Explain why rivers deposit sediment.

Rivers deposit sediment when the velocity of the water decreases, reducing its capacity to carry material. This can occur in various situations, such as when a river enters a wider body of water, like a lake or ocean, or when it flows onto a floodplain during high water events. Additionally, sediment is deposited in areas where the riverbed gradient is less steep, allowing particles to settle. Factors such as changes in water flow, the volume of sediment load, and the river's energy levels all play a crucial role in sediment deposition, shaping the landscape and creating features like deltas and sandbars.