Treatise on Geomorphology: Geomorphology of Human Disturbances, Climate Change, and Natural Hazards

301 Pages·2013·36.318 MB·English

by  Allan James, Carol Harden and John Clague (eds.)

13.1 Geomorphology of Human Disturbances, Climate Change, and Hazards
LA James, University of SouthCarolina, Columbia,SC,USA
CPHarden, University ofTennessee, Knoxville, TN, USA
JJ Clague,SimonFraser University, Burnaby,BC,Canada
r2013ElsevierInc.Allrightsreserved.
13.1.1 Introduction 2
13.1.2 Background 2
13.1.2.1 Early Concepts ofPopulation,Technology, and EnvironmentalImpacts 3
13.1.2.2 Structure oftheVolume 4
13.1.3 Human Impacts onGeomorphic Systems 4
13.1.3.1 Anthropogenic Geomorphology 4
13.1.3.2 Scales ofSpace andTime 5
13.1.4 Impacts ofClimateandClimateChange onGeomorphicSystems 5
13.1.4.1 ClimaticGeomorphology 5
13.1.4.2 Impacts ofClimate Change onGeomorphicSystems 6
13.1.4.3 The HumanRolein Early ClimateWarming 6
13.1.5 Geomorphic Hazards 7
13.1.6 NuclearDetonations asa Geomorphic Agent 8
13.1.7 Restoration, Stabilization, Rehabilitation, andManagement 9
13.1.8 Conclusion 10
References 10
Glossary vegetation,orantecedentconditions(Brunsdenand
Anthropogenicgeomorphology Asystematicsubfieldof Thornes,1979).Sensitivitytoerosionvariesspatiallyand
geomorphologyconcernedwiththestudyoflandforms mayexplaincomplexpatternsofdegradationtoregionally
createdormodifiedbyhumanactivity.Human-induced uniformclimatechangeorhumanalterations.
changesingeomorphicprocesses,processrates,and Naturalhazards Thethreatofanaturallyoccurringevent
landscapesensitivitytochangearealsoofconcern(Szabo´, withadverseeffectsonsocietyortheenvironment.They
2010). maybemeteorologically,geologically,orgeomorphically
Climatechange Astatisticallysignificantdeviationfrom inducedandincludestorms,floods,tsunamis,earthquakes,
meanclimateconditionspersistingforaperiodofdecades volcaniceruptions,sinkholecollapse,anddebrisflows.
orlonger.Climateparametersthatmaychangeinclude Sustainability Theabilityofprocessesoractivitiestobe
precipitation,airtemperature,watertemperature,humidity, maintainedoverextendedperiodsoftime‘‘ywithout
andwindspeed,direction,anddurationofevents.Changes compromisingtheabilityoffuturegenerationstomeettheir
intheseparametersmaybeintheformofmean,maximum, needs’’(WorldCommissiononEnvironmentand
orminimumvalues,ormeasuresofvariabilitysuchas Development(WECD),1987).Theconceptmaybeapplied
standarddeviationorseasonality,andmayoccuratspatial todevelopment,resourceuse,orenvironmental
scalesrangingfrommicrotoglobalclimates. managementandimpliesacommitmenttothestewardship
Landscapesensitivity Thevulnerabilityoflandscapesto ofnaturalsystems.Itbeganasasocialandphilosophical
changeinresponsetoenvironmentalforces.Sensitivitymay construct,butwaslateradoptedbythescientific
varywiththecharacteristicsofgeologicstructures,soils, communityassustainabilityscience(Katesetal.,2001).
Abstract
Anthropogenic geomorphology is an emerging systematic field that overlaps with climate change and natural hazards
research.Collectively,thesethreetopicsformahumandimensionofgeomorphologythatshouldgainincreasingprom-
inence in the twenty-first century with mounting concerns over the ability to reconcile population growth, dwindling
James, L.A., Harden, C.P., Clague, J.J., 2013. Geomorphology of human
disturbances,climatechange,andhazards.In:Shroder,J.(EditorinChief),
James,L.A.,Harden,C.P.,Clague,J.J.(Eds.),TreatiseonGeomorphology.
AcademicPress,SanDiego,CA,vol.13,GeomorphologyofHuman
Disturbances,ClimateChange,andNaturalHazards,pp.1–13.
TreatiseonGeomorphology,Volume13 http://dx.doi.org/10.1016/B978-0-12-374739-6.00339-0 1
2 Geomorphology ofHumanDisturbances, ClimateChange,andHazards
resources,globalenvironmentalchange,climatewarming,publicsafety,andsustainabilitywiththestabilityofgeomorphic
systems.Humanscreatelandformsdirectlyandindirectlybyalteringgeomorphicprocessratesandlandscapesensitivities.
Climatechangemayalsoalterprocessratesandsensitivities,orshiftstodifferentclimateregimesmayresultincomplete
changesinlandformprocesses.
13.1.1 Introduction several syntheses and reviews from writings on these topics
and show how geomorphology can benefit from an anthro-
In this day of increasing concern over global change and pogeomorphicviewpoint,andhowglobalchangeandhazards
humanimpactsontheenvironment,itisfittingthatavolume research can benefit from a geomorphic perspective. Chapters
of the Treatise on Geomorphology is dedicated to disturb- in this volume are grouped into three primary sections: (1)
ances, change, and vulnerability. Chapters or sections on the humanimpactsongeomorphicsystems;(2)impactsofclimate
subjectsofhumanagency,climatechange,andhazardsappear changeongeomorphicsystems;and(3)naturalhazards.
elsewhere in the Treatise within the context of a particular
geomorphicsystemorsetofmethodologies,butthisvolume
is focused on the human dimensions of geomorphology. 13.1.2 Background
Forgeomorphologytomakeasubstantialcontributiontothe
scienceofglobalenvironmentalandclimatechange,andtobe
Interrelationships among human activities, climate, and nat-
relevant to debates about the validity of those changes and
uralhazardsmaytakemanyforms,ofwhichdirectresponses
policies to mitigate them, geomorphic research will need to
of landforms to human activities are but one aspect
reach beyond compartmentalized treatments of these critical
(Figure 1). Human activities have indirect influences on
topicsandapproachtheminanintegratedmanner.Thesyn-
landforms through cascades, biological systems, and natural
theses in this volume hopefully will help lead to recognition
hazards. Cascades in the movement and storage of mass
of general characteristics and theories that are common to
or energy commonly link human activities to landform
multiplegeomorphicsystems.
responses, so that geomorphic responses may be propagated
This volume examines general concepts of anthropogenic
indirectlyandmaybedelayed,mitigated,orextendedintime
geomorphology, climatic geomorphology, impacts of climate
and space. Similarly, alterations to geomorphically relevant
change, and geomorphic hazards. Human impacts on geo-
biological systems, such as vegetative cover that inhibits ero-
morphology and geomorphic effects on humans through
sion,mayresultinindirectlinkagesbetweenhumanactivities
natural hazards clearly involve interactions between humans
and landform responses. For example, grazing animals may
and geomorphic systems. The human dimension of geo-
increase sensitivityof a landscape to erosion byreducing the
morphology is a vital area of research that has been largely
protective cover of vegetation. Thus, the extirpation of wild
neglected beyond the localandsubregional scale.Global en-
herbivores may reduce erosion, or the introduction of do-
vironmental change and climate change have become topics
mesticatedgrazinganimalsmayincreaseerosion.Conversely,
of great concern owing to recent realizations about the per-
landformresponsesmayhaveapositiveornegativefeedback
vasiveimpactsofsocietyatthisscale.Muchofthescholarship
on human activities. For instance, agriculturally induced
on environmental and climatic change, however, has been
centered on interactions with ecosystems, agrosystems, and
hydrologic systems (Slaymaker et al., 2009). Much less has
bageeenntsworirtttehneaibmopuatctthseoefffcelcimtivaetneecshsaonfgheuomnangesoassygsteeommso.rphic a t e a n d c l i m a t e c h
moSrptuhdicy siysstaelmsosnteoedbeudildofucpliomnateea-crlhyancgoenciempptsacotsf oclnimgaetoic- C l i m Human activities a n g e
geomorphology and improve knowledge of local-scale land-
scapesensitivitytoglobal-scalechanges.Forexample,itshould
bepossibletoanticipateresponsesofsoilerosionandsediment
yieldsatthehillslopescaletochangesinprecipitationregimes
andvegetationcoveratthescaleofgeneralcirculationmodels. Cascades Biological Natural
systems hazards
The effects of natural hazards on society also have not been
adequately addressed from a geomorphic perspective. Geo-
morphic hazards are a human dimension of geomorphology Social
in which physical systems drive change, and humans are the systems
responsevariable.Humansinfluencenaturalhazards,however,
and social vulnerability to hazards is clearly dependant on
Landform
humanbehavior,sotherelationshipbetweenindependentand
responses
dependentvariablescanbereversed.Together,humanimpacts
on geomorphic forms and processes, climate change, and
geomorphichazardsformatrilogyofconcernsthatwillneeda Figure1 Systemsdiagramforinterrelationshipsbetweenhuman
great deal of study and a better understanding in the twenty- activitiesandlandformresponses.Seetextforexplanationand
firstcentury.Thecentralgoalofthisvolumeistopulltogether discussion.
Geomorphologyof HumanDisturbances,Climate Change,andHazards 3
erosion that causes valley bottom aggradation and increased
flooding may reduce human activity rates or may push agri-
culture up onto highly erosive hillslopes, causing accelerated
erosion. Natural hazards may have a direct geomorphic im-
pact on landforms through erosion and sedimentation. Nat-
uralhazardsmayalsohaveanindirecteffectonlandformsby
altering social systems, such as local economic or political
stability and infrastructure that govern human rates of geo-
morphic activities. For example, the destruction of infra-
structure such as irrigation works may result in decreased
agricultural activity and reduced erosion and sedimentation,
or the destruction may result in neglect of erosion-control
measures and increased erosion and sedimentation. In add-
Figure2 DuststormemanatingfromtheBodeleDepressiontoward
ition,geomorphiceventssuchasdeflation,floods,andbeach
LakeChadinSaharanAfrica.Source:NASAEarthObservatory
erosion may be influenced by human activities. Rates and Aquasatelliteimage,2January2007.NASAVisibleEarth:http://
intensities of human activities are influenced by cultural fac- visibleearth.nasa.gov/
tors of the social system, especially the level of technology
employed, and population dynamics, such as population
are closely interconnected through transfers of energy, water,
growth and migrations. Social systems mayrespond to land-
sediment,anddiversechemicalcompounds.Tightcouplingof
form changes or natural hazards, resulting in complex inter-
systemsimpliesthatchangeinonesystemmaybepropagated
actions between physical and human systems. Agricultural
to other systems and result in collective local-scale changes
destabilization of soils that leads to catastrophic deflation,
that have cumulative effects at the global scale. Growing
regional economic decline, and out-migration is an example
awareness of this interconnectivity has been accompanied by
of this dynamic. Climate and climate changes may have a
increasing recognition that soils and biota influence climate
pervasive influence on human activities, landform responses
systems, not simply the converse (Claussen, 2004; Steffen
to those activities, the sensitivity of cascading and biological
et al., 2004). For example, Avissar and Liu (1996) simulated
systems to change, natural hazards, and social systems. In
spatialpatternsofprecipitationthatstronglyreflectedpatterns
addition, climate change, itself, is a response to human
of vegetation and bare soil. Hydrologic systems also play a
activities,sotheoverarchingeffectsofclimatecanbeviewedas
dualroleasindependentanddependentvariableswithclimate
partofthesystemofanthropogenicgeomorphology.
intheEarthsystem.Thisrealizationisexpandingtheemphasis
Geomorphic responses to climate change during the
of hydrology from flood control, drought, erosion, sedimen-
Holocene have commonly been difficult to distinguish from
tation, and eutrophication to integrated water resources
human impacts. Anthropogenic and climatic disturbances
managementandaglobalsynthesisbasedongeospatialana-
generallyinvolvecomplexinteractionsandfeedbacksbetween
lyses (Meybeck and Vo¨ro¨smarty, 2004). Aeolian processes
culturallyand physically induced processes.Attemptsto isol-
also demonstrate high spatial connectivity across continents
ateanthropogenicfromnatural changeis notalwaysfeasible
(Figure 2). For example, satellite remote sensing has docu-
ordesirable.Forexample,naturalclimatechangemayincrease
mentedsedimenttransportfromtheSaharaDesertinAfricato
landscape sensitivity and lower thresholds of response to
South America, where it provides a flux of nutrients to the
disturbance(Knox,2001).Thus,itisoftenpreferabletostudy
Amazonrainforest(Korenetal.,2006),fromJapantoNorth
integratedsystemsasawhole.
America (Uno et al., 2001), and between China and Japan
Given the allied topics of hazards and anthropogenic
(Iino et al., 2004). A map of global source areas for dust is
changeaddressedinthisvolume,thefocusisonlateHolocene
presented by Lancaster (see Chapter 13.9, Figure 3). These
andhistoricaltimescales.ReconstructingpastchangesinTer-
aeolian events may also have feedbacks to large-scale atmos-
tiaryorPleistoceneclimatesisnotanobjectiveexceptinsofar
pheric processes such as suppression of cyclogenesis (Evan
asearlyclimatesreflectprocessesthatmayberelevanttorecent
et al., 2006). Glaciation propagates the effects of climate
orfuturechanges.Considerationofpaleo-climatespriortothe
changethrough time and space. Downvalleychangesare im-
HoloceneisprovidedinothervolumesoftheTreatise.Changes
posed bymeltwater, outwash, and cold-air drainage, whereas
in climate and landscapes were much more rapid during
large-scale changes to atmospheric circulation may be gener-
the Quaternary than previously supposed, as evidenced by
ated by ice sheets that induce cold-cored high-pressure con-
GreenlandandAntarcticicecoredata(Dansgaardetal.,1993;
ditions over large areas. Rapid changes in global ice volumes
Petit et al., 1999). Modern effects of climate warming and
andthegeomorphiceffectsofdeglaciationaredocumentedby
anthropogenicchangehave increased these rates. Biodiversity
Haeberlietal.(seeChapter13.10).
hasshownmajorvariabilitythroughgeologictimeandisnow
decreasingataratethatrivalsmajorextinctioneventsinEarth
history (Wilson, 1992). Present rates of climate and anthro-
13.1.2.1 Early ConceptsofPopulation, Technology, and
pogenicchangecouldchallengecommonassumptionsofdy-
Environmental Impacts
namicequilibriaingeomorphicsystems.
Global anthropogenic changesare not confinedto the at- Exponentialgrowthintheglobalhumanpopulationisoften
mospheric and biologic spheres, but extend to geomorphic citedasafactorinfluencingrapidrates oflateHoloceneen-
systemsthroughstrongsysteminterconnectivity.Earthsystems vironmental change.Inadditiontoacceleratinggeomorphic
4 Geomorphology ofHumanDisturbances, ClimateChange,andHazards
change, the growing population also increases the vulner- geomorphology(seeChapter13.8).Itisfollowedbychapters
ability of society to natural hazards. Urbanization of lands on responses of aeolian, glacial, and periglacial systems to
that are susceptible to floods, tsunamis, volcanic eruptions, climate change, respectively (see Chapters 13.9, 13.10, and
and the likeput large numbersof people at risk andreduce 13.11).Thefinalsectionofthisvolumeconsistsofsixchapters
the resiliencyof society to catastrophic events. The relation- thatexaminemajorcatastrophes,tsunamis,volcanism,flood-
ship between population and environmental impacts has ing, wild fires/debris flows, and effects of climate change on
engaged philosophers from the time of Herodotus and slopestability, respectively (seeChapters13.12, 13.13, 13.14,
Seneca, toMalthusandDarwin, to Commonerand Erhlich, 13.16, and 13.17). In addition, a few brief discussions are
and to the present. During theenvironmental movement of providedin thischapterto broadenthe scopeof humanim-
the 1970s, a scientific debate emerged over the theoretical pactscoveredelsewhereinthevolume.
causality of global environmental impacts. Although these
ideaswereconcernedwithbroadenvironmentalimpacts,for
example,toxicity,waterquality,andecologicalsystems,they
13.1.3 Human Impacts on Geomorphic Systems
applyinaverygeneral, qualitative senseto impactson geo-
morphic systems. During these debates, the relative import-
Interest and focus on how humans change geomorphic sys-
ance of technology and population emerged as a central
tems accelerated in the late twentieth century as concerns
focus. In contrast with Commoner, Ehrlich held that popu-
mounted about global environmental change and growing
lation was the primary driver of environmental impacts.
populationpressures.Anewsubdisciplineofgeomorphology
A series of theorems presented by Ehrlich and Holdren
isemergingthatoperatesonavarietyoftemporalandspatial
(1971) ultimately led to a simple, iconic conceptual rela-
scales. The nature, extent, and timing of human impacts on
tionship, IPAT, that is commonly used to express environ-
geomorphic systems are not merely academic questions, but
mental impacts in terms of population, affluence, and
may have serious physical and social implications. For ex-
technology(HoldrenandEhrlich,1974):
ample, soil loss is a geomorphic consequence of human ac-
I¼PAT ½1(cid:2) tivities that is highly relevant to feeding global populations.
Most (99%) of the global food supply is derived from the
land; less than 1% comes from oceans and aquatic habitats
where I is environmental impact, P is population, A is con-
(Pimenteletal.,1994).Sustainabilityofterrestrialagriculture
sumption or affluence, and T is technology. The loadings for
is of essential importance, therefore, as global populations
Tcan begreater thanorlessthanone sothattechnologycan
increasefromthepresent6.9billiontoaprojected9.3billion
increaseordecreaseimpacts.AlthoughcritiquesofMalthusian
by the year 2050 (United Nations, 2011). Yet, soil erosion is
pessimismevokedthepositiveaspectsoftechnologicalinnov-
reducing arable lands at an alarming rate when considered
ations, Commoner (1972) concluded thatmost technological
againsttherateofpedogenesis.Pimenteletal.(1995)estimate
developmentsassociatedwithgrowthoftheUSeconomysince
that almost one-third of the global soil cropland was lost to
1946createdsubstantiallygreaterenvironmentalimpactsthan
erosionbetween1950and1995.
thetechnologiesthattheyreplaced.Thisviewpointissupported
by human-induced geomorphic changes in the form of earth
movementbyminingandroadbuildingthathaveproliferated
13.1.3.1 AnthropogenicGeomorphology
inthepastcentury(seeChapter13.6).Itisalsocorroboratedby
thepotentialuseofthermonucleartechnologyforgeomorphic Study of the effects of human activities on geomorphic sys-
changeasdescribedinthesectiononProjectPlowshareatthe temsisanemergingbranchofgeomorphologythatfocuseson
end of this chapter. The IPAT approach to assessing environ- humans as agents of change. Most systematic branches of
mental impacts has primarily been applied to global-scale geomorphology are named by the agents of change; that is
problemsandisdifficulttoapplytosmallerscalesofspaceand studiesoftheactionofrivers,glaciers,andwindaretherealms
time(Steffenetal.,2004). of fluvial, glacial, and aeolian geomorphology, respectively.
Anthropogenic geomorphology includes the study of surface
landforms created by humans (Szabo´, 2010), for example,
13.1.2.2 Structureof theVolume
open-pit mines, artificial levees, jetties, and groins. Anthro-
Thefirstsectionofthisvolumeisconcernedwiththeimpacts pogenic geomorphology is a systematicbranch of the discip-
of human activities on geomorphic systems, examined from line in which humans are the agents of change. Just as the
both a physicalandhistorical(stratigraphic) perspective. The processesandlandformsofothersystematicareascommonly
firstthreechaptersexamineimpactsoflanduseandvegetation overlap (e.g., coastal and aeolian), so human-induced influ-
clearance on watersheds and river channels at a variety of encesoverlapwithothersystematicprocessesandlandforms.
scales of space and time ranging from small watersheds to Several studies have been devoted to anthropogenic geo-
continents and from the Neolithic to present (see Chapters morphology for particular subdisciplines – fluvial geo-
13.2,13.3,and13.4).Thenextthreechapterscovertheeffects morphology (Brierley and Stankoviansky, 2003; Batalla and
of grazing, mining, and dams and reservoirs on geomorphic Garcia,2005; Syvitski etal., 2005;James andMarcus,2006),
systems,respectively(seeChapters13.5,13.6,and13.7).Four coastal geomorphology (Walker, 1988; Nordstrom, 2000;
chapters in the second section of this volume examine the Stutz and Pilkey, 2005), hillslope geomorphology (Walling
effectsofclimateandclimatechangeongeomorphicsystems. and Probst, 1997), aeolian geomorphology (Gill, 1996),
The first examines the long tradition of climatic and climatic geomorphology (Wolman and Gerson, 1978;
Geomorphologyof HumanDisturbances,Climate Change,andHazards 5
Montgomeryetal.,2001;Vandenberghe,2003).Otherstudies 13.1.3.2 Scalesof SpaceandTime
have covered the broader topic of human impacts on geo-
Human activities have long had an effect on environmental
morphicsystems(Slaymakeretal.,2009;Szabo´,2010).
systems at a local scale, and many studies have documented
Anthropogenic geomorphology is also concerned with
humanimpactsonisolatedlandformsorspatiallyconstrained
landforms and processes that result indirectly from human
systems such as individual hillslopes or river channels. Until
processes and alterations to natural rates of change (Szabo´,
the modern era, however, human impacts were considered
2010). Thus, where deforestation has accelerated erosion,
relatively ineffective at the regional or global scale, and few
rapidsedimentationdownstreammayresultintheformation
geomorphic studies considered human impacts at a broad
ofalluvialfansanddeltasthatare,inpartorwholly,anthro-
scale.Understandingglobalandclimatechangeinthemodern
pogenic landforms. As demonstrated in this volume, human
context, however, calls for consideration of anthropogenic
activities have direct or indirect impacts on hillslope, fluvial,
changestoEarthsystemsatalargergeographicscalethanhas
glacial, periglacial, aeolian, and coastal systems (Table 1).
commonlybeenaddressedbypastgeomorphicstudies.Given
Human activities may result in global-scale changes that in-
scale-linkage problems in which larger systems require a
fluence such a wide variety of landforms that the breadth of
longer time perspective, a shift toward global spatial scales
theirimpactswouldbeunderestimatediftheirrepresentation
may also require a longer temporal perspective (Schumm,
wasconfinedtoasinglesystem(Szabo´,2010).
2005;Slaymakeretal.,2009;seeChapter9.37).
Human-induced geomorphic changes accelerated during
A similar conclusion about the need for an historical per-
thelateHolocene.Thecurrentgeologictimeintervalhasbeen
spective may be reached from a different logic based on
referred toas theAnthropocene,adistinct butinformaltime
questions of regional- or continental-scale impacts of human
interval distinguished by major human impacts on geologic
activities. The common need to identify undisturbed geo-
processes (Crutzen and Stoermer, 2000). Formal inclusion
morphic conditions calls for recognition of early human
of the Anthropocene as an epoch of the geologic time scale
changesandthegeomorphic effectivenessof early humanac-
has been considered by the Stratigraphy Commission of
tivities. These inquiries raise questions of what is a ‘natural’
the Geological Society of London (Zalasiewicz et al., 2008).
geomorphicsystem.Thisquestionhasbeenexploredinsome
Potential criteria for defining the onset of the Anthropocene
detail for fluvial systemsbecause many regulatory and design
include the onset of increased CO in ice cores, climate
2 proceduresarepredicatedontheneedtoidentifyundisturbed
change, decreased biodiversity, the industrial revolution, and
reaches of rivers. Subsequent studies have concluded that an-
thepresenceofradionuclidesfromatomicbombtestinginthe
thropogenic changes to rivers have been so extensive that it
1960s. Most of the early criteria were gradual and time-
may be difficult to locate an undisturbed river (Graf, 1996;
transgressive, which precludes a precise designation of the
Wohl, 2001; James and Marcus, 2006; Newson and Large,
onset of the epoch. Some criteria, such as testing nuclear
2006; Wohl and Merritts, 2007; Fryirs and Brierley, 2009). In
weapons,arebasedoneventsthatoccurredwellafterextensive
fact, many fundamental fluvial theories were based on river
anthropogenicchangeshadbegun.Difficultiesinidentifyinga
systemsthathavebeensubstantiallyalteredbydeephistorical
specific time to characterize multiple changes that are time
sedimentation(Montgomery,2008;WalterandMerritts,2008).
transgressive are not unique to the Anthropocene and are
Thequestionofwhatisnaturalshouldberaisedinstudiesof
problematic to most existing geologic time divisions. It may
other landform systems where sediment budgets governing
sufficesimplytoidentifyaspecificdate,suchas1800,forthe
landform processes may have been substantially altered by
onsetoftheepoch(Zalasiewiczetal.,2008).
humanactivitiesandlandformsareproductsoftheseactivities.
13.1.4 Impacts of Climate and Climate Change on
Geomorphic Systems
Table1 Examplesofanthropogeomorphicchanges
Thesecondsectionofthisvolumehastwomainfoci:areview
System Anthropogenic Geomorphicresponse
changes ofclimaticgeomorphologyandsynthesesofgeomorphicim-
pacts of climate change in three systematic areas of geo-
Rivers Damming;bankand Sedimentation;de- morphology that are defined largely by climate: aeolian,
bedarmoring; position;flow glacial,andperiglacialsystems.
river-bedmining frequencies;roughness
changes
Coasts Dredging;armoring; Beacherosion;sediment 13.1.4.1 ClimaticGeomorphology
sea-levelrise redistribution
Hillslopes Deforestation,plow- Rills,gullies The first chapter in this section reviews the long history and
ing,roadcuts diverse concepts of climatic geomorphology, which has deep
Groundwater Mining Subsidence roots in thediscipline of geomorphology (see Chapter13.8).
Glacial Globalwarming Icemarginretreat Thebirthoftheconceptthatspecificmorphogeneticfeatures
Periglacial Roadembankments; Permafrostdegradation
areassociatedwithclimaticallydrivenprocessescanbetraced
globalwarming
to the glacial theory advanced by Louis Aggasiz (Derbyshire,
Arid&Aeolian Vegetationchange; Deflationanddeposition
1973). During the mid-twentieth century, this approach
vehiculartraffic
largelyfocusedontheidentificationofmorphogeneticzones,
6 Geomorphology ofHumanDisturbances, ClimateChange,andHazards
morpho-climatic regions, and the reconstruction of paleocli- climateregions.Thechapteronaeolianprocessesreviewsthe
mates from morphologic forms (Beckinsale and Chorley, impactsofclimatechangeindrylands,whichcoverB50%of
1991). Critiques of these methods arose from the lack of the land surface of Earth (see Chapter 13.9). Dune re-
unique linkages between climatic processes and form (equi- activation, generation of dust, influxes of nutrients to oceans
finality),poor-qualityclimatedata,interveningfactorssuchas anddistantlands,andhumanhealthimplicationsarecovered
geologic structure, and climate change. Climate change was with an emphasis on decadal time scales. Haeberli et al. (see
generally not a primary concern of early climatic geomorph- Chapter13.10)describethehistoryandrecentdevelopments
ology,becausethefrequencyanddegreeofQuaternaryclimate inglobalglacialmonitoringthatdocumentglacialretreatand
changes were not fully understood and because climate an acceleration of ice-mass loss over past decades. Impli-
changeintroducespolygeneticlandformsthatposesubstantial cations include effects on sea-level rise, seasonality of runoff
difficultiestotheidentificationofmorpho-climaticregions. andwaterresources,creation ofnew lakes,destabilizationof
Duringthelatetwentiethcentury,climaticgeomorphology deglaciatedslopes,andincreasedsedimentdeliverytostreams.
tendedtoevolveintospecializedsubfields,inwhichclimateis The increasing capabilities of Light Detection and Ranging
a defining element. The emergence of systematic subfields of (LiDAR)altimetrycombinedwiththedifferencingofgridded
tropical,glacial,periglacial,andaeoliangeomorphologyledto digital elevation models (DEMs) (James et al., 2012) are
less emphasis on the recognition of global-scale regions or producinganewgenerationofmonitoringandmorphometric
zones. Certain climates and processes werepresumed as pre- analyses that will lead to detailed glacial monitoring at the
conditions for membership to a given system (e.g., glacial scale of entire mountain ranges. The chapter on periglacial
geomorphology), which led to fewer comparisons between landscapesreviewsthenatureofclimate-changeimpactsinan
diverse climatic regions or process regimes. Nevertheless, environment that is highly susceptible to regional warming
identification and mapping of morphological evidence from andwilllikelyexperiencethegreatestdegreeofwarming(see
paleo-landforms, combined with radiometric dating, con- Chapter 13.11). These landscapes will likely experience ther-
tinuestobeaviablemeansofdocumentingtheformerextent mokarst and ice-wedge degradation, hillslope instability, and
andintensityofpastclimates.Theemphasishasshiftedfrom substantialerosion.Anestimated25%oftheEarth’ssurfaceis
identifying morpho-climatic zones to recognizing climate underlain by permafrost, so the release of CO gases by
2
change and reconstructing climate histories from landforms thawing is a serious concern. In addition to these three
and stratigraphic evidence. Knowledge of climate change chapters, chapters in other volumes of the Treatise are con-
withintheindividualclimaticsubfieldshasprogressedgreatly cerned with the effects of climate change; for example, the
as Quaternarygeomorphologistsdevelopeddetailed histories effectsofclimatechangeonrivers(seeChapter9.40).
and concepts of evolving process regimes within certain re- An impact of climate warming that has widespread geo-
gions.ExamplesofQuaternarychangestudiesareprovidedin morphicimplicationsistheon-goingriseinlevelsoftheglobal
chaptersinothervolumesofthisTreatise. oceans.Linkingglobalsea-levelbudgetstoenergybudgetsisan
on-going area of research that is essential to calibrating simu-
lationsofclimatechangeasscenariosofchangestoatmospheric
13.1.4.2 Impacts ofClimateChange onGeomorphic
chemistry (Church et al., 2011). From 1961 to 2003, global
Systems
mean sea levels rose B1.8mmyr(cid:3)1, whereas after 1993 they
Towardtheendofthetwentiethcentury,influencesofclimate roseatahigherrateofB3.1mmyr(cid:3)1(IPCC,2007).Mostofthe
change became a topic of great importance. Global warming rise since 1993 (1mmyr(cid:3)1 or 57%) has been attributed to
due to increased atmospheric greenhouse gases is causing thermal expansion of sea water, whereas glacial and ice cap
majorgeomorphicchangesassealevelsrise,glaciersmelt,and meltingwascreditedforonly0.5mmyr(cid:3)1(28%),andmelting
regional patterns in temperature and precipitation shift. Al- ofpolarice0.27mmyr(cid:3)1(15%)(IPCC,2007).Recentestimates
thoughdebatecontinuesabouttherelativeimportanceofthe ofsealevelrisefrom1972to2008indicateatotal1.8mmyr(cid:3)1
role of humans in climate warming, there is no doubt that rate with contributions of thermal expansion only 0.870.1
anthropogenicreleasesofCO haveincreased,sothequestion mmyr(cid:3)1, and melting of glaciers and ice caps contributing
2
is not whether humans have contributed to climate change, 0.7mmyr(cid:3)1 (Church et al., 2011). Mining of groundwater
but how much that they have done so. Climatic warming, produced a surplus of water that offset all but 0.1mmyr(cid:3)1 of
therefore, represents anindirect response to human activities waterstoredinreservoirsandlosttooceanicrecharge.Iftheice
that has extensive geomorphic implications. Within the field massesofGreenlandandAntarcticaweretomeltcompletely,sea
of geomorphology, interest in climate change took place levelswouldriseB64m(Bamberetal.,2001;Lytheetal.,2001;
largelywithintheframeworkofspecificgeomorphicsystems, IPCC,2007).Glacierandicecapmeltingratesincreasedinthe
such as glacial, fluvial, or soils geomorphology. A systematic late 1990s (Church et al., 2001, 2011) and this could increase
coverageofallgeomorphicsystemsgoesbeyondthescopeof ratesofgeomorphicchangeincoastalenvironments.
this volume, but by considering climate change in a variety
ofregimes,thisvolumeseekstoelucidatetheimplicationsof
atmosphericprocessesthatshiftfromoneregimetoanother.
13.1.4.3 TheHuman RoleinEarly ClimateWarming
From this broad perspective, climate can be seen as a geo-
morphicdisturbancefactor,notsimplyastaticdeterminantof Itwaslongheldthathumanshadlittleeffectonglobalclimate
regionalgeographicpatterns. (Thornthwaite, 1956), but this changed rapidly with the
Threechapters inthisvolumeexamine theimpactsofcli- realizationthatconcentrationsofgreenhousegasesinEarth’s
mate change on geomorphic systems associated with specific atmospherewererising(Plass,1956).Theeffectsofprehistoric
Geomorphologyof HumanDisturbances,Climate Change,andHazards 7
and preindustrial anthropogenic land use and land cover on later adapted and combined with annual precipitation vari-
globalclimatearecurrentlythesubjectofalivelydebate.Ithas ability for use with the Universal Soil Loss Equation (Arnol-
beenarguedthatmodernglobalwarmingcanbetracedback dus, 1978). A modeling approach based on geographic
toprehistoricdeforestationbyburningandlandclearancein informationsystem(GIS)analysiswasusedbyAsselmanetal.
the early Holocene that released enough CO to initiate a (2003)tosimulatethecombinedeffectsofclimatechangeand
2
global climate response (Ruddiman, 2003, 2007). Through land use on fine sediment production, transport, and de-
numerous Quaternary glacial advances and retreats, inter- position on floodplains in the Rhine Basin. They concluded
glacial warm periods tended to begin with high levels of that sediment production will increase in the Alps and de-
atmospheric carbon dioxide and methane that declined after creasedownstreaminGermany,producinganoverallincrease
interglacialwarmingbegan,followedbycoolingandareturn in erosion of B12% basin-wide with negligible changes to
to glacial climatic conditions. The Holocene, however, has sediment loads downstream in middle reaches, and an in-
beenquitedifferent.Greenhousegaseswereinitiallyhighand creaseinerosionofB13%intheRhineDelta.Although the
then declined in the early Holocene in keeping with most magnitude and frequency of floods is expected to increase,
interglacial periods, but CO concentrations began to rise floodplain deposition is expected to decrease owing to re-
2
approximately 8000 years ago and methane concentrations duced sediment loads during moderate floods with high
began to rise around 5000 years ago (Ruddiman, 2007). A floodplaintrapefficiencies.
numberofstudieshavedemonstratedthesensitivityofglobal Carbon-balance studies should consider not only the
climate to Holocene trends in atmospheric CO and CH contemporary cycling of carbon within the biomass but also
2 4
(methane) concentrations (Ruddiman, 2004; Vavrus et al., the long-term cycling of soil organic carbon (SOC). Re-
2008). Deforestation may have led to CO increases in the ductionsinSOCarealsorelevanttogeomorphologythrough
2
atmosphere, and the introduction of large populations of relationships between organic matter and soil erodibility.
grazinganimalsandriceagriculturemayhaveincreasedCH Studies of relatively recent changes in SOC have concluded
4
emissionstotheatmosphere(RuddimanandEllis,2009).This that substantial releases of SOC have accompanied deforest-
sensitivity has been demonstrated by recent paleoecological ationandthatmuchofthischangeisirreversibleoverdecadal
data suggesting that reforestation after the collapse of in- or centennial time scales. For example, Don et al. (2010)
digenouspopulationsinNeotropicalLatinAmericafollowing examined 385 studies of SOC in tropical forests and found
European contact wassufficient to perturb the global carbon thatconversionofprimaryforesttocroplandresultedinSOC
cycle and climate system and to contribute to Little Ice Age lossesontheorderof (cid:3)25%andconversionstograsslandon
cooling(NevleandBird,2008;Dulletal.,2010). the order of (cid:3)12%. They also found that secondary (re-
Some modeling studies that have attempted to estimate growth) forests contain typically 9% less SOC than primary
prehistoric and preindustrial anthropogenic CO and CH forests,andthatSOClossesareonly partially reversiblewith
2 4
emissions have concluded that the emissions were too small reforestation. Even larger SOC decreases have been docu-
to have had a substantial effect on global climate (DeFries mentedfollowingdeforestationinborealforests.Forexample,
et al., 1999; Olofsson and Hickler, 2007; Pongratz et al., Gru¨nzweigetal.(2004)measuredareductionof44%inSOC
2009), and attributed the observed trends in CO and CH followingdeforestationincentralAlaska.
2 4
concentrationstonaturalsources.Recentmodelrunsbasedon Changes in land use also have substantial impacts on
updated greenhouse gas concentrations for a low (natural) global climate through mechanisms other than greenhouse
scenario and a modern scenario simulate substantially lower gases. By including land-cover changes in global climate
temperaturesforthelowscenariothantheanomalouslyhigh models, the outcome of those models can be significantly
CO and CH concentrations since the industrial period changed(Kabatetal.,2002;Feddemaetal.,2005).Although
2 4
(Kutzbach et al., 2010). The regional temperature differences global climate changes are driven by carbon sequestration,
rangefrom21Ccoolerinthetropicsto4–81Ccoolerinpolar microclimate changes are commonly driven byalterations in
regions. Kutzbach et al. (2010) concluded that a state of in- localwaterbudgets.
cipientglaciationwouldbepresentifitwasnotforthecurrent
elevatedgreenhousegasconcentrations.
Several studies have documented changes to the global 13.1.5 Geomorphic Hazards
carbonbalance.Althoughinformationaboutratesofland-use
change and biomass densities has improved greatly over the Geomorphic hazards warrant focus from a modern geo-
pastdecades,thevariabilityin estimatesof carbonemissions morphic perspective. Hazards arising from geomorphic pro-
from these changes has increased (Houghton, 2010). Several cessescanhavelargeimpactsonsociety.Humansarenotonly
estimates of the relations between carbon sources and agentsofchange,buttheyarealsovulnerabletogeomorphic
sinks from land use and land-use change have been made processes operating outside what might be considered the
(Houseetal.,2003;Ramankuttyetal.,2007;Itoetal.,2008; normal magnitude range. The human dimension of geo-
Houghton,2010). morphology is concerned, therefore, not only with human
Climate change influences the sensitivity of landscapes to impactsonclimateandlandsystems,butalsowiththereverse
erosionandsedimentation.Therelationbetweenclimateand role,inwhichgeomorphicsystemsimpacthumans.Theeffects
soil erosion has long been shown by empirically derived that climate and environmental systems have on human
erosion models. For example, a climatic aggressiveness index societies is a central concern of natural hazards research.
introduced by Fournier (1960) linked annual sediment pro- Abroadviewshouldconsidernotonlytheimpactsofhazards
ductiontoclimaticandtopographicfactors.Thisconceptwas on society, but also how human activities influence hazards.
8 Geomorphology ofHumanDisturbances, ClimateChange,andHazards
For example, anthropogenic channel aggradation increases discussvolcanismbothasahazardandasamajorshaperof
flood risks. Human activities also clearly influence vulner- landscapesnearplateboundaries.Benito(seeChapter13.15)
ability and resilience to disasters stemming from hazardous focusesonriversasageomorphicagent.Streamsandriversare
naturalprocesses. importantagentsofdenudationanddeposition;theyproduce
Notallnaturalhazardsaresusceptibletochangebyhuman newlandintheformofdeltas,andovergeologictimescales,
activities. To make distinctions, it may be useful to separate modulate isostasy in orogens. The chapter by Santi (see
endogenic and exogenic processes in the classification of Chapter 13.16) deals with the geomorphic implications of
geomorphic hazards. The forces applied by endogenic pro- wildfire,especiallytheimpactoffireonsedimentsupplyand
cesses,suchasearthquakes,tsunamis,andvolcanism,arenot delivery to fluvial systems. Finally, Huggel et al. (see Chap-
appreciably altered by human action, although vulnerability ter 13.17) consider the impacts of recent climate change on
and resilience clearlyare affected by behavior. The forces ap- the stability of slopes in mountains. They show that the fre-
plied by exogenic geomorphic processes, however, such as quencyoflandslidesandiceavalanchesmaybeincreasingin
storms, floods, deflation, and fire, are commonly affected manymountainareasduetoglacierthinningandretreatand
stronglybylanduseandengineeringworks.Alterationsinthe tothawofalpinepermafrost.
magnitude and frequencyof these events mayresult in com- Linkages between hazards, climate, and vulnerability in-
plex interactions between society, hazards, and geomorphic dicatetheneedtoconsiderhazardsinlightofclimatechange
processes(Figure3). and human activities. Some hazards are directly related to
This volume includes several papers concerned with con- meteorological events such as relations between hurricane
cepts, implications, and processes of natural hazards, in- frequencyand seasurface temperatures. Vulnerability to haz-
cluding many of the individual geomorphic processes that ards, in turn, is affected by human activities, such as the lo-
underlieextremeevents,suchaslargeearthquakes,tsunamis, cation of human settlements in disaster-prone areas. Natural
volcaniceruptions,landslides,andfloods.Humans havesuf- catastrophes also influence the nature of human activities.
feredfromhazardousnaturalprocessesaslongasourspecies Clearlythetrilogyoftopicsinthisvolume–humanimpacts
hasexisted(seeChapter13.12).Thesituationtoday,however, ongeomorphicsystems,climatechange,andnaturalhazards–
differs at least in degree. Global population now exceeds 7 shouldnotbestudiedinisolation.
billionand peopleare increasinglychoosingto livein urban
areaslocatedinhighhazardareas,forexample,inearthquake
zones and areas where cyclones make landfall. Many of the 13.1.6 Nuclear Detonations as a Geomorphic Agent
worlds ‘megacities’ and much global wealth are located in
areassubjecttolargeearthquakes,tsunamis,floods,andsevere Although natural hazards, such as hurricanes, volcanic erup-
storms.Thepotentialforcatastrophiclossoflifeoreconomic tions, and earthquakes, can release more energy, the greatest
damageexceedinganythinghumanshaveexperiencedtodate potentialforrapid,purelyanthropogenicgeomorphicchange
represents a real threat. Further, we live in an economically comes from thermonuclear explosions. This potential was
integrated world, such that a catastrophic earthquake or tsu- demonstratedvividlyduringthepost-WorldWarIIperiodby
namiin,forexample,Japancanimpactallpeople. experiments conducted by the US government aimed at
In this light, an improved understanding of hazardous understanding the behavior of nuclear explosive devices
processes and of the relationship between hazard and risk both for warfare and peaceful uses. Project Plowshare was
is essential. Several papers in this volume explore these designedtoexplorethefeasibilityofpeacefulusesofnuclear
issues, as well as the frequency-magnitude concept that devices,specificallytheuseofundergroundnuclearexplosions
underpins many hazard studies. Goff and Dominey-Howes as geomorphic andresource-extraction agents.Although Pro-
(see Chapter 13.13) provide a review of tsunamis, both as a ject Plowshare never progressed beyond the experimental
geophysical process and as a profound threat to low-lying stage, the projects that were envisioned demonstrate the
coastal communities. Hickson et al. (see Chapter 13.14) tremendous capability of humans for geomorphic change
if the use of modern technology is unrestricted. The US
government envisioned earth-moving operations on a large
Natural hazards scale, including creation of canals and harbors, blasting
road cuts, and mining by removing or fracturing earth. In
Endogenic Exogenic
geomorphic geomorphic particular, widening the Panama Canal, excavating a roadcut
hazards hazards through the Bristol Mountains for a railroad line and Inter-
state 40 across the Mojave Desert, and cutting a 5km divide
to excavate a 400km canal connecting the Tennessee and
Tombigbee rivers were considered as applications of con-
trolled nuclear detonations. A similar program for peaceful
Human uses of nuclear detonations in the former Soviet Union was
Society
activities known as Nuclear Explosions for the National Economy
(Nordyke,2000).
Figure3 Systemsdiagramforinterrelationshipsbetweennatural
hazardsandhumanactivities.Bothendogenicandexogenichazards Thirty-five Plowshare experimental nuclear detonations
haveaneffectonsocietyandthereforeonhumanactivities.Human wereconductedfromDecember1961toMay1973,beforethe
activitiescanonlyalterexogenichazardssuchasstorms,floods, project was halted due to the dangers of radiation (US
andfire. DepartmentofEnergy,2000).Fifteenofthedetonationseach
Geomorphologyof HumanDisturbances,Climate Change,andHazards 9
14 000
Nuclear detonations, 1954 to 1973
12 000
10 000
s 8000
n
o
ot
Kil 6000
4000
2000
0
Jan-54 Jan-58 Jan-62 Jan-66 Jan-70 Jan-74
Figure5 Energyreleasedbyexperimentalthermonuclear
detonationsconductedfrom1954to1973.Thesedetonationsdwarf
the104kilotonsdetonationthatcreatedtheSedancratershownin
Figure4.ReproducedfromUSDepartmentofEnergy,2000.United
Figure4 ProjectPlowshareexperimentalblastswereconducted
StatesNuclearTests,July1945throughSeptember1992.Nevada
from1961to1973forpeace-timetestsofthefeasibilityofeffecting
OperationsOffice,DOE/NV-209-REV15.
geomorphicchangesforconstruction.TheSedancraterwas
producedbyatestnucleardetonationof104kilotonsattheNevada
TestSitein1962.Theblastis98mdeepand390mindiameter.
is roughly equivalent to the total combined movement of
Source:USDepartmentofEnergy,2000.UnitedStatesNuclearTests,
material by mining, agricultural, road building, and other
July1945throughSeptember1992.NevadaOperationsOffice,DOE/
NV-209-REV15. human activities each year. An estimated 3.8(cid:4)109 tons of
material are moved by mining each year in the US alone
(Hooke, 1994; see Chapter 13.6). However, many nuclear
releasedmoreenergythananequivalent massof 10kilotons
devicescoulddisruptgeomorphicsystemsinwaysthatcould
(kt) of trinitrotoluene. One of the largest Plowshare experi- initiate on-going geomorphic changes. For example, removal
mentswasconductedtotestthefeasibilityofbuildinganar-
orclosureofdams,lakesills,harbors,andrivermouths,and
tificial harbor at Cape Thompson, Alaska, which was never
destabilizationofvegetationandgroundcover,couldinitiate
constructed.A104ktblastwasdetonatedatadepthof194m
catastrophic geomorphic responses beyond the work of the
on the Nevada Test Site on 6 July 1962 as an experiment initial explosions. Clearly, the capacity for instantaneous
for the harbor project. The blast moved more than 11(cid:4)106 geomorphic change concentrated in specific places is a
tonsofrock,alluvium,andsoilandcreatedtheSedanCrater
frightening aspect of human geomorphic potential and the
(Figure 4). Other large detonations conducted to test the proliferation of nuclear weapons should be avoided at
feasibilityofusingnuclearexplosionsforexcavationswerethe
allcosts.
Flask(105kt),Kikitat(70kt),Stoddard(31kt),andSchooner
(30kt)tests.
Most nuclear detonations by the US Government were
for weapons testing. More than a thousand nuclear devices 13.1.7 Restoration, Stabilization, Rehabilitation,
weredetonatedbetween1954and1973.Theenergyreleased and Management
by the largest blasts was two orders of magnitude larger
thanthelargestdetonationsforProjectPlowshare(Figure5). The disruption of geomorphic systems by human activities
More than 30 detonations greater than one megaton or climate change may call for remediation to stabilize
were conducted between 1952 and 1971 (US Department the system or to return part or all of it to a previous
of Energy, 2000). Most large explosions were over islands in state.Remediationislikelytobeanimportantareaofgrowth
the tropical Pacific Ocean during the early period of testing, inthefutureofanthropogenicgeomorphologyastheimpacts
and the potential impact on geomorphic systems was not of humans become better understood. Before remediation
measured. programs are undertaken, however, careful attention should
The potential for nuclear weapons to do instantaneous be given to identifying alternatives, clearly defining the ob-
geomorphic work is tremendous and may exceed all other jectives, and reaching an agreement on the limitations to a
rates of human geomorphic change when considered over project.Variousapproachestotreatingdisturbedgeomorphic
short time periods and restricted areas. A simple linear ex- systems are available for consideration, and the costs and
trapolation of the energy released by the 104kt Sedan det- implications vary widely. Definitions of such terms as ‘res-
onation to larger 10Mt events that could be used in toration’ alsovarywidely, so afirst step towarddevelopinga
thermonuclear warfare suggests that each device could move program to treat a disturbed system should be to establish a
B108tonsofmaterial.Theproductof100suchnuclearwar- commonsetofdefinitions,suchasthosepresentedinTable2.
headsandthegeomorphicworkdonebyeachbombyieldsa Each of these approaches has different goals, yet the termi-
potentialmassof1010tonnesofearthmaterialthatcouldbe nology is commonly used interchangeably, which can cause
moved.Thetotalmovementofearthmaterialbythisprocess greatconfusion.
10 Geomorphology ofHumanDisturbances, ClimateChange,andHazards
Table2 Strategiesforremediationofgeomorphicchange
Restoration Reestablishstructureandfunctionofenvironmentalsystemstoapredisturbancecondition
Rehabilitation Improvesomestructuresandfunctionsbutnottopredisturbanceorstableconditions
Substitutionormitigation Createoralterfeaturestocompensateforhumanchanges,ofteninadifferentlocation
Reclamation Alteranaturalsystemtoadifferentstate;forexample,wetlanddrainageorflood-protectionprojects
Stabilization Reducinggeomorphicchangebyprotectiveengineeringmeasures
Adaptedfromdefinitionsusedinaquaticrestoration.
Source:FISRWG(1998),NRC(1992,1999).
‘Restoration’mayimplymanydifferentstrategieswithen- 13.1.8 Conclusion
tirelydifferentgoals,includingstabilization,enhancement,or
substitutionprojects.Acommondefinitionappliedtoaquatic This volume examines the human dimension of geomorph-
restorationrequiresthereturnofasystemtoapredisturbance ology, including anthropogenic geomorphology, climatic
state: geomorphology,climatechangeimpacts,andnaturalhazards.
These diverse processes can be indirect and may involve lag
times caused by storage and transfer of energy and mass,
[R]estoration isdefined as the returnof an ecosystem to a close
approximationofitsconditionpriortodisturbanceyMerelyre- shifting thresholds of stability caused bychanging landscape
creating the form without the functions, or the functions in an sensitivities, and feedbacks caused by changes in human ac-
artificial configuration bearing little resemblance to a natural re- tivitiespromptedbygeomorphicimpacts.Ratesofanthropo-
source, does not constitute restoration. The goal is to emulate a
genic geomorphic change are accelerating in response to the
natural, functioning self-regulating system that isintegrated with
increasing technological potential to do work and to the
theecologicallandscapeinwhichitoccurs.Often,naturalresource
restoration requires one or more of the following processes: re- growingglobalpopulation.Theeffectsofclimatewarmingare
construction of antecedent physical hydrologic and morphologic superimposed on the geomorphic potential of humans and
conditions; chemicalcleanuporadjustmentoftheenvironment; also involve lag times, shifting thresholds, and feedbacks.
and biological manipulation, including revegetation and the re-
Climate change is an anthropogenic phenomenon by itself,
introductionofabsentorcurrentlynonviablenativespecies.(NRC,
1992). butitalsohasgreatrelevancetohuman-inducedgeomorphic
change because it has widespread impacts on landscape sen-
sitivityandmayalterthenatureofimpactsandresponserates.
Restoration, therefore, may require identification of a refer- The effects of anthropogenic change can be traced back
ence system that is regarded as undisturbed or ‘natural’. This intotheNeolithic,buttheyacceleratedgreatlyintheindustrial
callsforanunderstandingofgeomorphicchangeandhistor- era.Itisnowcommonlyacknowledgedthathumanactivities
icalreconstructions. can change the Earth surface system at a global scale. These
Rehabilitation seeks to recover functionality of part a sys- changes are not confined to the atmospheric and biologic
temwithoutreturningittoapreviousconditionis(FISRWG, spheres, but extend to global geomorphic systems through a
1998;NRC,1999).Forexample,abeachmayberehabilitated strong interconnectivity among systems. Natural hazards are
by replenishing sand and protecting against erosion with an example of geomorphic processes affecting society, rather
groins, without restoring the natural sediment budget. Sub- than the converse. Exogenic hazards may be intensified by
stitutionormitigationcreatesanewsystem,characteristically humanactivities,andvulnerabilitytoallnaturalhazardstends
in a different location. For instance, a coastal dunefield may to increase greatly with population growth and dense settle-
be created to replace one that has been developed. In ment in hazardous areas. Nuclear detonations are both an
contrast, reclamation projects that alter natural systems effective geomorphic agent and a technological hazard that
from their natural condition for practical purposes, such as have the greatest instantaneous potential for anthropogenic
wetland drainage, are commonly antithetical to restoration. geomorphic change. Environmental management will in-
Similarly, stabilization projects seek to reduce geomorphic creasingly require and seek methods to stabilize and restore
change by protecting against erosion or sedimentation. geomorphicsystemsandthiswillbeanimportantgrowtharea
These approaches tend to resist natural processes to enhance ingeomorphology.
the human utility of systems, so they may be related to
reclamation.
An important beginning in remediation of a disturbed References
system is to halt the disturbance processes to allow recovery.
Once the disturbances are arrested, passive or natural restor- Arnoldus,H.M.,1978.AnapproximationoftherainfallfactorintheUniversalSoil
ation may be sufficient to repair the system (FISRWG, 1998; LossEquation.In:DeBoodst,M.,Gabriels,D.(Eds.),AssessmentofErosion.
NRC, 1999). Passive restoration methods, such as the cessa- Wiley,Chichester,UK,pp.127–132.
tion of grazing animals, tend to be slow but can be an in- Asselman,N.E.M.,Middelkoop,H.,vanDijk,P.M.,2003.Theimpactofchangesin
climateandlanduseonsoilerosion,transportanddepositionofsuspended
expensive method of restoration or rehabilitation. Active
sedimentintheRiverRhine.HydrologicProcesses17,3225–3244.
restorationinvolvesdirectmethodsthatassistintherecovery
Avissar,R.,Liu,Y.,1996.Athree-dimensionalnumericalstudyofshallow
process. In river restoration, for example, spawning gravels convectivecloudsandprecipitationinducedbyland-surfaceforcing.Journalof
andlargewoodydebrismaybereintroduced. GeophysicalResearch101,7499–7518.