Hydrogeomorphic Classification for Great Lakes Coastal Wetlands

J. Great Lakes Res. 31 (Supplement 1):129–146 Internat. Assoc. Great Lakes Res., 2005

Hydrogeomorphic Classiﬁcation for Great Lakes Coastal Wetlands

Dennis A. Albert1,*, Douglas A. Wilcox2, Joel W. Ingram3, and Todd A. Thompson4 1Michigan Natural Features Inventory Michigan State University Extension Mason Building, PO Box 30444 Lansing, Michigan 48909-7944 2U.S. Geological Survey Great Lakes Science Center 1451 Green Road Ann Arbor, Michigan 48105 3Canadian Wildlife Service Environment Canada-Ontario Region 4905 Dufferin Street Downsview, Ontario M3H 5T4 4Indiana Geological Survey Indiana University 611 N. Walnut Grove Bloomington, Indiana 47405

ABSTRACT: A hydrogeomorphic classification scheme for Great Lakes coastal wetlands is presented. The classification is hierarchical and first divides the wetlands into three broad hydrogeomorphic systems, lacustrine, riverine, and barrier-protected, each with unique hydrologic flow characteristics and residence time. These systems are further subdivided into finer geomorphic types based on physical features and shoreline processes. Each hydrogeomorphic wetland type has associated plant and animal communities and specific physical attributes related to sediment type, wave energy, water quality, and hydrology. INDEX WORDS: Classification, coastal wetlands, Great Lakes, geomorphology.

INTRODUCTION tion proposes finer distinctions between wetland There is a long-standing interest in classifying types than found in the previously published Great Great Lakes coastal wetlands to better understand Lakes wetland classifications, as well as physical wetland processes and biological composition, as attributes for each wetland type. In recent years, a well as to improve management (Geis and Kee hydrogeomorphic model (HGM) has been explored 1977, Herdendorf et al. 1981a, Herdendorf 1988, as a framework for wetland classification over a Bowes 1989, Dodge and Kavetsky 1995, Edsall and broad range of geographic and geologic conditions Charlton 1997). Several other articles relevant to (Smith et al. 1995, Brinson 1996). The HGM ap- Great Lakes wetland classification were contained proach to wetland classification was expanded to in a 1992 book edited by Busch and Sly on aquatic include Great Lakes coastal wetlands (Minc 1997, classification of lacustrine systems (Herdendorf et Chow-Fraser and Albert 1998, Keough et al. 1999, al. 1992; Leach and Herron 1992; McKee et al. Albert and Minc 2001). It has also been observed 1992; Sly and Busch 1992a and b). This classifica- that the distribution of geomorphic types is often regional, with certain hydrogeomorphic types con- *Corresponding author. E-mail: [email protected] centrated on specific lakes or shoreline segments of

129 130 Albert et al. lakes (Minc 1997, Chow-Fraser and Albert 1998, classification on the lacustrine formation process. Albert and Minc 2004, Wei et al. 2004). In addition, NWI only considers wetlands larger In 2002, a working group of Great Lakes wetland than 8 hectares to be lacustrine, while this classifi- biologists, all members of the Great Lakes Coastal cation includes smaller wetlands linked to the Great Wetland Consortium, developed a hydrogeomor- Lakes. NWI will include wetlands smaller than 8 phic wetland classification system that can be used hectares if a) a wave-formed or bedrock feature to consistently characterize and potentially map all forms part or all of the shoreline or, b) it has a low- of the coastal wetlands of the Great Lakes. This water depth greater than 2 meters in the deepest paper presents that hydrogeomorphic classification, part of the basin. along with oblique aerial photographs to illustrate Riverine (R---) system wetlands occur along and the types and attribute tables developed from exist- within rivers and creeks that flow into or between ing wetland sampling studies (Albert et al. 1987, the Great Lakes. The water quality, flow rate, and 1988, 1989; Environment Canada and Central Lake sediment input are controlled in large part by their Ontario Conservation Authority 2004; Wilcox et al. individual drainages. However, water levels and 2002; Wilcox 2005). The above-mentioned wetland fluvial processes in these wetlands are directly or sampling studies were conducted in over 200 wet- indirectly influenced by coastal processes because lands within all of the Great Lakes. Classifications lake waters flood back into the lower portions of were built with data collected from the U.S. Great the drainage system. Protection from wave attack is Lakes (Minc 1997, Minc and Albert 1998, Albert provided in the river channels by bars and channel and Minc 2004), but subsequent sampling was con- morphology. Riverine wetlands within the Great ducted in all of the Ontario Great Lakes, including Lakes also include those wetlands found along the North Channel of Lake Huron and Georgian large connecting channels between the Great Lakes; Bay. these connecting channels have very different dy- namics than smaller tributary rivers and streams. NWI excludes palustrine wetlands, defined as dom- A HYDROGEOMORPHIC CLASSIFICATION inated by trees, shrubs, persistent emergents, and FOR GREAT LAKES WETLANDS emergent mosses or lichens, from riverine systems. Great Lakes coastal wetlands can be separated In contrast, this classification includes all of these into three specific hydrogeomorphic systems, lacus- types of vegetation within the riverine system if the trine (L), riverine (R), and barrier-protected (B), wetlands or portions of wetlands are regularly influ- based on geomorphic position, dominant hydrologic enced by riverine processes. source, and current hydrologic connectivity to the Barrier-Protected (B---) system wetlands origi- lake. In this classification, each wetland type is nate from either coastal or fluvial processes, but given a four character code (Fig. 1). The first char- coastal nearshore and onshore processes separated acter (L, R, or B) is for the hydrologic system. The these wetlands from the Great Lakes by a barrier second character (C, D, L, O, P, R, S) is for the geo- beach or other barrier feature. The barriers may be morphic type. The third and fourth characters are active or part of relict coastal systems abandoned further geomorphic modifiers. along the lake’s margin. These wetlands are pro- Lacustrine (L---) system wetlands are controlled tected from wave action but may be connected di- directly by waters of the Great Lakes and are rectly to the lake by a channel crossing the barrier. strongly affected by lake-level fluctuations, When open to the lake, water levels in these wet- nearshore currents, seiches, and ice scour. Geomor- lands are determined by lake levels, but the rate of phic features along the shoreline provide varying water-level change in the wetlands is tempered by degrees of protection from coastal nearshore the rate of flow through the connecting channel. processes. Lacustrine, as defined by the U.S. Na- During isolation from the lake, groundwater and tional Wetland Inventory (NWI), would also in- surface drainage to the basin of the individual wet- clude dammed river channels and topographic land provide the dominant source of water input, al- depressions not related to Great Lakes. NWI does though the lake level may influence groundwater not consider wetlands with trees, shrubs, persistent flow and, hence, wetland water levels. Inlets to pro- emergents, emergent mosses or lichens with greater tected wetlands may be permanent or ephemeral, as than 30% cover to be lacustrine; in contrast, in this nearshore processes can close off connecting chan- classification these vegetation cover classes are nels. The frequency and duration of closures is re- considered to be lacustrine wetlands, focusing the lated to the rate of sediment supply to the shoreline, HGM Classification for Great Lakes Wetlands 131

FIG. 1. Hydrogeomorphic classification for Great Lakes marshes. grain size and sorting of sediment, type and duration development to relatively narrow nearshore tion of nearshore processes, lake-level elevation bands. Exposure to nearshore processes also re- and rate of change, and discharge rate of water exit- sults in a variable bathymetry, ranging from rela- ing through the inlet. Most of these wetlands would tively steep profiles to more shallow sloping be classified by NWI as palustrine, with small beaches. water bodies or streams within the wetland possibly being classified as inclusions of either lacustrine or Open Shoreline. (LOS-) This wetland type is riverine system. typically characterized by an erosion-resis- Within these hydrologically based systems, Great tant substrate of either rock or clay, with oc- Lakes coastal wetlands can be classified further casional patches of mobile substrate. Such based on their geomorphic features and shoreline systems are starved of detrital sediment. The processes (Fig. 1). resultant expanse of shallow water serves to dampen waves, and if littoral sediment is Lacustrine System (L---) available may result in sand-bar develop- Open Lacustrine (LO--) ment at some sites. There is almost no or- These lake-based wetlands are directly exposed ganic sediment accumulation in this type of to nearshore processes, with little or no physical environment. Vegetation development is protection by offshore geomorphic features (bars limited to narrow fringes of emergent vege- and spits). This exposure results in little accumu- tation extending offshore to the limits im- lation of organic sediment and restricts vegeta- posed by wave climate. Some smaller 132 Albert et al.

FIG. 2. Lacustrine hydrologic system: Open embayment (LOE-), St. Martin Bay (MI), Lake Huron. Sand bars in the foreground are indicative of a high-energy coastal environment.

embayments also fit into this class due to ex- on Lake Huron, Little Bay de Noc (MI) and posure to prevailing winds; most of these Green Bay (WI) on Lake Michigan, Long have relatively narrow vegetation zones of Point Bay (ON) on Lake Erie, and Black 100 meters or less. Examples include River Bay (NY) on Lake Ontario all fit in Epoufette Bay (MI) on Lake Michigan and this category. shoreline reaches in the Bay of Quinte (ON) on Lake Ontario. In past mapping efforts Protected Lacustrine (LP--) along the Great Lakes, few open shoreline This wetland type is also a lake-based system; wetlands were identified by either Herden- however, it is characterized by increased protec- dorf et al. (1981a–f) or NWI. Many open tion by a sand-spit, offshore bar, or till- or shorelines do not have large or dense bedrock-enclosed bay. Subsequently, this protec- enough areas of aquatic plants to be identi- tion results in increased mineral sediment accu- fied from aerial photography. mulation, shallower off-shore profiles, and more extensive aquatic vegetation development than Open Embayment. (LOE-) This wetland type the open lacustrine counterpart. Organic sediment can occur on gravel, sand, and clay (fine) development is also more pronounced. substrates (Fig.2). The embayments are often quite large—large enough to be subject Protected Embayment. (LPP-) Many stretches to storm-generated waves and surges and to of bedrock or till-derived shorelines form have established nearshore circulation sys- small protected bays, typically less than tems. Most bays greater than three or four three or four kilometers in width (Fig. 3). kilometers in diameter fit into this class. These bays can be completely vegetated These embayments typically support wet- with emergent or submergent vegetation. At lands that are 100 to 500 meters wide over the margins of the wetlands there is typically broad expanses of shoreline. Most of these 50 to 100 cm of organic accumulation be- wetlands accumulate only shallow organic neath wet meadow vegetation. Examples in- sediments near their shoreline edge. Large clude Duck Bay and Mackinac Bay in the parts of Saginaw and St. Martin bays (MI) Les Cheneaux Islands (MI) in Lake Huron, HGM Classification for Great Lakes Wetlands 133

FIG. 3. Lacustrine hydrologic system: Protected embayment (LPP-), Duck Bay (MI), northern Lake Huron.

FIG. 4. Lacustrine hydrologic system: Sand-spit embayment (LPS-), Pinconning Bay (MI) within Saginaw Bay, Lake Huron. 134 Albert et al.

FIG. 5. Riverine hydrologic system: Open drowned river-mouth (RRO-), Crooked Creek (NY), St. Lawrence River.

Matchedash Bay (ON) in Lake Huron, and ganic soils are typical, similar to those found Bayfield Bay (ON) on Wolfe Island in Lake in other protected embayments. Examples Ontario. A type of protected embayment en- include Pinconning Marsh (MI) in Saginaw countered along localized stretches of the Bay, Dead Horse Bay (WI) in Green Bay, Great Lakes shoreline is the solution embay- and Long Point (ON) in Lake Erie. ment (LPPS). These roughly circular inden- tations in the bedrock are formed by solution Riverine System (R---) processes in carbonate rock. These indenta- tions are occasionally open to the Great Drowned River-Mouth (RR--) Lakes, forming a protected embayment. The The water chemistry of these wetlands can be af- latter wetland type occurs along the shore- fected by both the Great Lakes and river water, line of northern Lakes Michigan, Huron, and depending on Great Lakes water levels, season, Ontario. One example is El Cajon Bay (MI) and amount of precipitation (drainage discharge). in northern Lake Huron. These wetlands typically have deep organic soils that have accumulated due to deposition of wa- Sand-Spit Embayment. (LPS-) Sand spits pro- tershed-based silt loads and protection from jecting along the coast create and protect coastal processes (waves, currents, seiche, etc.). shallow embayments on their landward side The terms “estuarine” or “fresh-water estuarine” (Fig. 4). Spits often occur along gently slop- are used by some researchers (Herdendorf et al. ing and curving sections of shoreline where 1981a) as alternatives to drowned river-mouth. there is a positive supply of sediment and sand transport is not impeded by natural or Open Drowned River-Mouth. (RRO-) Some man-made barriers. These wetlands are typi- drowned river-mouths do not have barriers cally quite shallow. Moderate levels of or- at their mouth, nor do they have a lagoon or HGM Classification for Great Lakes Wetlands 135

connection to the lakes because of the large prism of water that must exit through the barrier. The lagoons seldom support large wetlands and vegetation is concentrated where the stream enters the lagoon (if present), but can extend several kilometers upstream, typically forming a fringe of emergent and submergent vegetation along the edges of the channel. Organic deposits are often greater than two meters thick. Barred drowned river-mouths include both large rivers and small streams. The channel is seldom completely barred when the rivers are large, while smaller streams are often completely separated from the lake by a sand barrier. Smaller streams are occasionally or frequently separated from the lake until pressure from stream flow blows out the sand barrier. Most large rivers now have dredged channels with jetties that are main- tained open for boat traffic year round. Ex- amples of barred, drowned river-mouths on large rivers include the Kalamazoo, Muskegon, and Manistee rivers (MI) in Lake Michigan. Small barred streams include the Dead River (IL) in Lake Michigan, Old Woman Creek (OH) in Lake Erie, Sixmile Creek (MI) in Lake Superior, and Duffins Creek (ON) in Lake Ontario.

FIG. 6. Riverine hydrologic system: Barred Connecting Channel (RC--) drowned river-mouth (RRB-), Beaver Creek (ON), This wetland type includes the large connecting Lake Ontario. rivers between the Great Lakes; the St. Marys, St. Clair, Detroit, Niagara, and St. Lawrence rivers (Fig. 7). These wetlands are distinctive from the small lake present where they meet the shore other large river wetlands (drowned river-mouth) (Fig. 5). The wetlands along these streams by the general lack of deep organic soils and the occur along the river banks, and their plant often strong currents. The St. Marys and St. communities are growing on deep organic Lawrence rivers contain some of the most exten- soils. Examples include the West Twin River sive fringing shoreline and tributary drowned river-mouth wetlands in the Great Lakes, while on the Wisconsin shore of Lake Michigan, those along the Detroit and Niagara rivers have the Kakagon River on the Wisconsin shore been largely eliminated or degraded. The Detroit of Lake Superior, and the Greater Cataraqui River still has major beds of submergent aquatic River on the Ontario shore of Lake Ontario. plants. Connecting channels are large enough to con- Barred Drowned River-Mouth. (RRB-) Most tain several types of wetlands, each with their streams that are considered drowned river- classification. Recent mapping of the St. Marys mouths actually have a barrier that constricts and St. Lawrence rivers included 1000s of the stream flow as it enters the lake (Fig. 6). hectares of open embayment (Connecting Chan- Very often, a lagoon forms behind the bar- nel, open embayment (RCOE)), protected embay- rier. However unlike barrier beach wetlands, ment (Connecting Channel, protected embayment these wetlands maintain a relatively constant (RCPP)), open drowned river-mouth (Connecting 136 Albert et al.

FIG. 7. Riverine hydrologic system: Connecting channel (RC--), St. Marys River (MI, ON).

Channel, open drowned river-mouth (RCRO)), connecting river between Lake Superior and Lake barred drowned river-mouth (Connecting Chan- Huron. Fluvial processes are evident in the mor- nel, barred drowned river-mouth (RCRB)), (Con- phology of all three of these deltas, but the mor- necting Channel, barrier beach lagoon (RCBL)), phology of portions of the Goulais River delta are (Connecting Channel, swale complexes (RCBS)), strongly affected by wave action. and deltaic wetlands (Connecting Channel, delta (RCD-)). Other subtypes were also represented Barrier-Enclosed System (B---) along the connecting channels, but with lesser coverage. Barrier Beach Lagoon (BL--) These wetlands form behind a sand barrier (Fig. Delta (RD--) 9). Because of the barrier, there is reduced mix- Deltas formed of both fine and coarse alluvial ing of Great Lakes waters and exclusion of materials support extensive wetlands that extend coastal processes within the wetlands. Multiple out into the Great Lake or connecting river lagoons can form and water discharge from (Fig.8). These are extensive wetlands, typically ground water, upland areas, and incoming with 30 to 100 cm of organic soils associated drainages may all contribute significantly to the with their wet meadow zone, and often with deep water supply. These wetlands are common at the organics occupying abandoned distributary chan- east end of Lake Ontario and also on the Bayfield nels and interdistributary bays. Both fluvial Peninsula (WI) in western Lake Superior. Thick processes and wave action can contribute to the organic soils characterize these wetlands in Lake morphology of deltas along the Great Lakes. Ex- Superior and in many, but not all, of the Lake amples are the St. Clair River (MI and ON), Ontario wetlands. Examples of barrier beach la- Goulais River (ON), and the Munuscong River goon wetlands include Oshawa Second Marsh (MI) deltas. The Munuscong River delta (Fig. 8) and Big Sand Bay (ON), South Colwell Pond enters into the much larger St. Marys River, a (NY), and Round Pond (NY) in Lake Ontario, HGM Classification for Great Lakes Wetlands 137

FIG. 8. Riverine hydrologic system: Delta (RD--), Munuscong River (MI). Because the Munuscong River is a tributary of the St. Marys River, a connecting channel between Lake Superior and Lake Huron, the Munuscong River delta would be coded RCRD.

FIG. 9. Barrier-enclosed hydrologic system: Barrier beach lagoon (BL--), Big Bay (WI), Lake Superior. 138 Albert et al.

FIG. 10. Barrier-enclosed hydrologic system: Tombolo (BLT-), Stockton Island (WI), Lake Superior.

and Bark Bay, Siskiwit Bay, and Allouez Bay (WI) swales are separated from the Great Lakes, often in Lake Superior. Great Marsh (IN, IL) at the south- becoming shrub swamps with shallow organic ern tip of Lake Michigan formed in a similar set- soils. Within these sand-spit formations, there are ting. In addition to barrier beach lagoons, tombolo often embayments which remain attached to the (BLT-) are present in selected areas of the Great Great Lakes, thus maintaining their herbaceous Lakes (Fig. 10). These are defined as islands at- flora. tached to the mainland by barrier beaches, some of Ridge and swale complexes are composed of a which consist of one or two lagoons with deep or- series of beach ridges separated by narrow ganic soils. Small swale complexes are sometimes swales. These systems commonly occur in em- included within a tombolo. Small barrier beach la- bayments where there is an abundant supply of goons often are completely dominated by vegeta- sediment. More than 100 of these complexes tion, with no open water remaining. Such occur in the upper Great Lakes alone (Comer and completely vegetated barrier beach lagoons are Albert 1991, Comer and Albert 1993, Baedke et classified as Successional Barrier Beach Lagoons al. 2004). The ridges are interpreted to have (BLS-). formed in response to quasi-periodic fluctuations in lake level that have occurred during the past Swale Complexes (BS--) several thousand years (Thompson and Baedke There are two primary types of swale complex 1995, 1997; Baedke and Thompson 2000). For wetlands—those that occur between recurved fin- many of these complexes, only the first couple of gers of sand spits and those that occur between swales are in direct hydrologic connection to the relict beach ridges (Fig. 11). These are known re- lake, but in some, like Pte. Aux Chenes (MI) spectively as sand-spit swales (BSS-) and ridge along northern Lake Michigan, the connection and swale complexes (BSR-) (also referred to as continues for several swales and hundreds of me- dune and swale or strandplain). The former are ters inland (Comer and Albert 1991). Organic common within some of the larger sand spits of soil depths are quite variable, as is the vegetation, the Great Lakes, primarily Presque Isle (PA) and which ranges from herbaceous to swamp forest to Long Point (ON) in Lake Erie and Whitefish peatland. Of particular importance to these types Point (MI) in Lake Superior. Numerous small of wetland systems is the amount of groundwater HGM Classification for Great Lakes Wetlands 139

high/low water level) than would be observed in wetlands of the same classification. Identification of human modifiers in naturally occurring coastal wetlands is important to understanding coastal processes and response to change and thus should be noted when classification is undertaken. In this Great Lakes wetland classification, codes for system modifiers have not been developed for mapping purposes.

DISCUSSION Hydrologic Systems The greatest physical and biological differences between coastal wetlands are typically seen at the Hydrologic System level, resulting from differences in water-flow characteristics and residence time (Sly and Busch 1992a). Sly and Busch identified four aquatic systems, lacustrine, connecting channel, riverine, and estuarine. In this classification, aquatic systems are modified into three hydrologic systems, lacustrine, riverine, and barrier-enclosed. The lacustrine class is identical for both classifications, including all of the wetlands directly con- FIG. 11. Barrier-enclosed hydrologic system: nected to the Great Lakes. Three of Sly and Busch’s Ridge and swale complex (BSR-), Stockton Island classes are joined, connecting channel, riverine, and (WI), Lake Superior. estuarine, into a single “riverine” class, separating these flowing systems at a lower level in the classification. All members of the riverine class are char- supply that the embayment receives and the rela- acterized by flowing water, with variable levels of tive importance of drainages. The former can en- influence by the Great Lakes water chemistry and hance groundwater discharge into the system, movement. A third class of “barrier-enclosed” wet- whereas the latter is instrumental in removing lands is also added. These wetlands are nearly or groundwater and surface water. Other examples completely separated from the open Great Lakes by of this wetland type include the Ipperwash Inter- a barrier created by wave or current deposition of dunal Wetlands Complex along southern Lake mineral sediment. The most common form of bar- Huron (ON), the Grand Traverse embayment on rier is a sand-dune-capped beach ridge, but gravel the Keweenaw Peninsula (MI) in Lake Superior, and cobble bars form where the coastal sediment is and the adjacent Manistique and Thompson em- coarse and wave action extreme. Separation by a bayments (MI) in northern Lake Michigan. barrier results in barrier-enclosed wetlands having greater levels of distinction from the connected la- System Modiﬁers of Naturally Occurring custrine and riverine wetlands. In earlier classifica- Great Lakes Wetlands tions, lacustrine and barrier-enclosed wetlands were joined by some researchers (Minc 1997, Albert and The hydrology and/or geomorphology of all Minc 2001) because both wetlands were formed by Great Lakes coastal wetlands have been affected by lacustrine processes. human activities within the Great Lakes basin. This classification shares classes with that devel- These impacts are through whole-lake regulation, oped by Keough et al. (1999), but further divides watershed alterations, or activities within the wet- their hydrogeomorphic types into finer types. This land itself (i.e., diking, dredging, and in-filling). Di- finer subdivision is based on wetland differences rect modification of the hydrologic connection with observed during sampling; some of these physical the lake results in different hydrologic and wetland differences result in major floristic differences. For community responses to Great Lake events (e.g., example, protected embayments and sand-spit em- 140 Albert et al.

bayments are both protected lacustrine types, but marily by large flow from the upstream Great Lake the slope gradient of most protected embayments is rather than water flowing from adjacent uplands greater than that of sand-spit embayments. Floristic (Edsall et al.1988, Hudson et al. 1992). Some are change in response to water-level fluctuations is large enough to support wetlands along their mar- much more rapid and dramatic in the shallow sand- gins that resemble lacustrine wetlands. All of these spit embayments. Many sand-spit embayments be- large rivers are channelized and modified to allow come mudflats during low water levels, resulting in ship traffic between the lakes. This classification massive seed production by emergent plants like divides tributary streams into two classes, delta and stiff arrowhead (Sagittaria rigida), nodding beggar- drowned river-mouth. Delta wetlands form where ticks (Bidens cernuus), soft-stem bulrush (Schoeno- river-borne sediments are deposited into the shal- plectus tabernaemontani), bur-reeds (Sparganium low waters of the Great Lake. Where fluvial spp.), and nodding smartweed (Polygonum lapathi- processes dominate, the delta is more bird’s-foot folium). Another strong contract can be seen be- shaped. Wave-dominated deltaic systems are more tween barrier beach lagoons and ridge-and-swale wedge- or triangle-shaped. In contrast, drowned complexes, both barrier-protected wetland types. river-mouth wetlands form when Great Lakes water Barrier beach lagoons are typified by large areas of levels rise high enough to flood the lower reaches open water, while ridge-and-swale complexes are of a stream valley. Drowned river-mouths have often only flooded in one or two swales close to the been called estuaries or freshwater estuaries by shoreline. Such differences in water area result in some (Herdendorf 1990, Sly and Busch 1992a, Al- major floral and faunal contrasts. bert and Minc 2001), but the term estuary continues It should be noted that these systems are different to be controversial in the freshwater environment of than those defined by the United States Fish and the Great Lakes. Wildlife Service in the National Wetlands Inventory (NWI) (Cowardin et al. 1979) and the Ontario Min- Lacustrine Wetlands istry of Natural Resources, Wetland Evaluation Sys- tem (WES) (Ontario Ministry of Natural Resources The majority of the Great Lakes shoreline is 1993). Both classifications define three systems or characterized by high wave energy that does not site types, Lacustrine, Riverine, and Palustrine, with allow for the development of coastal wetlands. Wet- an additional Isolated type in the WES. Both sys- land plants cannot establish in this environment, ei- tems also have wetland classes or types (Aquatic ther because the sediment is too mobile for plants to bed or Emergent) that are included within this wet- root or because plant tissues are destroyed by wave land classification, which are identified based upon action. A few emergent plants, primarily bulrushes vegetative, hydrologic, and/or substrate attributes. or spike rushes (Eleocharis spp.), can establish lo- This hydrogeomorphic classification is viewed pri- cally in some open shore environments (Tables 1 marily as a tool for better understanding the dynam- and 2). Bulrushes can survive by sending roots and ics and biota of coastal wetlands, not as a rhizomes into underlying dense clay or by rapidly replacement or substitute for NWI or WES. How- expanding roots into shifting sand. Stems of bul- ever, it should also be noted that while participating rush are quite flexible, allowing survival in high in a Great Lakes-wide wetland classification and wave-energy environments. The spike rushes in this mapping project, it has became clear that there is a extreme environment are often annuals exploiting lack of consistence in NWI and WES coding of new, open habitat. None of the plants in this habitat Great Lakes coastal wetlands, and many wetlands require accumulations of organic material. were also not mapped by NWI. Open embayments are also characterized by rela- The subdivisions of riverine wetlands by Sly and tively high wave energy, but shallow water and Busch (1992a) into connecting channel, riverine, more stable sediments reduce the destructive effects and estuarine have been largely reworked in this of wave action on the existing emergent plant com- classification, although connecting channels con- munities (Tables 1 and 2). All of the open embay- tinue to be recognized as a distinctive type. The ments studied by the authors were underlain by connecting channels are limited to only five rivers, fine-textured (clay) soils, where much of the root- the St. Marys, St. Clair, Detroit, Niagara, and St. ing occurred. Even when the above-ground portions Lawrence, but these rivers and their wetlands are of bulrushes were destroyed by wave action during distinctly different from other Great Lakes riverine storms, the rhizomes persisted. Thin accumulations wetlands. All of the channels are characterized pri- of sand, typically less than 30 cm in depth, are HGM Classification for Great Lakes Wetlands 141 - o r e d k y a f l h

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u t e r l l B d r l s c v c y i a A a y n A L T H S R B 1 e HGM Classification for Great Lakes Wetlands 143

common throughout the shallow marsh. The high in the shallow sand-spit embayments, but these sed- wave energy results in little organic sediment accu- iments can be redistributed to the larger lake during mulation and relatively low plant diversity, as most high-water storm events. Inter-annual water-level emergent and submergent aquatic plants cannot tol- fluctuations result in some of the most dramatic erate this high energy environment. Higher diver- vegetation changes encountered in the Great Lakes. sity could be found locally in shallow, nearshore The organic sediments of the sand-spit embayments areas. In the shallowest open embayments, a strong contain a high diversity of seeds, with tremendous chemical gradient develops between the outer changes in plant composition, coverage, and struc- marsh and the protected inner marsh, resulting in ture sometimes occurring on an almost annual distinctly different invertebrate and fish fauna for basis. these marsh zones (Cardinale et al. 1998, Burton et al. 2002). Although the overall productivity of open Riverine Wetlands embayments is typically low, the overall area of the wetlands can be large, making them quite signifi- The connecting channels are the riverine wet- cant as wildlife and fish habitat. lands most similar to the lacustrine wetlands. Por- Protected embayments are typically much tions of the channel shorelines are protected, smaller than open embayments, creating a protected allowing for broad, diverse wetlands to develop, environment where the emergent and submergent with organic sediment accumulation reaching 50 marsh zones are broad and biologically diverse (Ta- cm in the wet meadow zone (Tables 1 and 2). Other bles 1 and 2). The wet meadow zone is also typi- portions of the channel are subject to ice scour and cally broad and biologically diverse, with wave action, resulting in narrower zonation. Great significant accumulations of organic material. Wave Lakes water-level fluctuations can affect the vege- action remains strong enough to limit the accumula- tation of large segments of some connecting rivers, tion of organic material, but allows for a diverse such as the St. Marys. High water levels in 1987 re- flora of floating and submergent plants. Major sulted in erosion of extensive areas of cattail in water-level fluctuations of the Great Lakes do not Munuscong Bay on the St. Marys River, while the typically result in major changes in vegetation; this same areas were being recolonized by a diversity of is one of the most biologically stable wetland types plants under 1989 low-water conditions (Albert, un- in the Great Lakes. Wave energy increases with the published data). size of protected embayments, resulting in greater Deltas occur on both tributary rivers and connect- response to water level fluctuations. Basin mor- ing channels. Main channels of these larger rivers phology is diverse in this wetland type and deter- are generally open, with little or no submergent mines the range of plants found in a specific vegetation, while smaller distributary channels sup- wetland. port diverse beds of submergent vegetation. Vari- Sand-spit embayments, a specialized type of pro- ability is perhaps the greatest in the deltas, tected embayment, also have broad zones of wet providing habitat for a broad range of plants and meadow, emergent, and submergent vegetation, but animals (Duffy et al. 1987, Edsall et al. 1988). are subject to more severe erosion during Great Water flow and temperature variability allow both Lakes high water conditions (Harris et al. 1977, warm and cold-water fish to feed and spawn within 1981; Albert, personal observation), when storm the larger Great Lakes deltas. Sediment ranges from waves can almost eliminate submergent and emer- mineral to organic, depending on the differing flow gent vegetation (Tables 1 and 2). Small sand-spit rates within the wetland. embayments, such as those found in Saginaw Bay Drowned river-mouths are often separated from (MI) in Lake Huron and Green Bay (WI) in Lake their associated Great Lake by a dune or sand-spit Michigan, are typically shallow, often with water barrier, resulting in distinctive differences in water less than 2 meters deep; vegetation often covers the chemistry between the two (Tables 1 and 2). The entire bay in these smaller wetlands. Water depth barrier and river channel also provide protection can be much greater and wave action much more from storm waves, resulting in accumulation of severe in the larger bays, such as those associated deep organic soils within the riverine wetland. The with Presque Isle (PA) and Long Point (ON) in lower reaches of the stream are often wide and deep Lake Erie. These large embayments have vegetation enough to form small lakes behind a protective sand much more similar to that found in open embay- barrier, and delta-like wetlands form where the ments. Sediment accumulation can be considerable streams meet these small lakes. The majority of this 144 Albert et al. wetland type is sedge-, grass-, or cattail-dominated duced waterbird diversity. In some of the more wet meadow growing on deep organic soils. The southern barrier beach lagoon systems, warmer open channels on smaller, slower flowing streams temperatures and higher alkalinity result in less ac- are typically rich in submergent vegetation, while cumulation of organic material. These more open the main channel of larger streams supports little or lagoons support a greater diversity of plants and no submergent vegetation due to strong currents animals. and unstable sediment. Water-level fluctuations of Swale complexes are also isolated from the open the Great Lakes can result in major changes to this lake (Tables 1 and 2). The upper portions of these wetland type, especially during low-water condi- complexes are completely isolated from the lake, tions. As water levels drop, exposed organic-rich receiving their water from ground-water flow and sediments along the stream margins are rapidly col- precipitation. These wetlands may be flooded only onized by annuals or short-lived perennials, such as seasonally and are typically dominated by shrub or soft-stem bulrush, cut grass (Leersia oryzoides), treed swamp or peatlands in more northerly areas. and nodding beggar-ticks. The wet meadow vegeta- The undisturbed accumulation of organic materials tion can also change dramatically as the deep or- has allowed stratigraphic documentation of the age ganic soils are exposed, sometimes forming steep and historic vegetation of these wetlands (Thomp- banks above the level of the river. Urban develop- son 1992, Thompson and Baedke 1995, Lichtner ment characterizes the watershed of many drowned 1998). Small streams flowing from the swale com- river-mouths, resulting in heavy nutrient and sedi- plexes allow small fish tolerant of low oxygen con- ment loading and highly turbid waters, often elimi- ditions to use portions of the wetland complex, and nating submergent vegetation. it is common to see raptors and other birds nesting in the wetland conifers. In the lower Great Lakes, Barrier-enclosed Wetlands hardwood swamps often dominate the swales. These wetlands, largely separated from the adjacent Great Lake, often have water chemistry and ACKNOWLEDGMENTS temperatures very different from the adjacent lake We thank all of the members of the Great Lakes (Tables 1 and 2). Lake water may enter during Coastal Wetlands Consortium for assisting in the storm overwash or seep through the porous sand or development of the Great Lakes wetland classifica- gravel barrier separating the two water bodies. The tion. We also thank Great Lakes Commission staff protective barrier also allows for accumulation of for their assistance in administering and coordinat- thick organic sediments, especially in barrier beach ing the classification project. This article was par- lagoons. Succession to swamp forest, shrub swamp, tially funded by Contribution 1331 of the USGS or peatland is common in this wetland type. 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