Collaborative Research: Rising seas, failing infrastructure: Characterizing microbial risks from exposure to tidal floods

Tidal flooding is occurring at increasing rates in coastal communities due to sea-level rise. Recent research demonstrates that tidal floodwaters can be contaminated with fecal matter from human and animal sources. However, we do not yet know what causes fecal contamination of floodwaters, or what are the risks to public health resulting from these contaminated floodwaters. The goal of this project is to characterize risks posed to people who encounter floods either directly, or through recreation in coastal waterways that receive floodwater drainage. To achieve this goal, the project team will measure pathogens and microbial markers in floodwaters to assess fecal contamination sources and develop models to predict public health risks. The movement of floodwater into coastal waters will be tracked and modeled, and fecal bacteria will be measured to understand risks faced by swimmers and other recreators. Society will benefit from the results of this research as stakeholders can use the information to protect human health from emerging threats posed by sea-level rise. Additional benefits to society result from findings that may lead to the development of new engineering approaches for preventing or eliminating tidal floodwater contamination. Educational and research training will increase scientific literacy and help develop the Nation’s STEM workforce.Older stormwater drainage networks in coastal areas that were designed to move rainwater away from developed areas now act as conduits for tides and rising seas to flow into communities, resulting in “tidal floods.” Recent research demonstrates that floodwaters often have elevated fecal bacteria concentrations indicative of hazardous contamination, potentially driven by sewage system failures. How these tidal floods mobilize and transport microbial pollutants is poorly understood, as are the impacts on coastal water quality. The goal of this project is to establish a quantitative understanding of the causes and risks from failing coastal stormwater infrastructure under sea-level rise. The specific objectives designed to achieve this goal are to: i) Characterize microbial risks through measurement of indicator organisms, pathogens, and microbial source tracking targets; ii) Determine the fate of contaminated floodwaters in adjoining recreational waters using measurements and a coupled hydrodynamic model; and iii) Evaluate the contribution of contaminated tidal floodwaters to adjoining coastal water quality. This project will provide the first quantitative measurements of microbial risk associated with exposure to tidal floodwaters, creating foundational insight on how coastal communities encounter water quality hazards due to tidal floods. These findings will contribute to a mechanistic understanding of tidal flood hydrodynamics that environmental regulatory agencies and public health officials can use to determine when mitigation actions should be implemented to address tidal flood risk.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.