Sedimentologically significant tributaries: characterizing sediment connectivity in the Lockyer Valley, SEQ

Understanding the potential for bedload sediment (dis)connectivity within and between trunk and tributary drainages is critical to characterizing the catchment-scale, geomorphic behavior of a basin. The ease with which sediment can flux between drainage system compartments is a key determining factor of geomorphic responses to disturbance events and the sedimentological significance of tributaries. We characterize the significance of tributary systems as bedload sediment sources to the trunk stream within the Lockyer Valley, SEQ. We used desktop analyses of tributary morphometry and sedimentary buffers and barriers to compare the (dis)connectivity dynamics of 20 tributaries of Lockyer Creek. The distribution of sediment buffers (floodplains, alluvial fans, terraces, and trapped tributary fills) and barriers (reservoirs and weirs) is a key
control on the significance of each tributary in contributing new sediment to the trunk stream. The development of these buffers is strongly controlled by the morphometry of each tributary and its location within the catchment. Desktop analyses of the distribution of sediment buffers and barriers provides quick
and reliable insights into where sediment is stored, sourced, and transported in basins. This provides the basis for stream managers to prioritize, target, and treat important tributaries and inter-tributary locations as part of sediment management plans.