Brook (stream)

This article is about the type of watercourse. For other uses, see Brook (disambiguation).

Stoughton's Brook flowing through South Windsor, Connecticut, United States.

A brook is a small natural stream or watercourse, sometimes also referred to as a rivulet. It is typically shallow and carries less water than larger streams and rivers. The term is sometimes used particularly for a stream that originates from a spring or seep.

The distinction between a brook and other small watercourses, particularly a creek, is not precisely defined. The names given to flowing watercourses vary according to regional usage, historical naming conventions and local geography, and there is no universally accepted width, depth or discharge at which a brook becomes a creek or river.

Terminology

A shallow brook flowing through moorland in England.

The English noun brook derives from Old English brōc, meaning a stream or watercourse. Cognates occur in other Germanic languages. The word has been used in English for small natural watercourses since before the 12th century. The word occurs frequently in English toponymy, particularly in the names of small watercourses and settlements associated with them.

The terms brook, creek, stream and rivulet overlap considerably and their meanings differ between regions. In hydrology, stream can be used as a general term for flowing water irrespective of size. The United States Geological Survey defines a brook simply as a "small stream". In some usage, a brook is regarded as smaller than a creek and is particularly associated with a shallow stream that can be crossed easily. Brooks may also be associated with watercourses issuing from springs or seeps. These characteristics are conventions rather than universally recognised hydrological criteria.

Creek has particularly variable geographical meanings. In Australia, Canada, New Zealand and the United States, it commonly denotes a small stream or tributary, whereas in British English it commonly refers to a narrow inlet or bay, particularly of the sea, for example Wootton Creek. Consequently, terms such as brook, creek and river do not necessarily indicate the physical size of a watercourse or correspond to formal hydrological classifications. The United States Geological Survey notes that there are no official definitions distinguishing such generic geographic terms and classifies all linear flowing bodies of water as streams, regardless of whether their names contain terms such as creek, river or run.

Characteristics and modification

A shallow woodland brook in Loantaka Brook Reservation, Morris County, New Jersey, United States.

A shallow woodland brook in Plaxtol, Kent, England.

Brooks generally consist of flowing freshwater confined within a relatively narrow natural channel. They may occur in forests, valleys, uplands and other landscapes and commonly form part of a larger drainage network. Water may originate from groundwater discharged through springs and seeps, surface runoff, rainfall, melting snow, or a combination of these sources. Because the term is descriptive rather than a formal hydrological classification, brooks vary considerably in their physical characteristics. Some flow throughout the year, while others are intermittent or ephemeral. Their beds may consist of bedrock, gravel, stones, sand, silt or organic material depending on local geology, gradient and water velocity. Brooks in steep terrain may have relatively fast currents despite their small size, whereas those on gentler gradients may flow slowly and form shallow pools. Small waterfalls, riffles and pools may occur along their courses.

Artificial stormwater channels may resemble brooks where they are narrow and carry a shallow flow of water, but are generally distinguished by their artificial construction and drainage function. A stormwater channel is a constructed channel designed to convey stormwater or floodwater, whereas a brook is a small natural stream. In urban areas, however, the distinction may be less visually apparent where natural streams have been modified or incorporated into stormwater systems. In Sydney, a number of natural creeks were historically channelised with concrete as part of the city's stormwater network; some have subsequently been naturalised by removing concrete and restoring more natural channel features.

Fords and culverts

Because brooks are typically small and shallow, they may be crossed at a ford, a shallow section of a watercourse where the bed can be traversed without a bridge. Natural fords commonly occur where the channel is relatively wide and shallow and the bed is sufficiently firm, such as where it consists of gravel or rock. Historically, fords across brooks and other small streams were important crossing points for footpaths, roads and livestock routes. The suitability of a brook for fording can vary with its discharge. A ford that is readily passable during normal or dry conditions may become difficult or dangerous to cross following heavy rainfall, when the depth and velocity of the water increase.

Brooks may pass through culverts where roads, paths or other infrastructure cross the watercourse. Culverts route streamflow beneath the crossing and are commonly constructed from materials such as metal, concrete or plastic. Unlike a bridge, a culvert generally confines the stream within an enclosed or partly enclosed structure for the length of the crossing. Poorly designed or positioned culverts can alter stream conditions and restrict the movement of fish and other aquatic organisms.

Formation and hydrology

Brooks form where water becomes concentrated within a natural channel. Some begin where groundwater reaches the surface at a spring or seep. Others originate from surface runoff collecting in depressions and drainage channels, particularly following rainfall or snowmelt. A brook may constitute one of the smallest components of a larger drainage system. Multiple small channels can converge to form progressively larger streams, which may themselves become tributaries of rivers. There is, however, no universal point at which a brook is considered sufficiently large to be termed a creek or another type of stream.

The amount of water carried by a brook can fluctuate considerably. Perennial brooks are maintained throughout much or all of the year, often through groundwater discharge, whereas intermittent brooks may cease flowing during dry periods. Short-lived channels produced primarily by rainfall or snowmelt may be ephemeral. Brooks may occupy or flow through gullies, which are small channels or hollows formed by the erosive action of running water. Unlike a brook, which is a small stream, a gully refers primarily to the eroded landform and commonly carries water only following rainfall or snowmelt.

Ecology

Despite their small size, brooks and other small headwater streams can form important freshwater ecosystems. Their channels and surrounding riparian zones provide habitat for aquatic and terrestrial organisms, including fish, amphibians and aquatic insects.

Shaded woodland brooks may remain relatively cool because surrounding riparian vegetation reduces direct solar radiation. Trees and other vegetation along stream banks also contribute leaf litter and woody debris to the water, providing food resources, cover and habitat for aquatic organisms. Fallen leaves and other organic matter entering small forest streams can form an important source of energy for aquatic food webs, while woody debris can increase the physical complexity of the channel and provide habitat. Small headwater streams also provide ecological connections between upland environments and larger rivers. Organic matter, woody material and invertebrates entering small streams can be transported downstream, where they may contribute resources to downstream aquatic communities.

See also

• Beck (stream)
• Riffle
• Spring (hydrology)
• Tributary