those that involve running water, encompass both the unchanneled downslope movement of surface water, called overland flow, and the channeled movement of water along a valley bottom, called streamflow
Valleys and interfluve
valleys normally have clear-cut drainage systems; interfluves do not
portion of the terrain in which a drainage system is clearly established. it includes the valley bottom that is partially or totally occupied by the channel of a stream, as well as the valley walls that rise above the valley bottom on both sides.
the higher land above the valley walls that separates adjacent valleys
Drainage basin or watershed
the area that contributes overland flow, streamflow, and groundwater to that stream. consists of a stream's valley bottom, valley sides, and those portions of the surrounding interfluves that drain toward the valley
line of separation between runoff that descends in the direction of one drainage basin, and runoff that goes toward an adjacent basin