What is directly proportional to the discharge in a stream regarding its sediment transport capacity?

The correct response is based on the relationship between a stream's discharge and its capacity to transport sediment. Sediment transport capacity refers to the total amount of sediment a stream can carry at any given time. As discharge increases, the energy and velocity of the water also tend to increase, allowing the stream to transport more sediment. Therefore, the capacity for carrying sediment is directly proportional to the discharge.

When a stream experiences higher discharge, it can lift and carry larger volumes of sediments. This capability reflects a fundamental principle in fluvial geomorphology, where greater water flow allows for more sediment movement, influencing the overall landscape over time.

Competence, while related to the size of particles a stream can carry, does not directly correspond to the overall volume of sediment the stream can transport. Siltation pertains to the deposition process rather than the transport capacity. Sorting refers to the distribution of different sizes of sediment particles that are deposited by the stream and is not a measure of transport capacity.