A Holistic Approach to Improving the Resilience of Road Stream Crossings using HEC RAS 2D Modeling
Cory Trego
Gannett Fleming
Audubon, PA
Liz DiNatale, PE
Gannett Fleming
Raleigh, NC
Authors: Cory Trego & Liz DiNatale, PE
Increases in intense storm event frequency have heightened the need to modify the approach to road stream crossings to ensure long-term resiliency. Historic watercourse and floodplain modifications associated with past development and land use practices can exacerbate channel instability around stream crossings and adjacent roadways, necessitating a more holistic approach that addresses these modifications to improve channel and infrastructure stability. The S.R. 1029 (Smoketown Road) bridge over Sacony Creek in Berks County, PA is an example of how legacy channel and floodplain modifications can result in infrastructure failure. Poor roadway alignment, historic floodplain alterations, and upstream channelization and channel incision contributed to conditions that resulted in severe scour and streambank erosion that led to lateral undermining of a bridge abutment and the approach roadway.
To improve the resiliency of the replacement structure, approximately 650-feet of stream channel upstream and downstream of the bridge crossing was redesigned to restore the channel to a more natural pattern and profile and improve floodplain connectivity to reduce shear stress adjacent to the bridge abutments. The re-designed channel incorporated improved pool-to-pool spacing and sinuosity to increase energy dissipation, grade control structures to ensure long term stability around the bridge abutments, floodplain benches for additional flood water attenuation, and rootwads and wrapped soil lifts with live staking for streambank protection and habitat improvement. We utilized HEC RAS 2D modeling to analyze shear stresses and velocity vectors through the designed project reach, assess flow on the designed floodplain benches, and locate and design in-stream structures
The resulting design not only enhances the resilience of the bridge to high-flow events but also minimizes maintenance requirements, improves the stability of the approach roadway, and amends historic floodplain and channel alterations to restore the adjacent stream channel. This presentation will explore the integration of HEC RAS 2D modeling into stream restoration design, highlighting its critical role in developing resilient infrastructure. By showcasing the S.R. 1029 bridge project, we will demonstrate how improved 2D modeling capabilities can be used to effectively improve infrastructure resiliency, restore adjacent streams and floodplains, and ensure long-term infrastructure protection and stability.
About Cory Trego
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About Liz DiNatale, PE
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