Middle Brook is a tributary

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 of the Raritan River

Raritan River

The Raritan River is a major river of central New Jersey in the United States. Its watershed drains much of the mountainous area of the central part of the state, emptying into the Raritan Bay on the Atlantic Ocean.-Description:...

 in Somerset

Somerset, New Jersey

Somerset is a census-designated place and unincorporated area located at the easternmost section within Franklin Township, in Somerset County, New Jersey. At the 2000 United States Census, the CDP population was 23,040...

, New Jersey

New Jersey

New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...

 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. The stream can be referred to as Rha-weigh-weiros, a Native American name meaning "running from a deep hole", on early maps of the area.

The Middle Brook's western and eastern branches drain the Washington Valley between the first and second Watchung Mountain ridge

Watchung Mountains

The Watchung Mountains are a group of three long low ridges of volcanic origin, between 400 ft. and 500 ft. high, lying parallel to each other in northern New Jersey in the United States...

s in Bridgewater Township

Bridgewater Township, New Jersey

Bridgewater Township is a township in Somerset County, New Jersey, United States. , the township population was 44,464.Bridgewater Township was originally created by Royal Charter on April 4, 1749, from portions of the Northern precinct, and was incorporated as one of New Jersey's initial group of...

 and the western part of Warren Township

Warren Township, New Jersey

Warren Township is a Township in Somerset County, New Jersey, United States. As of the 2010 United States Census, the township population was 15,311....

. The two branches unite in the Bound Brook Gap and the Middle Brook runs southward where it enters the Raritan in Bound Brook

Bound Brook, New Jersey

Bound Brook is a borough in Somerset County, New Jersey, United States. At the United States 2010 Census, the population was 10,402.Bound Brook was originally incorporated as a town by an Act of the New Jersey Legislature on March 24, 1869, within portions of Bridgewater Township...

. The total drainage area is 17.2 m².

The Western Branch is followed by the Middle Brook Trail, a public hiking trail. In Washington Valley Park

Washington Valley Park

Washington Valley Park is a public park between the first and second Watchung mountain ridge in the Martinsville section of Bridgewater Township, New Jersey that is administered by the Somerset County Park Commission...

, the brook forms an artificial lake, the Washington Valley Reservoir. The smaller Eastern Branch is also dammed and then cascades over the Buttermilk Falls in Washington Valley Park.

The Middle Brook section in Bound Brook is being regulated as part of the Green Brook Flood Control Project

Green Brook Flood Control Project

The Green Brook Flood Control Project is a flood control project in Somerset County in central New Jersey first proposed in the early 1970s in the wake of two major flooding events: a 1971 flood event and a major flood in August 1973, which ravaged the Green Brook and Raritan River basins with...

in an attempt to spare Bound Brook flooding from backwater from the Raritan that can enter the terminal section of the Middle Brook.