Coasts Are the Dynamic Junction of Water,

¶ … Coasts are the dynamic junction of water, air, and land. Winds and waves, tides and currents, migrating sand dunes and mud flats, a variety of plant and animal life -- all combine to form our ever-changing coasts." (USGS, 2004) Coastlines all over the world are subjected to a wide variety of erosion and denudation effects. Some of these effects are natural occurrences while many are the result of human interaction with the environment. While natural occurrences have be taking place for thousands of years, threats to coastlines from coastal communities in the form of recreational and residential development, waste disposal, spill accumulation and waste disposal are all cause damages to the coast line at a much faster rate.

Wave action, wind, surf and rising sea levels are all impacting coastlines all over the world. Many of these actions of coastlines are very gradual; the effects on the coastlines take many years to occur. Hurricanes however, can cause changes in the coastline within a short period of time. Storm surges and wave action during hurricanes and coastal storms can move large quantities of sand and sediment from or to coastlines. Currents and winds have the ability to move and shape coastlines constantly and this process is never ending or stable. There are many different types of coastlines ranging from rocky shores like the coastline in California and Ireland, sand beaches like the ones in Florida and South Carolina to the marshlands and wetlands of Louisiana.

Traditional rivers carrying sediments have had the ability to deposit large quantities of these sediments at the mouth of the rivers. Deltas formed as a result of this extend the coastline continuously into the ocean. Human activity at different points along the river also impacts the ability of the river to form deltas and provide sediments for the formation of new coastlines where the river enters the sea. As rivers become more polluted the waste and pollutant levels damage the beaches where the river enters the sea. In addition, the pollutants and waste wash up to beaches and all cause extensive damages to the continental shelf. Global warming has also resulted in the elevation of the sea level, which, in turn, has resulted in covering sections of coastlines that were previously above water.

It has also been observed that the population density along coastlines continues to increase. The U.S. coastal areas support five times the population density than the national average. Historically, populations were established around natural ports and waterways all over the world. All major cities grew around these ports or waterways. As the population all over the world continues to grow and develop the strain on the coastline continues to increase. The impact of supporting large populations can be seen in the manner in which the waste disposals for the large urban areas are handled. This can affect the wildlife in the area that depend son the coastline for survival.

Another growing threat to the coastline is the mining of heavy mineral and gold. (UNESCO, 2004) Unchecked use of the sand as building material to support new construction can also negatively impact sandy beaches and the erosion patterns that can result due to removal of this sand. Sandy coastlines are prone to easier reconfiguring than rocky coastlines. Constant shifting of tides and the sand dunes make documenting of the changes on the coastline more of a challenge. Wetlands, brown fields and marshes are now being recognized as an integral part of the coastline. These areas are very essential to the ecosystems of the region and support the growth and survival of many of the young ones of many species. In most places where they exist, these features are increasingly being lost to human development. (ENS, 2004)

The natural process of coastline involves a complex dynamics of many different forces of nature working collectively to create any coastline. What is eroded from one area is generally deposited in another. Longshore currents for example are primarily responsible for moving large volumes of sand that help build barrier reefs and erode them as well. Rip tides or undertows can also significantly change the continental shelf of the coastline. Excessive erosion can result in a steep continental shelf in the region. The different types of tides (high tide and low tide) also determine the extent of the coastline formation that takes place. Where the water temperature differs significantly between summer and winter the intensity of the wave action might also change based on seasons. Storms and hurricane can also create surges that are abnormally high and the intensity of these tides can cause concentrated damages to coastlines in the area. (Wernicke, 2004)

Seasonal changes that depend upon melting snow and glacial activity along coastlines that are in frigid locations can change the salinity of the seawater and change wave activity and currents in the region. This can introduce seasonal changes in the manner in which either erosion or deposition occurs in the region. The picture in the appendix shows that the coastline of the U.S. has changed significantly over the years. While some changes are observed in a short period of time (the break up of the barrier reef during the hurricane), some take thousands of years to occur. (Richmond, 2004)