Download A METHODOLOGY FOR QUANTIFYING STORM

A METHODOLOGY FOR QUANTIFYING STORM-DEPOSITED SEDIMENTS WITHIN NAVIGATION
CHANNELS IN THE ABSENCE OF HYDROGRAPHIC SURVEY DATA
Daniel Barone and Stewart Farrell, Richard Stockton College, Coastal Research Center
Following Superstorm Sandy, the State of New Jersey was in need of a method for quantifying
storm-deposited sediments within the state’s navigation channels in the absence of pre-storm
hydrographic survey data to compare with post-storm hydrographic survey data. This
information was necessary to be eligible for receiving federal disaster funds to dredge state
channels. A major challenge was the requirement to differentiate between “Sandy-related”
storm deposited sediment and other sediments deposited within channels under normal
conditions (i.e. shoals existing within channels prior to Sandy). The Richard Stockton College
Coastal Research Center (CRC) developed a methodology determining the volume of Sandydeposited sediment within a channel by collecting a series of 2-inch sediment cores along predefined, regularly-spaced transects where shoals were identified by comparing post-Sandy
bathymetry to the channel’s “design” template. A total of 925,242 cubic yards of Sandy-related
sediment was identified from 3,384 cores collected in 160 out of the 214 navigation channels.
In general, two types of Sandy-related sediment deposits (or Sandy-deposited sediment layer
thickness within each core) were identified: 1) Sediment deposited from re-suspension and
redistribution of lagoon or tidal channel material from within the tidal creeks, bays and
estuaries and 2) sediment deposited from overwash of the Atlantic Ocean facing barrier islands
into the bays and marshes. The dominant form of debris in the channels were the vast
quantities of marsh grass and other plant materials that were picked up by the storm surge,
mixed with re-suspended bay floor sediments in the water column and transported to the
downwind bay shorelines where it was deposited across the uplands landscape and within
small creeks, coves and marinas associated with the New Jersey’s bay environments.