Using Hydrogeomorphic Criteria to Classify Wetlands on Mt. Desert Island,Maine-Approach,Classification System, and Examples

2006·2.3 MB·English

by  Neilsen, M.G.

scienceforachangingworld
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Using Hydrogeomorphic Criteria to Classify Wetlands on
—
Mt. Desert Island, Maine Approach, Classification
System, and Examples
Scientific Investigations Report 2005-5244
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Cover Photograph:Wetland at the base ofChamplain Mountain, Bar Harbor, Maine, by Hilary A. Neckles
Using Hydrogeomorphic Criteria to Classify
—
Wetlands on Mt. Desert Island, Maine Approach,
Classification System, and Examples
By Martha G. Nielsen
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this item from
Resource Room
IncooperationwiththeNationalParkService
Scientific Investigations Report2005-5244
U.S. Department ofthe Interior
U.S. Geological Survey
U.S. Department of the Interior
Gale A. Norton, Secretary
U.S. Geological Survey
P. Patrick Leahy, Acting Director
U.S. Geological Survey, Reston, Virginia: 2005
Forsale byU.S. Geological Survey, Information Services
Box25286, DenverFederal Center
Denver, CO80225
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1
CONTENTS
Abstract 1
Introduction 1
Purposeand Scope 3
Wetland Classification System 3
Description of StudyArea 4
Approach: Designing a Hydrogeomorphic Classification System 5
Methodology 5
Use of GIStoAssign HGN Subclasses 5
Classification System forWetlands on Mt. Desert Island 6
Preliminary HGM Classification System 6
RiverineWetlands 6
Riverine-Upper Perennial 6
Riverine-Nonperennial 6
Riverine-Tidal 6
Depressional Wetlands 10
Depressional-Closed 10
Depressional-Semiclosed 10
Depressional-Open 10
Depressional-No Ground-Water Input 11
Mineral Soil Flats 11
Organic Soil Flats 11
Tidal Fringe 14
Lacustrine Fringe 14
Slope 14
Application of Classification System 16
Dichotomous Keyforthe Identification ofWetland Subclasses 16
Expected Hydroperiod Characteristics 16
Example of Classifying Wetlands: ATestCase in Acadia National Park 16
Data CollecitonfortheTestWetlands 16
Hydrogeomorphic Classification Without Hydroperiod Data 19
Hydrogeomorphic Classification Revision Using Hydroperiod Data 21
Comparison of Disturbed and Undisturbed Wetlands 21
Summaryand Conclusions 24
References Cited 24
Figures
1. Map showing extent of shallowwater, nonmarinewetlands on Mount Desert Island, Maine 2
2. Index map showing location of example wetlandfigures, Mount Desert Island, Maine 7
3. Map showing Riverine-UpperPerennial example: wetlands adjacentto Old Mill Brook
Bar Harbor, Maine 9
4. Map showing Riverine-Nonperennial example: wetland east of Round Pond and north of Long Pond,
Mount Desert, Maine 9
5. Map showing Closed Depressional example: wetland north ofthe Beehive, Bar Harbor, Maine 10
6. Map showing Semiclosed Depressional example: wetland westof Old Norway Drive, Bar Harbor, Maine 1
7. Map showing Open Depressional example: wetland west of Eagle Lake, Bar Harbor, Maine 12
IV
Figures continued
8. Mapshowing Mineral Soil Flat example: wetlandwestof Rt. 102/198, nearJones Marsh,
Bar Harbor, Maine 12
9. Map showing Organic Soil Flat example: southeast of Bass Harbor, Southwest Harbor, Maine 13
10. Map showingTidal Fringe example: wetland atthe mouth of Northest Creek, Bar Harbor, Maine 13
11. Map showing Lucustrine Fringe example: near Ripple Pond, west of Somes Sound, Mount Desert, Maine 14
12. Schematiccross section of oneexample of slopewetlandformation 15
13. Mapshowing Slope Wetland example: wetlands in Heath and Lurvey Brookwatersheds,
Mount Desert, andand Tremont, Maine 15
14. Map showing locations ofwetlands greaterthan 2 hectaresandwetlands sitesfortestclassification,
Mount Desert Island, Maine 20
15. Graphs showing example hydroperiod datafor selectedwetland subclasses 25
Tables
1. Hydrogeomorphicclassification forMt. Desert Island, Maine 8
2. Hydrogeomorphicclassification keyfor Mt.Desert Island 17
3. Expected hydroperiod characteristicsforhydrogeomorphic subclasses, Mt. Desert Island, Maine 18
4. Classification ofexamplewetlands using dichotomous keyforwetland classification,
Mt. Desert Island, Maine 22
Conversion Factors
Multiply By To obtain
centimeter(cm) 0.3937 inch (in.)
millimeter(mm) 0.394 inch (in.)
meter(m) 3.281 foot(ft)
kilometer(km) .6214 mile (mi)
Area
hectare (ha) 2.471 acre
square kilometer(knf) 0u..3d8b6b1i square mi(mr
Vertical coordinate information is referencedtothe NorthAmerican Vertical Datum of 1988 (NAVD 88).
Horizontal coordinate information is referencedtothe North American Datum of 1983 (NAD 83).
Using Hydrogeomorphic Criteria to Classify Wetlands on
—
Mt. Desert Island, Maine Approach, Classification
System, and Examples
By Martha G. Nielsen
Abstract tems, including the hundreds ofwetlands thatexist in the park.
Developing a wetland monitoring plan for the shallow-water
(less than 2 m), nonmarine wetlands at Acadia National Park
A wetland classification system was designed forMt. (ANP)isahighpriority in thepark'sWaterResourcesManage-
Desert Island, Maine, to help categorize the large numberof ment Plan (Kahl and others, 2000). To implement a wetland
wetlands (over 1200mapped units), and to help resource man-
monitoring plan effectively, park managers need a tool tocate-
agers decide which to monitor. The National Park Service at gorize and then prioritize wetlands formonitoring. The tool
Acadia National Park, which covers more than 50 percent of must easily be applied to all existing ANP wetlands, and to
Mt. Desert Island, is interested in developing a wetland moni- otherwetlands on Mt. Desert Island that might becomeacandi-
toring program fora subset ofwetlands at the park. The classi- date forprotection (fig 1). Calhoun and others (1994)pointout
fication system, developed by the U.S. Geological Survey
that "The nature ofthe wetland community, be it microbial,
(USGS) in cooperation with the National Park Service, uses a
invertebrate, vertebrate, orplant, reflects the relationship of
modified hydrogeomorphic (HGM) classification approach, waterwiththelandscape-itstopography,geology, landusehis-
and assignscategories basedon position in the landscape, soils
and surficial geologic setting, and source ofwater. A dichoto- tory, and soils." Itisnotonly water's relation with the wetland
mouskey wasdevelopedtodetermineapreliminary HGMclas- eticoonstyosttheemltahragterislaimnpdosrctaapnet,thbatutdettheerwmeitnleasndm'asncyonotfetxhteiwnetrellaan-d
sificationofwetlandsontheisland.Thiskey isdesignedforuse
functions that are valued by society.
with USGS topographic maps and 1:24,000 geographic infor- The method ofhydrogeomorphic (HGM) classification
mation system coverages (GIS) as an aid to the classification,
has been accepted asavery useful way oforganizing groups of
but may also be used with field data.
wetlands bytheirhydrologic function (Brinson, 1993,Coleand
Because the method presented in this study does not use
Brooks, 2000; Cole and others 1997; Gwin and others 1999;
field hydroperiod data as part ofthe classification, a test was
Shafferand others 1999). Themethodcandiscern variations in
conducted to determine whether the preliminary classification
HGM wetlandecology thathave notbeen welldifferentiatedby other
ofindividual wetlands using this approach yielded
classification systems (Cole and others 1997). The incorpora-
classes that were consistent with actual hydroperiod data. In HGM
tion ofhydrologic function, through the application of
undisturbed wetlands, 9 out of 10 wetlands were assigned pre-
classification, will aid the National Park Service in selecting
liminary classifications thatagreed with the field hydroperiod
wetlands formonitoring.
data. In disturbed wetlands, 8 ofthe 10 wetlands were assigned
Many hydrologic stresses to wetland integrity exist at
preliminary classifications that agreed with the field hydrope-
ANP, including ground-waterand surface-water availability
riod data. The slight difference between the disturbed and
undisturbed cases may relate to factors such as road building, and quality. Lack ofwateravailability during drought is most
likely to stress non-lacustrine-fringe wetlands in ground-water
ditching, flowconstriction, orexcavation that were notdiscern-
able at the scale ofthedata(1:24,000) used in the method. The recharge areas or in areas lacking a good hydraulic connection
method therefore appears to work somewhat better with undis- to the ground-watersystem. Stresses caused by ground-water
quality problems are most likely to occur in wetlands within
turbed wetlands than with disturbed wetlands.
ground-waterdischarge areas, especially those with human
activity in the contributing basin area. The hydrogeomorphic
classification ofwetlands on Mt. Desert Island is the first step
Introduction
in fulfilling thegoal ofidentifyingpotential hydrologicstresses
to wetlands on the island. Further steps could include develop-
AcadiaNational Park covers more than 50percent ofMt. ing acalibrated ground-water flow model to identify areas of
Desert Island on the Coast ofMaine, and is dedicated to the ground-waterdischarge that may be related to wetland loca-
preservation ofmany types ofsensitive and importantecosys- tions;delineatingwatershedboundariesforwetlands;anddeter-
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2 Using Hydrogeomorphic Criteriato ClassifyWetlandson Mt. DesertIsland, Maine Approach, Classification System,and
Examples
68°25' 68*121
(
//
4475'
-'.'•..-S
44°15
BasefromU.S.GeologicalSurvey
DigitallinegraphBassHarbor, BarHarbor,
BartlettIsland,SealHarbor,SalsburyCove,
andSouthwestHarbor,Maine, 1:24,000
quadrangles. Shadedrelieffrom10-mdigital
elevationmodel.WetlandsfromU.S. Fishand
WildlifeService(1998)NationalWetlands 5>\
Inventory. °* xLocation of
Mt. Desert
Island
Figure1. Extentofshallowwater, nonmarine wetlands on MountDesert Island, Maine.
Introduction 3
HGM
mining whether individual wetlands are more likely to be The classification presented here is designed to
affected by possible ground-waterdischarge effects (primarily facilitateapreliminaryclassification ofwetlandson Mt. Desert
related to nutrient delivery), or whetherthey are relatively iso- Island without the need for new hydrologic data. To check the
lated from the ground-watersystem andtherefore more suscep- validity ofthis approach, a test was performed on 20 wetlands
tible to drought orotherclimate-change effects. on the island that have been studied by other investigators and
Wetlandscanbegroupedaccordingtomanyclassification have hydroperioddatacollectedovertwo field seasons in 2000
systems. The wetlands at Acadia National Park have been clas- and 2001 (Little, 2005).
sified by Calhoun and others (1994) forthe National Wetland
Inventory (NWI) using the system ofCowardin and others Wetland ClassificationSystems
(1979), which is based on plant communities, soils, and to a
HGM
lesserextent,hydrology. Recently classificationhasbeen
Although initially designed by the Corps ofEngineers for
usedas aconvenientway toorganize groups ofwetlands based HGM
use in wetlands permitting, the concept of classification
on three fundamental factors that influence how wetlands func- can also be applied to otheruses. The traditional HGM classifi-
tion: position in the landscape, dominant source ofwater, and
cation approach requires detailed surveying ofreference wet-
hydrodynamics(flowandfluctuationsinwaterlevelswithinthe lands that span the functional capacity from pristine to highly
wetland overtime) (Brinson, 1993; Cole and others, 1997; degraded wetlands in each category. Thus, a wetland whose
Shaffer and others, 1999). In other parts ofthe northeastern alteration issubjecttoregulation by theCorpsofEngineerscan
UnitedStates, hydrogeomorphicclasseshavebeen showntobe be evaluated with respect to these reference wetlands todeter-
significant organizing variables forcharacterizing wetland minehow wellitfunctionsin itsexistingconditioncomparedto
hydrology and have capturedecological differences that other how well it might function undera predetermined reference
classifications have missed (Cole and others, 1997). In particu- standard (Smith and others, 1995). Although this level of
lar,theclassificationaddressesthequestion,"Whyarewetlands detailed assessment could undoubtedly help the National Park
wet?". To date (2005), no comprehensive hydrogeomorphic Service to determine which wetlands should be monitored, the
classificationsystemforwetlandshasbeenpublishedforMaine costs forsuch an investigationare currently prohibitive. A sim-
or northern New England. plified version ofthe HGM concept also can be ofgreat use to
In 2003, the U.S. Geological Survey (USGS) and the the National Park Service to categorize and evaluate a large
National Park Service beganacooperative study toclassify the numberofwetlands in a short period oftime. Theevaluation is
wetlands on Mt. Desert Island, Maine. The study was designed intendedtodetermine the mostprobablesourceofwaterforthe
to assist park managers by classifying wetlands according to wetlands,sothatlikelyhydrologicthreatstothosewetlandscan
theirhydrologic functionanddegree ofsusceptibility tothreats be identified.
HGM
posed by degradation (potential and current) ofground-water The approach identifies wetlands that function sim-
aquifers on Mt. Desert Island. The first part ofthe study (this ilarly. Wetland function refers to the characteristic set ofactiv-
report) involved developing and testing a hydrogeomorphic itiesthattakeplace in wetlandecosystems,andmayrangefrom
classification scheme. Additional planned phases ofthe the very small (nitrogen and nutrient cycling on a microscopic
HGM
National Park Service study include implementing the level) to very large scales (maintaining ecological integrity in
classification for wetlands on Mt. Desert Island, anddesigning theareaasawhole).Wetlandsdonotallperformthe samefunc-
asystem toevaluatewetlandsusceptibility tocontamination by tions(Smithandothers, 1995). Slopewetlands,forexample,do
various hydrologic pathways (precipitation, ground water, or notabsorband filterfloodwatersasdomany riverine wetlands.
HGM
surface water), andsusceptibility tochangesin hydrology from The approach is based on three fundamental factors that
predictedfuturechangesinclimate.Aconceptualground-water influence how wetlands function in the landscape: geomorphic
flow model is planned as an aid to understanding the ground- setting,watersource,andwetlandhydrodynamics.Geomorphic
watersystem on the island, with particularregard to the loca- setting encompasses the geologic/geomorphic evolution ofthe
tions ofground-waterrecharge and discharge zones in relation wetland and its topographic position in the landscape. Water
to the location ofwetlands. sourcereferstotheimmediate, proximal sourcesofwatertothe
HGM
wetland. Hydrodynamics are usually also included in
classification, and referto thedirection and frequency ofwater
PurposeandScope movement in and out ofthe wetland (Smith and others, 1995).
In this classification, typical hydrodynamics are described for
Thisreportpresents awetlandclassification system based eachcombinationofgeomorphicsetting/watersourceidentified
on hydrogeomorphic criteria. It was designed to be applied to in the classification.
medium-sized (between 1 and 2 ha) and large freshwater wet- Because HGM classification is fundamentally based on
lands (more than about 2 ha (5 acres)) on Mt. Desert Island, hydrological segregation, it results in asegregation and organi-
HGM
Maine. The classification system is generalized and zationofwetlandsaccordingtodifferentfunctionsandbenefits.
shouldonlybeusedasascreeningtoolformonitoringpurposes. This makes HGM a good classification system to help in the
It is subject to revision, based on field observations. design ofa wetland monitoring plan, by providing managers
—
4 Using Hydrogeomorphic CriteriatoClassifyWetlandson Mt. Desert Island, Maine Approach, Classification System,and
Examples
with informationthatcanberelatedtothespecific functionand lizedtodate.Anothersystemforsegregatingwetlandsbasedon
benefits ofeach wetland to beconsidered for monitoring. hydrologicindiceswasdevelopedbyLentandothers(1997)for
The mostrecentclassification for wetlands on Mt. Desert wetlands with known waterbudgets. Their hydrologic indices
Islandwascompletedin 1992,andisbasedontheU.S.Fishand categorized wetlands by dominant source ofwater (ground
Wildlife Service's "Classification ofWetlands and Deepwater water,surface water, orprecipitation)andby thedominantsink
Habitats ofthe United States" (Cowardin and others, 1979). ofwater (evaportranspiration, surface water, orground water).
Wetlandsgreaterthan0.4ha(1 acre)weremappedforthatclas- The U.S. Fish andWildlife Service (USFWS) isdevelop-
sification (Calhoun and others, 1994). This classification is inganewclassificationsystem looselyorganizedaroundHGM
published on the National Wetland Inventory (NWI) maps (U. principles(RalphTiner,U.S. FishandWildlifeService, written
S. Fish and Wildlife Service, 1998). The NWI maps are avail- commun., 2002). This classification system, called "landscape-
able digitally as geographic information system (GIS) cover- level wetland assessment", is intended toprovide an additional
agesfromseveralpublicsources(forexample,theMaineOffice layerofinformation toexisting NWI maps. This system identi-
ofGIS, http://apollo.ogis.state.me.us/catalog/). The NWI clas- fies landscape position, water-flow regimes, and interactions
sification and delineation provide thegeographic coverage of with otherwaterbodies foreachclassifiedwetland. In termsof
thewetlandsshowninfigure 1. Arecent(2003)vegetationanal- waterflow, itis muchmore detailedthan traditional HGM clas-
ysisofAcadiaNational ParkandMt. Desert Island(interpreted sification.
from 1997 photography)conducted by the National Park Ser-
vice alsodelineated wetlands based on vegetation patterns
(Lubinski andothers, 2003). DescriptionofStudyArea
TheCowardinclassificationsystem(Cowardinandothers,
1979) is primarily vegetation- and soil-based, with less empha- Mt. DesertIsland,withanareaof285km2(110mi2),isthe
sispaid tothesourcesofwatermaintaining the wetlandecosys- largestislandontheAtlanticcoastofthe UnitedStatesnorthof
tem's function in the hydrology ofthe landscape. Understand- Cape Cod, Massachusetts (fig. 1). Its topography ranges from
ing sources ofwaterto the wetland is critical to being able to gentlyrollinghillswithslopesofaround5percenttomountains
identify factors that change how wet the wetland is ormay withslopesgreaterthan60percent. Rainfall isabout 145 cm/yr
become. The degree ofwatersaturation in turn is critical in (National Oceanic and Atmospheric Administration, 2002),
determining what vegetation the wetland can support, and its which is about 20cm more than othercoastal areas in Maine.
ecological function in the landscape. Ifthe sources oramounts ANPcovers more than 50percent ofthe island. The island is
ofwaterfeeding the wetland change, an ecological shift in the divided into four municipalities (the towns ofBar Harbor,
wetland can be expected, especially ifthe shift is perpetuated Mount Desert, Southwest Harbor, andTremont) (fig. 1) with a
overseveral years. HGM classification identifies the primary total year-round population of8,770 in 2000 (U. S. Bureau of
sources ofwaterforthe wetland in question, which leads to the Census, 2001). Summertime population is much higher, as
more informed decisions about threats to the wetland's ecolog- ANPreceives approximately 2.5 million visitors peryear.
ical function and integrity. Vegetation patterns forthe island were determined in a
Calhoun and others (1994) provide an excellent overview surveyoflow-altitude infraredaerialphotostakenin May 1997
ofthehydrologyandgeologichistoryofwetlandsonMt.Desert (Lubinski andothers, 2003). Wetlandscover6 to 10percent of
Island. Hydrologic processes and landscape position ofthe the island (depending on which data layer is used), and 1 1 per-
island's nontidal freshwater wetlands are discussed in relation centofANP(including areasofANPnoton Mt. DesertIsland)
toNovitski's (1982) classification ofWisconsin wetlands, (Calhoun and others, 1994). Ofthese, 32 percentare palustrine
which includes surface-water-depression, surface-water-slope, freshwaterwetlands (nonlacustrine, nonmarine wetlands).
ground-water-depression, and ground-water-slope wetlands. More than 75 percent ofthe Island is forested.
However, in the mapped classification ofMt. Desert Island's The bedrockgeology ofMt. Desert Island consists prima-
wetlands using the Cowardin system, most ofthis hydrologic rily ofgranitic intrusions in the central area ofthe island, sur-
information is not included, because Cowardin's hydrologic roundedbyazoneofcontactmetamorphism. Beyondthiszone,
variablesforfreshwaterwetlandsarequitegeneralized.Mostof whichextendstotheoceanonthenortheastandsoutheast,area
the nontidal freshwaterwetlands on Mt. Desert Island (not group ofmetamorphosed layered volcanic rocks to the south
countingthemanylargedeepwaterlakes)fall intothepalustrine (including some interbedded siltstones and slates); agabbro-
hydrologic system and their sources ofwaterare not further diorite band to the northwest and west; limited areas ofsilt-
delineated. stones and sandstones on the north and northeast side ofthe
A wetlandclassification system basedon hydrogeological island;andahighlydeformedschiston thenorthandwestsides
variablesforNewEnglandwasproposedby O'BrienandMotts ofthe island (Gilman and others, 1988). The fractures, which
(1980). Theirdetailed system incorporated geologic, hydro- allow limited amountsofground watertoaccumulate and flow
logic, and topographic factors, and stressed the importance of in the bedrock, provide waterto many wetlands in low-lying
thewetland'soverall interactionwiththelandscapein itsrolein areas ofthe island.
the hydrology ofan area. Proposed as a tool fordecision-mak- Discontinuous layers ofglacial and postglacial sediments
ing on watersupply issues, this system has not been widely uti- overlie the bedrock. Most ofthe higher mountains as well as