Short Virtual Presentation & Digital Poster 10th Australian Stream Management Conference 2021

Cost Effectiveness of Bendway Weir Stream Re-Training Techniques in Australia (#29)

Reece Fraser 1
  1. Neilly Group Engineering, Townsville, AUSTRALIA, Australia

Through a 2D hydraulic modelling exercise we examine the applicability of bendway weirs to reduce adverse hydraulic properties against three separate eroding river banks which were impacted by the 2019 Monsoon Trough event in Townsville, North Queensland. The weirs are compared to more traditional stream re-training techniques such as timber pile fields in terms of hydraulic performance, advantages and disadvantages as well as construction costs. 

Bendway weirs are not uniformly applicable to all scenarios, especially in highly ephemeral streams with a strong seasonal flow pattern. A number of negative effects that must be incorporated into the design such as the formation of scour holes on the downstream side of the structures and long-term scalloping of the bank. Bendway weirs impact a higher depth above the crest than pile fields and reduce adverse hydraulic conditions for a wider width, but pile fields reduce the magnitude of forces exerted near the bank for the same flow event. Bendway weirs are effective at reducing hydraulic properties that induce erosion for significant depths above the crest of the structures, much more so than pile fields. For the sites investigated, construction and implementation costs of bendway weirs was much higher than pile fields to achieve a similar hydraulic benefit.  

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