Question: What are river terraces? Group of answer choices River terraces are what's left after a neck cutoff or chute chutoff occurs. River terraces filled in oxbow lakes. River terraces are the former floodplain of streams that have changed their equilibrium in a way to erode down into the former floodplain. River terraces are flat surfaces in a river channel. These can be either lower plane beds formed when flows are low or upper plane beds when flows are much higher.