THE COASTAL ENVIRONMENT

The coastal environment, is the area where land meets the ocean, or an area of coastline which forms the boundary between the land and the ocean.

The term coastal zone is a region where interaction of the sea and land processes occurs.

The term pelagic coast refers to a coast that fronts the open ocean, as opposed to a more sheltered coast in a gulf or bay. A shore or a beach, on the other hand, can refer to parts of land adjoining any large body of water, including oceans (seashore) and lakes (lake shore). 

 

According to the UN atlas, an estimated 44% of people live within 150 km or 93 miles of the ocean.

 

 

UNDERSTANDING COASTAL ENVIRONMENTS

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Tides often determine the range over which sediment is deposited or eroded. Areas with high tidal ranges allow waves to reach farther up the shore, and areas with lower tidal ranges produce deposition at a smaller elevation interval. The tidal range is influenced by the size and shape of the coastline. Tides do not typically cause erosion by themselves; however, tidal bores and storm surge can erode as the waves surge up beaches and river estuaries from the ocean.

 

Waves erode coastline as they break on shore releasing their energy; the larger the wave the more energy it releases and the more sediment it moves. Coastlines with longer shores have more room for the waves to disperse their energy, while coasts with cliffs and short shore faces give little room for the wave energy to be dispersed. In these areas the wave energy breaking against the cliffs is higher, and air and water are compressed into cracks in the rock, forcing the rock apart, breaking it down. Sediment deposited by waves comes from eroded cliff faces and is moved along the coastline by the waves. This forms an abrasion or cliffed coast.

Sediment deposited by rivers is the dominant influence on the amount of sediment located on a coastline. Today riverine deposition at the coast is often restricted or blocked by dams and other human regulatory devices, which remove the sediment from the stream by causing it to be deposited inland.

 

Like the ocean which shapes them, coasts are a dynamic environment with constant change. The Earth's natural processes, particularly sea level rises, waves and various weather phenomena, have resulted in the erosion, accretion and reshaping of coasts as well as flooding and creation of continental shelves and drowned river valleys.

Environmental importance

The coastal environment and its adjacent areas on and off shore are an important part of a local ecosystem: the mixture of fresh water and salt water (brackish water) in estuaries provides many nutrients for marine life. Salt marshes and beaches also support a diversity of plants, animals and insects crucial to the food chain.

 

The high level of biodiversity creates a high level of biological activity, which has attracted human activity for thousands of years.

Human impacts

 

In Africa and many other parts of the world, coastlines regrettably serve as a public waste dump.

 

Properties close to the coast are especially desirable encouraging more and more of the world's people to want to live in coastal regions. Many major cities are on or near good harbours and have port facilities. Some landlocked places have achieved port status by building canal systems.

The coast is a frontier that nations have typically defended against military invaders, smugglers and illegal migrants. 

Fixed coastal defences have long been erected in many nations and coastal countries typically have a navy and some form of coast guard.

 

Coasts, especially those with beaches and warm water, attract many tourists. In many nations tourism is essential and central to the local economy. Coasts offer recreational activities such as swimming, fishing, surfing, boating, and sunbathing. Growth management can be a challenge for coastal local authorities who often struggle to provide the infrastructure required by new residents and tourists.

Threats to coastlines

 

Coasts face many human-induced environmental impact threats. The human influence on climate change is thought to contribute to an accelerated trend in sea level rise which threatens coastal environments and habitats.

 

Pollution can occur from a number of sources: garbage and industrial debris; the transportation of petroleum in tankers, increasing the probability of large oil spills; small oil spills created by large and small vessels, which irresponsibly flush bilge water into the ocean.

Fishing has declined due to habitat degradation, overfishing, trawling, bycatch and climate change. Since the growth of global fishing enterprises after the 1950s, intensive fishing has spread from a few concentrated areas to encompass nearly all fisheries.

The scraping of the ocean floor in bottom dragging is devastating to coral, sponges and other long-lived species that do not recover quickly. This destruction alters the functioning of the ecosystem and can permanently alter species composition and biodiversity. Bycatch, the capture of unintended species in the course of fishing, is typically returned to the ocean only to die from injuries or exposure. Bycatch represents about a quarter of all marine catch. In the case of shrimp capture, the bycatch is five times larger than the shrimp caught.

 

It is believed that melting Arctic ice will inevitably cause sea levels to rise and flood many coastal areas.

 

Marine pollution and Marine debris

Conservation

 

Extraordinary population growth in the 21st century has placed enormous stress on the planet's ecosystems. The harvesting of mangroves for timber and clearing for fishing has drastically reduced the mangrove forests, resulting in a loss of habitat and spawning grounds for marine life unique to affected area. These mangrove forests also help to stabilize the coastlines. Conservation efforts since the 1980s have partially restored the ecosystems but there is still much to be done.

Coastline Categories

 

Emergent coastline and Submergent coastline

 

According to one principle of classification, an emergent coastline is a coastline which has experienced a fall in sea level, because of either a global sea level change, or local uplift. Emergent coastlines are identifiable by the coastal landforms, which are above the high tide mark, such as raised beaches. In contrast, a submergent coastline is one where the sea level has risen, due to a global sea level change, local subsidence, or isostatic rebound. Submergent coastlines are identifiable by their submerged, or "drowned" landforms, such as rias (drowned valleys) and fjords.

 

According to a second principle of classification, a concordant coastline is a coastline where bands of different rock types run parallel to the shore. These rock types are usually of varying resistance, so the coastline forms distinctive landforms, such as coves. Discordant coastlines feature distinctive landforms because the rocks are eroded by ocean waves. The less resistant rocks erode faster, creating inlets or bay; the more resistant rocks erode more slowly, remaining as headlands or outcroppings.

Concordant coastline and Discordant coastline

 

A cliffed coast or abrasion coast is one where marine action has produced steep declivities known as cliffs.

A flat coast is one where the land gradually descends into the sea.

A graded shoreline is one where wind and water action has produced a flat and straight coastline.

 

Coastal landforms

 

Bay

Headland

Cove

Peninsula

 

Cliff erosion

Much of the sediment deposited along a coast is the result of erosion of a surrounding cliff, or bluff. Sea cliffs retreat landward because of the constant undercutting of slopes by waves. If the slope/cliff being undercut is made of unconsolidated sediment it will erode at a much faster rate then a cliff made of bedrock.

 

A natural arch is formed when a headland is eroded through by waves.

 

Sea caves are made when certain rock beds are more susceptible to erosion than the surrounding rock beds because of different areas of weakness. These areas are eroded at a faster pace creating a hole or crevice that, through time, by means of wave action and erosion, becomes a cave.

 

A stack is formed when a headland is eroded away by wave and wind action.

 

A stump is a shortened sea stack that has been eroded away or fallen because of instability.

 

Wave-cut notches are caused by the undercutting of overhanging slopes which leads to increased stress on cliff material and a greater probability that the slope material will fall. The fallen debris accumulates at the bottom of the cliff and is eventually removed by waves.

 

A wave-cut platform forms after erosion and retreat of a sea cliff has been occurring for a long time. Gently sloping wave-cut platforms develop early on in the first stages of cliff retreat. Later, the length of the platform decreases because the waves lose their energy as they break further off shore.

Coastal features formed by sediment

 

Beach

Beach cusps

Raised beach

Cuspate foreland

Dune system

Mudflat

Ria

Shoal

Strand plain

Spit

Surge channel

Tombolo

Coastal features formed by rivers

 

Lagoon

Salt marsh

 

Other features on the coast

 

Concordant coastline

Discordant coastline

Fjord

Island

Island arc

Machair

Geologic processes

Geologic processes that affect a coastal zone

 

Attrition

Currents

Denudation

Deposition

Erosion

Flooding

Longshore Drift

Saltation

Sea Level Change

Eustatic

Isostatic

Sedimentation

Coastal Sediment Supply

Sediment Transport

Solution

Subaerial Processes

Suspension

Tides

Water Waves

Diffraction

Refraction

Wave Breaking

Wave Shoaling

Weathering

Wildlife

Seashore wildlife and Coastal fish

 

Animals

Some of the animals live along a typical coast. There are animals like puffins, sea turtles and rockhopper penguins. Sea snails and various kinds of barnacles live on the coast and scavenge on food deposited by the sea. Most coastal animals are used to humans in developed areas, such as dolphins and seagulls who eat food thrown for them by tourists. Since the coastal areas are all part of the littoral zone, there is a profusion of marine life found just off-coast.

 

There are many kinds of seabirds on the coast. Pelicans and cormorants join up with terns and oystercatchers to forage for fish and shellfish on the coast. There are also seals, sea lions, turtles and penguins found on the coasts around the world.

 

Plants

Coastal areas are famous for their kelp beds. Kelp is a fast-growing seaweed that grows up to a metre a day. Corals and sea anemones are true animals, but live a lifestyle similar to that of plants. Mangroves, seagrasses and salt marsh are important coastal vegetation types in tropical and temperate environments respectively.

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CARING FOR OUR OCEANS