Which of the following are two common types of alluvial channels?

Alluvial channels are formed by the sediment that rivers carry and deposit, responding dynamically to changes in water flow, sediment load, and other environmental factors. The two common types of alluvial channels are meandering and braided channels.

Meandering channels are characterized by their sinuous path, creating loops and bends that evolve over time due to erosion and deposition along the banks. This type of channel forms in areas with a low gradient and where the river's flow is gentle, allowing the sediment to be distributed across the floodplain, enhancing the complexity and biodiversity of the ecosystem around the river.

Braided channels, on the other hand, consist of multiple interwoven streams or bars created by the deposition of sediment in areas of higher gradient or during times of high flow. This type of channel typically occurs in environments where there is a high sediment load, and river flows can change rapidly, causing the river to split into several branches that can eventually merge back together downstream.

In contrast, the other options refer to different channel types that do not classify as alluvial channels. Straight and crescent channels lack the dynamic sediment processes associated with alluvial structures. Delta and ponded channels pertain to areas where rivers meet standing water but do not represent the active sediment transport seen in