Drainage Improvements Along Otterdale Rd; Uncertainty in the Field and the Data: A look into Risk Perception and Infrastructure Design in Norfolk, Virginia 14 views

Coastal and inland communities are becoming increasingly vulnerable to flooding year after year. This is because of global warming and changing environmental conditions, insufficient infrastructure, and the increase in impervious materials have caused previously unharmed areas to experience flooding risk. Norfolk, Virginia is experiencing sea level rise, and it is subsiding at a rate that poses a major threat to the area. Projections estimating 16.5 inches of sea level rise by 2050 highlight the risk that is posed to the people and infrastructure. Chesterfield County is experiencing unexpected stormwater volumes due to an increase in impervious infrastructure and insufficient design for water capacity causing flooding of up to 3 feet during 100-year storms. Addressing this risk requires technically advanced solutions along with feedback such as public concerns and risk perceptions. Though modeling technology today can estimate sea level rise projections, uncertainty in environmental data and stakeholder priorities is still present. This uncertainty complicates engineering decision making beyond that of a technical solution. This project addresses the challenge of improving flood mitigation infrastructure by examining both the technical design of roadway infrastructure and the social factors that influence those designs. The technical project focuses on the issue that is experienced on Otterdale Road that crosses over Blackman Creek in Chesterfield County, Virginia. This road experiences frequent flooding due to its insufficient design capacity of a 100-year storm event and the flooding directly affects residents and emergency responders that rely on it. This project’s objective was to design a structure that achieved a 100-year storm hydraulic opening and met the FEMA No Rise requirement. HEC-RAS was used for hydraulic modeling of the area so that an evaluation of multiple designs could be done which included a steel truss bridge and a three CON/SPAN O-Series Arch Bridge. Culverts were quickly eliminated as a design alternative due to the inability to meet the hydraulic requirements of the project. After extensive modeling in HEC-RAS to justify the hydraulic capacity and in OpenRoads to model the new road design, a final design of a prefabricated Triple CON/SPAN O-Series Bridge composed of three 53’-span cells. The final design consists of 12.9’ arch rises, a 9’ road raise, and a total span length of 159’ was chosen. Steel H-piles were used to satisfy geotechnical recommendations due to the varying subsurface below. The final design reflects VDOT standards, cost, and constructability while meeting the No Rise requirement and the 100-year storm flow. The project shows the process of how engineering design balances hydraulic capacity, cost, safety, constructability, and regulatory standards to mitigate flood risks. The STS research project investigates the flooding in Norfolk, Virginia and how engineering uncertainties and public risk perception shape flood mitigation design. Research found that sea level rise modeling contains significant uncertainty due to assumptions made for variables such as ice sheet melt, thermal expansion, land water storage, and storm surge behaviors. The uncertainty requires engineers to use their judgement for assumptions that seem most applicable to the site when designing infrastructure and mitigation projects. Engineers most consistently use assumptions that are conservative to ensure safety. Public risk perception in this project is the amount of risk one is willing to take based off personal experience and past attempts by local authorities to mitigate floods. This perception directly influences the designs that are accepted in the area. News articles from Norfolk show community opposition to floodwall plans in the area due to concerns about property impacts and the failed attempts of the past. This led engineers to redesign the project, and the engineers and stakeholders are in ongoing negotiations. The research provides evidence that flood mitigation infrastructure is not purely technical, but a socially intertwined process that relies on community input and engineering constraints. Engineers are tasked with balancing public acceptance, technical constraints, and cost so that an effective flood mitigation strategy is presented. These projects highlight that effective flood mitigation projects rely on balancing technical requirements with social dynamics. The technical report demonstrates the ability to design based off hydraulic requirements, while the STS report demonstrates the importance of public input and how engineers actively change designs based on the feedback they receive. This approach of technically based solutions and a socially driven discussion provide a deeper understanding of the complex technical and social factors that are involved in flood mitigation design.

BS (Bachelor of Science)

Civil Engineering; Otterdale; Risk Perception; Norfolk; Flooding

School of Engineering and Applied Science Bachelor of Science in Civil Engineering Technical Advisor: Jonathan Goodall STS Advisor: Kent Wayland Technical Team Members: Finn Kelleher, Paige Linton, Julia Miele, Mia Sheldon

English

All rights reserved by the author (no additional license for public reuse)

2026-05-09