Cardno model helps tackle stream bank erosion

Stream bank erosion can cause significant land loss, threaten infrastructure such as roads, bridges and buildings, and affect in-channel and riparian habitat for native species. Eroded soil causes further sedimentation problems where it is deposited downstream, affecting water quality, channel capacity, channel stability, and in some cases reducing in-stream habitat by covering riffles and filling pools. 

While at the USDA-National Sedimentation Laboratory, Cardno scientists developed a model, known as the Bank Stability and Toe-Erosion Model, or BSTEM, to predict stream bank erosion and test the effectiveness of mitigation and restoration measures.

This model has been utilised by Cardno across a range of projects in Australia, New Zealand and the United States to help reduce erosion of stream banks and put in place restoration programs.

Cardno Senior Consultant and Geomorphologist, Dr Andrew Simon, explains that the BSTEM can afford a number of benefits in helping manage stream bank erosion.

“The BSTEM allows our clients to confidently manage their sediment and watershed plans by showing the degree and extent of erosion, bank stability impacts, and mitigation and restoration impacts over time and under varying flow conditions,” said Dr Simon.

“The applications for the BSTEM are quite extensive, it can aid in stream bank stabilisation design, mitigation options analysis, sediment load estimates, and infrastructure planning.”

As the lead developer of BSTEM, Dr Simon is continuing to work with the US Army Corps of Engineers to integrate BSTEM with the industry standard one-dimensional (1-D) flow and sediment-transport model HEC-RAS.

A sub-model that can account for the effect of boat waves on bank erosion has also been recently developed and incorporated into BSTEM through collaboration between Cardno and the National Centre for Computational Hydroscience Engineering (University of Mississippi). This addition marks an advancement in the modelling of stream banks and shorelines by providing the ability to quantify undercutting of banks due to the impact of boat waves.

Locally in Australia, Cardno has utilised the model across several projects, including one such project on the Burnett River System in Queensland.

“Cardno was engaged by the Burnett-Mary Regional Group to conduct a study following the severe flooding experienced by the Burnett River in 2011 and 2013,” said Dr Simon.

“The primary objectives of the study were to provide strategies for cost-effective protection of local assets and to determine the relative contributions of bank sediment (particularly fine-grained material) to overall sediment loads to the Great Barrier Reef.

“We used the BSTEM to model stream bank stability, erosion rates and volumes at five sites along the River.

“The results were then used to develop cost-effective bank mitigation strategies for each of the five sites, while extrapolation of these site-specific results provided estimates of fine sediment load contributions from banks of the study reach.”

Cardno was able to deliver to the Burnett-Mary Regional Group mitigation strategies that would not only protect local assets by limiting land loss and bank retreat, but would help maintain reservoir and harbour capacity, minimise downstream flooding, reduce dredging costs, and protect marine resources.

Dr Andrew Simon is presenting on the Burnett River project at the Water New Zealand’s 2015 Asia Pacific Stormwater Conference, taking place in Auckland from 20 – 22 May.

Dr Simon will also be presenting a Master Class on Principles of Streambank Analysis and Application of the Bank Stability and Toe-Erosion Model at Cardno’s Melbourne office on 18 May and at the Brisbane office on 25 May.

You can contact Dr Simon via email: andrew.simon@cardno.com