What is the impact of lack of sediment replenishment on river ecosystems?

• A. Erosion and loss of habitats for aquatic life.
• B. Increased biodiversity and ecosystem resilience.
• C. Increased sediment deposition downstream.
• D. No significant ecological changes.

Answer: (A)

Sediment flow shapes river channels and provides the substrates that many organisms rely on. When sediment replenishment is missing, the river must erode its own bed and banks to carry material downstream. This leads to deeper, scoured channels and destabilized banks, washing away gravel and cobble habitats where fish spawn and many invertebrates live. The overall effect is a loss of habitat complexity and can reduce species richness and ecosystem function. Downstream areas receive less sediment, which can alter floodplains and reduce habitat formation there, but the immediate ecological change inside the river is erosion and habitat loss for aquatic life.