Dramatic increase in mud distribution across a large sub-tropical embayment, Moreton Bay, Australia

Abstract

Major flood events can dramatically alter the coastal sediment environment. This study established the current sediment distribution in a large sub-tropical embayment, Moreton Bay, Australia, and examined the effect of three recent floods on modifying this distribution. In 2015, surface sediment samples were collected from 223 sites across the study area and analysed for particle size distribution with the resultant sediment distribution mapped. In addition, sampling of flood waters during two major events in 2011 and 2013 was undertaken and particle size distribution of suspended sediment was determined. Data was compared to the result of an earlier large-scale survey completed in 1970, with three large flood events occurring between the two surveys. The sediment environment has undergone a dramatic change with muddy sediments now covering an estimated area of over 860km², more the double the area found in 1970. Mud is now the dominant sediment type within Moreton Bay.

Keywords: Catchment inflow; Moreton Bay; Mud expansion; Sediment load; South East Queensland; Sub-tropical embayment.