Coasts are places where land meets ocean; a coast’s shape, as seen from above, is its coastline. Coastlines alter when the land or the ocean alters. Land changes include destruction, deposition (increase of land by the arrival of solid material, often small particles brought to the coast by rivers), or rising or falling of the land itself due to geological processes. The ocean may change by movement its current and wave patterns or by rising or falling in level. Human activity also affects the development of the coast, as it is a complex space. The coastal zones of the Earth are tremendously different and enormously important, not only for humankind.
They cover around 20 per cent of the Earth’s surface;
There are many transport tracks and industrial objects
A lot of people go to rest in the coastal areas
They function as an important sediment trap that consolidates sediments from the rivers;
They influence many global parameters in their role as a buffer between the land and sea;
75 per cent of mega-cities with populations over ten million are located in coastal zones;
A significant proportion of world fisheries are carried out in coastal waters (90 %);
About half of the world’s population lives and works in them (more than 45%).
A large part of the world community lives in flat coastal regions that can radically change their form within a short time. The populations in coastal regions are growing faster than in any other region on Earth.
The form of a coast is exerted by many factors. One significant factor is the shifting of sediments, such as dirt, sand and gravel. These deposits are carried mainly by waves, currents, rivers that flow into the sea, or tides. Because of courses sediments can accumulate, redistribute or erode. If sediments are moved instead of reallocation, the shape of the shore will change . One example of this is Cape Cod. Because of erosion, park officials have shifted observation decks and removed constructions. In January 2014, part of the Nauset Light Beach stairs washed away during a storm just months after having $200,000 in repairs .
The sea is continually changing the form of the land. On stormy days, large waves fall on the shore and blur the coastline by erosion. The sea moves the material it has eroded and accumulate it in areas where the water is calm. This skill of the sea to blur, transport and accumulate big number of substances creates a diversity of coastal landforms . On solid, rocky coasts, which are more stable to destruction than loose sand, the form of the shoreline changes relatively slowly. A shore usually decrease due to erosion: More deposits is lost than is changed by the currents. The developmental statute of a coast, however, is not only certain by its deposits balance . There are shore zones that are sustainable over the long time because sediment is just transferred along them. Many coastal areas are not receiving sediments because of building dams. Even trying to protect one part of the coast, sometimes the other zone is damaged, because of changing the coast that is caused by protection measures.
Over the past 8000 years, during the final phase of sea-level rise after the last ice age, sedimentation has contributed enormously to the formation of the shores. Shore land zones grew by the precipitation of transported material, and in some regions large river deltas were formed. Rivers are very important transport paths for carrying sediments to the coasts. The volume that they carry depends on several factors:
The size of the catchment basin from the source to the estuary;
The relief in the catchment basin (rivers in high-relief mountainous areas move more depositions than rivers that flow through flatlands);
The rock and sediment characteristics (for example, grain size) or the amount of available sediments from weathering and mechanical erosion;
The climate in the catchment area and its impact on weathering;
The amount of surface water flowing downstream and the storage capacity of the soil (how much water flows also depends on the amount of precipitation, which is, in turn, dependent on climate) .
If the rivers are blocked, the precipitation will not be able to move. Cutting down mangroves will lead to the shedding of the banks, as their roots hold silt and sand. Pumping gas, oil and water will cause the earth to sink. This human activity affects the development of the coast .
Human societies also damage the biotic environment through the tremendous growth rates of coastal cities. New land areas are often created in the sea to make room for the overflowing development. Many large projects worldwide, including the airport in Hong Kong, have been built in this way.
In order to accurately predict the future fate of shore regions, researchers must first define if the present measurable changes are actually a consequence of climate change or an expression of natural climate variability . “We can only speak of climate change if climate-related changes are statistically discernable from natural fluctuations. Our role is to defend the beauty and wildlife of this amazing stretch of coast. By working with our farming tenants and partners, we can seize the opportunity of climate change to make it even better” – Richard Neale, Wales Coast Project Manager .