COASTAL SEDIMENTARY ENVIRONMENTS, GEOMORPHOLOGICAL PROCESSES AND LANDFORMS, THEIR EVOLUTION AND THE ECONOMEIC ASPECTS
The coastal zone contains the near-shore area together with the entire continental shelf and the resources of the overlying waters as delimited by existing international agreements. Both play a vital role in the coastal environment – offshore and onshore.
Coastal zone is the transition area between the land and the ocean and is an area of complex, dynamic and delicate environment. External factors influencing the coastal zone are the sediment supply by the rivers and the coastal processes. Shoreline is one of the most rapidly changing landforms of the ...view middle of the document...
In order to utilize the coastal zone to its capacity, and yet not plunder its resources, we must have extensive knowledge of the complex environments contained along the coasts.
The many environments within the coastal zone include bays, estuaries, deltas, marshes, dunes and beaches. A tremendously broad range of conditions is represented by theses environments. Coastal environments may be in excess of a hundred meters deep (fjords) or may extend several meters above the sea level in the form of dunes. Some coastal environments are well protected and not subjected to high physical energy except for occasional storms, whereas beaches and tidal inlets are continuously modified by waves and currents.
Because of their location near terrestrial sources, coastal environments contain large amounts of nutrients. The combination of this nutrient supply with generally shallow water gives rise to a diverse and large fauna and flora. Coastal areas also serve as the spawning and nursery grounds for many open-ocean organisms. Many species in coastal environments are of great commercial importance, such as clams, oysters, shrimp and many varieties of fish. It is certain that we need better management of these resources. We also need to develop more and improved methods for cultivating these environments.
Some of the important coastal environments are as follows:
1) River Deltas: Deltas result from interacting fluvial and marine forces. Deltas are defined more broadly as coastal accumulations, both subaqueous and sub aerial, of river-derived sediments adjacent to, or in close proximity to the source stream, including the deposits that have been secondarily molded by waves, currents or tides. By this definition deltas include all delta plains, regardless f plan-view shape or of the suite of individual landforms present. Delta-plain landforms span nearly the entire spectrum of coastal features and include distributory channels, river mouth bars, open and closed inter-distributory bays, tidal flats, tidal ridges, beaches, beach ridges, dunes and dune fields, and swamps and marshes.
The range of deltaic environments is equally broad. Some deltas occur along coasts that experience negligible tides and minimal wave energy; others have formed in the presence of extreme tide ranges and large waves.
2) Estuaries: In geomorphic terms “estuaries” may be defined as “a semi enclosed coastal body of water which has fee connection with the open sea within which sea water is measurably diluted with fresh water derived from the land drainage (Pritchard, 1967).” Estuaries exhibit diverse geomorphic, oceanographic and sedimentologic characteristics but share several important attributes. They occur at the mouths of the rivers that have low sediment dissipative forces. Subsidence, at least in the short term, exceeds sediment accumulation rate and the estuary exhibits open water. Tidal currents are active and mix fresh and salt water. Estuaries are found...