Geospatial Modeling Suggests Threats from Stormy Seas to Rhode Island’s Coastal Septic Systems

Abstract

Coastal communities preparing for climate change and sea-level rise need to consider the impact large storms will have on belowground infrastructure. Although these communities often rely on on-site wastewater treatment systems (OWTSs) to treat wastewater, there is little research describing how these systems might be impaired after a large storm. A geographic information system (GIS)–based model was used to examine the potential impact of storms (1 in 25 to 1 in 500 years events, Category 1–4 hurricanes) on OWTSs along the southern Rhode Island shore. Based on geographic location, coastal geologic setting, and proximity to coastal features, the number of OWTSs threatened by wave inundation and storm surge ranges from ∼2,000 in a Category 1 hurricane to ∼3,000–3,800 in major flood events, to more than 4,600 from a Category 4 hurricane. The number of affected OWTSs increases by ∼200 if 0.3 m of sea-level rise expected over the next 30 years is considered. Damages incurred can cost homeowners from $1,000 to more than $30,000. Compromised systems will also threaten human and environmental health as untreated wastewater enters groundwater and coastal waters. Methods from this study can be applied to improve coastal communities’ resilience planning globally.