4 Geohazards in the Northeastern U.S.: Investigation and Mitigation

Sunday, 17 March 2024
8:00 AM - 12:00 PM
Piscataquog Room

URBAN STORM SURGE PROTECTIVE MEASURES-SYNTHETIC DUNE CONSTRUCTION - COMPARISIONS TO JURASSIC SAND DUNES FROM LOW STANDS THRU HIGH STANDS SYSTEM TRACT FACIES

Paper number: 4-10
Program: Theme Sessions
Time: 10:40 AM – 11:00 AM

Authors

Abstract

The Rockaway Peninsula is in the 100 and 500-year flood zone, with potential sea level rise of between 8- 31 inches ( 20.32-78.7cm) from 2000 to 2050, and 15-75 inches ( 38.1-190.5 cm) for the entire 21st century.. The Peninsula contains 124,000 residences , with cumulative real estate assets worth 15 billion dollars. In 2012 Super Storm Sandy removed 1.5 million cubic feet of sand from the Peninsula.

Massive construction and population increases have continued on the Peninsula. In 2013 an environmental impact study of the effects and possible future steps for coastal protection was done under then Mayor Bloomberg utilizing a team of geologists and engineers and concluded a dune field would significantly protect the coastline.

The U S Army Corps of Engineers, New York District, is constructing significant rock jetties and synthetic dunes over the 10-mile coastline at a cost of over 700 million dollars. Over 2 million cubic yards of sand have been redeposited from dredging to the beach from near shore accumulations. A massive undertaking including the multi-step synthetic dune construction, involving a cement and sand bag nucleus covered by sand and salt tolerant greenery for dune anchoring.

Sensitivity of dunes to sea level fluctuations can be analogous to the well bore cores (15,000’) Jurassic dune fields of the Norphlet Formation in the Gulf of Mexico, which reflect significant dune migration from a transgression from low stand to high stand system tract facies. Provenance of the Rockaway Peninsula is due to Hudson River transport, erosion from the metamorphic Cambro-Ordovician Manhattan Schist, Fordham Gneiss, and Inwood Marble, part of the Northern Appalachians. Surface sediment samples contain well sorted quartz and other material grains. In comparison the Jurassic Norphlet Formation contains quartz grains rounded to sub angular derived from the southern Appalachian forelands. Mapping based on the stratigraphy from hydrocarbon exploration wells over the past 40 years have increased the extent of the dune fields from onshore Alabama to offshore in the Gulf of Mexico, truly sensitive to relative sea level fluctuations.

Geological Society of America Abstracts with Programs. Vol. 56, No. 1

doi: 10.1130/abs/2024NE-396854

© Copyright 2024 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.