Coastal Systems and Landscapes

Comprehensive practice flashcards reviewing coastal systems, wave mechanics, weathering, mass movement, erosion, depositional landforms, sea level changes, shoreline management, the Holderness Coast case study, and the Sundarbans case study.

How does negative feedback maintain dynamic equilibrium in a coastal system during and after a storm?

Sediment is eroded from the beach in a storm and deposited offshore to form a bar. Waves then break over the offshore bar before reaching the beach, which reduces erosion on the beach and allows sediment to return to the beach.

What sequence illustrates a positive feedback mechanism in a coastal or oceanic environment?

Temperature increases, which causes sea ice to melt and shrink. The exposed ocean absorbs more sunlight, which causes the temperature to continue to increase.

What are the four primary inputs to a coastal system?

Wind, wave, tide, and current.

How is a wave created by wind?

Wind hits the water to form ripples. As ripples grow, they are pushed more easily by the wind; the stronger the wind and the longer the fetch, the larger the wave.

How are the backshore, nearshore, and offshore coastal zones defined?

The backshore is the area between the high water mark and the landward limit. The nearshore is the area tending seaward where waves begin to break (made up of the swash, surf, and breaker zones). The offshore is the area beyond which waves do not impact the seabed.

Why do waves break as they approach the shore?

Waves start at sea with a circular orbit. As they approach the shore, friction slows the base of the wave, creating an elliptical orbit. This increases the height and steepness of the wave until the upper part breaks onto the shore.

What are the key characteristics and landforms associated with constructive waves?

They are low waves with long wavelengths up to $100\,\text{m}$, a low frequency of $6\text{–}8\,\text{per min}$, and a strong swash with a weak backwash. They create wide, gently sloping beaches and constructive landforms such as spits.

What are the key characteristics and landforms associated with destructive waves?

They are high in proportion to length, have a high frequency of $10\text{–}14\,\text{per min}$, and have a strong backwash with a weak swash. They create narrow, steep beaches and erode the coastline to create wave-cut platforms or headlands.

How do high energy coasts differ from low energy coasts in energy, processes, and landforms?

High energy coasts have strong wave power, long fetch, and rate of erosion $>$ rate of deposition, creating headlands, wave-cut platforms, and cliffs. Low energy coasts have weak wave power, rate of deposition $>$ rate of erosion, are often found in estuaries and inlets, and form spits, tombolos, and salt marshes.

What is upwelling and what are its geographic effects?

Upwelling is the movement of cold water from the deep ocean to the surface, replacing warmer surface water with nutrient-rich water and forming global ocean circulation currents.

How often do high and low tides occur in the UK, and what is the interval between high tides?

The UK experiences $2$ high tides and $2$ low tides per day, with an interval of $12\text{ hours }25\text{ minutes}$ between high tides.

What alignment of celestial bodies creates neap tides, and what tidal range do they produce?

Neap tides occur when the Sun, Moon, and Earth are at $90^\circ$. They alternate weeks with spring tides and produce the lowest tidal ranges.

What alignment creates spring tides, and how frequently do they occur?

Spring tides occur when the Sun, Moon, and Earth are aligned. They occur twice in a lunar month and produce the largest tidal range.

What are the five sources of sediment in a coastal system?

Deposition in estuaries, rivers and streams flowing into the sea, cliff erosion, offshore sandbanks, and material from biological action (e.g. shells).

What is a sediment cell, and how many sediment cells exist in England and Wales?

A sediment cell is a distinct coastal area where sediment moves, separated by boundaries like headlands or deep water; they are closed systems in theory and can be divided into smaller sub-cells. England and Wales have $11$ sediment cells.

What is meant by a positive versus a negative sediment budget?

A positive sediment budget means sediment is being added and the shoreline is advancing. A negative sediment budget means sediment is being removed and the shoreline is retreating.

Which specific processes belong to physical, chemical, and biological weathering?

Physical weathering includes freeze–thaw, salt crystal growth, and hydration. Chemical weathering includes carbonisation and hydrolysis. Biological weathering includes root action and burrowing animals.

How does rotational slumping differ from a landslide in terms of slip plane and movement?

In a landslide, cliffs slip in a straight line when lubricated (often after heavy rain). In rotational slumping, soft rocks become lubricated and slip on a concave slip plane.

What is cavitation in coastal erosion?

Intense erosion due to the surface collapse of air bubbles in rapid flows of water, creating microjets that produce extreme stress onto a very small area.

How does wave quarrying differ from hydraulic action?

Hydraulic action is the compression of air in joints and lines of weakness, creating pressure that expands cracks. Wave quarrying is the actual removal of rocks and debris from a cliff or wave-cut platform via wave action once those cracks develop.

What are the four processes of coastal sediment transportation?

Suspension (fine material carried floating in the water), solution (minerals dissolved in the water), traction (large boulders and rocks rolled along the bed), and saltation (small pebbles and stones bounced along the bed).

How do headlands and bays form on discordant coasts, and what are two real-world examples?

Alternating bands of hard and soft rock meet the sea at right angles; waves erode the softer rock faster, causing it to retreat inland to form bays while resistant rock projects as headlands. Examples include Swanage Bay and Ballard Point (Wealden clays and chalk), and Dublin Bay and Howth Head (quartzite and sandstone).

How does a cave evolve into an arch and then a stack, and what are named examples of arches and stacks?

Weaknesses in headlands expand into a cave, which erodes completely through the headland to form an arch. The unsupported arch roof collapses due to biological weathering, leaving an isolated stack. Examples of arches include Durdle Door (UK) and Azure Window (Malta); examples of stacks include Old Harry (UK) and Totem (Australia).

What is a geo, how does it form, and what are named examples?

A geo is a steep-sided inlet into a cliff formed when the weakest part of a cliff line erodes inland, or when a pre-existing cave roof is weathered away and collapses. Examples include Calder's Geo (Shetland) and Silfra (Iceland).

How does a blowhole form, and what are named examples?

Hydraulic action and abrasion erode faults at the cliff base into an inland/upward tunnel until the cave roof collapses; incoming powerful waves trap air and water, ejecting high-pressure jets out the top. Examples include Devil's Bellows (Cornwall) and Nakalele Blowholes (New Zealand).

What are the stages in sand dune formation, and what examples are cited in the notes?

Onshore wind blows sand, which accumulates around vegetation into small mounds that progress into embryo dunes, foredunes, and larger dunes. Examples include Merthyr Mawr (South Wales) and the Great Dune of Pilat (France).

How does a barrier beach form, and how can it become a barrier island?

Prevailing winds drive longshore drift, extending a beach into a spit across a bay to form a barrier beach. Storm breaching can disconnect sections from the mainland, turning them into barrier islands (e.g. Chesil Beach, Miami Beach for barrier beaches; Scolt Head Island, Padre Island for barrier islands).

What distinguishes simple spits from compound spits, and what are examples of each?

Simple spits extend via longshore drift and feature a single hook caused by wave refraction (e.g. Spurn Point, Farewell Spit). Compound spits form in the presence of multiple prevailing wind directions, producing multiple recurved hooks (e.g. Hurst Spit, Cape Cod).

How does a tombolo form, and what are two named examples?

Waves refract around an offshore island, creating a sheltered zone of deposition behind it; deposited sediment builds a ridge that permanently connects the island to the mainland. Examples include St Ninian's Isle (Shetland) and Angel Road (Japan).

How do swash-aligned beaches differ from drift-aligned beaches?

On swash-aligned beaches, waves break parallel to shore with little or no longshore drift, producing wide profiles with berms (e.g. Lulworth Cove, Cable Beach). On drift-aligned beaches, waves break at an angle with strong longshore drift, producing narrower profiles and creating spits (e.g. Spurn Head, Sandy Hook).

What ecological succession takes place in mud flats and salt marshes?

Pioneer species like green algae and eel grass trap sediment; Spartina with its long roots colonises next; once the area is submerged less than $1/8$ of the time, sea lavender and sea aster colonise (the sward zone); finally, rushes grow where land is submerged only at high tide.

What is the difference between eustatic and isostatic sea level change?

Eustatic change is a global, relatively rapid change in sea level caused by changes in cryosphere water volume and thermal expansion. Isostatic change is a local, long-term vertical movement of the land caused by ice sheet weight depressing the land or melting causing post-glacial rebound.

What are the historic and projected sea level statistics recorded in the notes?

Sea levels have risen by $130\,\text{m}$ in the last $24{,}000\text{ years}$, rose by $1.7\,\text{mm/year}$ between $1880\text{–}1980$, and are predicted to rise by $30\,\text{cm}\text{–}1\,\text{m}$ by $2100$.

What is a ria, how does it form, and what are two examples?

A ria is a submerged, V-shaped river valley forming a deep estuary with a wide profile and tributaries, created by vertical river erosion (hydraulic action and abrasion) followed by post-glacial sea level rise. Examples include Kingsbridge Estuary (UK) and Ria de Arousa (Spain).

How do fjords and Dalmatian coasts form as features of submergence?

Fjords form when glaciers erode steep U-shaped valleys via abrasion that are subsequently flooded by melting ice (e.g. Loch Fyne, Sogne Fjord). Dalmatian coasts form when tectonic collisions fold limestone into parallel ridges and post-glacial sea level rise floods the intervening valleys, leaving parallel offshore islands (e.g. Dalmatian Islands, Croatia).

What are raised beaches and marine platforms, and what examples represent them?

They are emergent landforms left stranded above the water when sea level falls; wave-cut notches and cliff bases form wave-cut platforms and beaches that become raised terraces. Examples include Isle of Arran and San Diego Marine Terraces (raised beaches); Beachy Head and Santander Coast (marine platforms).

What are the costs, advantages, and disadvantages of sea walls?

Sea walls cost £$6000\,\text{per metre}$ to build and £$5000\,\text{per metre}$ to repair. Advantages include a long lifespan and effective prevention of beach recession; disadvantages include high costs and restriction of beach access (e.g. the $2\,\text{km}$ concrete wall in Withernsea).

What are the costs, advantages, and disadvantages of groynes and rock armour?

Groynes cost £$5\text{–}10{,}000$ each, trap sediment to build protective beaches, but cause the terminal groyne effect down-drift (e.g. $2$ granite groynes at Mappleton). Rock armour costs £$1000\text{–}3000\,\text{per metre}$, is durable and quick to install, but restricts access and traps debris (e.g. $70{,}000\,\text{tonnes}$ at Withernsea).

What are the costs, advantages, and disadvantages of beach nourishment and managed retreat?

Beach nourishment costs £$15\,\text{per m}^3$, preserves natural appearance, and boosts tourism, but requires ongoing cumulative costs. Managed retreat costs £$5\text{–}10{,}000\,\text{per hectare}$ in land compensation, creates natural salt marsh defences, but involves land loss and compensation disputes with farmers.

When were Shoreline Management Plans (SMPs) introduced, how many exist in England and Wales, and what time horizons do they plan for?

Introduced in $1995$, there are $22$ SMPs around England and Wales. They plan for the short term ($0\text{–}20\,\text{years}$), medium term ($20\text{–}50\,\text{years}$), and long term ($50\text{–}100\,\text{years}$).

What are the four management policy options used in Shoreline Management Plans (SMPs)?

1. Hold the line, 2. Do nothing but monitor, 3. Retreat the line, and 4. Advance the line.

What are the geology, erosion rates, and historical losses of the Holderness Coast?

The coast is mostly made of weak boulder clay (glacial till), with chalk at Flamborough Head. It erodes at $1.5\text{–}2\,\text{m}\text{ per year}$, having lost $20\,\text{villages}$ ($3\,\text{miles}$ of land) since Roman times, leaving exposed pipes at Atwick and abruptly ending roads at Skipsea.

What are the sediment cell and coastal transport dynamics of the Holderness Coast?

Holderness forms part of sediment cell $2\text{A}$. Longshore drift moves south, transporting $500{,}000\,\text{tonnes}$ of boulder clay per year southward to form Spurn Head, a $3\text{-mile-long}$ spit across the River Humber.

What are the geographic dimensions, population, and biodiversity counts of the Sundarbans?

Spanning a $350\,\text{km}$ width in Southern Bangladesh and Eastern India along the Bay of Bengal, the delta features $10{,}000\,\text{km}^2$ of forest ($4143\,\text{km}^2$ land and $874\,\text{km}^2$ water in Bangladesh) and $7.8\,\text{million}$ people. It supports $334$ species of plant, $49$ mammal, $400$ fish, $320$ bird, $53$ reptile, and $11$ amphibian species.

How effective are mangrove forests against tropical storms in the Sundarbans?

Mangrove forests decrease the intensity of tropical storms by absorbing up to $90\%$ of their energy, while their root systems stabilise shorelines and trap sediment.

What are the flooding risks in the Sundarbans, and what human adaptations have been implemented?

Risks include sea level rise of $3\text{–}8\,\text{mm/year}$, storm surges breaching mud embankments, and $800\,\text{km}$ of embankments vulnerable to failure. Human responses include building houses on stilts, using salt-tolerant rice varieties that tolerate submergence for up to $2\,\text{weeks}$, building coastal barrages, and banning commercial logging since $1989$.

What damage did Cyclone Sidr cause in 2007, and what defences mitigate storm impacts in the Sundarbans?

Cyclone Sidr caused $3500\,\text{deaths}$ and affected millions along the coast. Defences include mangroves absorbing up to $90\%$ of storm power, $1000$ multi-purpose cyclone shelters, and improved early warning systems.

How has shrimp farming grown in the Sundarbans, and what are its environmental and social limitations?

Aquaculture expanded from $32{,}000\,\text{hectares}$ in $1999$ to $52{,}000\,\text{hectares}$ in $2019$. While providing income in infertile areas, fine mesh nets catch wild fry (harming wild fish recovery), overfarming can lead to shortages, and mechanized operations reduce long-term manual jobs.