When knickzones limit upstream transmission of base-level fall: An example from Kaua‘i, Hawai‘i

Abstract A threshold drainage area limits fluvial transmission of base-level fall and may be expressed in the form a waterfall or series waterfalls, defined here as knickzone. Knickzones on west coast Kaua‘i, Hawai‘i (USA), exhibit evidence area. Eighteen (18) 25 knickzones our study are located at tributary junction, have <1.5 km2, been stationary for least 1.5 m.y. The other seven >1 km upstream from nearest junction range 1 to 5.5 km2. Both sets limit incision relative canyons without knickzones. Field observations show strong ‘a‘ā flows dikes always crop out lip knickzones, suggesting these resistant rocks coarse sediment generated them act inhibit knickzone migration. model incorporating flood records channel conditions above shows thresholds entrainment never exceeded below Our results demonstrate Kaua‘i enduring features explained by lava physical bedrock incision.