What is coastal erosion?
Coastal erosion occurs due to waves and currents. High winds and storms can drastically accelerate beach erosion. Coastal erosion can be slowed or stopped by implementing structures along the beach face. The construction of breakwaters and jetties has the ability to slow the process of longshore drift (the movement of sand on the beach). Beach nourishment is a technique used to bring sand from another area (through the process of dredging) and deposit it onto the eroded beach. Dredging and coastal engineering projects like jetties are often temporary solutions as beach sand is still at risk of eroding in the future. A natural solution to prevent coastal erosion are seagrasses. Seagrasses anchor and stabilize soil with their root systems.
The slope of the beach can be a factor that drives erosion. Mass wasting, or gravity-induced slope collapse due to prolonged weathering events, can occur on steep beaches. As shown in the diagram below, intermediate and reflective beaches are at the most risk for future mass wasting events.
Types of Beaches:
What is dredging?
Dredging is the removal of sand and other types of sediment from waterways. It is used to keep waterways free from excessive build-up of sediment, which could prevent harbors from being navigable. When sediment is removed from a naturally accreting area, future sediment will be deposited in its place. Dredged material can be placed offshore to remove it entirely from the forces of shoaling and sedimentation. Offshore dredging debris alters wave patterns and contributes to long-term shoreline erosion. Dredged material that remains closer to shore (a part of the sediment system), can be transferred to beaches that need nourishment, helping to counteract wave erosion. The redistribution of sediment on beaches can wreak havoc on intertidal ecosystems. Dredged materials' sediment grain size is often different from native beach sediment when nourishing. Grain-size differences can negatively disturb native ecosystem functions.
Dredging in Beaufort:
A massive dredging project took place in March 2022 to replenish southeastern Radio Island beaches. This area was hit hard during recent severe storms that led to beach loss. The sand that is being brought to Radio Island comes from a few miles away in east Taylor’s Creek.
What is grain size?
The Udden-Wentworth Scale classifies sediment based on grain size. Grain size is the diameter of an individual particle of sediment. On Radio Island, the primary sediment type is sand. Sand is divided into five categories:
-Very fine sand (1/16 – 1/8mm)
-Fine sand (1/8 – 1/4mm)
-Medium sand (1/4mm – 1/2mm)
-Coarse sand (1/2mm – 1mm)
-Very coarse sand (1 mm – 2mm)
Logging Tasks:
- Observe the steepness of the beach. Is Radio Island a dissipative, intermediate, or reflective beach?
- Based on your observations at the GZ and what you’ve learned in the description, name two solutions that the city of Beaufort is using to mitigate coastal erosion on Radio Island.
- Using the Udden-Wentworth Scale, examine the grain size of the sand near the water line and the sand near the top of the beach. Does one of these areas contain larger grain sizes, or does the sand at this beach appear to contain a uniform grain size?
- As of June 2019, earthcaches contain required photo logging tasks. Please provide a photo of yourself, your GPSr, or a personal item that proves that you have visited this site. Please post this in your log.
Sources:
https://www.nps.gov/articles/dredging.htm
https://www.seawallprosfl.com/ways-to-prevent-beach-erosion/#:~:text=Coastal%20erosion%20occurs%20when%20the,wave%20currents%2C%20and%20tidal%20currents
https://www.publicradioeast.org/2022-03-25/radio-island-beach-access-closes-for-dredging-project
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