Coastal Environments 1

• Prevailing Winds
• Sea floor features
• Heat & Temperature

- Provides energy, causes molecules to expand
- Most heat found near the equator
- Shallower waters heat more quickly

Littoral Drift

A geographical process that consists of the transportation of sediments (clay, silt, sand and shingle) along a coast at an angle to the shoreline, which is dependent on prevailing wind direction, swash and backwash

Littoral Drift

• Most waves approach the shoreline at an angle, generating a flow or water running parallel
• Transports sediment parallel ti shoreline and moves water along the surf zone

Rip Currents

• Strong currents move away from shoreline
• Develop when sea water is "piled up" along the coastline by incoming waves
• Current may initially run parallel to the coast before flowing into the breaker zone
• Can be hazardous to swimmers and small boats

Global Surface Currents

• Movement of cold water from deep in the ocean to the surface
• More dense cold water replaces warmer surface water, creating nutrient rich cold currents
• Part of the pattern of global ocean circulation

• Larger tidal range means there is a larger zone subject to erosion
• Smaller tidal range means part of the coastline is more consistently subject to prevailing wave action
• Significant flow of sea in and out of coastal sections can generate strong currents, influencing the direction and scale of sediment movement
• Increased flood risk for coastal settlements when low-pressure systems coincide with high tides
• The combined effect of the high tide rising further due to low air pressure can lead to storm surges overwhelming coastal defences
• Energy can fuel tidal power generators 

Swansea Bay, Wales, has a major scheme in development to generate renewable energy from the twice daily rise and fall of coastal waters.

Ocean Currents:

• Caused by wind, gravity and water density
• Surface circulation and deep circulation
• Wind is the most important cause of surface currents
• Global Conveyer Belt is driven by density variation
• Begins North near Greenland and travels South

Sediment Sources

• Rivers - Majority of sediment originates from rivers, especially in high rainfall areas
• Cliff Erosion - Important local sediment source, especially with soft or unconsolidated rock
• Longshore Drift - Sediment transported from the input to the output
• Wind - Glacial or hot environments, wind blown sand can be deposited in coastal areas

Related to underlying geology and lithology

Lithology

• Strata - Layers of rock
• Bedding Planes - horizontal natural fractures in strata caused by gaps in time during periods of rock formation
• Joints - Vertical cracks caused either by concentration as sediments dry out, or by Earth mivements during uplift
• Folds - Formed by pressure during tectonic activity which makes rock buckle and crumple
• Faults - Formed when stress inflicted on a rock exceeds its internal strength
• Dip - Refers to the angle at which rock strata lie (horizontally, vertically, towards the sea or inland)

Concordant:
Parallel

Discordant:
90 degree angle

Headlands and Bays

• Erosional processes predominate in areas with less resistant rock
• Erosion forms bays and leaves more resistant rock protruding as headlands
• When coastline is concordant marine processes form bays and headlands
• Refraction: headlands recieve high energy waves so are more more vulnerable to erosion
• Bays experience low-energy waves, allows sediment to accumulate

• Erosion is concentrated to a small area on the rock face due to waves breaking
• Cliff begins to become undercut, forming a wave cut notch
• Further erosion increases cliff stress until the cliff weighs too much to be supported
• Cliff collapses, forming a wave cut platform 

What is a spit?

• Sand/shingle moved by longshore drift
• If coastline changes direction, sediment builds up and forms a spit
• Outward river flow prevents extension across estuary mouth
• Wave refraction carries material into more sheltered water behind (recurved tip

Simple spits

• Neither straight nor recurved
• Do not have minor spits or recurved tips

Compound spits

• Occur where transport processes are variable over time, producing barbs along the spit
• May have similar features to to simple spits
• Have a number of recurved ridges, or minor spits, along their landward side, possibly marking the position where the spit terminated in the past

Embryo Dunes

• Suitable for colonisation by grasses
• Able to grow upwards by accumulating wind blown sand, stabilising the surface
• Long roots of marram help bind sand, plants aff organic matter and water retention

Foredunes

• Upward growth of embryo dunes creates dunes beyond the reach of all but highest tides

Yellow & Grey Dunes

• Dunes are initially yellow due to little organic matter growing
• Vegetation cover inreases, humus is added to the sand making it look more grey
• Can reach heights of 20m in places

Woodland

• Plants and animals eventually colonise to form woodland

• Develop on sheltered shorelines that are not espised to powerful waves
• Often located in estuaries where rivers meet the sea or on the landward side of a spit
• Low lying areas of the shore that are submerged at high tide are composed of silt and clay
• They develop in estuaries where the flow of fresh water out of the river us slow and sea water flows into the river mouth with each high tide and out of the river mouth with each low tide
• Where salt water gently flows into the estuary, it brings large amounts of fine sediment
• This meets with an equally slow flowing river carrying its own fine silt and clay
• As the two flows meet, the fine particles settle out of suspension in a process known as flocculation where individual particles aggregate to form larger heavier particles that sink
• At low tide, the inter-tidal area of mud is exposed, showing exidence of a shaped surface
• Mudflats can be extensive, covering tens of square km, but they are not necessarily permanent features
• Mudflats are common globally and often develop into saltmarshes
• Saltmarsh ecosystems change over time
• The vegetation succession that develops is known as a Halosere, which is tolerant of salty conditions

1. Low lying vegetation (eg. eel grass) begins to grow on mudflats. This slows the currents and leads to further and more uneven deposition

2. Pioneers begin to colonise the area. The plants are able to tolerate salty conditions & periodic submergence. They are known as halophytes. Spartina has two root systems - a fine mat of surface roots to bind the mud and long, thick roots that can secure up to 2m of deposited material. This enables the plant to trap more mud than other pioneers,, and thus it has become the dominant vegetation on the tidal flats of the British Isles

3. The Pioneers gradually develop close vegetation over the mud, allowing colonisation by other plants such as marsh grass. These form a dense mat of vegetation up to 15cm high. The growth of vegetation has the effect of slowing the tidal currents even more, leading to more mud+salt accumulation. Dead organic matter also helps build up the surface

4. As mud levels rise, complex creek systems develop, chanelling tides and deepening as the marsh becomes higher. Hollows may form where seawater becomes trapped and evaporates, leaving salt-pans uninhabitable for plants. As the land rises above sea level, rushes and reeds become established, eventually leading to the growth of trees such as alder, ash and oak to complete the succession. The land is rarely covered by the sea.

Eustatic Change:

• A global change that usually happens relatively quickly
• A change in sea level relative to land
• Usually due to glacial freezing or melting

Isostatic Change:

• A local change
• Usually happens relatively slowly over an extended period of time
• Can be caused by addition of ice during ice ages (causes land to sink), removal of glacial ice (causing land to rise) or erosion

Tectonic Change

• Occurs particularly at tectonic plate margins
• Can be a few metres as a result of one seismic event

• As the land rises as a result of isostatic recovery, former wave-cut platforms and their beacher were raised above present sea level
• Raised beaches are common on the west coast of Scotland, where the remains of eroded cliff lines (relic cliffs) can often be found behind raised beaches, with wave cut notches and caves as evidence of past marine erosion
• Wave cut platforms can also be exposed if sea levels fall sufficiently, although these are often hidden beneah fresh sea deposits

• As sea levels dropped, land rose, causing an emergent coastline
• Relic cliffs remain, showing wave cut notches and platforms

Rias

• Sheltered winding inlets with irregular shorelines
• Rias form when valleys in a dissected upland area are flooded
• Common in south west England where sea levels rose after the last ice age
• The lower parts of many rivers and their tributaries were drowned to form rias
• They often form natural harbours

Fjords

• Glaiers move and meet the sea
• Over time they melt, leaving a U-Shaped valley
• Sea water sometimes floods the valleys, forming fjords

Ria vs Fjord

Ria = uniformly deep

Fjord = lip between fjord and sea

• According to the IPCC (Intergovernmental Panel for Climate Change), sea levels stabilised 3000 years ago and there has been little change since that time - until recently
• From the late 19th and early 20th centuries, sea levels rose globally by about 1.7mm per year
• This increased to 3.2mm between 1993 and 2010
• The IPCC estimates that by 2100, sea levels could rise between 30cm and 1m from their current levels
• Sea level rise is primarily due to:

- Thermal expansion of water, due to heating

- The melting of freshwater ice in Greenland, Antarctica and from Alpine glaciers

The nation if Kiribati consists of 33 islands in the Pacific Ocean that stretch across an area almost as wide as the USA.

• The ismands are very low-lying sand and mangrove atolls, in most places only 1m or so above sea level
• Predicted that many islands could disappear under the sea in the next 50 years
• In places, sea level is rising by 1.2cm a year (4x faster than global average)
• In 2014, President Anote Tong finished the purchase of 20km sq. of land on one on one of the islands of Fiji - 2000km from Kiribati
• Rising sea levels are contaminating groundwater and affecting the ability to grow crops
• Land in Fiji will be used in the immediate future for agriculture and fish-farming projects
• In the future, people could move there from Kiribati
• Government has launched 'migration with dignity' policy to allow people to apply for jobs in neighbiuring countries such as New Zealand
• If the islands are submerged, Kiribati will become environmental refugees, people will be forced to migrate as a result of changes to the environment

Examples:

• Hold the Line
• Advance the Line
• Strategic Retreat
• Do Nothing

SMPs are found in England and Wales, and aim to manage the shorelines sustainably and in an environmentally friendly manner. Shoreline Management Plans affect ONLY England and Wales, as opposed to Integrated Coastal Zone Management, which takes place globally.

• The movement of sediment around the British Isles occurs mainly within distinct cells
• Boundaries rarely coincide with administrative boundaries of the Local Authorities
• The Integrated system of SMPs was introduced in 1995
• There are 22 SMPs around England and Wales corresponding to sediment vells and sub-cells
• They're designed to identify the most sustainable approach to flood and erosion management

AIMS:
To plan for:

• Short term (0-20 years)
• Medium/Mid Term (20-50 years)
• Long Term (20-100 years)

Many short term responses are nearing completion, most have been/are being reviewed to create a second generation of SMPs.

• Provide an assessment of the risks associated with the evolution of the coast
• Provide a framework to addressthe risks to people and the developed, historic and natural environment
• Address risks in a sustainable way
• Provide the policy agenda for coastal defence management planning
• Aim to be technically sustainable, environmentally acceptable and economically viable
• Ensure management plans comply with international and national conservation and biodiversity legislations
• Incorporate a 'route map' to allow decision makers to make changes to the short and medium term plans, and to ensure that long term sustainability is maintained
• Provide a foundation for future research and the development of new coastal management strategies in the future
• Are 'live' working documents to be continually reviewed and updated, setting new targets for future management strategies

Each SMP describes how each management unit, or stretch of coastline covered by the plan, is to be managed.

GLOBAL

• Aim at having a 'common integrated approach'
• They are sustainable
• They aim to look at the coastline or sections of the coastline as a whole
• Avoids 'peacemeal' approaches to management