Introduction | Location and Physical Setting | Freshwater | State of the Aquifer System | Interactive Content | References

Long Island, the eastern-most part of New York State, extends east-northeastward roughly parallel to the Connecticut coastline. It is bounded on the north by Long Island Sound, on the east and south by the Atlantic Ocean, and on the west by New York Bay and the East River. Long Island is joined to the mainland specifically, to the Borough of the Bronx, which is one of the five boroughs of New York City by two bridges and it is also joined to Manhattan Island and Staten Island by several bridges and tunnels.

Politically, Long Island is divided into four counties — Kings, Queens, Nassau, and Suffolk Counties. Kings and Queens, the two westernmost counties, are also boroughs of New York City. Several smaller islands are included within the political boundaries of Long Island; the better known of these are Fire, Shelter, Gardiners, Plum, and Fishers Islands (figure 1).

Location map of Long Island and the generalized glacial moraines.

Figure 1: Location map of Long Island and the generalized glacial moraines.

The total length of Long Island is about 120 miles, and its maximum width is about 23 miles. The total area of Long Island (including the smaller islands within the political boundaries of the island, but excluding the bordering bays) is about 1,400 square miles. Kings County has an area of about 71 square miles; Queens County about 109 square miles; Nassau County about 291 square miles; and Suffolk County about 934 square miles.

Fire Island is the longest of several barrier beaches that parallel the south shore of Long Island. It's maximum width is about a quarter of a mile, and is separated from Long Island by Great South Bay, a shallow body of salty water that ranges up to 5 miles in width. The other barrier beaches along the south shore also are separated from the main island by salty bays, one of the best known of which is Jamaica Bay along the south shore of Kings and Queens Counties.

The northern and eastern coastlines of Long Island are indented by deep bays that form excellent harbors. Peconic Bay, which is about 30 miles long, divides the eastern end of the island into two long, narrow peninsulas that are locally referred to as the North and South Forks (Cohen and others, 1968).

  • Topography

      The present landforms of Long Island are the result of many geologic processes, some of which began many millions of years ago and some of which began only recently. Most of the major features of the present-day topography, however, are related to the last glaciation, which ended approximately 22,000 years ago. The most prominent landforms of Long Island are (a) the two lines of hills that form the "backbone" and the "forks" of the island, (b) the gently sloping plain that extends southward from the hills, (c) the deeply eroded headlands along the north shore, and (d) the barrier beaches along the south shore.

      Topography map of Long Island.

      Figure 2: Map of Long Island topography and the generalized glacial moraine locations.

      The two lines of hills, known as "terminal moraines" reach a maximum altitude of about 400 feet above sea level, and are separate and distinct in the central and eastern parts of the island, but merge in the western part (figure 2). The southernmost lines of hills the Ronkonkoma moraine is the older of the two; it extends eastward to form the South Fork. The northern line of hills — the Harbor Hill moraine — extends eastward along the north shore of Long Island to form the North Fork. The moraines are composed of poorly sorted rock debris (glacial till) consisting of boulders, gravel, sand, silt, and clay, which was pushed ahead of and incorporated within the continental ice sheets when the ice advanced onto the island, and which was subsequently deposited during melting of the ice sheets.

      The moderately flat surface that extends southward from the Ronkonkoma and Harbor Hill moraines to the south-shore bays is called an outwash plain. It is mainly a depositional feature composed of and underlain by well sorted sand and gravel deposited by streams that were fed by glacial melt water. The outwash plain generally begins at an altitude of about 100-150 feet, and slopes southward at a rate of about 20 feet per mile until it merges with recent swampy deposits along the coast (Cohen and others, 1968).

      The eroded headlands along the north shore are composed mainly of glacial deposits, but streams and waves sculptured their final form. After the ice sheets retreated northward, the land surface of Long Island rose slightly (rebounded) with respect to sea level. The headlands were deeply eroded, and the many wide and deep harbors along the north shore were carved by northward-flowing streams. Wave erosion has steepened the northern slopes of the headlands into nearly vertical bluffs that, in places, are about 100 feet high.

      Along the south shore, waves and ocean currents have reworked the deposits along uplifted shoreline to form off-shore bars (commonly referred to as barrier beaches). In terms of geologic time, these barrier beaches are ephemeral features that are gradually being eroded by wave action, and whose positions are continually changing owing to ocean currents. Sand and silt, as well as organic deposits, deposited by the wind, streams, salt-water currents, and storms (washover fans), tend to fill the shallow bays behind the barrier beaches (Cohen and others, 1968).

  • Population

      About 7.56 million people lived on Long Island in 2010. Of these, about 2.50 million are in Kings County, 2.23 million in Queens County, 1.34 million in Nassau County, and 1.49 million in Suffolk County (figures 3A-E). During the first two decades of the 20th century, population growth on Long Island, in terms of both rate and magnitude, was greatest in Kings County (figures 3A-3B). At that time, Kings County was characterized mainly by multiple-family dwellings and was moderately industrialized; Queens County was largely suburban, and Nassau and Suffolk Counties were rural. In the next decade (the 1920's), the largest increase in population occurred in Queens County (figure 3C), mainly as a result of the extension of the rapid transit system into the county, the concurrent increase in construction of multiple-family dwellings, and the moderate growth of industry in the area (Cohen and others, 1968).

      Total Population Per County.
      Total Population in Kings County.
      Total Population in Queens County.
      Total Population in Nassau County.
      Total Population in Suffolk County.

      Figure 3A-E: Graph of decadal population from 1900-2010 for a) Long Island; b) Kings County; c) Queens County; d) Nassau County and e) Suffolk County.
      Source: http://www.census.gov/prod/www/decennial.html

      Beginning soon after the end of the Second World War and extending into the late 1940's and the 1950's, marked suburban expansion into Nassau County caused a dramatic increase in the population of that county (figure 3D). The wave of suburban expansion, characterized mainly by large-scale developments of single-family homes, has been moving eastward with time. As a result, the population of central and eastern Nassau County increased rapidly in the mid 1950's. In 1980, the population in Nassau County decreased over 7% and from 1990-2010 the average rate of increase was about 6,000 per decade. The population of western Suffolk County began to increase markedly from 1950 to 1960 and increased over 141%. The second largest concurrent decadal increase occurred between 1960 and 1970 when the population increased over 61%. In 1980 the population of Suffolk County surpassed that of Nassau County. The population of Suffolk County has more than doubled from 1960 to 2010 however, from 1990-2010 the average rate of increase was about 70,000 per decade (figure 3E).

      The present (2010) population density on Long Island ranges from very dense in the western part to sparse in the eastern parts (figure 4). The pattern of population density mainly reflects the gradual eastward transition from the highly urban communities characterized by high-rise apartment buildings in Kings County, to the suburban communities in Nassau and western Suffolk Counties, and finally to the rural areas in eastern Suffolk County. Along with the general pattern of progressive eastward decrease in population density there has been a trend of preferential urbanization along the north and south shores.

      Population Density of Long Island in 2010.

      Figure 4: Map of 2010 population density calculated from U.S. Census data using block group areas.

      As urban development changes the immediate areas of land use, effects throughout the local environment can be observed. Losses of undeveloped land have direct impacts on the physical, biological, and social resources of an area. Once agricultural land is lost in a given area, its food production potential is also likewise diminished. Between 1970 and 1990, metro New York's population grew only 5 percent, but consumed 61 percent more land, (McMahon, Edward T., 1997, "Stopping Sprawl by Growing Smarter"). Often quality of life issues and cultural changes occur to the human population as result of this transformation. Population increases the demands for fresh water. Culture changes demand more water, land, and transportation per person.

      Source: USGS Land Cover Institute

      Changes in land use may have equally dramatic effects on local natural resources, as well as the human and physical ecology. Human induced changes to stormwater drainage affect aquatic habitats through changes in stream runoff (more rapid response to precipitation, higher discharges, and longer lasting peak flow events), water quality (temperature and contaminants), and diminished recharge to the water table (which affects water supplies for existing communities). The culture is also altered because lifestyles are changed as suburban growth encroaches on small towns and agriculture communities.

      The USGS Urban Dynamics Research Team documented urban extent through time to evaluate land use/land cover changes and assess the impact of development. They prepared datasets showing over 60 years of urban change, from 1928 to 1993. Within the New York Metropolitan region, urban annotation and digitization for 1930's, 1950's, 1960's, 1970's, 1980's, and 1990's, have been completed for a 29 county area; and are presented in the animation below.

      Land Use on Long Island from 1930 to 1990.
  • Land Use & Land Cover

      On Long Island, land use includes the human activities and management practices for which land is used. Land cover is a mosaic of developed, forest, agriculture, and wetlands areas. Both land use and land cover are usually discussed in similar environments. The National Land Cover Database (NLCD) serves as the definitive LANDSAT-based, 30-meter resolution, land cover database for the Nation. NLCD provides spatial reference and descriptive data for characteristics of the land surface such as thematic class (for example, urban, agriculture, and forest), percent impervious surface, and percent tree canopy cover.

      Source: http://pubs.usgs.gov/fs/2012/3020/

      Dominant covers across Long Island are developed, open space and forests, with locally dense urban development. More than half (53 percent) of the land cover area across Long Island in 2006 was developed, open space, low and medium-intensity categories (figures 5 - 6). About 10 percent is developed, high intensity, and Kings County attributes to about 60 percent of this category area within its political boundaries. About 3 percent of Long Islands area is cultivated crops or agricultural (Homer and others, 2011; Fry and others, 2011).

      Hover mouse cursor over counties below to view additional information:


      Figure 5: Map of Land use for Long Island, 2006.
      Hover mouse cursor over figure below to view legend:


      Figure 6: Graph of 2006 land cover in square miles a) see above for each County; b) see below for Long Island.

      From the early 1900's, land cover on Long Island has trended toward the conversion of open space and agricultural land into residential, industrial, and commercial development.

      The accompanying web sites are available showing the use of land on Long Island and were compiled from reports prepared by the Nassau County Planning Department, the Suffolk County Planning Department, and the New York City Department of Planning. Data for the four counties on Long Island are not available for precisely the same time. Furthermore, the three agencies did not use precisely the same land classifications. Despite these inconsistencies, however, the data shown are reasonably representative for the period designated as present “2005-2010", and provide considerable insight to the general characteristics of land use on Long Island at the present time (2014).

      Additional Information

      Several websites that show land use are provided below.

      Suffolk and Nassau:
      Long Island Land Use Interactive Map

      New York City:
      New York City Land Use Maps
      New York City Land Use Tabular Data

      Rauch Foundation reports:
      Land Use in Nassau and Suffolk Counties
      What Happens When We Run Out of Land?
Kings County Queens County Nassau County Suffolk County