C-channels, also known as coastal or channel incised valleys, are formed primarily through fluvial and marine processes, often linked to changes in sea level or tectonic activity. Here’s how they are formed and reduced:
Formation of C-Channels:
- Sea Level Drop: When sea levels fall due to glaciation or tectonic uplift, river systems extend their courses and cut into the continental shelf, creating deep incised valleys or channels.
- Erosion: Rivers erode the bedrock or sediment as they flow, carving out channels over time. The erosion can be intensified by factors such as sediment load, water velocity, and the type of substrate.
- Tectonic Activity: Uplift of the landmass or subsidence of the sea floor can cause rivers to incise further, leading to the development of deeper channels.
- Glacial Activity: Glacial movements and melting can also contribute to the formation of channels by eroding the landscape and creating pathways for meltwater to flow.
- Tidal or Marine Influences: As sea levels rise or fall, marine processes such as tidal currents can also shape and deepen C-channels.
Reduction or Infill of C-Channels:
- Sea Level Rise: As sea levels rise, channels can become submerged and begin to fill with marine sediment, gradually reducing their depth and width.
- Sediment Deposition: Rivers or ocean currents deposit sediments in the channel, filling it over time. This sediment can come from upstream sources or from marine environments.
- Reduced Erosion: When the water flow reduces, either due to changes in climate, hydrology, or human interventions (like dam construction), erosion slows, allowing deposition to dominate.
- Vegetation Growth: Over time, plants and other vegetation can colonize the sediment-filled channels, stabilizing them and contributing to further infill.
In summary, C-channels form through erosion caused by fluvial, marine, or glacial processes, often linked to changes in sea levels or tectonics. They are reduced or infilled as sediment accumulates, water flow decreases, or sea levels rise.