Hurricane flooding and water quality issues: opportunities for increased
resilience
Abstract
Hurricanes that cause damage to lives and property are often accompanied
by poor water quality that threatens the health of human communities and
aquatic species. North Carolina has experienced 3 devastating 500-yr
storms within 2 years; wastewater treatment plants and sanitary sewer
overows occurred up to 300 km inland, as well as coal ash spills,
breaches of confined animal feeding operation (CAFO) waste lagoons, and
numerous fish kills. Many in-situ sensors went offline and hazardous
conditions precluded field sampling during and after these events.
Publicly available satellite data enables delineation of flooding over
broad areas, which can aid in quantifying the extent of flood exposure
and potential water quality impacts. We mapped flooding across the North
Carolina Piedmont and Coastal Plain due to Hurricane Matthew (2016) and
Hurricane Florence (2018) with Sentinel-1 synthetic aperture radar. We
assessed how impacts were distributed across indicators of social
vulnerability at the census tract level and freshwater ecological
vulnerability at a watershed scale using quantile regression. Finally,
we identied flood-prone infrastructure relevant to water supply and
treatment, and mapped locations where nature-based solutions could be
implemented to store floodwaters and process contaminants. Flooding
mapped with >91% accuracy extended beyond the 500-year
floodplain—furthermore, the legal floodplain systematically
underestimated impacts to more vulnerable human populations and surface
waters. Repeated flooding affected both point and non-point sources of
nutrients, including 188 wastewater treatment plants representing
>46% of treatment capacity and 77 swine CAFOs that
generate ~ 478,926,961 tons of manure per year.
Conservation of ~4,600 ha of currently unprotected
forest and wetland, and restoration or changes in land management on
~3,100 ha represent key opportunities to protect human
and natural communities under future storms. Our results suggest that
current flood hazard maps are inadequate for resilience planning.
Changes to design standards, land-use planning policies, and operation
of infrastructure that conveys and treats water are warranted to improve
floodplain resilience.