The area drained by a river. Catchment shape can be expressed by its circularity ratio:
where
Rc is the circularity ratio,
A is the area of the catchment, and
Ac is the area of a circle with the same circumference as the catchment. Catchment shape is a major influence on hydrological relationships in a landscape:
where
L = the length of the stream from its highest topographical point to the river mouth, and
A = the area of the catchment. See K. Fryirs and G. Brierley (2012), for more detail. Sólyom (2011
ESPL 36, 4, 533) finds an intimate relationship between catchment shape and channel initiation. The initiation of a channel on an initially unchannelized surface sets up the initial flow-path structure, which consequently defines the boundaries of the channel’s first-order catchment.