The Passaic River Basin is the land area draining to the Newark Bay through the Passaic River. The Basin has an area of 935 square miles, mostly in New Jersey but extending north into Orange and Rockland Counties, NY. The Basin originally was part of the homelands for the indigenous Lenape peoples (also identified as Leni Lenape and Lenni Lenapi, and by English settlers as the Delaware), but with centuries of European settlement and later growth, it is now home to more than 2.4 million people of many racial/ethnic backgrounds (including Native American) and a wide variety of industrial, retail commercial and office properties. As such, it is home to a large share of New Jersey’s population and economic wealth; it also provides the water supplies used by all those people and more.
The Passaic River Basin has also suffered from a long history of industrial activity, development in risky locations, and pollution from all the people and economic activity. In the 1960s, the Passaic River itself was identified at one of the ten most polluted rivers in the United States. While conditions have improved greatly in many areas, many environmental quality problems remain, and developed areas still exist in areas that are exposed to floods and contamination of soils, groundwater and surface waters. An exploration of the Passaic River Basin in regional maps was developed by Rutgers University, The Passaic River Basin in Maps.
What is the Passaic River Basin?
A river basin is a large watershed, defined as the land area that drains to a single surface water outlet. Within a river basin are multiple smaller watersheds, each of which has even smaller subwatersheds, each of which has a river or stream that collects all the water flow from the land area. The Whippany, Rockaway, Wanaque, Ramapo and Saddle Rivers are some of the major watersheds. There are 102 subwatersheds in the New Jersey portion of the Basin. The boundaries of each watershed and subwatershed will follow the high points around the streams and rivers draining that area, as shown in the figure at right. While rivers and streams are easy to see, watershed boundaries are less obvious and rarely are the same as political boundaries for municipalities and counties. We often have used rivers as political borders, splitting watersheds between multiple municipalities and counties. For example, the lower Passaic River is the border between Essex County on the west bank and Bergen and Hudson Counties on the east bank.
Watersheds and river basins drain from high points to their lowest point, or elevation. For the Passaic River Basin, the lowest point is sea level where the Passaic River reaches Newark Bay. Its highest points are in the Highlands region of New Jersey and New York, which is also the location of many water supply reservoirs, built decades ago to serve the historic urban cities and large suburbs that grew around them.
Most days of most years, all the rivers and streams stay within their banks, carrying a combination of natural flows that are there every day (which come from the movement of groundwater into the streams), discharges of treated wastewater from municipal and industrial treatment plants, and runoff from smaller storms. However, major storms can cause streams and rivers to overflow their banks into the flood plain. Where the flood plains are undeveloped or used for parks that aren’t damaged by floods, no problem. Where the flood plains are developed, damages can result.
The movement of water from high points to low also carries with it all the water pollutants from higher elevations to lower elevations. Therefore, the lower Passaic River carries with it all the water quality problems from the entire river basin.
The amount and character of flooding varies within the three main regions of the basin:
The Highlands are a series of parallel ridges running in a northeast/southwest direction. This area drains 489 square miles of watershed. Most major tributaries of the Passaic River drain from the Highlands. These are the Whippany, Rockaway, Pequannock, Wanaque, Ramapo, and Pompton Rivers.
The Public Vision for the Future of the Highlands Region is that it remain an oasis of open land that can provide a sustained quality of life and environmental integrity…Preamble, 1992 New York – New Jersey Highlands Regional Study
These waterways and their tributaries are characterized by flash floods; the valleys are narrow and steep sided. Development in this area has been limited, compared to the other two regions, due to the topography.
Flooding, however, is a common occurrence in established towns. For example, Morristown, on the Whippany River, and Denville and Dover on the Rockaway River are representative municipalities in the Highlands that have had major flood damages.
The Central Basin is comprised of large areas of meadows and swamps. At least 27, 000 acres of freshwater wetlands still exist in the Central Basin. It is a broad and relatively flat valley that extends from Long Hill Township in the south, to Pequannock Township in the north.
Flooding has occurred primarily in Wayne, Lincoln Park, Pequannock, Pompton Lakes, and Fairfield. The flood plain of the Passaic River ranges from 5,000 to 20,000 feet in width throughout much of the Central Basin, narrowing to approximately 100 to 4,000 feet at Chatham Borough.
The Lower Valley extends from Little Falls to Newark Bay. It is 173 square miles in size. The Lower Valley is fairly flat and the flow of the Passaic River is quite slow as it broadens out and empties into Newark Bay. The Lower Valley is the most extensively developed area of the watershed, including cities such as Paterson, Passaic and Newark, where the waterfronts are nearly entirely developed and public access is limited. Flooding is especially prevalent where the Passaic River is constrained, such as Little Falls and Paterson, and along the Saddle River in Bergen County.
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