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iii

Abstract 

Weixelman, D. A., B. Hill, D.J. Cooper, E.L. Berlow, J. H. Viers, S.E. Purdy, A.G. Merrill, and S.E. 

Gross. 2011. A Field Key to Meadow Hydrogeomorphic Types for the Sierra Nevada and Southern 

Cascade Ranges in California. Gen. Tech. Rep. R5-TP-034. Vallejo, CA. U.S. Department of Agriculture, 

Forest Service, Pacific Southwest Region, 34 pp. 

The purpose of this document is to provide a dichotomous key to meadow hydrogeomorphic types for the 

Sierra Nevada and Southern Cascades of California. This classification and field key uses both hydrology 

and geomorphology to identify fourteen meadow types. Strengths of the classification include its ability 

to clarify the relationship between hydrology and geomorphology and meadow function. 

Meadows are extremely valuable to society and to the natural systems that support society. 

Meadows reduce peak water flow after storms and during runoff, recharge groundwater supplies as they 

release water into the ground, protect streambanks and shorelines, filter sediments, provide habitat for a 

wide variety of wildlife, and serve important recreational and cultural functions. Because of these 

multiple purposes, land managers face a special challenge to maintain, restore, and manage meadows. To 

aid in management, a classification of meadows is needed that uses both hydrology and geomorphology 

in identifying types and functioning of meadows. Potential uses for this classification include stratifying 

meadows for condition assessment and as an aid in mapping or delineating meadow features on the 

landscape. 

Keywords: meadow, hydrology, hydrogeomorphology, geomorphology, wetland, Sierra Nevada 

The Authors 

Dave A. Weixelman (dweixelman@fs.fed.us), Regional Rangeland Ecologist, Pacific Southwest Region, 

USDA Forest Service, Vallejo, CA. 

Barry Hill, Regional Hydrologist, Pacific Southwest Region, USDA Forest Service, Vallejo, CA. 

David J. Cooper, Senior Research Scientist, Department of Forest, Rangeland and Watershed 

Stewardship, Colorado State University, Fort Collins, Colorado. 

Eric L. Berlow, Ecologist, Western Ecological Research Center , US Geological Survey, Yosemite Field 

Station, Yosemite, CA. 

Joshua H. Viers, Associate Research Scientist, Department of Environmental Science and Policy, and 

Associate Director, Center for Watershed Sciences, UC Davis 

Sabra E. Purdy, Research Scientist, Center for Watershed Sciences, UC Davis, Davis, CA 

Amy G. Merrill, Senior Riparian Ecologist, Stillwater Sciences, Berkeley, CA 

Shana E. Gross, Ecologist, US Forest Service, Lake Tahoe Management Basin, South Lake Tahoe, CA 

 
iv

ACKNOWLEDGEMENTS 

The authors wish to thank Anne Yost, Regional Range Program Manager for the Pacific Southwest 

Region of the USDA Forest Service in Vallejo, CA, for general support and funding for this document. 

The authors wish to thank the Grants Pass Water Laboratory, Grants Pass, OR, for permission to modify 

and use an illustration from their website. All photos in this document were taken by Dave Weixelman. 

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not 

imply endorsement by the U.S. Government. The authors also wish to thank the following reviewers: 

Todd Keeler-Wolf, Chief Vegetation Ecologist, California Department of Fish and Game 

Sherman Swanson, Department of Natural Resources and Environmental Science, University of NevadaReno 

Jeff Tenpas, Pacific Southwest Region Watershed Improvement Program Mgr., US Forest Service 

Sylvia Haultain, Ecologist, National Park Service, Sequoia and Kings Canyon National Parks 

Leigh Sevy, Rangeland Conservationist, US Forest Service 

Kathleen Sevy, Rangeland Conservationist, US Forest Service 

Matthew Freitas, Department of Plant Sciences, UC Davis 

Dawn Coultrap, Rangeland Conservationist, US Forest Service 

Kendra Sikes, Vegetation Ecologist, California Native Plant Society 

Gregg Riegel, Ecologist, US Forest Service 

Gail Bakker, Hydrologist, US Forest Service 

John Lorenzana, retired range conservationist, US Forest Service 

Erin Lutrick, Hydrologist, US Forest Service 

Nick Jensen, Botanist, UC Davis 

Peggy Moore, Plant Ecologist, US Geological Survey, Western Ecological Research Center 

Tom Kimball, Research Manager, US Geological Survey, Western Ecological Research Center 

 
v

TABLE OF CONTENTS 

 

page 

Introduction 1 

Characteristics of meadows 1 

Classification of meadows 

Using the key 4 

Key to meadow hydrogeomorphic types 5 

Basin peatland 8 

Mound peatland 9 

Discharge slope peatland 10 

Depressional seasonal 11 

Depressional perennial 12 

Lacustrine fringe 13 

Dry 1 

Discharge slope 15 

Riparian low gradient 16 

Riparian middle gradient 17 

Riparian high gradient 18 

Subsurface low gradient 19 

Subsurface middle gradient 20 

Subsurface high gradient 21 

Potential uses for this classification 22 

References 24 

Appendices 

Appendix A. Definitions 27 

Appendix B. Dendrogram of major meadow hydrogeomorphic types 30 

Appendix C. Example photos of meadow hydrogemorphic types 31 

 

3 

4
vi

LIST OF FIGURES 

page 

Figure 1 Geographic range of the key 3 

Figure 2 Hydrogeomorphic sites sampled in Leavitt Meadow 4 

Figure 3 Photo of a basin peatland type 8 

Figure 4 Landform positions of basin peatland type 8 

Figure 5 Photo of a mound peatland type 9 

Figure 6 Landform position of a mound peatland 9 

Figure 7 Photo of a discharge slope peatland type 10 

Figure 8 Landform position of a discharge slope peatland 10 

Figure 9 Photo of Depressional Seasonal type 11 

Figure 10 Landform position of Depressional Seasonal type 11 

Figure 11 Photo of Depressional Perennial type 12 

Figure 12 Landform position of Depressional Perennial type 12 

Figure 13 Photo of Lacustrine Fringe type 13 

Figure 14 Landform position of Lacustrine Fringe type 13 

Figure 15 Photo of Dry type 14 

Figure 16 Landform position of Dry type 14 

Figure 17 Photo of Discharge slope type 15 

Figure 18 Landform position of Discharge slope type 15 

Figure 19 Photo of Riparian Low Gradient type 16 

Figure 20 Landform position of Riparian Low Gradient type 16 

Figure 21 Photo of Riparian Middle Gradient type 17 

Figure 22 Landform position of Riparian Middle Gradient type 17 

Figure 23 Photo of Riparian High Gradient type 18 

Figure 24 Landform position of Riparian High Gradient type 18 

Figure 25 Photo of Subsurface Low Gradient type 19 

Figure 26 Landform position of Subsurface Low Gradient type 19 

Figure 27 Photo of Subsurface Middle Gradient type 20 

Figure 28 Landform position of Subsurface Middle Gradient type 20 

Figure 29 Photo of Subsurface High Gradient type 21 

Figure 30 Landform position of Subsurface High Gradient type 21 

Figure 31 Map of hydrogeomorphic types on the Tahoe National Forest 23

2

inflow, and throughflow describe whether a meadow is a source, sink, or pass-through system 

respectively. Meadows perform different functions, depending on the gradient of the groundwater table 

and the topography of the land surface. The relationship of the groundwater table and the land surface 

dictates which function - groundwater recharge or discharge - a meadow performs. Groundwater 

recharge adds water to the groundwater system whereas groundwater discharge takes water from the 

groundwater system. Meadows may include areas that are wetland, but depending upon the wetland 

definition being used, not all areas within meadows will necessarily meet that definition's criteria. 

Therefore, when trying to determine if a meadow or part of a meadow is a wetland, the user must first 

decide on the wetland definition to be used, and then determine if the meadow or part of the meadow 

meets these criteria. 

Meadows that develop on mineral soils can be separated from meadows that occur on organic 

soils (peatlands) where an accumulation of peat creates the substrate, influences groundwater 

conditions, selects for specialized vegetation, and modifies surface morphology of the wetland. 

Sources of water in meadows can be precipitation, groundwater, or surface flow, or a 

combination of these sources. Meadows that receive little groundwater inflow or surface water 

inputs are often precipitation and/or snowmelt dominated and become dry during summer. 

Sometimes these precipitation and/or snowmelt dominated meadows are located in depressions 

with an impervious layer which retains precipitation and prevents the discharge of groundwater. 

Precipitation dominated meadows can also occur on a number of different landforms and 

typically results in a dry meadow type. 

Meadows also form in landscape positions where water actively discharges in the form of springs or 

seeps, particularly on hillslopes, at the base of hills and at the base of alluvial fans. These groundwater 

dominated meadows may also receive overland flow but they have a steady supply of water from 

groundwater. Most meadows in low points and in areas of valley fill (alluvium) are dominated by 

overland surface flow or a combination of surface and groundwater flow. Meadows that occur on 

alluvium or in valley bottoms or swales that lack a stream channel are often fed by subsurface 

groundwater without significant surface water inputs. Riparian meadows are found on floodplains and 

terraces associated with stream channels. Riparian meadow systems are fed both by surface water from 

flood events and by subsurface groundwater. The amount of lateral groundwater inflow from the 

hillslopes as compared to basal-groundwater inflow is often a key determinant of the type and pattern of 

meadow vegetation (Loheide et al. 2009). Further, groundwater inflow from the hillslope, to the 

hillslope/riparian interface, and ultimately to the riparian zone is strongly affected by bedrock 

permeability in granitic regions (Katsuyama and Ohte 2005). 

Riparian meadows can be further broken down based on slope steepness as low, middle, or high gradient. 

Stream gradient is correlated with riparian vegetation (Quistberg and Stringham 2009), flow velocity, 

substrate material, floodplain development, channel morphology and stream habitat types (pools, riffles, 

runs, etc.)(Rosgen 1994, Montgomery and Buffington 1997). Lacustrine fringe meadows are located 

along lake shores where the water elevation of the lake influences the water table of the adjacent meadow. 

These riparian (associated with a stream or river), and lacustrine (associated with a lake) meadows come 

in contact with, store, or release large quantities of water. 
3

CLASSIFICATION OF MEADOWS 

Efforts to classify meadows in the Sierra Nevada have used plant communities (Sumner 1941, Bennett 

1965, Pemble 1970, Chabot and Billings 1972, Taylor 1976, Ratliff 1979 and 1982, Benedict and Major 

1981, Jackson and Bliss 1982, Benedict 1983, Taylor 1984, Halpern 1985, Manning and Padgett 1995, 

Cheng 2004, Potter 2006, Barbour et al. 2007, Sawyer et al. 2009), general topography (Harkin and 

Schultz 1967, Benedict and Major 1982, Ratliff 1986), elevational range (Sharsmith 1959), site potential 

(Weixelman et al. 1999, Rundel et al. 2009), stratigraphy from the Holocene record (Wood 1975), 

moisture gradient as wet, moist, and dry (Klikoff 1965), and peatland types (Cooper and Wolf 2005, 

Weixelman and Cooper 2009, Sikes et al. 2010). 

This classification and field key uses both hydrology and geomorphology to identify fourteen meadow 

hydrogeomorphic types and takes many concepts from Brinson (1993). The geographic extent where this 

classification has been used is shown in Figure 1. Plant nomenclature in this document follows Hickman 

(1993). Strengths of the classification include its ability to clarify the relationship between hydrology and 

geomorphology and meadow function. Landform features, water sources, and water flow directions are 

an integral part of this hydrogeomorphic classification. Patterns of landform occurrence, the source and 

amount of water in a meadow, and the path the water takes through the meadow have reoccurring 

characteristics that help identify and stratify meadows for management interpretations. The individual 

types in this classification, together with plant species information, would allow for a determination of 

ecological function based on the relationship between meadow type, ecological functioning, and plant 

functional groups. 

Figure 1. The geographic extent (green shading) covered by the classification for the Sierra 

Nevada and Southern Cascade ranges in California. 
4

USING THE KEY 

Meadows, as defined above, may contain one or more hydrogeomorphic types depending on 

landscape position, water sources, and flow direction. The dichotomous key is designed to help the 

user identify these individual hydrogeomorphic types. In some cases, the meadow may be composed of 

only one hydrogeomorphic type, in other cases there will be two or more hydrogeomorphic types present. 

To use this key, start by locating a representative section of the meadow. The representative section 

should generally be consistent in soil moisture, and occur on a single dominant landform. Once this 

representative section of the meadow area has been located, the dichotomous key can be used to 

determine the hydrogeomorphic type. Definitions of terms used in the key can be found in Appendix A. 

If the meadow includes sites that are distinctly different in landscape position and/or soil moisture 

characteristics, those sites may need to be keyed separately. In that case there may be more than one 

hydrogeomorphic type present in the meadow. 

An example of a meadow is shown in Figure 2. In this figure, there is a stream channel running the 

length of the meadow and the predominant landform is a floodplain adjacent to the stream channel. 

Representative sampling locations are marked by an “X.” At these sampling locations, the dichotomous 

key was used to identify a hydrogeomorphic type. The dominant type was the riparian low gradient. 

Also present were two other hydrogeomorphic types within the meadow, a discharge slope type located 

on a toeslope and a dry type located on a terrace at the outer edge of the meadow. This example 

illustrates the concept of a meadow and component hydrogeomorphic types which make up the meadow. 

Figure 2. Illustration of a meadow and the component hydrogeomorphic types which make up the 

meadow. Also shown are the representative locations (marked by X’s) where the dichotomous key was 

used in the field to identify the component hydrogeomorphic types. 
5

FIELD KEY TO MEADOW HYDROGEOMORPHIC TYPES 

Note: More than one hydrogeomorphic type may occur in a meadow area. 

1a. At least 20 cm of organic soil material present in the top 40 cm of soil. Water table is typically within 

20 cm of the surface for most of the summer, and clonal peat forming plant species are typically present 

(e.g. members of the Cyperaceae or Juncaceae) 2 

2a. Occurs in a basin typically without inlets or outlets, or at the margins of lakes or ponds 

 Basin peatland, page 8 

2b. Not as above. Not occurring in a basin or at the margin of a lake or pond. Fed by a spring or a 

series springs 3 

3a. Occurs at the base of slopes, on toeslopes, or valley bottoms where peat has accumulated 

creating a mound. The mound is a result of a single, strong source of upwelling 

water (groundwater discharge) to the surface. There typically is a surface water 

outlet so they are not classified as basin peatlands 

 Mound peatland, page 9

3b. Not as above. Occurs on a hillslope, toeslope, or at the base of an alluvial fan where 

groundwater discharges to the surface and flows downslope in a gravity-driven system. No 

distinct mound structure is apparent. Discharge slope peatland, page 10

1b. Not as above. Less than 20 cm of organic soil material present in the top 40 cm of soil. Water table is 

within 20 cm of the surface for most of the summer or not, clonal peat forming species may be present 

or not 4 

4a. Occurs in a topographic depression with a closed elevation contour that allows accumulation of surface 

water. If standing water is present, the water depth is less than (or is judged to be less than) 2 meters 

(6.6 feet) deep. The depression may have any combination of inlets and outlets or lack them completely. 

Water either does not flow through the depressional meadow or the flow is essentially imperceptible. 

Includes artificially created depressions due to impoundments, causeways, and roads. May or may not 

be surrounded by upland vegetation 5 

5a. Has no standing water after late July during most years. Also includes vernal pools 

 Depressional seasonal, page 11

5b. Not as above. Has some amount of standing water after late July during most years 

 Depressional perennial, page 12 

 
6

FIELD KEY TO MEADOW HYDROGEOMORPHIC TYPES (Cont’d.) 

4b. Not as above. Not occurring in a topographic depression 6 

6a. Occurs along a lake or reservoir or within its basin (i.e. on the relatively flat area contiguous to the lake 

or reservoir). Depth of water in the lake is greater than (or is judged to be greater than) 2 meters (6.6 

feet) deep. Meadow is immediately adjacent to the waterbody, and nearly at the same elevation as the 

waterbody. The upper limit of the lacustrine fringe meadow is defined by the upstream influence of the 

lake which is approximated by the limits of the nearly flat or gently sloping lake margin 

 Lacustrine fringe, page 13

6b. Not as above. Not occurring along the fringe of a lake or reservoir 7 

7a. Dominated by perennial dryland grasses (Poaceae spp.), dryland sedges (Carex spp.), or herbaceous 

dicots adapted to drying conditions during summer, e.g. plants that have a wetland rating of Facultative 

Upland (FACU), Upland (UPL). Soil surface generally becomes dry by midsummer. Groundwater 

level (water table or zone of saturation) is usually below 1m during the growing season. Occurs at all 

elevations, from the foothills up into the alpine zone and occurs on many landforms such as stream 

terraces, benches, swales, drainageways and occurs on alluvial, colluvial, and lacustrine deposits. May 

occur adjacent to wetter meadow types that receive groundwater Dry, page 14 

7b. Not as above. Not dominated by dryland plant species. Dominated by plant species indicative of a 

shallow water table and that have a wetland rating of Obligate (OBL), Facultative Wetland (FACW), or 

Facultative (FAC). Groundwater level (water table or zone of saturation) is at the surface or within 1 m 

during all or part of the growing season. Soil surface generally moist or wet after mid-summer. 

 8 

 

8a. Dominant source of water is from groundwater that emerges at or near the meadow surface in the form 

of springs or seepage areas. This type occurs on hillsides, toeslopes, and at the bases of alluvial fans 

where groundwater discharge is a dominant source to the meadow surface. In some cases, the emerging 

groundwater flows downhill through very small channels Discharge slope, page 15 

 
7

FIELD KEY TO MEADOW HYDROGEOMORPHIC TYPES (Cont’d.) 

8b. Not as above. Dominant source of water is not from a spring or seep. Meadow receives surface water 

from a channel (perennial or intermittent, stream or river) above the meadow. Inflow and outflow 

channels are visible at the top end of the meadow and bottom end of the meadow. The meadow itself 

may or may not have a channel (intermittent or perennial, stream or river) running through it. 

 9 

9a. Meadow contains a channel or multiple channels (perennial or intermittent, stream or river) for a 

majority of its length and the meadow occurs on a floodplain or terrace adjacent to a stream or river. 

Channel may occur to one side of the meadow. Note: if a side-valley tributary meadow occurs adjacent 

to the main axial valley, include the meadow part of the side valley up to the base of the main axial 

valley hillslope. 10 

10a. Stream gradient is less than 2 % Riparian low gradient, page 16 

10b. Not as above, stream gradient is 2 % or more 11 

11a. Stream gradient is 2 % to 4 % Riparian middle gradient, page 17 

11b. Stream gradient is greater than 4 % Riparian high gradient, page 18 

 

9b. Not as above. Does not contain a channel (perennial or intermittent, stream or river) for a majority of 

the meadow length. A stream or river (perennial or intermittent) may enter or exit this type of meadow 

but it does not flow through it as a channel. May have rills or ditches. Found on a variety of gradients 

from nearly flat to sloping. Note: if a side-valley tributary meadow occurs adjacent to the main axial 

valley, include the meadow part of the side valley up to the base of the main axial valley hillslope 

 12 

12a. Downvalley slope is less than 2 % Subsurface low gradient, page 19 

12b. Not as above, downvalley slope is 2 % or more 13 

13a. Downvalley is slope is 2 % to 4 % Subsurface middle gradient, page 20 

13a. Downvalley slope is greater than 4 % Subsurface high gradient, page 21
8

Figure 3. Photo of a basin peatland located on the 

margin of a lake on the Modoc National Forest. 

Figure 4. Illustration showing a basin peatland 

type occurring as a floating mat at the edge of 

open water. 

Basin Peatland 

Setting 

Basin peatlands occur on a horizontal surface, have a flat water table, are found in basins typically with 

no inlets or outlets, or on the fringes of lakes or ponds. The basin peatland type may also occur as small 

patches within the lacustrine fringe meadow type. There is at least 20 cm of organic soil in the top 40 cm 

of soil. This definition departs from a true histosol, which requires 40 cm of organic soil material in the 

top 1 m. Organic soil material that occurs within the rooting zone of herbaceous species is a key factor in 

describing peatlands in the Sierra Nevada, thus the emphasis on the upper soil layer. Organic soil 

material is composed primarily of dead plant parts in various stages of decomposition and accumulates in 

meadows and wetlands as a result of anaerobic conditions created by poorly drained conditions. By feel, 

organic soil material is dark in color, generally contains fibers, and feels greasy when rubbed. 

Hydrology 

Basin peatlands, also called topogenous peatlands (Mitsch and Gosselink 2000), are supported by surface 

runoff from the basin edges and/or surface water and/or groundwater inflow from an adjacent water body 

such as a lake or pond. Water levels in this type tend to be very stable, and some basin peatlands develop 

a unique feature-- a floating peat mat on the margins of open water. 

Vegetation 

Peatlands are typically dominated by obligate or facultative wetland graminoid and moss species 

that are peat forming. Scattered shrubs or coniferous trees may be present. The vegetation of 

peatlands varies widely and appears to be controlled by the hydrologic regime (water depth, water inflow 

rates), as well as water chemistry (pH, cation, anion, and nutrient concentrations) (Cooper and Wolf 

2005). 

 
9

Figure 5. Photo of a mound peatland at the base 

of a toeslope and fed by upwelling ground water. 

Located on the Tahoe National Forest. 

Figure 6. Illustration showing the position of a 

mound peatland type occurring on a toeslope. 

Mound Peatland 

Setting 

This type often occurs at the base of slopes associated with sloping fens or on valley bottoms where there 

is a strong upwelling of groundwater discharge. This strong upwelling source of water helps create a 

mound of peat. There is at least 20 cm of organic soil material in the top 40 cm of soil. This definition 

departs from a true histosol, which requires 40 cm of organic soil in the top 1 m. An organic soil layer 

present within the rooting zone of herbaceous species is a key factor in describing peatlands in the Sierra, 

thus the emphasis on the upper soil layer. Organic soil material is composed primarily of the remains of 

plants in various stages of decomposition and accumulates in meadows and wetlands as a result of 

anaerobic conditions created by poorly drained conditions. By feel, organic soil material is dark in color, 

generally contains fibers, and feels greasy when rubbed. The mound peatland type may also occur as 

small patches within the discharge slope meadow type. 

Hydrology 

Mound peatlands are raised areas where peat has accumulated due to a single strong source of upwelling 

of water. There typically is a surface water outlet and thus these sites are not classified as basin peatlands. 

Vegetation 

Peatlands are typically dominated by obligate or facultative wetland graminoid and moss species that are 

peat forming. Scattered shrubs or coniferous trees may be present. The types and concentration of 

nutrients present in the peatland have a strong influence over the type of vegetation that occurs. Peatlands 

are often classified along a chemical gradient and the gradient is typically as follows: a peatland that is 

“poor” is characterized by low pH and low cation concentration, whereas “intermediate” and “rich” 

peatlands are characterized by higher pH and higher cation concentration. Most peatlands in the Sierra 

Nevada are considered “intermediate” or “rich.” 

 
10

Figure 8. Illustration showing a discharge slope 

peatland type occurring on: 1) a hillslope fed by 

ground water discharge springs; and 2) the base 

of an alluvial fan. 

Discharge Slope Peatland 

Setting 

Discharge slope peatlands, also called soligeneous peatlands (Mitsch and Gosselink 2000), are the 

most common type of peatland in the Sierra Nevada and southern Cascades. They occur over 

peat soils on hillslopes, toeslopes, at the base of alluvial fans, and at slope breaks on terraces. 

The discharge slope peatland type may also occur as small patches within the discharge slope 

meadow type. There is at least 20 cm of organic soil material in the top 40 cm of soil. This 

definition departs from a true histosol, which requires 40 cm of organic rich soil in the top 1 m. 

Organic soil material within the rooting zone of herbaceous species is a key factor in describing 

peatlands in the Sierra, thus the emphasis on the upper soil layer. Organic soil material will be 

very dark in color, contain fibers, and will feel greasy when rubbed. 

Hydrology 

Discharge slope peatlands are commonly fed by springs, or a complex of springs, where 

groundwater discharges at the surface. A discharge slope peatland is an outflow system, where 

there is a continuous outflowing of groundwater and/or surface water in a gravity-driven sloping 

system. 

Vegetation 

Peatlands are typically dominated by obligate or facultative wetland graminoid and moss species that are 

peat forming. Scattered shrubs or coniferous trees may be present. The types and concentration of 

nutrients present in the peatland have a strong influence over the type of vegetation that occurs. Peatlands 

are often classified along a chemical gradient and the gradient is typically as follows: a peatland that is 

“poor” is characterized by low pH and low cation concentration, whereas “intermediate” and “rich” 

peatlands are characterized by higher pH and higher cation concentration. Most peatlands in the Sierra 

Nevada are considered “intermediate” or “rich.” 

Figure 7. Photo of a discharge slope peatland on 

the Tahoe National Forest. 
11

Depressional Seasonal 

Setting 

Depressional meadows are places where runoff accumulates in a topographic depression. Water either 

does not flow through the meadow or the flow is essentially imperceptible. Depressional basins are less 

than 2 meters (6.6 feet) in depth. Depressional landforms may be either manmade (e.g. stock ponds, 

irrigation ponds, road impoundments), or natural. 

Hydrology 

Depressional seasonal meadows have no standing water or the standing water dries up before August in 

most years. Depressional seasonal meadows are characterized by irregular hydroperiods; many fill with

water only occasionally and dry quickly. Direct precipitation appears to be the primary water source but 

overland runoff and groundwater in seasonal perched water tables may also be important. Dominant 

hydrodynamics are vertical fluctuations (rise and fall of water levels), which is primarily seasonal. 

Vegetation 

Fluctuations in water availability often promote diverse herbaceous plant growth, but the communities 

that develop will be shaped by the timing and length of inundation or dryness. Often, the center of the 

depression will have a longer hydroperiod resulting in a stratification of plant communities. The 

vegetation of these sites is so variable temporally and spatially (Holland & Jain 1984, Barbour et al. 2003) 

that it is difficult to identify indicator species to characterize these seasonal depressional habitats. Plant 

genera that are common in these habitats include Eleocharis, Madia, Navarretia, Danthonia, 

Plagiobothrys, Juncus, and Carex. 

Figure 9. Photo of Depressional seasonal 

meadow on the Plumas National Forest. 

Figure 10. Illustration showing a depressional 

seasonal meadow located in a topographic 

depression. 
12

Figure 11. Photo of depressional perennial 

meadow on the Plumas National Forest. 

Figure 12. Typical landscape position for the 

depressional perennial meadow occurring in a 

topographic depression. 

Depressional Perennial 

Setting 

Depressional meadows are places where runoff accumulates in a topographic depression. Water either 

does not flow through the meadow or the flow is essentially imperceptible. Depressional basins are 

smaller than lakes and are less than 2 meters (6.6 feet) in depth. Depressional features can be natural or 

manmade. Stock ponds, irrigation ponds, and road impoundments are examples of manmade depressional 

features. 

Hydrology 

Depressional perennial meadows have standing water all year or late into the growing season in most 

years. Dominant sources of water are precipitation, groundwater inputs, and interflow from adjacent 

uplands. The direction of water movement is normally from the surrounding uplands toward the center of 

the depression. Depressional perennial meadows are separated from basin peatlands by the absence of a 

peat layer.

Vegetation 

Depressional perennial meadows are characterized by more stable hydroperiods than the depressional 

seasonal meadow type. These meadows are often dominated at their centers by wetland vegetation 

(obligate and facultative wetland plant species) that requires saturation near the surface and/or late season 

moisture. Plant communities may reflect a strong zonation due to changes in flooding depth from center 

to edge. 

 

 
13

Figure 13. Photo of a lacustrine fringe meadow 

occurring on the edge or fringe of Mono Lake, CA. 

Figure 14. Landscape position of a 

lacustrine fringe meadow occurring on the 

edge of a lake. 

Lacustrine Fringe 

Setting 

Lacustrine fringe meadows occur along a lake or reservoir or within a lake basin (i.e. on the relatively flat 

area contiguous to the lake, or reservoir). This meadow type is immediately adjacent to the lake and is at 

the same (approximate) elevation as the lake. The upper limit of the lacustrine fringe meadow is defined 

by the upstream influence of the lake which is approximated by the limits of the flat or gently sloping lake 

margin. A lake is defined as being greater than (or judged to be greater than) 2 meters (6.6 feet) deep. In 

some cases, these meadows consist of a floating mat attached to land. 

Hydrology 

The primary water input in the lacustrine fringe type is generally inflow from the lake adjacent to the 

meadow. Additional sources of water are precipitation and groundwater discharge, the latter dominating 

where lacustrine fringe meadows intergrade with slope discharge meadows or either riparian or 

subsurface throughflow meadows. Lacustrine fringe meadows lose water by surface and subsurface flow 

returning to the lake and also by evapotranspiration. Organic matter may accumulate in areas sufficiently 

protected from shoreline wave erosion. 

Vegetation 

Vegetation is generally dominated by hydric meadow graminoid species (obligate and facultative wetland 

plant species) with scattered riparian shrubs including willow (Salix spp.) or alder (Alnus spp.). Plant 

communities may reflect a strong zonation due to changes in water inputs going from the lake or pond 

edge toward the uplands. 

 
14

Figure 15. Photo of a dry meadow type occurring 

on a stream terrace on the Stanislaus National 

Forest. 

Figure 16. Typical landscape positions for the 

dry meadow type. 

Dry 

Setting 

Dry meadows occur where the main source of water is precipitation or runoff. Dry meadows are located 

on benches, swales, drainways, terraces, slopes, and gentle summit ridges where soil has become 

relatively stabilized. Groundwater is generally deeper than 1 m for most or all of the growing season. 

They may occur adjacent to a wetter meadow that receives groundwater. These sites may resemble the 

depressional seasonal meadow type in general appearance, but are differentiated by not being located on 

a depressional landform. 

Hydrology 

Dry meadows occur at all elevations and on a variety of landforms. Dry meadows occur on sites where 

water from rains, snow, or snowmelt is concentrated near the soil surface and provides early season 

moisture sufficient for establishment of perennial graminoids and herbaceous dicots. They lose water by 

evapotranspiration, overland flow, and seepage to the underlying groundwater. At higher elevations, dry 

meadows are common where cool temperatures and snowmelt allow soil moisture to linger long enough 

for graminoid species and herbaceous dicots to flower and reproduce before the dry season comes. This 

type may mix with other meadow, forest and woodland types at a fine scale. Above treeline, this type 

may intergrade with alpine fell field communities in areas with decreasing levels of soil development. 

Vegetation 

Dry meadow vegetation is generally dominated by grasses (Poaceae family), dryland sedges (Carex spp.), 

or dryland rushes (Juncus spp.). This type includes a very broad range of moisture conditions from low 

elevation stream terraces and swales to subalpine and alpine areas on gravelly slopes. High elevation 

sites on gravelly soils may be dominated by shorthair sedge (Carex exserta) or Parry’s rush (Juncus 

Parryi). High elevation sites that are saturated early in the season may be dominated by shorthair 

reedgrass (Calamagrostis breweri) or Sierra ricegrass (Ptilagrostis kingii). 

 
15

Figure 17. Photo of a series of discharge slope 

meadows occurring on a toeslope above a 

riparian low gradient meadow system, Modoc 

National Forest. 

Figure 18. The discharge slope type occurring 

on two different settings: 1) hillslopes; and 2) at 

a toeslope. The discharge slope type is 

distinguished from the discharge slope peatland 

type by the absence of a peat layer. 

Discharge Slope 

Setting 

Discharge slope meadows are found in association with the discharge of groundwater to the land surface, 

or near surface in the form of springs or a complex of springs or seeps, or at sites with saturated overland 

flow with no channel formation. They normally occur on hillslopes, toeslopes, or the bases of alluvial 

fans on gradients ranging from very gentle to steep. The discharge slope type is distinguished from the 

discharge slope peatland type by the absence of a peat layer. However, a discharge slope type may have 

small areas of discharge slope peatlands within it. 

Hydrology 

Discharge slope peatlands are commonly fed by springs, or a complex of springs, where groundwater 

discharges at the surface. Direct precipitation is often a secondary contributing source of water. 

Hydrodynamics are dominated by downslope unidirectional water flow. This meadow type may develop 

channels, but the channels serve only to convey water away from the discharge area. Discharge slope 

meadows are distinguished from depressional meadows by the lack of a closed topographic depression, 

and the predominance of the groundwater/interflow water source. 

Vegetation 

Vegetation is generally dominated by hydric meadow graminoid species that are obligate or facultative 

wetland species and occasionally with scattered riparian shrubs including willows (Salix spp.). Hydric 

vegetation may be restricted to the immediate boundaries of the groundwater discharge, or it may extend 

outward where surface and/or groundwater flows outward and moistens soil. 

 
16

Riparian Low Gradient 

Setting 

The riparian low gradient meadow type is associated with a stream or river channel where the average 

stream or river gradient is less than 2 percent. Streams in this type have a riffle-pool morphology 

composed of migrating pools and point bars, are sinuous, and have well developed floodplains. To 

qualify as a riparian type, a majority of the meadow length must contain a stream channel with a 

discernable bed and bank morphology. This distinguishes them from the subsurface meadow type where 

a majority of the meadow does not contain a stream channel with a definite bed and bank morphology. 

Hydrology 

Riparian meadow types are throughflow meadows; there is an inflow channel (perennial or intermittent) 

at the top of the meadow and an outflow channel at the bottom. Water inputs include overbank flow from 

the channel, subsurface hydraulic connections between the stream channel and meadow, and groundwater 

inputs from the hillslopes. Additional water sources may be interflow or occasional overland flow from 

adjacent uplands, tributary inflow, and precipitation. When overbank flow occurs, surface flows down the 

floodplain may dominate hydrodynamics. 

Vegetation 

Vegetation is generally dominated by hydric meadow graminoid species (obligate and facultative wetland 

plant species) and occasionally with scattered riparian shrubs including willows (Salix spp.) or alders 

(Alnus spp.). Steeper gradients have a higher probability of shrubby occurrence. At sites where there is 

little groundwater input from the adjacent uplands, or where terracing occurs, there may be a strong 

zonation from hydric to drier soils going from the streambank toward the uplands. 

 

Figure 19. Photo of a riparian low gradient 

meadow occurring on the Modoc National Forest. 

Figure 20. Landscape position for a riparian 

low gradient meadow occurring on alluvium in 

low gradient valley bottoms. 
17

Riparian Middle Gradient 

Setting 

The riparian middle gradient meadow type is associated with a stream or river channel where the average 

stream gradient is 2 percent to 4 percent. In these streams, rapids predominate with occasional pools; 

have less developed floodplains than in the low gradient type, and generally low rates of aggradation and 

streambank erosion. Riparian types are distinct from subsurface types by having a majority of the 

meadow length contain a stream channel with a discernable bed and bank morphology. The channel may 

be perennial or intermittent. Near headwaters and first-order streams, as drainages consolidate (moving 

downstream) into defined channels and floodplains, discharge slope meadows often intergrade with 

riparian middle gradient and riparian high gradient meadows. 

Hydrology 

Water inputs include overbank flow from the channel, subsurface hydraulic connections between the 

stream channel and meadow, and groundwater inputs from the hillslopes. Additional water sources may 

be interflow or occasional overland flow from adjacent uplands, tributary inflow, and precipitation. When 

overbank flow occurs, surface flows down the floodplain may dominate hydrodynamics. 

Vegetation 

Vegetation is generally dominated by hydric meadow graminoid species that have an obligate or 

facultative wetland rating. Scattered riparian shrubs including willows (Salix spp.) or alders (Alnus spp.) 

are often prominent and may be locally dominant. At sites where there is little groundwater input from 

the adjacent uplands, there may be a strong zonation from hydric to drier soils going from the streambank 

toward the uplands. 

 

Figure 21. Photo of a riparian middle gradient 

meadow occurring on the Inyo National Forest. 

Figure 22. Landscape position of a riparian 

middle gradient meadow occurring on a sloping 

valley with a gradient of 2percent to 4percent. 
18

Riparian High Gradient 

Setting 

The riparian high gradient meadow type is associated with a stream or river channel where the average 

stream gradient is greater than 4 percent. A majority of the meadow length contains a stream channel 

with a discernable bed and bank morphology, which distinguishes the riparian types from the subsurface 

meadow types. Riparian high gradient meadows are often associated with headwaters and low-order 

streams. Streams in this region have a sequence of step-pools which are composed of channel-spanning 

pools and boulder/cobble steps. They have little floodplain development, and have nearly straight 

channels. The channel may be perennial or intermittent. Near headwaters and first-order streams, 

discharge slope meadows often intergrade (moving down in elevation) with riparian high gradient

meadows. 

Hydrology 

Water inputs include overbank flow from the channel, subsurface hydraulic connections between the 

stream channel and meadow, and groundwater inputs from the hillslopes. Additional water sources may 

be interflow or occasional overland flow from adjacent uplands, tributary inflow, and precipitation. When 

overbank flow occurs, surface flows down the floodplain may dominate hydrodynamics. 

Vegetation 

Vegetation is generally dominated by hydric meadow graminoid species that are obligate or facultative 

wetland plant species and by tall herbaceous dicots such as California corn lily (Veratrum californicum), 

and lupine (Lupinus spp.). Riparian shrubs including willows (Salix spp.) or alders (Alnus sp.) are 

prominent and may be locally dominant. At sites where there is little groundwater input from the adjacent 

uplands, there may be a strong zonation from hydric to drier soils going from the streambank toward the 

uplands. 

 

Figure 23. Photo of a riparian high gradient 

meadow occurring on the Humboldt-Toiyabe 

National Forest. 

Figure 24. Landscape positions for riparian 

high gradient meadows occurring on sloping 

valleys with a gradient of more than 4percent. 
19

Subsurface Low Gradient 

 

Setting 

Subsurface low gradient meadows contain no stream or river channel, or a majority of the meadow does 

not contain a stream or river channel with a discernable bed and bank morphology. Ditches or rills may be 

present. This meadow type occurs on alluvium or colluvium and typically is connected to a distinct 

topographic flow line (perennial or intermittent channel) above and below the meadow. This type occurs 

where the down valley slope averages less than 2 percent. 

Hydrology 

The dominant water sources are surface water and groundwater throughflow. Additional water sources 

are groundwater inputs or overland flow from surrounding uplands, tributary inflow, and precipitation. 

Inflow and outflow stream channels (perennial or intermittent) are typically visible at the top end of the 

meadow and bottom end of the meadow. Subsurface low gradient types are distinguished from the 

groundwater discharge type by being a throughflow groundwater/interflow system with a water source 

(surface or subsurface) at a higher elevation and outflow (surface and/or subsurface) at the bottom of the 

meadow. 

Vegetation 

Vegetation is generally dominated by hydric meadow graminoid species (obligate and facultative wetland 

plant species). Occasionally scattered riparian shrubs including willows (Salix spp.) and coniferous tree 

species are present. Sites often exhibit a strong zonation from hydric to drier soils going from the center 

of the meadow toward the uplands. 

 

Figure 25. Photo of a subsurface low gradient 

meadow occurring on the Stanislaus National 

Forest. 

Figure 26. Typical landscape positions for 

subsurface low gradient meadows occurring in 

low gradient valleys. 
20

Subsurface Middle Gradient 

Setting 

Subsurface middle gradient meadows contain no stream or river channel, or a majority of the meadow 

does not contain a stream or river channel with a discernable bed and bank morphology. Ditches or rills 

may be present. This meadow type occurs on alluvium or colluvium and typically is connected to a 

distinct topographic flow line (perennial or intermittent channel) above and below the meadow. This type 

occurs where the down valley slope is 2 percent to 4 percent. 

Hydrology 

The dominant water sources are surface water and groundwater throughflow. Additional water sources 

are groundwater inputs or overland flow from surrounding uplands, tributary inflow, and precipitation. 

Inflow and outflow stream channels (perennial or intermittent) are typically visible at the top end of the 

meadow and bottom end of the meadow. Subsurface low gradient types are distinguished from the 

groundwater discharge type by being a throughflow groundwater/interflow system with a water source 

(surface or subsurface) at a higher elevation and outflow (surface and/or subsurface) at the bottom of the 

meadow. 

Vegetation 

Scattered riparian shrubs including willows (Salix spp.) and coniferous tree species are often present. 

Sites often exhibit a strong zonation from hydric to drier soils going from the center of the meadow 

toward the uplands. 

 

Figure 27. Photo of a subsurface middle 

gradient meadow occurring on the Stanislaus 

National Forest. 

Figure 28. Typical landscape position of a 

subsurface middle gradient meadow occurring 

on a slope of 2 percent to 4 percent. 
21

Subsurface High Gradient 

Setting 

Subsurface high gradient meadow types contain no stream or river channel or a majority of the meadow 

does not contain a stream or river channel with a discernable bed and bank morphology. Ditches or rills 

may be present. This meadow type occurs on alluvium or colluvium and typically is connected to a 

distinct topographic flow line (channel, drainway, or swale) above and below the meadow. Downvalley 

slope averages greater than 4 percent. Near headwaters and first-order streams, discharge slope meadows 

often intergrade (moving down in elevation) with subsurface high gradient meadows. 

Hydrology 

The dominant water sources are surface water and groundwater throughflow. Additional water sources 

are groundwater inputs or overland flow from surrounding uplands, tributary inflow, and precipitation. 

Inflow and outflow stream channels (perennial or intermittent) are typically visible at the top end of the 

meadow and bottom end of the meadow. Subsurface high gradient types are distinguished from the 

discharge slope meadow type by being a throughflow groundwater/interflow system with a water source 

(surface or subsurface) at a higher elevation and outflow (surface and/or subsurface) at the bottom of the 

meadow. 

Vegetation 

Vegetation is generally dominated by hydric meadow graminoid species that are obligate or facultative 

wetland plant species and by tall herbaceous dicots such as California corn lily (Veratrum californicum), 

and lupine (Lupinus spp.). Riparian shrubs including willows (Salix spp.) and conifer tree species are 

typically present, and may be locally dominant. At sites where there is little groundwater input from the 

adjacent uplands, there may be a strong zonation from hydric to drier soils going from the center of the 

meadow toward the uplands. 

 

Figure 29. Photo of a subsurface high gradient 

meadow near headwaters on the Sequoia National 

Forest. 

Figure 30. Typical landscape positions for 

subsurface high gradient meadows occurring in 

sloping valleys. 
22

POTENTIAL USES FOR THIS CLASSIFICATION 

1. Condition assessment: there is a need for condition assessment of meadows across the Sierra 

Nevada and southern Cascades in California. Meadow ecological functions, plant communities, 

response to various disturbances, and wildlife habitat characteristics vary by geomorphic setting and 

hydrologic inputs and outputs. This classification can provide a means of stratifying meadows for 

assessment of these characteristics. Protocols for assessing condition and functionality for each of 

the hydrogeomorphic types in this classification would provide a framework allowing meadow 

managers the ability to report on the overall distribution, abundance, and condition of meadows 

within watersheds or regions across the Sierra Nevada. 

2. Mapping: A fundamental requirement of any meadow management program is the inclusion of 

comprehensive information about the distribution of meadows and wetlands, mapped and classified 

at an appropriate scale, with sufficient detail to allow management actions to be implemented or for 

further mapping and inventory work to be undertaken. This hydrogeomorphic classification can 

provide the physical and hydrologic settings for meadow types. Vegetation composition of these 

types can then be described and mapped using, for example, plant groupings at the alliance or 

community levels currently being developed (Sawyer et al. 2009). 

There are a number of techniques to map meadows. Examples are surveying with a high-grade GPS 

in the field, digitizing aerial photographs, and remote sensing. Appropriate attribution 

(hydrogeopmorphic or vegetation composition for example), even if provisional, can be followed up 

or accompanied by field validation. An example of a mapping project for delineating meadow 

hydrogeomorphic types is shown in Figure 31. As part of a mapping exercise, meadows larger than 

0.5 acre were delineated on an aerial photo at a scale of 1:18,000. In the field, the hydrogeomorphic 

types were determined using field reconnaissance and the dichotomous key to meadow 

hydrogeomorphic types. The dominant hydrogeomorphic type in this drainage area was the riparian 

low gradient hydrogeomorphic type. This example illustrates the concept of a meadow and 

component hydrogeomorphic types which make up the meadow. In practice, after the meadow has 

been identified on an aerial photo or in the field, the key will help the user identify the component 

hydrogeomorphic type(s) in the meadow. In some cases, the transitions or boundaries between types 

can be indistinct due to subtle hydrologic gradients, or where microtopography causes meadows to 

be interspersed with uplands or other meadow hydrogeomorphic types at fine scales. For these 

situations, changes in plant community, landform, and/or changes in soil moisture as determined by 

ground-truthing can be used to draw boundaries between hydrogeomorphic types. 

3. Restoration: A majority of meadows in the Sierra Nevada have been in the past, and 

continue to be impacted by tree encroachment, changes in water table due to stream 

incision, overgrazed areas, recreational use, hydrologic alteration including stream 

diversions, climate change, and fire suppression. Restoration attempts are being made to 

improve ecological functioning in meadows that have been degraded. This 

hydrogeomorphic classification can potentially link restoration methods to geomorphic 

setting and hydrologic characteristics of a meadow. Questions exist on restoration methods 
23

Figure 31. Map of hydrogeomorphic meadow types on the Tahoe National Forest. 

and application of methods. For example, which hydrogeomorphic meadow types are most 

vulnerable to the above stressors, and further, what types of restoration measures are most 

appropriate for the different meadow hydrogeomorphic types. While restoration of meadows in the 

Sierra Nevada has been undertaken for decades, there is little guidance on appropriate restoration 

methods for different meadow types. At a time when climate change is putting unprecedented 

pressure on water supplies with less snowpack and earlier snowmelt being predicted, restoring 

mountain meadows has become even more of a priority (Null et al. 2010). 
24

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27

Appendix A. Definitions. 

Alluvial fan - a fan-shaped deposit of fluvial sand and gravel, usually located at the mouth of a tributary 

valley. 

Alluvium - sediment deposited by flowing water, as in a floodplain, terrace, streambed, or riverbed. 

Colluvium - a loose deposit of rock debris or soil accumulated through the action of rainwash or gravity at 

the base of a gently sloping cliff or slope. 

Depression - Any relatively sunken part of the Earth's surface; especially a low-lying area surrounded by 

higher ground. A closed depression has no natural outlet for surface drainage (e.g. a sinkhole). An open 

depression has a natural outlet for surface drainage. A depression, for the purposes of this document, is 

less than 6.6 ft. (2 meters) deep. 

Ditch - 'Ditch or canal' means a man-made channel other than a modified natural stream constructed for 

drainage purposes.. A ditch or canal may have flows that are perennial, intermittent, or ephemeral and 

may exhibit hydrological and biological characteristics similar to perennial or intermittent streams. 

Down-valley gradient - down-valley axis represented by a hypothetical straight channel down the central 

axis of the valley. The down-valley gradient is usually steeper than the stream gradient because meanders 

develop, which lengthen the course of the stream, decreasing the gradient. 

Drainageway - areas that convey surface water runoff from single storm events, or flows from highly 

localized snow melt, or flows from man-made drainage devices that intercept ground water. Similar to a 

swale. 

Fellfield - "rock field" or "stone field" which is alpine land that is 35 percent to 50 percent rockcovered and which supports lichens, mosses, and cushion plants. Boulder fields are similar to 

fellfields except with larger rocks. The typical alpine landscape is a checkerboard-like 

arrangement of alpine meadow interspersed with fellfields and boulder fields. 

Floodplain - level or very gently sloping surface bordering a river that has been formed by river erosion 

and deposition; it is usually subject to flooding and is underlain by fluvial sediments; similar to alluvial 

plain. 

Graminoid - members of the grass (family Gramineae or Poaceae) and grasslike plants such as 

sedges (family Cyperaceae) and rushes (family Juncaceae). 

Groundwater - Water that collects or flows beneath the Earth's surface, filling the porous spaces in soil, 

sediment, and rocks. Groundwater originates from rain and from melting snow and ice and is the source 

of water for aquifers, springs, and wells. The upper surface of groundwater is the water table. 

Groundwater discharge - is the movement of water out of an area of saturated soil. 

Herbaceous dicot (= forb) - a flowering plant lacking a permanent woody stem, and having flower parts 

in multiples of four or five. The leaf veins are reticulate in pattern and not parallel in pattern. These 

plants are the common wildflowers seen in meadows. 

Hillslope - the inclined surface of a hill above the toeslope. 
28

Histosol - soils that contain a minimum of 40 cm of organic horizons within the upper 80 cm of the soil 

profile. The organic horizons contain at least 12 – 18% organic carbon content by dry weight, depending 

upon the percent clay in the mineral fraction. 

Hydric - of, relating to, formed in, living in, or growing in soils that formed under conditions of 

saturation, flooding, or ponding long enough during the growing season to develop anaerobic conditions 

in the upper part. 

Hydroperiod - the period of time during which a meadow or wetland is covered by water.

Hydrodynamics - the movement and action of water in a meadow or wetland. 

Interflow - The water, derived from precipitation, that infiltrates the soil surface and then moves laterally 

through the upper layers of soil above the water table. 

Lacustrine - of, relating to, formed in, living in, or growing in lakes. 

Organic soil material - soil that contains a minimum of 12 percent organic carbon when no clay is present 

or a minimum of 18 percent organic carbon when clay content is 60 percent or greater. 

Paludification - the process by which expansion of peat soil occurs over mineral soil. 

Peat - a term that sometimes is applied to organic soils. A soil that contains a minimum of 12 percent 

organic carbon when no clay is present or a minimum of 18 percent organic carbon when clay content is 

60 percent or greater. 

Peatland - a type of ecosystem, also referred to as a mire, in which organic matter is produced faster than 

it is decomposed, resulting in the accumulation of partially decomposed vegetative material termed peat. 

Must contain at least 20 cm thickness of peat in the top 40 cm of soil. 

Riffle - the sections of the streambed with the steepest slopes and shallowest depths at flows below 

bankfull, i.e. areas of a distinct change in gradient where flowing water can be observed. Riffles typically 

have a poorly defined thalweg. 

Rill - A rill is a very small channel of water, caused mainly by runoff water that has eroded the soil. In 

this process, sediment particles on the soil surface are detached in the interrill areas and move to the rills 

by the processes of splash as the result of raindrop impact, and by suspension in overland flow.

Riparian - pertaining to the boundary between water and land. Normally represents the streamside zone 

and the zone of influence of the stream toward the upland. 

Soligenous peatland - peatland that is maintained by slow lateral gravitational seepage of water through 

the substrate or the peat. 

Stream channel - the physical confine of a stream (or river) consisting of a bed and more or less defined 

stream banks. The bed of a stream or river is the physical confine of the normal water flow. The lateral 

constraints (channel margins) during all but flood stage are the stream banks. Usually the bed is kept 

clear of terrestrial vegetation, whereas the banks are subjected to water flow only during unusual or 

infrequent high water stages, and therefore can support vegetation much of the time 
29

Stream terrace - one of a series of level surfaces on a stream valley flanking and parallel to a stream 

channel and above the stream level, representing the uneroded remnant of an abandoned floodplain or 

stream bed. Also known as river terrace. 

Subsurface Flow - water leaves via groundwater. 

Surface water - is water collecting on the ground or in a stream, river, lake, wetland, or ocean. 

Swale - a shallow, open depression in unconsolidated materials which lacks a defined channel but can 

funnel overland or subsurface flow into a drainageway. 

Terrene meadow- meadows surrounded or nearly so by uplands and lacking a channelized outlet stream. 

Throughflow - water entering and exiting, passing through; a throughflow meadow receives significant 

surface or groundwater which passes through the meadow and is discharged to a stream, wetland or other 

waterbody at a lower elevation; throughflow may be perennial, intermittent, or associated with an 

entrenched stream. 

Toeslope - the base of an inclined surface of a hill. 

Topogenous peatland - peatlands that develop in topographic depressions or horizontal surfaces with at 

least some regional groundwater flow. 

Vernal pool - a temporarily flooded basin or depression. These pools are surrounded by upland 

vegetation and are usually flooded from winter through early summer 

Wetland rating (plant categories) - five categories are used to describe the likelihood of a particular plant 

species occurring in a wetland area: 

OBL: obligate wetland, Occurs almost always (estimated probability 99%) under natural conditions 

in wetlands. 

FACW: facultative wetland, Usually occurs in wetlands (estimated probability 67%-99%), but 

occasionally found in non-wetlands. 

FAC: facultative, Equally likely to occur in wetlands or non-wetlands (estimated probability 34%-

66%). 

FACU: facultative upland, Usually occurs in non-wetlands (estimated probability 67%-99%), but 

occasionally found on wetlands (estimated probability 1%-33%). 

UPL: obligate upland, occurs almost always (estimated probability 99%) under natural conditions 

in non-wetlands in the regions specified 

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Appendix C. Examples of meadow hydrogeomorphic types 

 

Riparian middle gradient type on the Modoc National Forest 

Subsurface low gradient type on the Plumas National Forest 
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Appendix C (cont’d.) Examples of meadow hydrogeomorphic types 

Depressional perennial type located in Mt. Lassen Volcanic National Park. 

Riparian middle gradient type on the Modoc National Forest. 
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Appendix C (cont’d.) Examples of meadow hydrogeomorphic types 

Dry meadow type on a bench near treeline on the Inyo National Forest. This 

photo shows dry meadow areas intermixed with alpine fellfields. 

Lacustrine fringe meadow type located in Mt. Lassen Volcanic National 

Park. 

U.S. GOVERNMENT PRINTING OFFICE: 2011 — 76- 0 / Region No. 10 5 42 23002