Abstract
Stream restoration and bridge design represent two distinct applications of river engineering. In designing bridges, engineers model river flows to size bridge crossings that successfully convey the large amounts of rainfall demanded by storm events. For this purpose, deep and narrow river channels are favorable for their ability to pass large flows while minimizing the length of the bridge and its material cost. Stream restoration has a different philosophy of a favorable river channel: one with wide, shallow flows that are more reminiscent of its natural state. However, the large footprint of human settlement creates a system where human infrastructure is prioritized over ecosystem integrity. This thesis portfolio will explore the technical process of modeling river flows for bridge design alongside exploring the actor-network system behind the creation of the stream restoration industry.
In Chesterfield, VA the Otterdale Road crossing over Blackman Creek experiences recurring flooding due to its undersized bridge design. The road serves as a vital connector for nearby neighborhoods and first responders. Its frequent closure has occasionally cut off emergency vehicle access with the bridge overtopping 15 times in the past 5 years alone. My capstone project creates a revised bridge design that’s capable of conveying river flows for the precipitation and runoff demands of the 100-year storm. The 100-year storm represents a engineering estimate of the most intense rainfall event forecasted for a 100-year period. To design a bridge capable of conveying these flows, we used HEC-RAS which is a hydraulic modeling software developed by the Army Corps of Engineers. Using HEC-RAS to model the 100-year storm’s ability to overtop the bridge and surrounding roadway, we iterated to a final design that expanded the length of the bridge by over 100 feet. This final design consists of 3 prefabricated concrete arch bridges connected in series, creating a large opening capable of conveying intense storms. To accommodate the increased size of the new bridge, we raised the height of the road, improving driver safety and curve visibility where possible. Lastly, we produced foundation designs to ensure the bridge’s stability even against scouring from river flows.
My participation in the river-focused Otterdale Road capstone project was inspired by my aspiration to work in the stream restoration industry. Through the capstone project and attending a stream restoration conference in October, I became curious about the industry’s roots. I honed this curiosity into an STS research paper that analyzed the combination of actors that turned a grassroots environmental idea into a multibillion-dollar industry. Leveraging my conference attendance as a starting point, my analysis consisted of a literature review to understand the industry’s creation and explosion. My review processed evidence into the categories of damage to natural streams, enabling environmental thought & policy, and shifting restoration science. Naturally, an Actor-Network Theory framework emerged from the analysis and connected events including by not limited to 19th century dam construction, 1940’s land ethics and the predominant modern restoration framework. By the exploring the roots of the stream restoration industry, we can better understand the historical precedent behind the industry’s success and pitfalls. In doing so, we learn how to build on these going forward.
Stream restoration and bridge design represent two distinct but complementary perspectives on river engineering. One optimizes rivers for human infrastructure, the other works to restore what that infrastructure has cost the environment. The Otterdale Road bridge redesign demonstrates how hydraulic modeling can produce practical solutions to flooding and safety concerns, while the STS paper reveals the broader social and historical forces that shape how society even comes to value restoration in the first place. Together, these projects reflect a tension at the heart of river engineering: the competing demands of human settlement and ecological health. Understanding both the technical tools and the actor-networks behind river management is essential for engineers who hope to navigate that tension thoughtfully. Ultimately, this portfolio argues that good river engineering requires not only hydraulic competence, but an awareness of the historical and institutional context in which that work takes place.
