Classification of nested tributary basins in analysis of drainage basin shape

Tributary basins in Strahler‐ordered drainage systems may be classified as order w formative or order w excess according to whether the order w mouth stream outflows into a stream of order equal to or greater than w. This classification distinguishes spatial nesting among tributary basins, formative tributaries locating farther from the main basin mouth than excess tributaries. Basin shape is analyzed by using standard indices and applying the method of unrolling perimeter radials for Fourier series analysis. The empirical results from 336 drainage basin shapes demonstrate differentiation of basin shapes between gemorphologic environments, between basin order levels 3 and 4, and between formative and excess tributary basin types at the order 3 level. The order level contrasts indicate scale dependency in drainage basin shapes, and the tributary order type contrasts suggest spatial nesting controls such that basins sampled solely by Strahler order level are not homogeneous with regard to shape properties.