Characterization of wetland hydrology using hydrogeomorphic classification

Abstract

Hydrologic data are essential for understanding relationships between wetland morphology and function and for characterizing landscapeTscale patterns of wetland occurrence. We monitored water levels in 45 wetlands for three years to characterize the hydrology of wetlands in the vicinity of Portland, Oregon, USA and classified wetlands by hydrogeomorphic (HGM) class to determine whether hydrologic regimes differed in wetlands in different HGM classes. We also compared hydrologic regimes in naturally occurring wetlands (NOWs) and nutigation wetlands (MWs) and in wetlands with/without a human-made water-retention structure to determine whether and how human modifications are changing the hydrology of wetlands. We found no relationship between hydrologic attributes and land use, soil association, or wetland area. We did find significant differences related to presence of a water-retention structure and to wetland type (NOW or MW). Water levels were higher and had less temporal variability and more extensive inundation ~as % wetland area) in MWs and in wetlands modified to include a retention structure. HGM class was very effective for characterizing wetland hydrology, with significant differences among HGM classes for water level and for extent and duration of inundation. For three regional classes, we found the lowest water levels and lowest extent/duration of inundation in slope wetlands, intermediate conditions in riverine wetlands, and the highest water levels and greatest extent and duration of inundation in depressions. In "'atypical" classes tGwin et al. 1999), average water level and extent of inundation were similar to conditions in depressions, but the within-site variability in water levels in depressions-in-slope-setting and in-stream-depressions was significantly smaller than in the regional classes <p < 0.001). Results highlight the importance of both geornorphic setting and wetland structure in defining wetland hydrology and support the use of HGM for wetland classification. Because hydrology is an important determinant of many wetland functions, resource managers using restoration and mitigation to offset wetland losses should strive for project design and siting that re-estabfish the hydrogeomorphology of natural wetlands to improve the likelihood of replacing wetland functions.

Aboveground decomposition dynamics in riparian depression and slope wetlands of central Pennsylvania

“…There has been some work using HGM to organize and understand wetland function, most notably hydrology (e.g., Shaffer et al 1999;Cole and Brooks 2000), and stressors such as sedimentation (Wardrop and Brooks 1998), but there have been few empirical studies investigating functional differences between HGM classes. For HGM to be most useful as a classification tool, it is critical for wetland managers to have the ability to derive some understanding of wetland function based on a wetland's designation into a subclass (Cole et al 1997).…”

Estimating hydroperiod suitability for breeding amphibians in southern Rhode Island seasonal forest ponds

“…Researchers in New England (e.g., Windmiller 1996) have suggested a positive relationship between pond size and hydroperiod, but research conducted elsewhere in the United States has shown the correlation to be weak (Snodgrass et al 2000a) or nonexistent (Shaffer et al 1999;Babbitt and Tanner 2000). In central Massachusetts, Brooks and Hayashi (2002) found that pond area, depth, and volume individually explained less than one-third of the variation in hydroperiod (r ranged from 0.45 to 0.58).…”

Evaluation of a wetland classification system devised for management in a region with a high cover of peatlands: an example from the Cook Inlet Basin, Alaska

“…The low similarity produced by the LLWW system agrees with findings of other investigations (cf. Shaffer et al 1999). Although Cole et al (1997Cole et al ( , 2002 found similarities in hydrological conditions among flow-path classes within the state of Pennsylvania (USA), within-class similarity was low when the classes were extended across a wider region (Cole et al 2008), or applied across the continent in the state of Oregon (Cole and Brooks 2000).…”