Free surface breakwaters are essentially barriers located near the water surface where the energy flux is maximal. The total height of such barriers is usually far smaller than the water depth which helps water circulation around the structures. These barriers can be constructed on a group of piles driven into sea floor, or held floating as floating breakwaters. Wave reflection and dissipation are the primary energy damping mechanisms inherited by these barriers. Free surface breakwaters are most suitable to be built at semi-protected sites where the soil condition is poor.
In off-shore waters, that substrate is usually provided by the limestone secreted by earlier stony corals on rock (often volcanic). However, if there is a firm, rocky base present, as in fringing reefs, sedentary rivals can settle in great numbers without waiting for reef-building corals to lay the foundations (Stafford-Deitsch 20). Thus, the stony corals do not have to be the major constituents of the reef. Sponges, soft corals, and corraline algae are abundant throughout the fringing reef. Some of the finest fringing reefs in the world are along the edges of the Red Sea, where the conditions are premier for the growth of the reef.
It is the process of sediment being deposited to form natural features. This is when the rock fragments from Otakamiro Headland are ripped away by waves, broken down by attrition and transported along the coast where they are deposited as beaches and sand dunes. The movement of the material is called Longshore Drift; the direction of the deposit depends on the direction of the winds. Titomagnetite sand (black sand) was deposited at Muriwai when it was bought from the south by Longshore Drift. Coastal Erosion, Coastal Transportation and Coastal Deposition are natural processes that have occurred at Muriwai's coastal geographic environment.
Elevated external water pressure at high tide helps to hold back toe advance (Hutchinson 1988). At low tide, when the ground water table is located within the beach sand and is under lower (atmospheric) interstitial pore water pressure, a large difference in head and therefore steepened hydraulic potential gradient exists between the landslide toe and the external environment (sea level) (fig. 6b). Under these conditions, sliding and the formation of
Salt pans are small, roughly-circular pools on the surface of the marsh. The suggestion has been made that the very high salinity of the water contained in these pools inhibits plant colonization and resultant infilling. Finally, mention should be made of the human influence on salt marsh habitats. Once a marsh has built up to such a level that it is seldom covered by tides, It is relatively simple to enclose it with a bank or wall, drain it, and replace the natural vegetation with cultivated pasture. Obviously at that ultimate stage in salt marsh development, the plant cover is almost wholly a result of human interference rather than a response to natural conditions.
Investigation on Coastal Erosion In Porlock Bay Aims ---- Aim 1: To find out if beach material is moved across Porlock Bay by longshore drift. Aim 2: To find out which type of sea defense is best for Porlock bay. If L.S.D. (long shore drift) were taking place I would expect to find: a) Deposition at one end of the bay and against any abstractions such as groynes. b) An increase in pebble roundness in the direction of long shore drift.
Erosion of Shorelines The erosion of shorelines is a natural process that can have beneficial or adverse impacts on the creation and maintenance of habitats. Sands and gravels eroded from the shores of coastal bays maintain the beach as a natural barrier between the open water and coastal wetlands. Beaches move back and forth onshore, offshore and along shore with changing wave conditions. The finer-grained silts and clays derived from the erosion of shorelines are sorted and carried as far as the waters of wetlands or tidal flats, where benefits are derived from addition of the new material. However, excessively high sediment loads can smother submerged aquatic vegetation beds, cover shellfish beds and tidal flats, fill in riffle pools, and contribute to increased levels of turbidity and nutrients (http://www.epa.gov/OWOW/NPS/MMGI/Chapter6/ch6-4.html).
The core solutions to improving the quality of water running into the reef involve the options of finding alternative pesticides, removing the need for them entirely through genetic modification of crops, or implementing methods of filtration that gradually decrease pollution inputs. These advances in agricultural practices will begin a reduction in sediment and nutrient run-off into coastal river systems. Although it is expected to be a long time before there are positive, long term improvements on marine quality, now is clearly the time to act in order to lessen the overall effects on the reef. INTRODUCTION As the world's largest coral reef system The Great Barrier Reef must be protected from the increasing number of pressures threatening its biodiversity, health and overall survival. The environmental stresses impacting the reef include degraded water quality from run-off containing suspended sediments, excess nutrients, herbicides and pesticides affecting much of the inshore area.
Firstly, wave reflection induced by the wall may result in scour and subsequent lowering of the sand level of the fronting beach. Secondly, seawalls may accelerate erosion of adjacent, unprotected coastal areas because they affect the littoral drift process. The design and type of seawall that is appropriate depends on aspects specific to the location, including the surrounding erosion processes. There are three main types of seawalls: vertical, curved or stepped, and mounds. Project proposal is to construct a curved sea wall.
As long as the waves hit the shoreline “straight on”, the wave crests are parallel to the shoreline, the sand grains will be picked up and redeposit in the same general area. In this case, no real net movement of sand occurs in the swash zone. Waves generally do not form parallel to the shoreline, and thus, usually approach the shore at an angle. Consequently, beach sand will have a net movement up or down the beach, depending on the direction of incoming waves. Sand grains are transported as the waves move onto the beach.