HGMandwetlandfunctionalassessmentSixdegreesofsepar

HGMandwetlandfunctionalassessment:Sixdegreesofseparationfromthedata?CharlesAndrewCole*PennStateUniversity,CenterforWatershedStewardship,227EastCalderWay,StateCollege,PA16801,USAReceived4February2005;receivedinrevisedform20June2005;accepted27June2005AbstractEcologistsroutinelyuserapidassessmentprotocolstotryanddetermineleveloffunctionforwetlands.IntheUnitedStates,oneofthemoreintensivelyusedapproachesisthehydrogeomorphic(HGM)approach.Usingthissystem,wetlandsareclassifiedbytheirlocation,thesourceofwater,andtheirhydrodynamics.Modelsarebuilttoattempttodeterminelevelsoffunction,butmodelsrelyalmostexclusivelyuponstructuralindicatorsthatmay,ormaynot,relateinanymeaningfulwaytofunction.InthispaperIexamineseveralmodelsfromPennsylvaniawhereaconsiderableamountofdataexistsforthesitesfromwhichthemodelsweredeveloped.Ishowthat,evenwithalargedataset,modelsstillrelyuponstructurewithatenuousconnectiontorealfunction.IthenexamineseveralothermodelsfromaroundtheUnitedStatesrelatedtohydrology,andassesstherelationshipofthemodelstoactualfunction.Suggestionsforchangeincludeslowingthepermitprocessdown,continuingtodeveloplargesetsofreferencewetlands,reducingtheuseofindiceswithinindices,anddevelopingaresearchagendathataddressestherelationshipsbetweenstructureandfunction.#2005ElsevierLtd.Allrightsreserved.Keywords:Functionalassessment;HGM;Hydrogeomorphic;Rapidassessment;Wetlands1.Introduction1.1.CleanwateractIntheUnitedStates,theenactmentoftheFederalWaterPollutionControlAct(hereinafterreferredtoastheCleanWaterAct)of1972begantheprocessofregulatingthedisposalofdredgedorfillmaterialsin‘‘watersoftheUnitedStates’’.TheintroductiontotheActreadsasfollows:‘‘TheobjectiveofthisActistorestoreandmaintainthechemical,physical,andbiologicalintegrityoftheNation’swaters.’’TheFederalWaterPollutionControlAct(asamendedthroughP.L.107-303,November27,2002)[33U.S.C.1251etseq.].Alldecisionsofaregulatorynaturewithrespecttowetlandsstemfromthatverysimplestatement.FromThisarticleisalsoavailableonlineat:(2006)485–493*Tel.:[phone];fax:[phone].E-mailaddress:[e-mail].1470-160X/$–seefrontmatter#2005ElsevierLtd.Allrightsreserved.doi:10.1016/j.ecolind.2005.06.004thatbroadlystatedobjectiveaverycomplexreg-ulatoryprogramhasarisenforthewatersoftheUnitedStates,onlysomeofwhicharewetlands.Section404oftheCleanWaterAct(CWA)isthesectionthathasbeenusedtodevelopaprogramdesignedtoregulatethedisposalofdredgedmaterialsorfillintowatersoftheU.S.AsmanywetlandsareconsideredtobewatersoftheU.S.,acomplexpermittingprogramhasbeendesignedunderSection404todealwithissuespertainingtoimpactstowetlandsfromdredgeandfillactivities.Earlypermitsunderthatprogramtypicallylookedforthereplacementofacreageona1:1basisforanywetlandslostduringadevelopmentactivity.However,theCWArefersto‘‘...biologicalintegri-ty...’’.Assuch,theU.S.EnvironmentalProtectionAgencyandtheU.S.ArmyCorpsofEngineers(thetwofederalagencieswithSection404responsibilities)agreedin1990thatwetlandfunctions,notmerelyacreage,wouldbetheunitsofwetlandmitigation(USEPAandUSACE,1990).Withthatagreementcametheneedforsomerapidmethodthatwouldassesswetlandfunction.1.2.RapidassessmentsAinsley(1994)describedtheroleofrapidwetlandfunctionalassessmentwithinthecontextoftheSection404regulatoryprogram.Hefeltthattheuseoffunctionalassessmentwasintegraltoimplementa-tionoftheSection404programandthatregulatorsneededtounderstandwetlandfunctioniftheyweretoproperlyimplementtheprogram.Heobservedthatthereweredeficienciesintheprogramwithoutsomeformalleveloffunctionalassessment.‘‘Thedeterminationofwhetheraprojectwillresultinsignificantdegradationisbaseduponbestprofessionaljudgementoftheprojectmanagerandotherresourceagenciesandtendstoplacemuchemphasisonlossofwildlifehabitat’’(Ainsley,1994;p.436).InthedecadesinceAinsley’s(1994)statement,therehavebeennumerousattemptstomeasurefunction,albeitindirectly,throughtheuseofindicators.However,functionitselfisnotsoreadilydefined,eventhoughtheNationalResearchCouncil(1995;p.34)definedfunctionas‘‘...allprocessesandmanifestationsofprocessesthatoccurinwetlands.’’Ifafunctionequatestoaprocessorarate,thentrulycalculatingafunctionrequiresmultiplemeasurementsthroughouttheyear(e.g.,forproduction,DilustroandDay,1997).Kentulaetal.(1992;p.7)suggestedusingindicators,orthosevariablesseenascloselyrelatedtoaparticularfunction,notingthat‘‘Measuresofwetlandstructure,e.g.,sitemorphologyorspeciespresent,arereadilyavailableandmoreoftenmeettherequirementsofexpediencyandeconomythandomeasuresoffunction.’’MeasurementoffunctioniscomplexandexpensiveandtheNRC(1995)itselfhaslistedseveralmeasurementsthatmightbeconsideredasindirectindicatorsofwetlandfunction.TheCorpsofEngineersbegantodevelopacomprehensiveclassificationandfunctionalassess-mentprotocolintheearly1990’sbaseduponhydrogeomorphic(HGM)principles.Brinson(1993a)showedthatclassifyingwetlandsbypositionwithinthelandscape,thesourceofwater,andhydrodynamicswasveryusefulinexplainingwetlandfunction.Functionalaspectsofseeminglydisparatewetlandtypescouldbeseentobesimilarwhe