In
geomorphology,
drainage systems are the patterns formed by the
streams,
rivers, and
lakes in a particular
drainage basin. They are governed by the topography of the land, whether a particular region is dominated by hard or soft rocks, and the gradient of the land. Geomorphologists and hydrologists often view streams as being part of drainage basins. A drainage basin is the topographic region from which a stream receives runoff, throughflow, and groundwater flow. The number, size, and shape of the drainage basins found in an area vary and the larger the
topographic map, the more information on the drainage basin is available.