Detection of Changes in Sediment Distribution in the Hudson River Estuary with Repeated Subbottom Profiling

Tuesday, 16 December 2014
Frank Oliver Nitsche and Timothy C Kenna, Lamont -Doherty Earth Observatory, Palisades, NY, United States
During the last decade, several major storms have impacted the US Atlantic coast, including tropical storm Sandy in 2013 and tropical storms Irene and Lee in 2012. These storms, in particular, had major impacts on the watershed of the Hudson River Estuary, resulting in changes in the delivery and distribution of sediments. While Sandy generated a large storm surge that mostly effected the lower estuary, Irene and Lee caused significant flooding in the upper estuary that delivered ~2.7 million tons of sediment to the Hudson River Estuary, which according to USGS estimates is an amount equal to three times the annual load of ~700,000-800,000 metric? tons (Wall et al. 2008; Ralston et al., 2013).

Here we report results from high-resolution Chirp subbottom surveys conducted in selected areas of the Hudson River in 2014. Areas were selected with the goal of investigating changes in the sediment deposition and storage in the Hudson River as a result of these events. The new survey lines were acquired following the tracks of earlier subbottom profiles that were collected as part of the Hudson River Benthic Mapping Project in the early 2000s, i.e. before the storms of 2012 and 2013, in a dense grid of subbottom profiles. We then compared these co-located profiles to determine changes between the profiles and to map out the spatial distribution of increased deposition in the selected areas. In several places, the data show clear increases of the thickness of depositional layers of over 0.25 m while in other areas these changes are less clear. Changes based on sub-bottom data will be compared to results obtained on sediment cores taken from the same areas. Preliminary analysis of the sediment cores indicates clear layers of recent sediments in some areas that correspond to the results of the subbottom analysis.