What is the effect of dam construction on sediment transport?

• A. Sediment transport increases downstream
• B. No effect on sediment
• C. Sediment trapping reduces downstream sediment transport, altering channel form and floodplain ecosystems
• D. Sediment transport doubles downstream

Answer: (C)

Dam construction changes sediment transport by creating a reservoir where water slows and sediments settle out. This traps large amounts of sediment that would normally travel downstream, so less material moves downriver. With reduced sediment supply downstream, the river can erode its bed and banks more easily, which alters the channel’s shape. This sediment-starved condition also affects floodplain ecosystems that rely on regular sediment deposition for nutrients and habitat structure. Over time, these processes can lead to changes in channel form, such as incision or altered meandering, and disrupt floodplain habitats. The other options don’t fit because they imply more sediment moves downstream or no change at all, which isn’t consistent with how reservoirs trap sediment.