Drainage spacing regularity on a fault‐block: A case study from the eastern Ruahine Range

Recent research has indicated river basin outlets draining linear sections of large, uplifting mountain belts often show a regularity of spacing, transverse to the main structural trend. A morphometric analysis of part of the Ruahine Range, on the North Island was undertaken to test whether drainage regularity may exist in smaller, younger mountain ranges. The ratio, R, of the half‐width of the mountain belt, W, and the outlet spacing, S, was used to characterize drainage networks on the eastern side of the range. The spacing ratio for the range of 1.31 is lower than R results from studies of larger mountain belts (R = 1.91–2.23). We suggest the cause of this lower ratio is related to eastward migration of the Ruahine drainage divide.