The Stanley River feeds into Lake Somerset which is a part of the water supply system in South East Queensland.  Increased sediment has been observed at downstream storages and water treatment plants and is of concern due to risks to the water treatment process and associated costs of treatment. 

Water Technology assessed a 3km reach of the Stanley River and floodplain to determine the source and reason for the increased sediment load through:

• Assessment of the vegetation, ecology, sedimentology, hydraulics, hydrology, water quality and geomorphology of the reach
• Obtaining detailed site surveys and high resolution LiRAR DEM
• Identifying, quantifying and mapping head-cuts in the system
• Identifying and assessing areas of likely bed degradation and the fate of suspended and bedload sediments in relation to dam water quality and capacity

Based on the assessments undertaken, a downstream reach of the Stanley River was found to be highly degraded, having been heavily impacted by recent flooding events.  Modelling and quantitative assessments enabled an estimate of the amount of fine sediment being eroded from this reach of the river to be obtained.

Mitigation options were identified to tackle the identified bed degradation and a multi-criteria assessment was undertaken to rank the options.  A management approach was recommended which involved a combination of works including rock beaching of the banks, bank battering, stock exclusion and revegetation.

A design analysis was undertaken to accurately assess the conditions and inform the key design parameters for the detailed design of the erosion mitigation measures.