Final answer:
Floodplains form by sediment deposition during river floods. Natural levees, oxbow lakes, backswamps, and yazoo tributaries are all features that emerge from the dynamics of river systems and the interaction of water flow, sediment, and the surrounding landscape.
Step-by-step explanation:
The formation of a floodplain is a dynamic process that takes place over time as a river erodes and deposits sediment. During periods of flooding, rivers overflow their banks and deposit sediment across the surrounding land. This sediment layer gradually builds up to form a floodplain which is typically a flat area adjacent to the river.
Natural levees are created when a river overflows its banks and deposits heavier sediments close to the river edge, forming raised embankments along the sides of a river channel. Oxbow lakes are formed when a meandering river channel is cut off from the main stem, leaving a free-standing water body in the old channel path. Backswamps occur in lower areas of a floodplain where water from floods accumulates, and the drainage is slow, leading to swamp-like conditions. Lastly, yazoo tributaries are small rivers that run parallel to a larger river because natural levees prevent them from joining the main river channel.
Distinct patterns can occur in river systems such as straight-channel, braided, and meandering streams. These patterns are part of stream evolution and depend on a variety of environmental factors including sediment supply, flow velocity, and channel slope.
Processes that lead to flooding include heavy rainfall, rapid snowmelt, and the inability of the ground to absorb water quickly, often exacerbated by human activities such as deforestation and urbanization which reduce natural water absorption.