Hurricane Irene made landfall in New York on August 28, 2011. The storm mobilized Hudson River sediments and their associated contaminants, including toxins, such as polychlorinated biphenyls (PCBs), pathogens and excess nutrients, which were stirred up with river mud and washed down from the surrounding land, tributaries and wetlands of the watershed.
A driving force behind the deployment of Beacon Institute’s River and Estuary Observatory Network (REON) is Dr. James S. Bonner’s dictum that large episodic events are responsible for the majority of changes on the Hudson. But because they are unpredictable and occur only a fraction of the time, understandng their function and impact requires a monitoring presence that is full-time. Bonner is Beacon Institute's chief research officer.
REON was in operation during Irene. The results of data collected were just published in the April edition of the journal Environmental Engineering Science. “Impacts of an extreme weather-related episodic event on the Hudson river and Estuary,” by Mohammad S. Islam, REON project manager, Bonner, Christopher S. Fuller, and William Kirkey, demonstrates that inland flooding, caused by Irene, resulted in dramatic increases in the suspended sediment concentrations throughout the Hudson and Mohawk Rivers and the Hudson River estuary. So powerful were the Hudson's flood waters they even overpowered the normal inland tidal influence in the estuary.
We talked with Jim Bonner about the work.
John Cronin: How does this research by the REON team help us better understand the workings and behavior of the Hudson River and estuary?
Jim Bonner: The storm related sediment load from Irene represented a major fraction of the river’s annual total sediment load. The observed changes in sediment transport illustrate important mechanisms with respect to the river’s water quality especially considering that many relevant contaminants, for example PCBs, tend to bind and accumulate in aquatic sediments. When such contaminated sediments are re-suspended during a flood event, they can be transported downstream, effectively extending the area contaminated and potentially affecting larger wildlife and human populations.
JC: The interaction of the Hudson's net downriver flow with the ocean's tidal push inland is a fascinating aspect of the estuary's mechanics. How was that affected by Irene?
JB: The effects of the flood flows extended well into the estuarine sections where the flood flows dampened and/or over whelmed tidal flows that normally demonstrate a characteristic upstream flow during a flood tide. Notable effects from this flood mechanism included suppression of tidally induced sediment resuspension and a shift in the salt front toward the Atlantic. The occurrence of significant shifts in normal salinity gradient may affect the distribution of estuarine species.
Based on my communications with NOAA, 50% of the flooded shoreline was a result of freshwater flow from the Hudson.
JC: What questions for further research were revealed by the study?
JB: Further study is required to differentiate the source of the observed sediment as either water shed (i.e. tributary) input or in-situ sediment resuspension. Such information would be valuable toward developing strategies to mitigate mobilization of potentially contaminated sediments (e.g. capping) and/or minimizing erosion in upstream stream reaches through better management practices such ensuring the existence of stream bank buffer zones in agricultural areas.
JC: Did you gain insights into a next generation of innovations that are necessary?
JB: To fully characterize the relevant environmental forces responsible for the observed effects requires a comprehensive long-term high frequency monitoring program to provide data at relevant time and space scales to detect the frequency, extent, and magnitude of the measured parameters of interest (for example water temperature, acidity, water flow rate, water velocity, sediment size and concentration etc.). Integration of REON data with geospatially (i.e. GIS) represented data, for example land type/use, may allow determination of important causal relationships.
JC: There is increasing concern that climate change will create more severe and frequent storm events. Sea level rise is a certainty. What is the role of REON?
JB: REON and similar observatories will be critical to quantitatively document the changes allowing resource managers to effectively make informed decisions regarding the sustainable use and protection of our valuable natural resources. It is widely accepted that storm Intensity, duration and frequency will have significant impact on water resources.