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Bridge Scour

The number one cause of bridge failure is bridge scour, defined as the erosion or removal of soil and other material from underneath or around bridge abutments or piers due to the erosion from streamflow. Bridges damaged due to scour are extremely costly to fix and may be shut down for weeks or months for repairs. This is especially damaging to low resource rural communities who may depend on just one bridge for transportation or disaster relief.

My research on bridge scour focused on developing a bridge retrofit specifically designed for low transportation volume bridges in low resource, rural communities. This design stemmed from the empirical observation during Tropical Storm Irene in Vermont that most bridges which survived had their embankments washed out, allowing potentially damaging floodwaters to flow around instead of underneath the bridge. My work sought to investigate this phenomena, which found that this embankment damage was an order of magnitude quicker and less expensive to fix compared to scour damage.

I then sought to purposefully design a new style of bridge where the embankments were made of a purposefully erodible material which is "sacrificed" during potentially dangerous storms, but saves the bridge from life threatening scour damage. These embankments could be quickly reconstructed by rebuilding the embankment in a day or less, allowing for emergency vehicles to pass and bridge repairs finished much quicker than equivalent scour damage. This work found sacrificial embankments represented a viable solution for rural communities with older bridges in need of scour retrofit. Additionally, using Bayesian analysis on future streamflows I found that the sacrificial embankments could be an economically viable retrofit for modern bridges depending on the uncertainty in the streamflow record. Further details are available in the published work from the journal Natural Hazards, cited below.

Brand, M. W., Dewoolkar, M. M., Rizzo, D. M. (2017), Use of sacrificial embankments to minimize bridge damage from scour during extreme flow events. Natural Hazards, 87:1469–1487. DOI 10.1007/s11069-017-2829-z

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Results from physical study of scour in a flume using a traditional embankment (left) and a sacrificial embankment (right). Note the significant scour hole which has developed underneath the traditional embankment (left) compared to the sacrificial embankment (right) which shows minimal scour damage.

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