DOWNSTREAM VARIABILITY OF CHANNEL MORPHOLOGY AND BED MATERIAL IN THE BRAIDED KELLER RIVER, JAMES ROSS ISLAND, ANTARCTICA

Changes in sediment supply and water availability in rivers are associated with ongoing climate change and glacier melting. The processes connected with increasing temperatures largely determine braidplain activity within glacier forefields. This work focuses on downstream changes in channel morphology (i.e., channel width and braiding intensity) and bed material (i.e., petrological types and clast roundness), as well as possible controlling factors (i.e., sediment sources and sediment connectivity). The study area is the Keller River catchment located on the James Ross Island (JRI), Antarctica. This paper describes the 8.6 km-long Keller River in terms of morphology, including river braidplains, sediment sources and connectivity within the catchment. Eight sediment sources and three types were identified: one moraine sediment source, four debris-flow-dominated sediment sources and three fluvial-flow-dominated sediment sources. Along with high sediment connectivity, the occurrence of lateral sediment sources from tributaries significantly impacted downstream changes in channel morphology and processes. Channel width and braiding intensity showed an increasing downstream trend, although the channel width trend was irregular. As for bed material, sediment sources markedly control clast roundness with little effect of petrological properties.