A backwater slough consists of the aquatic community of quiet to stagnant, typically warm waters located in embayments and old meanders. Although classified as part of a riverine system, many hydrological characteristics resemble those of lacustrine communities.

Examples of this river type may be relatively short-lived in dynamic river complexes, transforming into oxbow lakes through permanent formation of downstream levees or into associated river types through permanent breaching of the upstream levee.

Four to seven ecoregional variants are suspected to exist in New York and differ in dominant and characteristic vascular plants, fishes, mollusks, insects, and birds as well as in water chemistry, water temperature, underlying substrate type, surrounding forest type and associated stream type.

Backwater sloughs are only connected to associated riverine communities at their downstream end and are often bounded by an upstream levee.

Characteristic biota are pool specialists and may resemble lacustrine or marsh headwater stream species assemblages. Aquatic vegetation is usually abundant; characteristic aquatic plants include waterweed (Elodea canadensis), milfoil (Myriophyllum spp.), duckweed (Lemna minor), and pondweeds (Potamogeton spp.). Emergent aquatic plants such as green arrow-arum (Peltandra virginica), pickerelweed (Pontederia cordata), common arrowhead (Sagittaria latifolia), and swamp loosestrife (Decodon verticillatus) may be abundant along the shores. Characteristic fishes are golden shiner (Notemigonus crysoleucas), pumpkinseed (Lepomis gibbosus), brown bullhead (Ictalurus nebulosus), and chain pickerel (Esox niger). Macroinvertebrates may include odonates (Odonata), stoneflies (Plecoptera), diving beetles (Dytiscidae), mosquitoes (Cuculidae), true flies (Tipula spp., Atherix spp., Simulum spp.), midges (Chironomidae), crustaceans (Hyalella spp.), clams (Pisdium spp.) and mayflies (Stenonema). Wading birds and other water birds such as pied-billed grebe (Podilymbus podiceps) and great blue heron (Ardeas herodias) may be characteristic. A characteristic mammal may be muskrat (Ondatra zibethicus).

Known examples of this community have been found at elevations between 535 feet and 1575 feet.