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For information on Wisconsin's natural communities, contact:
Ryan O'Connor
Natural Heritage Inventory Ecologist

Riverine Mud Flat

State Rank: SU     Global Rank: GNR   what are these ranks?


Detailed Community Description from Ecological Landscapes of Wisconsin

General natural community overview

Counties shaded blue have documented occurrences for Riverine Mud Flat in the Wisconsin Natural Heritage Inventory database.

As riverine water levels drop following spring floods, patches of bare sand, mud, gravel, and cobbles are exposed. The riverine mudflat community is best developed within the floodplains of the state's largest, low gradient rivers, especially in central and southwestern Wisconsin. Soil development on the flats and bars is minimal, owing to the frequent flood disturbance. During the growing season these areas are colonized by an assemblage of herbs, and sometimes shrubs and saplings. The mudflats and beaches are highly variable in cover, being basically unvegetated in late spring/early summer transitioning to sparsely covered and eventually to locally dense stands of graminoids and forbs by late summer. Usually the vegetation is of short stature.

Significant floods affect this community annually, which may be accompanied by erosive scouring, sediment deposition, and sometimes (though not always) by shifts in the locations of the bars, mudflats and channels. Colonizing plants tend to be annuals, short-lived perennials, or perennials with light, wind, or water dispersed propagules adapted to quickly colonizing unvegetated substrates.

Plants that become established on these newly exposed, somewhat ephemeral habitats, include sedges, grasses, and a few woody species such as sandbar willow (Salix interior) and cottonwood (Populus deltoides). Short graminoids are initially prevalent, such as some of the "flat sedges", for example (Cyperus odoratus and C. squarrosus), spike-rushes (Eleocharis acicularis, E. obtusa, E. palustris), creeping love grass (Eragrostis hypnoides), tufted love grass (E. pectinacea), autumn sedge (Fimbristylis autumnalis), and small-flowered hemicarpha (Lipocarpha micrantha). Other native herbs associated with this assemblage are water star-grass (Lindernia dubia), marsh purslane (Ludwigia palustris), and moist bank pimpernel (Lindernia dubia).

In common with other high energy and frequently disturbed environments, such as the beaches and dunes along the Great Lakes, some opportunistic weedy species are also characteristic of riverine mudflats and beaches. However, as the slate is erased virtually every year, these tend not to be problems except in cases where the flood regime has been altered in a way that favors the weeds and development of a weed-dominated community. Examples include green carpetweed (Mollugo verticillata), black mustard (Brassica nigra), winged pigweed (Cycloloma atriplicifolia), and Russian thistle (Salsola tragus).

Rare animals

Species of Greatest Conservation Need

Wisconsin Wildlife Action Plan graphic

The following Species of Greatest Conservation Need are listed according to their level of association with the Riverine Mud Flat natural community type, based on the findings in Wisconsin's 2015 Wildlife Action Plan.

Scores: 3 = high association, 2 = moderate association, and 1 = low association. See the key to association scores for complete definitions.

Pickerel FrogLithobates palustris3

Rusty BlackbirdEuphagus carolinus2
American BitternBotaurus lentiginosus1
Black-crowned Night-HeronNycticorax nycticorax1
Black-necked StiltHimantopus mexicanus1
Great EgretArdea alba1
King RailRallus elegans1
Least BitternIxobrychus exilis1
Piping PloverCharadrius melodus1
Rufa Red KnotCalidris canutus rufa1
Upland SandpiperBartramia longicauda1
Whooping CraneGrus americana1
Yellow RailCoturnicops noveboracensis1
Yellow-crowned Night-HeronNyctanassa violacea1

Grasshoppers and alliesScore
Gladston's Spur-throat GrasshopperMelanoplus gladstoni3
Spotted-winged GrasshopperOrphulella pelidna1

Big Brown BatEptesicus fuscus3
Little Brown BatMyotis lucifugus3
Silver-haired BatLasionycteris noctivagans3
Eastern PipistrellePerimyotis subflavus2
Northern Long-eared BatMyotis septentrionalis2
Water ShrewSorex palustris1

Please see Section 2. Approach and Methods of the Wildlife Action Plan to learn how this information was developed.

Rare plants

The Natural Heritage Inventory has developed scores indicating the degree to which each of Wisconsin's rare plant species is associated with a particular natural community or ecological landscape. This information is similar to that found in the Wildlife Action Plan for animals. As this is a work in progress, we welcome your suggestions and feedback.

Scores: 3 = "significantly associated," 2 = "moderately associated," and 1 = "minimally associated."
Scientific Name Common Name Score
Eclipta prostrata Yerba-de-tajo 3


The following Ecological Landscapes have the best opportunities to manage for Riverine Mud Flat, based on the Ecological Landscapes of Wisconsin Handbook.

Map of the Ecological Landscapes of Wisconsin.

Major (3 on map)
A major opportunity for sustaining the natural community in the Ecological Landscape exists, either because many significant occurrences of the natural community have been recorded in the landscape or major restoration activities are likely to be successful maintaining the community's composition, structure, and ecological function over a longer period of time.

Important (2 on map)
Although the natural community does not occur extensively or commonly in the Ecological Landscape, one to several occurrences do occur and are important in sustaining the community in the state. In some cases, important opportunities may exist because the natural community may be restricted to just one or a few Ecological Landscapes within the state and there may be a lack of opportunities elsewhere.

Present (1 on map)
The natural community occurs in the Ecological Landscape, but better management opportunities appear to exist in other parts of the state.


Wisconsin Wildlife Action Plan graphic

What are conservation actions?

Conservation actions respond to issues or threats, which adversely affect species of greatest conservation need (SGCN) or their habitats. Besides actions such as restoring wetlands or planting resilient tree species in northern communities, research, surveys and monitoring are also among conservation actions described in the WWAP because lack of information can threaten our ability to successfully preserve and care for natural resources.

Threats/issues and conservations actions for natural communities


Riverine Mud Flat Photos

Riverine Mud Flat Photo

Meanders of the Black River have created unvegetated steep cutbanks and extensive flats of exposed sand and silt, which receive heavy use by waterbirds, turtles, and invertebrates.

Photo by Eric Epstein.

Riverine Mud Flat Photo

Riverine mud flats are temporary communities usually dominated by annual species that occur along rivers and streams during periods of low water.

Photo by Ryan O'Connor.

Riverine Mud Flat Photo

Riverine mudflat along the Black River in Jackson Co.

Photo by Ryan O'Connor.

Note: photos are provided to illustrate various examples of natural community types. A single photograph cannot represent the range of variability inherent in a given community type. Some of these photos explicitly illustrate unusual and distinctive community variants. The community photo galleries are a work in progress that we will expand and improve in the future.

Last revised: Wednesday, June 16, 2021