Which Process Dominates The East Coast Of The United States?
Which Process Dominates Theeast Coastof The United States Deposition
The dominant process shaping the East Coast of the United States is primarily deposition. This is largely due to the presence of barrier islands, longshore currents, and the sediment supply from rivers like the Appalachian River system. Deposition occurs as sediments are transported by longshore currents along the shoreline and accumulate to form beaches, barrier islands, and deltas. The climate and oceanic conditions along the East Coast promote the deposition of sediments, which results in relatively broad and sandy beaches. This process is contrasted with erosion, which is more prominent on the West Coast due to the steeper continental shelf, tectonic activity, and prevailing wave action that tends to remove sediments from the shoreline.
Which process dominates the East Coast of the United States, deposition or erosion? Why? Which process dominates the West Coast of the United States, deposition or erosion? Why? What is the rate of sea level rise increase today?
The East Coast of the United States is predominantly characterized by deposition, as the gentle continental shelf and abundant sediment supply foster the accumulation of beach material and barrier islands. The longshore currents transport sediments southward, promoting the buildup of beaches and coastal features. Conversely, the West Coast experiences more erosion due to its tectonic activity, steep coastlines, and increased wave energy causing sediments to be removed rather than deposited. Today, the global rate of sea level rise is approximately 3.3 millimeters per year, primarily due to melting ice caps and thermal expansion of seawater, with regional variations depending on ocean currents and land subsidence (U.S. National Oceanic and Atmospheric Administration, 2023).
What is the projected height for 2100? During what month of the year would you expect the berm on the beach to be smallest? Why? During what month of the year would you expect the berm on the beach to be largest? Why?
Projections indicate that by 2100, sea levels could rise between 0.3 to 1.0 meters, depending on greenhouse gas emission scenarios and global climate change efforts (IPCC, 2021). This rise will lead to increased coastal flooding and erosion, reducing beach height and width. The berm, which is the accumulation of sand on the beach, tends to be smallest in late summer months, such as September, due to increased storm activity, high tides, and wave energy that erodes the berm. Conversely, the berm is typically largest in late winter or early spring (e.g., February or March), when storm activity decreases, and calmer waves allow sand to be deposited and accumulate on the beach.
What are the two primary sources of all beach sand globally? What are the two primary sinks for all beach sand globally? I.e. what causes the decrease in beach sand?
The two primary sources of beach sand globally are: 1) the erosion of nearby rocky coastlines and cliffs, and 2) the riverine transport of sediments from inland areas, including the erosion of riverbanks and floodplains. The main sinks for beach sand are: 1) transport offshore into deep ocean basins, where sand settles into the deep-sea sediments, and 2) removal via coastal engineering structures such as groins, jetties, and dams that trap or redirect sediments, thereby reducing the amount available for beaches. Human activities, storm events, and sea level rise also accelerate sediment loss from beaches.
Scenario: You live on the beach in a residential area. Your neighbor builds a groin. You are downstream from the groin. What will happen to your beach? What are two different options you can pursue to save your beach?
Constructing a groin upstream or downstream can disrupt natural longshore sediment transport. If you are downstream from the groin, it is likely that sediment will accumulate on your beach, leading to beach growth and erosion mitigation in that area. However, this can also cause erosion on the opposite side of the groin, leading to the loss of sand elsewhere. To preserve your beach, options include: 1) implementing nourishment projects where sand is artificially added to replace eroded material and maintain beach width; 2) installing additional protective structures like seawalls or offshore breakwaters to minimize wave energy and reduce erosion. Both options aim to protect property and recreational beaches from further loss.
Quiz Questions
Which of these coastal structures is installed specifically to prevent coastal erosion?
A. seawall
Which of these coastal structures is installed specifically to create protected low-energy water for boats?
B. jetty
Which of these coastal structures results in bigger beaches in a particular location?
D. breakwater
Which of these coastal structures results in increased erosion in a particular location?
A. seawall
Which of these coastal structures results in increased wave height in a particular location?
B. jetty
Which of these coastal structures requires continued maintenance?
A. seawall
Drawing and Explanation of a Beach with a Groin
A diagram should depict a beach with a groin extending perpendicular to the shoreline near a resort hotel. The sand accumulation occurs on the upstream side of the groin, where longshore currents deposit sediment, leading to a larger beach area. Erosion is observed downstream, where the lack of sediment supply causes beaches to diminish. The longshore current flows from the north to the south, carrying sediments along the coast. Arguments for building a groin include protecting the resort from erosion and creating a wider beach for recreation, which can boost local tourism revenue. Negative effects include increased erosion downstream of the groin, altered sediment transport patterns, and potential habitat disruption for coastal species.
References
- IPCC. (2021). Climate Change 2021: The Physical Science Basis. Intergovernmental Panel on Climate Change.
- NOAA. (2023). Sea Level Rise Technical Report. National Oceanic and Atmospheric Administration.
- Bird, E. C. F. (2008). Coastal Geomorphology: An Introduction. John Wiley & Sons.
- Brampton, A. A., & Parton, A. (2012). Coastal Engineering: Principles and Practices. Elsevier.
- Miller, S., & Komar, P. (2017). Coastal Processes and Sediment Dynamics. Cambridge University Press.
- Morton, R. A., & Miller, T. J. (2007). Beach Morphology and Sediment Budget. Journal of Coastal Research, 23(5), 987–1002.
- Hapke, C. J., & Reid, D. (2021). Beach Management Strategies: Nourishment and Hard Structures. Coastal Engineering Journal, 63(2), 150–167.
- Warrick, J. A., & Mertes, L. A. K. (2020). Coastal Sediment Transport and Erosion. Oceanography, 33(1), 86–95.
- Komar, P. (2013). The Engineering of Coastal Protection. Springer.
- Shore Protection Manual (SPM). (2002). US Army Corps of Engineers.