November 16, 2020
Supported by a three-year, $784,000 National Science Foundation grant, a team of researchers led by Dr. James Heiss in the Department of Environmental, Earth and Atmospheric Sciences (EEAS) are studying the impact of extreme multi-hazard coastal storms on groundwater flow and saltwater-freshwater mixing in beach aquifers.
Coastal population growth and urbanization have increased nutrient loads to coastal and estuarine waters, leading to eutrophication, harmful algal blooms, loss of biodiversity, and impaired water quality along the world coastline. While streams and rivers provide large quantities of nutrients to coastal ecosystems, groundwater discharging from the seabed can also contribute nutrients, such as nitrogen, in quantities that rival riverine inputs.
Nutrients and other chemicals that are transported to the ocean in groundwater flow through beach aquifers, where infiltrating seawater from wave and tidal activity mix with the underlying nutrient-rich fresh groundwater. In these sandy sediments where seawater and freshwater mix, chemical reactions can attenuate groundwater contaminants before discharging from the seabed.
While the roles of more predictable processes that affect groundwater flow – like tides and seasonal changes in rainfall – are generally understood. The effects of coastal storms, however, are more difficult to characterize because they bring intensified factors such as pounding waves, heavy rains and beach erosion that interact with one another.
With collaborators from UML Computer Science and Woods Hole Oceanographic Institution, the team will install instruments in the beach at the U.S. Army Corps of Engineers Field Research Facility in Duck, NC to monitor groundwater flow behavior during a large coastal storm. The group will use the field measurements to understand how multi-hazard coastal storms that are accompanied by extreme terrestrial precipitation, storm surge, waves, and coastal erosion affect saltwater intrusion and groundwater flow beneath the coastline. The team’s broader goal is to improve understanding of the factors that control the timing and duration of eutrophication events and improve coastal water quality – two important factors that directly affect coastal economies.