Streaming Media

Abstract

It is now well established that the Great Bay Estuary is (and has been) suffering from poor environmental health, resulting in a significant loss of eelgrass and oysters, an increased growth of macroalgae and epiphytes, and increased concentrations of dissolved nitrogen and total suspended solids (NHEP, 2013). Effectively managing ecosystem health requires an accurate assessment of the nutrient balance from both tributaries and sediments. Recent results (Wengrove, et al. 2015) show that sediments could be a significant internal source of nutrients to the Great Bay. Essential to estimating nutrient fluxes from sediments is accurate estimation of near bed fluid shear stresses. The problem is that bed stress and total nutrient load from sediments over the large spatial scales of the Great Bay (as well as other tidally modulated estuaries) cannot be directly measured everywhere (including intertidal mudflats), and is further exacerbated by the strong temporal variability ranging hourly to monthly time scales. What is required is a robust numerical model capable of estimating bed stresses under combined wave and current fluid forcing that accounts for wetting and drying of extensive mudflat regions.

In this work we discuss what is known about Great Bay bathymetric evolution, hydrodynamic conditions, and seabed sediment characteristics, all based on field observations obtained within the past 10 years. These efforts include a quantitative assessment of the changes to the Great Bay bathymetry between 2009 and 2015, tidal variability through the Piscataqua River from ADCP measurements obtained in 2007, 2011, and 2015, and acoustic observations obtained in 2013-2015 to remotely characterize the seafloor (including mud fraction and geotechnical properties). We will further discuss our efforts to implement a numerical modeling system for the Piscataqua River and Great Bay Estuary, how we intend to verify the model using field observations, and how the verified model can then be used to estimate total nutrient fluxes for the Great Bay.

A great many people participated in the field efforts discussed and we gratefully acknowledge their efforts, including Jim Irish, Salme Cook, Jon Hunt, Meagan Wengrove, Diane Foster, Linda Kalnejais, Larry Ward, Semme Dijkstra, Ray Grizzle, Ken Baldwin, Ben Sweeney, Anna Simpson, and Cody Lanpher, all from UNH, Carl Kammerer from NOAA, Nina Stark and Greg Lucking from Virginia Tech, and Griffin Sperry from Norwich University. Our portion of this work was funded in part by NOAA, ONR, NH Sea Grant, and NH DES.

Presenter Bio

Dr. Thomas C. Lippmann conducts research focused on shallow water physical oceanography, sediment transport, and bathymetric evolution. His current areas of interest include field observations and numerical modeling of shallow water marine processes associated with inlets, estuaries, beaches, and coastlines, and assessing remote methods for sampling seafloor characteristics

Tom received a B.S. degree in mathematics and biology from Linfield College located in McMinnville, OR, in 1985 and M.S. and Ph.D. degrees in Oceanography from Oregon State University, Corvallis, OR, in 1988 and 1992, respectively. He was a National Research Council Postdoctoral Fellow at the Naval Postgraduate School in Monterey, CA, from 1992 to 1995, a Research Oceanographer at the Center for Coastal Studies, Scripps Institution of Oceanography in La Jolla, CA, from 1995-2003, a Research Scientist at the Byrd Polar Research Center, Ohio State University in Columbus, OH, from 1999-2008, and has been an affiliate member of the Flathead Lake Biological Station, University of Montana, Yellow Bay, MT, since 2014. Dr. Lippmann is currently an Associate Professor in the Department of Earth Sciences and the Center for Coastal and Ocean Mapping at UNH. He is the Coordinator of the Graduate Program in Oceanography, and serves on the Executive Committee of the Center for Ocean Engineering.

Publication Date

4-15-2016

Document Type

Presentation

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