Antecedent controls on river character and behaviour in partly confined valley settings: Upper Hunter catchment, NSW, Australia

A partly confined river is one along which the contemporary channel abuts the valley margin along 10–90% of its length. They occur along sections of longitudinal profiles that are transitional from fully bedrock confined to fully alluvial rivers. At this position in the landscape, there is sufficient accommodation space for discontinuous floodplain pockets to form. Segregation of the river's load and dissipation of flow energy result in sediments being stored outside the channel. Bedrock- and planform-controlled variants of these rivers, and associated floodplains, are differentiated. Terraces, fans, and piedmont zones act as secondary confining features on channel planform and floodplain formation in these valleys. The influence of these antecedent features on contemporary river character and behaviour in partly confined valleys of the upper Hunter catchment, New South Wales, Australia is appraised. The balance of formative and reworking processes, and associated capacity for geomorphic adjustment, is influenced by the site-specific configuration of antecedent controls at any floodplain pocket. Downstream patterns of these river types are analysed along all major tributaries of the upper Hunter catchment to highlight the extent of antecedent control on contemporary river forms and processes in this landscape setting.