However, beach nourishment has also become a controversial shore protection measure, in part because it has the potential to adversely impact a variety of natural resources. Consequently, these projects must comply with a wide range of complex laws and regulations. Beach nourishment is also expensive: check the Beach Nourishment Viewer to explore details about sand placement efforts for more than 2, beach nourishment projects since Adding sand to a beach does not guarantee that it will stay there.
Some communities bring in huge volumes of sand repeatedly, only to see it wash out to sea in the next season's storms. When completed in , the beach was 60 feet wide and sloped up to 5 feet above mean low water. Nonetheless, many communities still practice beach nourishment. Army Corps of Engineers USACE is authorized to carry out beach nourishment for shoreline protection: their Beach Nourishment site describes the benefits of adding sand to beaches.
Recently, the U. Army Corps of Engineers has re-emphasized the need to consider a whole range of solutions to coastal erosion, not only structural solutions. Even with the implementation of coastal shoreline erosion and risk reduction measures, residual risk remains.
Some areas are constantly in danger during severe storms. For some regions of the country, the more intense storms are predicted to increase in strength and frequency as climate continues to change, though the overall frequency of all storms may decrease.
Significant episodes of coastal erosion are often associated with extreme weather events coastal storms, surge and flooding but also from tsunami, both because the waves and currents tend to have greater intensity and because the associated storm surge or tsunami inundation can allow waves and currents to attack landforms which are normally out of their reach.
On coastal headlands, such processes can lead to undercutting of cliffs and steep slopes and contribute to mass wasting. In addition, heavy rainfall can enhance the saturation of soils, with high saturation leading to a reduction in the soil's shear strength, and a corresponding increase in the chance of slope failure landslides. Coastal erosion is a natural process which occurs whenever the transport of material away from the shoreline is not balanced by new material being deposited onto the shoreline.
Many coastal landforms naturally undergo quasi-periodic cycles of erosion and accretion on time-scales of days to years.
This is especially evident on sandy landforms such as beaches, dunes, and intermittently closed and open lagoon entrances. However, human activities can also strongly influence the propensity of landforms to erode. For example, the construction of coastal structures such as breakwaters, groynes and seawalls can lead to changes in coastal sediment transport pathways, resulting in erosion in some areas and accretion in others.
The removal of sediments from the coastal system e. At larger scales, natural and human-induced climate change can modulate the likelihood and rate of coastal erosion. Coastal erosion becomes a hazard when society does not adapt to its effects on people, the built environment and infrastructure. Lake Michigan's 1, miles of shorelands has every shore type characteristic of the Great Lakes. 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.
Great uncertainty still exists regarding predictions for local changes in wind regime and wave climate caused by climate change. The sea level will rise globally as a consequence of global warming, but regional differences are considerable.
This holds in particular for relative sea-level rise, i. Some coasts experience uplift especially in previously glaciated regions while others are subject to subsidence. Uplift can always be considered "natural", whereas subsidence often has an important human-induced component groundwater, oil, gas extraction.
According to the so-called " Bruun rule ", an increasing relative sea level will cause a shoreline setback, which is approximately equal to the sea level rise divided by the average slope of the active coastal profile, when considering equilibrium profiles.
Consider, for example, a sea level rise of 0. The setback caused by such a sea level rise will be 50 m. Littoral coasts consisting of fine sediments will be exposed to higher setbacks than coasts consisting of coarser sediments. Log in. Page Discussion. Read View source View history. Jump to: navigation , search. Shoreline management guidelines.
Sediment exchange between the sub-aqueous and sub-aerial coastal zones. Proceedings of the International Conference on Coastal Engineering 1 Article reviewed by. Job Dronkers See the discussion page. Categories : Articles by Mangor, Karsten Reviewed articles Coastal protection Physical coastal and marine processes Beaches Sediment Climate change, impacts and adaptation Sea level rise.
This page was last edited on 21 August , at Privacy policy About Coastal Wiki Disclaimers. The main author of this article is Mangor, Karsten Please note that others may also have edited the contents of this article. Citation: Mangor, Karsten : Natural causes of coastal erosion.
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