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 sys- tems, 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 fea- tures 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 dura- tion 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