Tidal sources of sediment primarily consist of eroding shorelines and nearshore areas, along with the resuspension of previously eroded sediments.
Sediment sources in tidal environments are dynamic and influenced by a combination of factors. Here's a more detailed breakdown:
- Eroding Shorelines: The constant ebb and flow of tides, coupled with wave action, leads to the erosion of coastal landforms. This erosion releases sediment into the tidal system. Factors affecting erosion rates include:
- Wave Energy: Higher wave energy, often during storms, dramatically increases erosion.
- Vegetation: The presence or absence of shoreline vegetation plays a crucial role. Root systems help stabilize the soil, reducing erosion. Removal of vegetation leads to increased erosion.
- Sediment Composition: The type of material making up the shoreline (sand, mud, rock) influences its erodibility.
- Nearshore Areas: Subtidal areas adjacent to the shoreline also contribute sediment. Processes like scouring by tidal currents and wave action can dislodge and transport sediment.
- Bay Grasses (Submerged Aquatic Vegetation - SAV): Like shoreline vegetation, SAV plays a vital role in stabilizing sediment in shallow offshore areas. A lack of bay grasses means increased wave action impacting the shoreline, leading to erosion.
- Resuspension of Eroded Sediments: Sediments that were previously eroded and deposited within the tidal system can be resuspended by tidal currents and wave action. This process redistributes sediment throughout the environment.
- Riverine Input: While not exclusively tidal, rivers flowing into tidal areas can also be significant sources of sediment. These sediments can be redistributed by tidal currents.
- Biological Sources: In some areas, biological activity can contribute to sediment. Shell fragments from shellfish reefs, for instance, can add to the sediment budget.
In summary, the sediment budget within a tidal environment is a complex interplay of erosion, deposition, and resuspension. Eroding shorelines, nearshore areas, and previously eroded sediments are the primary ingredients. Maintaining healthy vegetation along shorelines and in nearshore shallow waters is important in mitigating tidal erosion.
