Sediments in the Marine Environment
This review of current knowledge (ROCK) is concerned with the movement of sediments in the marine environment. This is an important subject with influence on all nations with a coastline. The ROCK provides an outline of the subject and a description of some of the methods used in the analysis of the many complex processes. However, for details of the analytical methods it is necessary to consult major text books on the subject.
The sediments of the marine environment are evident in natural coastal features such as beaches and coastal inlets, and in port dredging. Sediments are the result of erosion of the earth’s surface over the history of the planet. They have been subject to periods of erosion and deposition, working of the material and long term deposition in deep water. The processes of erosion and deposition are natural phenomena which, in the past, were largely unaffected by man. However, as civilisations developed, these changes have intensified, particularly since the start of the industrial revolution.
Coastal sediments are in continuous motion, driven by waves, currents and tidal flows. The quantities of sediments which are moving vary according to the energy of the water motion and the availability of mobile sediment. Often, these sediments will be in dynamic equilibrium. However, when this equilibrium is disturbed by a change in conditions, or by human interference such as coastal development, there may be erosion or deposition on the coastline. This can cause significant problems to human use of ports and beaches. The success of civilisations has often hinged on the stability of their port sedimentation.
Knowledge of the sediment budget, that is the balance of supply and loss of sediment to marine systems, and of their motions in the marine environment, provides a means of predicting future changes as affected by the climate and the activities of man. For example, in port development, the ability to predict the volumes of maintenance dredging will determine the viability of the port and the project operating costs.
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