Most impressive is the expanse of sand dunes that extend almost continuously from the Indiana Dunes National Lakeshore on southern Lake Michigan northward along Michigan's western shore to the Leelanau Peninsula.
Large areas of high erodible bluffs exist along both the Michigan and Wisconsin shores, which all too often are used as prime building sites because of their exceptional natural view.
By contrast, Lake Huron's miles of coastline is characterized by rocky and boulder areas with some high cliff-backed beaches; elsewhere, the shore is sandy with low dunes and bluffs. Lake Erie with miles of coastline is predominately high and low erodible bluff. The southwestern area contains wetlands and a Tow erodible plain. This shore type changes to a low bluff and sparse dune area in western Ohio, before becoming a high erodible bluff in central and eastern Ohio.
Approximately 12 percent of Lake Erie's shore is artificial fin. Lake Ontario's miles of coastline consists of bluffs of glacial material and rock outcrops at the shore. Bluff heights range from 20 to 60 feet and are occasionally broken by low marshes.
A short reach of low dunes and barrier beaches separates this erodible bluff type shore from the erosion-resistant rock outcrops extending northward to the St. Lawrence River. Differences in the level of development, use, and engineering structures at the shore complicate this natural di- versity. Sediment sources and sinks, which are highly susceptible to human activities at the shore and in adjoining rivers and waterways, are also a major concern for erosion zone management.
As a result of these multiple factors, it is necessary to consider both local con- ditions and broad regional issues when establishing a coastal erosion zone management program. Carbognin, L. Gatto, and F. Cooper, W. Coastal Dunes of California. Geological Society of America, Memoir No. Dean, R. Sediment interaction at modified coastal inlets: Processes and policies. Aubrey and L. Weishar, eds. Berlin: Springer-Verlag. Dolan, T. Castens, C.
Sonu, and A. Review of sediment budget methodology: Oceanside littoral cell, California. II, pp. Edil, T. Flinn, J. October 26, Beaches Imperiled by Weak Cliffs. San Francisco Examiner, pp. A1 and A9. Gabrysch, R. Shore Use and Erosion, Appendix Herron, W. Artificial beaches in Southern California. Shore Beach Inman, D. On the tectonic and morphologic classification of coasts.
Johnson, J. The significance of seasonal beach changes in tidal boundaries. Kenyon, E. Edited by J. Leatherman, S. Shoreline evolution of North Assateague Island, Mary- land. Geomorphic and stratigraphic analysis of fire island, New York. Marine Geol. Cliff stability along western Chesapeake Bay, Maryland.
Marine Tech. Reworking of glacial sediments along outer Cape Code: Development of Provincetown spit. Fitzgerald and P. Rosen, eds. New York: Academic Press. Coasts and beaches. Geological Society of America. Magoon, O. Haugen, and R. National Research Council.
Washington, D. Wash- ington, D. Olsen, E. Mary's En- trance, Florida. Oradiwe, E. Sediment Budget for Monterey Bay. Naval Postgraduate School, Monterey, California. Ritter, J. Geological Survey Open-File Report. Seltz-Petrash, A. Subsidence a geological problem with a political solu- tion. Civil Eng. Shepard, F. Our Changing Coastlines. New York: McGraw-Hill. Smith, O. Smith, M.
Cialone, J. Pope, and T. Paper CERC Army Corps of Engineers. Jacksonville, Fla. Williams, S. More and more of the nation's vast coastlines are being filled with homes and vacation resorts. The result is an increasing number of structures built on erosion-prone shores—with many of these structures facing collapse or damage. This book from the National Research Council addresses the immediate question of how to develop an erosion insurance program—as well as the larger issues raised by the continually changing face of our nation's shorelines.
Managing Coastal Erosion explores major questions surrounding a national policy on coastal erosion: Should the federal government be in the business of protecting developers and individuals who build in erosion-prone coastal areas? How should such a program be implemented? Can it prompt more responsible management of coastal areas?
The volume provides federal policymakers, state floodplain and resource managers, civil engineers, environmental groups, marine specialists, development companies, and researchers with invaluable information about the natural processes of coastal erosion and the effect of human activity on those processes.
The book also details the workings of the NFIP, lessons to be learned from numerous state coastal management programs, and much more. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website. Jump up to the previous page or down to the next one.
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Managing Coastal Erosion Chapter: 2. Get This Book. Unfortunately, this book can't be printed from the OpenBook.
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This wave-cut platform will form at the low-tide level and is evidence of where the cliff face once stood before erosion caused the cliff face to retreat.
Sea Caves Sea Caves form when cracks in rock at the base of cliffs are eroded and expanded by the sea. The processes of compression and hydraulic are key to the creation of sea caves. Sea Arch Sea Arches are formed when a cave continues to be eroded and expanded until it cuts right through a headland. Sea Stack A sea Stack forms when a sea arch continues to be eroded and widened until the rock becomes too weak to support the roof of the sea arch and collapses into the sea.
The remaining pillar of rock is known as a sea stack. Sea Stump A sea stump is formed when a tall sea stack is eroded and worn down until it juts just above the surface of the sea. Tile 1 Description. Tile 2 Description. Tile 3 Description. Tile 4 Description. Tile 5 Description. Tile 6 Description. Tile 7 Description. Tile 8 Description. Tile 9 Description.
Tile 10 Description. Tile 11 Description. Many rivers consist of a steep upper part, the mountain part, and a gently sloping lower part, where the river crosses the coastal plain. Sand extraction in the upper part of the river causes lowering of the river bed and a similar lowering of the water level, hence no changes in the sediment transport capacity.
Thus the sand extraction in the upper part of the river is almost entirely balanced by local bed degradation, and has hardly any immediate impact on the supply of sand to the coast. Sand mining in the lower part of the river at some distance from the river mouth causes a local lowering of the river bed. However, the water level will not lower as much, which results in a local decrease in the flow velocity and in the sediment transport capacity.
The river bed depression will gradually be filled in from upstream supply and will travel towards the coast. When the impact of sand mining reaches the coast there may be an accumulated deficit in available river bed material corresponding to several decades sediment supply from the catchment. This means that an immediate halt in the sand mining will have hardly any remedial effect on the supply of sand to the coast, as the entire river bed has to rebuild before the original supply is re-established.
Sand mining close to the river mouth causes an immediate decrease in the supply of sand to the coast, and halt of the sand mining in this situation will quickly cause recover of the supply of sand to the coast. These impacts of sand mining on coastal sediment supply are observed in many rivers, for example for rivers in Sri Lanka [14].
Coastal erosion is not the only impact of river sand mining. Other impacts also have to be taken into consideration:. Hence, river sand mining requires an integrated approach taking into account all the impacts.
This calls for close collaboration between river authorities and coastal authorities. Small sandy bays enclosed between headlands have in general a crescentic shape, which is due to wave diffraction at the headlands and wave refraction in nearshore shallow water see Shallow-water wave theory. However, the shape and position of the shoreline depends not only on the wave climate, but also on sand supply to the bay.
There are two possible sources see Fig. The overall transport mechanisms in a crescent-shaped bay can be characterised as follows. The supply of sand from the upstream bay Q B will pass the headland and cross the bay via a bar.
If a river also contributes Q R to the littoral budget, this material will be transported downdrift into the bay, partly along the shoreline and partly onto the bar. The shape of the crescent-shaped bay is stable, apart from seasonal variations, as long as the supply of material to the bay Q S1 is not changed.
This means that human interventions, which cause changes in one bay will gradually penetrate into the downdrift bays. Hence, crescent-shaped bays, although they appear fairly stable, are actually very sensitive to interventions that modify the supply of sand.
Wakes from fast ferries cause shore degradation in sheltered coastal environments [15] [16]. The special wake generated by fast ferries is characterised by a series of approximately 10 relatively low waves significant wave height below 1 m , but relatively long waves.
These wake waves are very similar to swell waves and they are exposed to considerable shoaling when approaching the coast. They often break as plunging breakers. If a fast ferry navigates through protected waters, the wake waves are very different from the natural waves along the navigation route. The wake waves caused by fast ferries may influence coastal conditions in the following ways:.
A precondition for approval of a new fast ferry route is therefore to perform an environmental impact assessment study [17]. This will often result in navigation restrictions for certain parts of the route. An example of the impact of such waves is presented in Fig. Note the violent breaking, turbid water and rip currents. The mining of sand and gravel along beaches and in the surf-zone will cause erosion by depleting the shore of its sediment resources.
In connection with maintenance dredging of tidal inlets, harbours, and navigation channels, sand is very often lost from the littoral budget because the sand, unless otherwise regulated by legislation, is normally dumped at deep water. Coral mining and other means of spoiling the protective coral reefs, for example, fishing by the use of explosives or pollution, will also cause coastal erosion and beach degradation.
The protective function of the reef disappears and the production of carbonate sand stops. In conclusion, it can be seen that nearly every type of development and coastal protection along a littoral shoreline or along rivers will result in erosion of the adjacent shores and coasts.
Log in. Page Discussion. Read View source View history. Jump to: navigation , search. Article reviewed by. Job Dronkers See the discussion page. Shoreline management guidelines. Coastal erosion and control. Journal of Ocean and Coastal Management, 54 12 , — Rip current types, circulation and hazard.
Toe structures management manual.
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