River adjustments, geomorphic sensitivity and management implications in the Waipā catchment, Aotearoa New Zealand.

Assessment of River Styles, accompanied by time series analysis of historic imagery and geomorphic change detection techniques are used to explain the capacity for river adjustment (geomorphic sensitivity) in relation to the distribution of stream power along 3000 km of channels (3rd Strahler order and greater) to better inform management initiatives in the Waipā catchment, the largest tributary of the Waikato River on the North Island of Aotearoa, New Zealand. Unlike most dynamically adjusting physical landscapes of Aotearoa, most reaches within the Waipā catchment are resistant to geomorphic change. Only 3% of the studied river length has experienced significant planform adjustment since the 1950s and is considered highly sensitive to adjustment. Contemporary alluvial dynamism is largely restricted to gravel bed reaches in high energy rivers within the piedmont zone. The capacity for lateral adjustment in headwater stream courses is restricted by the imprint of past volcanic activity. Further downstream capacity is also limited because of terrace constraints as a result of post-glacial base-level fall, and the entrenchment of the Waikato Fan. Anthropogenic modifications in the catchment include drained wetlands, straightened channels, reinforced banks and emplaced artificial levees (stopbanks) in the few reaches that were prone to adjustment. Highlighting geomorphologically-sensitive reaches at the catchment-scale helps to better prioritise rehabilitation efforts and to support the design and implementation of proactive management plans. [Display omitted] • Rivers in volcanic landscapes of the Waipā have limited capacity to adjust. • Geologic controls determine river geodiversity and sensitivity. • Anthropogenic impacts modify reaches that have capacity for geomorphic adjustment. • Sound management builds on coherent catchment-scale geomorphic understanding. [ABSTRACT FROM AUTHOR]