high water mark and the low water mark

spring tides/king tides

tides that have the greatest tidal range due to the alignment of the earth, moon and sun (moon is new or full)

neap tides

tides with minimum tidal range that occur during the first and third quarters of the moon (when the moon is not in line with the earth and sun)

amphidromic point

a location on the planet where there is no tidal range (eg: oteranga bay near wellington)

microtidal

tidal range of less than 2m (smallest tidal range)

mesotidal

tidal range of 2-4m (medium tidal range)

macrotidal

tidal range higher than 4m (largest tidal range)

tidal bore

occurs when the flow of water from the river into the ocean reverses, and the tide pushes water up the river

storm surge

an abnormal rise of water generated by a storm, over and above the predicted astronomical (expected) tides

rip currents

a strong flow of water running from a beach back to the open ocean, sea, or lake

embayment

an indentation of a shoreline larger than a cove but smaller than a gulf (usually known as a bay)

headland

a coastal landform where a cliff juts out into a body of water when resistant rock is surrounded by softer rock that erodes away

groyne

low lying wood or concrete structures situated out to sea from the shore — designed to trap sediment, dissipate wave energy and reduce the removal of material from the beach by longshore drift

wave pounding

erosion caused by the forceful impact of waves against cliffs along a coastline which lead to the weakening and eventual breakdown of rock

slaking

the chemical weathering of calcium by acidic water — tends to occur in rock pools due to the presence of organisms secreting organic acids

salt weathering/salt crystallisation

when sodium and magnesium compounds expand in joints and cracks, thereby weakening rock structures (eg. dead sea, jordan)

solution weathering

materials disintegrate/dissolve when exposed to water — this can be caused by hydration cycles

wash loads

fine sediment particles (like clay and silt) that are carried in suspension within a stream or river flow, but are not found in significant quantities on the riverbed

littoral cell

a coastal compartment that contains a complete cycle of sedimentation including sources, transport paths and sinks

dredging

the removal of sediments and debris from the bottom of lakes, rivers, harbours, and other bodies of water

dynamic equilibrium

when inputs and outputs in a system are balanced, despite the system being in a constant state of change and movement (eg: a beach experiences constant deposition AND erosion)

composite cliffs

cliffs made up of more than one type of rock/sediment

strata

alternating layers/sections of hard and soft rock — form headlands or notches (depending on orientation) when the sea erodes a section of the coast

bevelled cliff

a coastal cliff with a steeper base and a gently sloping top due to periglacial processes (thawing and freezing) or simply differential erosion where the top of the cliff is made up of softer and easily eroded rock

solifluction

the gradual movement of wet soil or other material down a slope, forming a deposit — occurs when seasonal freeze-thaw cycles prevents water from percolating through the material

swash-aligned coast

when waves approach the shore parallel to the coastline — limited longshore drift and wide, curved beaches

drift-aligned coast

when waves approach the shore on an angle — longshore drift and formation of spits

littoral deposits

sediment such as sand and pebbles deposited by the sea into the littoral zone — these deposits form landforms such as beaches, spits and bars

neritic/sublittoral deposits

deposits made in the area that is constantly covered by water

cusps (beach cusps)

crescent-shaped indentations that form on beaches where there is a junction between sand and shingle — once the curving shape is created, swash is concentrated in the small bay that forms in the centre, leading to more erosion in that area, hence forming hollow, u-shaped cusps

berm

area along a coastline where high tide is marked by deposits made there (seaweed, driftwood, etc)

swales/bioretention

a long, narrow and shallow depression in the land, often with gently sloping sides, that can be either natural or human-made (reduces risk of flooding by slowing surface run off and therefore increasing infiltration)

offshore bar

a submerged ridge of sand or shingle, running parallel to the coast, formed by the deposition of sediment offshore where waves lose energy

bioconstruction

when organisms actively or passively contribute to the formation of landforms or structures, such as reefs, mounds, or crusts, through their biological activities

hard engineering

the building of artificial structures to try control natural processes like erosion or flooding — eg: sea walls, groynes, rock armour, dams

soft engineering

manipulating and modifying natural systems to achieve desired outcomes, rather than trying to stop or impede them — eg: dune stabilisation, beach nourishment, managed retreat…

sand mining

the removal of sand from its natural environment for commercial purposes — eg: removal from beaches, inland dunes, riverbeds, open pits FOR various industries including construction and manufacturing