Sand dredgers, also known as dredges, remove sand and other sediment from the seabed. They function like giant underwater vacuum cleaners, using various methods to collect and transport the material.
Types and Mechanisms
Several types of dredgers exist, each employing different techniques:
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Trailing Suction Hopper Dredgers (TSHDs): These are commonly used for dredging sand, silt, and gravel. As described in the provided video and numerous sources (https://www.youtube.com/watch?v=MhysyOJHY8A), a drag head, much like a giant vacuum cleaner, moves across the seabed, sucking up a mixture of sand and water. This mixture is then pumped into the dredger's hopper (a large onboard storage area). (https://www.royalihc.com/dredging/dredging-vessels/trailing-suction-hopper-dredgers/how-does-trailing-suction-hopper-dredger-work) The hopper is then transported to a designated location where the sand is released.
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Cutter Suction Dredgers (CSDs): These dredgers use a rotating cutter head to loosen compacted sand, soil, or sediment before suctioning it up. (https://www.martide.com/en/blog/all-about-dredgers) This allows them to work in more challenging environments with denser materials.
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Hydraulic Dredgers: These dredgers, as explained by the US Army Corps of Engineers (https://www.sam.usace.army.mil/Missions/Spatial-Data-Branch/Dredging-Quality-Management/Education/About-Dredging/), suck up a mixture of dredged material and water from the channel bottom. The water-to-material ratio is carefully controlled.
The Process: A Simplified Overview
Regardless of the type, the basic process involves:
- Excavation: The dredger's equipment loosens and removes sand from the seabed.
- Pumping: The excavated sand and water mixture is pumped onboard.
- Transportation: The material is transported to another location (often for beach nourishment or land reclamation).
- Disposal/Deposit: The sand is released at the chosen location.
Applications of Sand Dredging
Sand dredging is used for various purposes, including:
- Beach nourishment: Restoring eroded beaches. (https://www.usdredge.com/learn/understanding-beach-reclamation-and-sand-dredging)
- Harbor dredging: Maintaining navigable waterways. (https://www.ci.oceanside.ca.us/government/public-works/harbor/harbor-dredging)
- Land reclamation: Creating new land by depositing dredged material.
- Mineral extraction: Some dredgers recover valuable minerals from the seabed.
