Anthropogenic Land Changes and Sedimentation Response in the Tidal Straits of New York City Author(S): Nicholas K

Anthropogenic Land Changes and Sedimentation Response in the Tidal Straits of New York City Author(s): Nicholas K. Coch, Meagan Lenna and Aislinn Deely Source: Journal of Coastal Research , March 2017, Vol. 33, No. 2 (March 2017), pp. 273- 285 Published by: Coastal Education & Research Foundation, Inc. Stable URL: https://www.jstor.org/stable/44161434 JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at https://about.jstor.org/terms is collaborating with JSTOR to digitize, preserve and extend access to Journal of Coastal Research This content downloaded from 86.59.13.237 on Thu, 08 Jul 2021 11:15:04 UTC All use subject to https://about.jstor.org/terms Journal of Coastal Research 33 2 273-285 Coconut Creek, Florida March 2017 Anthropogenic Land Changes and Sedimentation Response in the Tidal Straits of New York City Nicholas K. Coch*, Meagan Lenna, and Aislinn Deely School of Earth and Environmental Sciences Queens College, City University of New York Flushing, NY 11367, U.S.A. abstract mmĒĒĒĒĒĒĒĒĒĒĒĒĒĒĒĒĒĒĒĒĒĒĒĒĒĒiĒĒĒĒĒĒmĒĒĒĒm^^^m^^^^m^^^^^^^^m Coch, N.K.; Lenna, M., and Deely, A., 2017. Anthropogenic land changes and sedimentation response in the tidal straits of New York City. Journal of Coastal Research, 33(2), 273-285. Coconut Creek (Florida), ISSN 0749-0208. The sand and gravel mixtures found in the northern part of New York Harbor {i.e. Upper Bay) have long been attributed to the transport of coarse-grained sediments into the harbor from the Atlantic. A recent sedimentological study of New York Harbor suggested that the origin of this facies may have been from the East and Harlem rivers. Today, there are no tributaries supplying sediment to the East River-Harlem River system. A review of oceanographic and historical data and a detailed bottom sediment mapping program has established the historical drainage changes in New York City and the effect on sediments supplied to the East River-Harlem River system. Before the 18th Century, the East River and the Harlem River were major suppliers of coarse sediments to New York Harbor. However, development and filling in of almost all of New York's tributaries have cut off this sediment supply. The decrease in surface drainage has increased the danger of New York City flooding from Nor'easters and hurricanes. Finally, this research has shown that there are three, not two, sources of sediment for New York Harbor. ADDITIONAL INDEX WORDS: Tidal straits, urban estuaries, urban stream elimination. INTRODUCTION oceanic sediments. A box core taken in the fine facies shows The Harlem and East rivers have historically alternationbeen referred of coarse- and fine-grained sediments (Figure to as rivers , despite being tidal straits that connect 4B). Athe detailed Hudson view of the lowermost sand layer shows plane River Estuary with Long Island Sound (Figure laminated 1). Neither poorly sorted sand along with sediment deforma- water body has been studied in detail. However, tionunderstanding features (convolute laminae) indicative of high current their sediment dynamics is vital to a holistic understanding velocities. of sediment transport in the estuarine system of Thesouthwestern resolution of the origin of this coarse facies would require New York. a detailed analysis of bottom sedimentation in the Harlem and The traditional view of New York Harbor sedimentation is East rivers. It would also require an analysis of historical that the harbor was filled by a combination of finer-grained records to determine whether there were any river changes estuarine sediments, supplied by the Hudson, and coarse- that would have altered sediment dynamics in the past. The grained shelf sediments moved northward through the harbor results of this study are the body of this article. (Figure 2). This has been the understanding presented in previous studies, as well as the initial thoughts of the authors. Geology of the Harlem-East River System The Harlem River extends SW from the Hudson River and However, a recently completed study of New York Harbor by Coch (2016) showed a different picture. Detailed sampling joins the East River to the S (Figure 5). Both tidal straits are showed a mass of coarse sediment extending W and SW from lithologically and structurally controlled by the outcrop of the lower Manhattan into the Hudson River Estuary (Figure Cambro-Ordovician3). Inwood Marble, which is the weakest This suggested that the East River could have been a major metamorphic rock in the New York City series (Schuberth, sediment source for New York Harbor. However, reconnais- 1968). Outcrops of the Inwood Marble account for many of the sance sampling showed there was no sediment being low areas in northern New York City. Each outcrop area is deposited in the East River today. In addition, there are no bordered on both sides by ridges developed on the more- modern tributaries that could supply sediments to the resistant Manhattan schist and Fordham gneiss. These low system. areas are places where streams might be expected to develop, but none are visible. Coch (2016) studied this anomalous coarse facies in detail (Figure 4). He noted that the coarse facies was bounded on Oceanography of the Harlem-East River System the south by fine sediments, similar to those in the Hudson The Harlem River and East River tidal straits are among Estuary (Figure 4A). It was also isolated from supply by the most complex waterways in the United States. Tidal velocities can be quite high. For example, one of the 50 DOI: 10.2112 /JCOASTRES-D-16A-00012 received 10 June 2016; highest tidal velocities in the United States occurs near Hell accepted in revision 4 July 2016; corrected proofs received Gate (Figure 6) in the East River. The system is composed of 5 September 2016. Corresponding author: [email protected] a series of tidal straits and estuaries that are out of phase ®Coastal Education and Research Foundation, Inc. 2017 tidally. In addition, there are major inputs of fresh water This content downloaded from 86.59.13.237 on Thu, 08 Jul 2021 11:15:04 UTC All use subject to https://about.jstor.org/terms 274 Coch, Lenna, and Deely i&ppan ¿i» ^^^^larlem ft// X. Estuarine J 7 <r¿ fine sands, silts and clays J J I Yonkers ) J PREVIOUS rmyí ) ¡ff**™ PICTURE OF r ' Ä?/#-harlem " r. HARBOR > r Jm Ä?/#-harlem " r. si£>soUHO STUDY ) SEDIMENTATION AREA Mixtures V» jí J nł duomi - sediments f Brooklyn H '1 f iihmm {Jamaica ' k ' Shelf gravelly sands ^ J Na and sands ' Raritan r]) lower bay ^ /lURarltan Bay <r' ^ S«ndy'' «V Hook *11 *>* Figure 2. Previous interpretation of sedimentation in the Upper Bay of New Figure 1. Map showing study York Harbor. (Color area for this figure and is available locations in the online version of this cited in the text. SD = Spuyten Duyvil, RI = Roosevelt paper.) Island, HG = Hell Gate, GI = Governors Island. (Color for this figure is available in the online version of this paper.) York Harbor (Figure 1). Distinct topographic features moved from New York City Marmer sewage (1935) to subdivide plants. the East River into Thelower and East River receives a large quantity of both treated and untreated sewerage upper river areas. The lower East River is a narrow channel waste. The dry weather discharge of secondarily treated approximately 400 m wide, with an average depth of 12 m. It sewerage in the Upper East River amounts to 580 million gal extends 11.5 km from the Battery to Hell Gate. The northern d_1 (2,196 million L d-1). This is 43% of the average dry- end of the lower East River is split by Roosevelt Island into weather discharge of the New York City sewage system two channels. The western channel is deeper and most (Interstate Sanitation Commission, 1971). significant for tidal flow. The upper East River, from Hell There have been several studies of the water characteristics Gate to Throggs Neck, is 11 km long and is larger and wider in the system but no published data, to our knowledge, on than the lower East River. It has numerous islands and its sediment dispersal within the system. The purpose of this average depth is less than that of the lower East River section is to review the published oceanographic studies (Marmer,to 1935). make inferences about sediment dispersal within the system. The East River was the focus of most hydrographie studies of New York Harbor conducted before 1950. This interest was Harlem River based on the erroneous assumption that the nontidal transport The Harlem River is a narrow strait about 12 km long from the Hell Gate to its confluence northward with the Hudson was the sole determinant of pollution transport in the East River. It was thought that the observed net flow toward the River at Spuyten Duyvil (Figure 1). Its average depth is about 6.8 m (below the mean low water level), and its harbor provided a means of flushing sewage through the Narrows during low-runoff conditions, when the Hudson River topography and cross-section are relatively uniform. Blum- flow was insufficient for that purpose (Jay and Bowman, 1975). berg and Pritchard (1997) reported mass balance and flux Future research was to show that was not the case. calculations, which indicated that the Harlem River had Bowman (1976) conducted a current-meter study in the East large variations in flux.

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