Poster 17-27

HYDRAULIC EFFECTS OF TEMPORARY BRIDGE CONSTRUCTION ACTIVITIES

PI: Brian Bledsoe

Co-PI(s): Devan Fitzpatrick, Tanner Buggs, Timothy Stephens, Roderick Lammers

Institution(s): The University of Georgia

Abstract

Bridge construction often requires the installation of temporary features such as rock jetties and cofferdams in stream and river channels. Environmental permitting agencies seek documentation, and in some cases quantification, of the potential effects of these temporary features on instream velocities and channel bank and bed scour; however, there is no existing guidance or standard method for evaluating the potential effects of these temporary structures on hydraulics, bank stability, and biological habitats. This research improves the Georgia Department of Transportation?s ability to effectively respond to environmental permitting agency concerns about the potential geomorphic and hydraulic effects of temporary instream jetties associated with bridge construction. New modeling and risk assessment tools were developed for predicting average changes in velocity and shear stress in the reach affected by a jetty using readily available information. The results can be used to determine hydraulic and geomorphic effects of jetties prior to installation, and provide information about the spatial distributions of velocity and shear stress changes near jetties. A risk assessment approach was developed that synthesizes these results and predictive regressions for shear stress and velocity into one comprehensive spreadsheet-based tool for predicting the potential hydraulic and geomorphic effects of jetties when more complex modeling is infeasible. This research can be applied to a large array of unsubmerged structures and advances the current set of tools available for preliminary structural design and environmental management decisions.

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