13 Barrier Island and Backbarrier Sediment Dynamics

Friday, 17 March 2023
1:30 PM - 5:30 PM
Lake Audubon

COASTAL RISK MANAGEMENT- A GEOLOGICAL PERSPECTIVE, ROCKAWAY BEACH, QUEENS, NEW YORK

Paper number: 13-1
Program: Theme Sessions
Time: 1:30 PM – 1:50 PM

Authors

Abstract

The Rockaway Peninsula is a classic barrier bar typical of the south shore of Long Island, sitting above glacial outwash gravel deposited after the Young Dryas, 11,000 to 13000 years ago, also marked by a major rise (396 feet) in sea level due to de-glaciation, stabilizing 5000 years ago.

Sediment samples contain well sorted quartz and other mineral grains, reflecting multiple cycles of erosion, weathering and redeposition from the metamorphic Cambro-Ordovician Manhattan Schist, Fordham Gneiss, and Inwood Marble.. Additionally, heavy minerals include magnetite, zircon, garnet, and glauconite Provenance appears to be associated with transportation related the Hudson River during the Pleistocene when the river experienced significantly higher flow rates.

In 2013, New York City concluded the Rockaway Peninsula is in a 100 and 500-year flood zone, with a potential rise of up to 31 inches (78.7cm) from 2000 to the 2050’s. Our previous studies focused on of tectonically stable low subsidence areas of Pliocene aggradational carbonate rocks, sensitive to sea level (photic zone) in Florida and Bahamas comparable rates of sea level rise of 8 inches (20 cm.) per 50 years. The NYC Climate Report also predicted storm surge of most likely case of to 7.5 feet by the 2050’s. New construction on the Peninsula requires 10 feet of elevation above street level.

The U. S. Army Corps of Engineers began the construction of a dune field parallel to the coastline ($336 million), and a series of sizeable metamorphic rock groins to baffle the transportation capabilities the longshore currents and storm surges.

Over the past 15 years the Peninsula, has experienced significant population growth reflected in new townhomes, multi-story residences, and commercial development, representing billions of dollars in market value. Road and infrastructure construction has not occurred in proportion to population migration, resulting in increased evacuation times Thus shelter in place survival measures are critical.

Using the Rockaway Peninsula as a case study, we will examine the total financial and emergency management risk of the community with respect to coastal flooding and storm damage tools that emergency planners and insurers can use to assess the risk of a given zone as well as the potential cost of increased flood zone development.

Geological Society of America Abstracts with Programs. Vol. 55, No. 2

doi: 10.1130/abs/2023SE-384704

© Copyright 2023 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.