Which phenomenon is described as a transient solitary wave in a narrow channel?

The phenomenon referred to as a transient solitary wave in a narrow channel is known as a bore. Boars are characterized by a sudden increase in water level that travels upstream against the current of a river or tidal river due to a change in tidal conditions. They occur when a tide enters a narrow channel and compresses, creating a steep wave that can move upstream.

This phenomenon is particularly common in areas where rivers meet tides, resulting in dramatic changes in water flow and wave behavior. The uniqueness of a bore lies in its ability to maintain its shape and speed over distances, making it distinct from more typical waves.

The other options, while related to water movement, do not accurately describe the specific characteristics of a solitary wave in a narrow channel as effectively as a bore does. Tsunamis are generally larger and generated by seismic activity, rip currents are focused currents created by water returning to the sea, and wave surges can refer to various types of wave movements but do not encapsulate the solitary wave characteristic found in bores.