Which of the following best describes an 'ephemeral stream'?

An ephemeral stream is characterized by its flow being seasonal rather than constant. It typically flows during certain periods, particularly following significant rainfall or snowmelt, but does not maintain a continuous flow throughout the year. This contrasts with perennial streams, which have a consistent flow year-round. The nature of ephemeral streams often means that they can dry up completely during drier seasons or in times of drought.

The other options describe characteristics that do not align with the definition of an ephemeral stream, hence reinforcing why the chosen option is the best descriptor for this type of stream.