Geoscience and sustainablecatchment and resourcemanagement: the Ben ChifleyCatchment case studyDhia Al Bakri

Abstract This article demonstrates a key role thatgeoscience and geoscientists could be playing inpromoting sustainable catchment and resourcemanagement. A new geoscience-based approachsupported by a landscape-genesis (LG) model wasemployed to provide an alternative approach forintegrated catchment management and sustainableresource use and development. The Ben ChifleyCatchment case study is used to explain the appli-cation of the approach and the landscape-genesismodel. The study confirmed that lithological com-position, tectonic and diagenetic processes, andlandform were critical factors in determining theintrinsic properties and variation in soil type, landuse, land capability, steepness of terrain, erosion,and resource degradation within the catchment. Thelandscape-genesis model, which is based on thegeological and geomorphic genesis of the landscape,proved to be a powerful tool to predict the inherentcarrying capacity and resilience of the various bio-physical systems in the catchment. Although thisapproach is still in its infancy, its application hasdemonstrated that it has a strong potential in termsof undertaking sound integrated assessment, pre-dicting potential resource degradation under dif-ferent land uses, and developing sound managementpractices and solutions to advance the goal ofecological sustainability.

Keywords Geoscience Æ Catchment ÆSustainability Æ Resources Æ Landscape Æ Genesis ÆNew South Wales

Introduction

This paper builds on work carried out by the author andassociate researchers and published in several articles(Al Bakri 1994, 1996, 2001; Al Bakri and Kittanah 1997;Al Bakri and others 1997a, 1997b, 1999; Al Bakri andChowdhury 1999). It aims to demonstrate that geoscienceand geoscientists could make a more critical contributionto ecological sustainability than what is currently per-ceived. The Ben Chifley Catchment is used as a case studyto illustrate aspects of a new geoscience-based approachfor sustainable catchment and resource management. Thecatchment (985 km2) exists upstream of the Ben ChifleyReservoir, the main water supply for the country town ofBathurst, New South Wales (Fig. 1). The catchment islocated in a cold-temperate region with an annual rainfallof 750–950 mm. Land clearing for agricultural purposesbegan around 1850. According to the land-use map of thecatchment, pastureland, soft-wood plantation and nativetimber occupy more than 99% of the area, whereas crop-ping and horticultural land represents less than 1% of thecatchment (Taylor 1994).Despite the predominance of a non-intensive agricultural-use system (pasture and timber), which has been ongoingfor a relatively short period (approximately 150 years), thecatchment suffers serious land- and water-degradationproblems. Fertility decline, soil acidity, sodicity (soilenriched with sodium), soil-structural decline, erosion,waterlogging, salinity, and weed infestation are some of themost common land-degradation problems (Cox 1999, BenChifley Catchment Management Coordinator, personalcommunication). Approximately 80% of the grazing land isimproved pasture where superphosphate fertilizer is ap-plied once every 2 years at the rate of 20 kg/ha to improvesoil fertility. Lime is also applied regularly to moderateacidity and improve productivity. Considerable earthwork,gully filling, and fencing are employed to combat erosion.The Ben Chifley Reservoir and other catchment waterwaysexhibit chronic algal blooms and degraded aquatic ecosys-tems, together with serious water-quality problems, such asturbidity, siltation, and eutrophication. Given the need for ahigh farming-input system and costly management practice,coupled with modest productivity and low commodityprices, the land use in the catchment is becoming increas-ingly less sustainable, both ecologically and economically(Cox 1999, Ben Chifley Catchment Management Coordina-tor, personal communication).

Received: 3 December 2001 / Accepted: 18 March 2002Published online: 15 May 2002ª Springer-Verlag 2002

D. Al BakriThe University of Sydney,PO Box 883, Orange NSW 2800, AustraliaE-mail: dalbakri@orange.usyd.edu.auTel.: +61-2-63605655Fax: +61-2-63605517

Original article

588 Environmental Geology (2002) 42:588–596 DOI 10.1007/s00254-002-0577-0

Landscape genesis and integratedcatchment management

The concept of integrated catchment management (ICM)is widely accepted as the most appropriate framework forundertaking sound natural-resource assessments and de-veloping sustainable planning and management strategies.This entails a holistic consideration of the biophysicalsystems, socio-economic factors, and management pro-cess (DNR 1999; Savory 1999; Grayson and others 2000).One of the main impediments to the successful imple-mentation of the integrated catchment management has

been the lack of or poor integration of reliable scientificinformation about the underlying biophysical factors andprocesses.Areas and resources react differently to the impact ofsocio-economic development and management practices(anthropogenic activities). Areas with inherently fragileand vulnerable biophysical systems tend to be veryeasily upset by a variety of anthropogenic activities. Onthe other hand, areas with robust and resilientbiophysical systems withstand much more pressure andabuse associated with socio-economic developments(Savory 1999). In this context, the term ‘carryingcapacity’ is used to describe the intrinsic fragility or

Fig. 1Landscape genesis (LG) map ofthe Ben Chifley Catchment

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Environmental Geology (2002) 42:588–596 589

resilience of the biophysical systems in terms of theirresponse to the various anthropogenic activities. It isimperative, therefore, that the inherent carrying capacityis evaluated carefully in order to understand and, in-deed, predict the impact of different land-use scenariosin any given area.As discussed by Al Bakri (2001), the biophysical systemconsists of essentially three independent factors (geology,climate, and time) and several dependent factors (e.g.,soil, water, fauna, flora, topography, and other naturalresources). The intrinsic properties of the dependentvariables are ultimately controlled by the independentvariables. Given that geology encompasses the time factorand strongly influences microclimatic variability, geolog-ical and geomorphic information provides crucial insightinto the intrinsic carrying capacity of any given landscape(Al Bakri 2001). The proposed geoscience approach,supported by the LG model, offers an alternative meth-odology to improve the adoption and integration of thebiophysical data in the integrated catchment managementprocess. This approach differs essentially from other in-tegrated resource and catchment management approaches(Wright 1973; Al Bakri 1975; Mitchell and Hollick 1993;Hooper 1995; Brierly and others 1996; Grayson and others1997; DNR 1999). The approach determines the geologicaland geomorphic genesis of the landscape as a prerequisiteto: (1) assess the intrinsic biophysical characteristics andinherent carrying capacity of the natural ecosystems, (2)predict resource degradation due to anthropogenicactivities, and (3) then undertake an integratedassessment to develop appropriate planning andmanagement strategies.

Methods

Using geographic information systems (GIS) and fielddata, the geological units in the catchment (Bathurstgeological map, 1:100,000) were analyzed in terms of theirlithological composition, geological history, tectonic evo-lution, and geomorphic setting. Based on this analysis, apreliminary LG model for the catchment was developed bygrouping the geological units into LG genesis units thatreflect a relative uniformity regarding the above geologicaland geomorphic characteristics. These units were thenused as the framework to characterize the catchment interms of the following five land attributes.

Soil type (S)For the purpose of this study, the different soils in thecatchment, as shown in the Bathurst 1:250,000 soil-landscape map (Kovac and Lawrie 1990), were classified aspoor, fair, or good with respect to their potential andresponse to agricultural land use. This grouping took intoconsideration soil depth, soil fertility, and soil degradationin terms of structure, salinity, sodicity, and acidity. One ofthe authors of the soil-landscape map was consulted indetermining the above three soil categories (Lawrie,personal communication, 1998).

Land capability (C)Using the land-capability map of the catchment (Taylor1994), the eight land-capability classes (Charman andMurphy 1991) were grouped into the following fourcategories:

• Classes 1, 2, and 3: land suitable for regular cultivation;requires limited to moderate soil conservationmeasures.

• Classes 4 and 5: land suitable for grazing and occasionalcultivation; requires moderate to intensive soil conser-vation measures.

• Class 6: land suitable for grazing only. Judicious soilconservation measures are required to ensure that anadequate ground cover is maintained.

• Classes 7 and 8: land unsuitable for general rural pro-duction. Land best protected by green timber because oferosion hazard, steepness, soil shallowness, or infertility.

Land use (U)Based on the land-use map of the catchment, the land-useclasses were grouped into pasture, cropping/horticulture/agroforestry, and native timber (Taylor 1994).

Soil erosion (E)Based on the soil-erosion map (Taylor 1994), the catch-ment was classified into surface erosion, stream bank/gullyerosion, and no appreciable erosion.

Slope (Se)Using the digital terrain model of Bathurst, slope gradientin the catchment was divided into gentle slope (0–10%),moderate slope (11–20%), and steep slope (>20%).

Rating and ranking systemA rating system was applied to condense the informationobtained from analyzing the above five attributes into asingle ranking index of sustainability (RIS). The RIS isdetermined by adding the rating scores of the attributesconsidered (RIS = S + C + U + E + Se). The scoring proce-dure involved assigning an equal weight to all five attributes.For each attribute, the LG units were assigned a ratingbetween a minimum of 1 and a maximum of 10. Because fiveattributes are covered in this study, the maximum possibleRIS score for any landscape unit is 50. The RIS is used torank the carrying capacity of the units as reflected in theirresponse to land-use activities. The higher the RIS score, thehigher the carrying capacity of the biophysical system. Thisin turn defines the level of robustness and resilience, andsubsequently the sustainability, of the LG units. The choiceof the attributes reflects the desire to develop a focused casestudy and the limitation imposed by non-availability of GISdata concerning other attributes.

Results and discussion

Igneous, sedimentary, and metamorphic rocks and de-posits ranging in age from Early Ordovician to Quaternary

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590 Environmental Geology (2002) 42:588–596

cover the Ben Chifley Catchment, which is part of theLachlan Fold Belt of southeastern Australia. Low to mod-erate regional metamorphism, associated with complexfolding and faulting systems, characterize this area (Pog-son and Watkins 1998). A hypothetical LG model wasestablished by grouping the 38 geological units exposed inthe catchment into 13 LG units. This preliminary modelwas then tested by analyzing the LG units in terms of theirassociated soil type, land use, land capability, soil erosion,and slope. Based on this analysis, the LG model wasrefined by grouping the 13 initial units into 11 LG units(Fig. 1). The results of this analysis are presented inTable 1, and their rating scores and RIS rating are shownin Tables 2 and 3. The characteristic features of the 11 LGunits, arranged in a descending order of carrying capacityand sustainability, are discussed below.

Tertiary basalt (Tb)This group of volcanic rocks belongs to the Aively andAbercombie Provinces of the Tertiary basalt of the CentralWest of NSW. It consists of olivine basalt, basanite, andalkali basalt, with trachyandesite and minor nephelinite(Pogson and Watkins 1998). This LG unit was rankednumber 1 with an RIS of 47.5 out of 50 (Table 2). Thisranking was consistent with the predicted behavior of suchgeology, which offers the most sustainable biophysicalsystem in the catchment (Table 1). Consisting entirely ofsuch highly unstable minerals as feldspars, dominated bycalcium plagioclase, and ferromagnesians, the Tertiarybasalt produces deep, fertile, stable, and highly productivesoil. Therefore, the biophysical system associated with thisLG unit tends to have a high carrying capacity that cansupport intensive agricultural use and displays a resilientecosystem with little degradation potential. Consequently,it requires limited conservation and management-protec-tion measures. The minor surface erosion that appears in59% of the unit (Table 2) is partly due to the presence oftrachyandesite and nephelinite. These rocks, which arerelatively enriched with sodium plagioclase, tend to pro-duce dispersing and sodic soil that is inherently prone toerosion (Gray and Murphy 1999; Al Bakri 2001).

Ordovician mudstone (Oa, Oac)This LG unit belongs to the Ordovician Adaminaby Group,which is the oldest geological unit in the catchment. It isdominated by mudstone with thin beds of siltstone andshale, and minor amounts of quartz sandstone and slate(Pogson and Watkins 1998). This unit was ranked number 2,with the second highest RIS of 44.5 (Table 2). These Ord-ovician deposits provide the second most sustainable bio-physical system in the catchment, in terms of soil type, landuse, land capability, slope, and resource degradation (Ta-ble 1). Given that the LG unit is associated with the oldestrocks and probably oldest landscape in the catchment, itshigh ranking challenges the conventional view that oldlandscapes produce fragile soil and vulnerable ecosystems(Beckman 1983). The primary reason for the development ofa more superior biophysical system than those associatedwith much younger landscapes is that the unit is dominatedby argillaceous rocks consisting of silt and clay derived from

mafic igneous material. The underlying geology providesthe genetic basis for the development of an inherently re-silient biophysical system (Gray and Murphy 1999; Al Bakri2001). This example further confirms that geology wasparamount in determining the carrying capacity, preferredland use, and sustainability of a given landscape.

Ordovician mafic intrusions (Om)These mafic intrusions of the Late Ordovician are domi-nated by monzodiorite and monzogabbro. Although thegeology of this area is completely different from that of theabove unit, similar characteristics in terms of the five landattributes were evident, and it was, therefore, rankednumber 2 with an RIS of 43.5 (Tables 1 and 2). Beingintermediate–mafic igneous intrusions, the rocks offer lowresistance to chemical weathering, producing a productive,but resilient biophysical system (Gray and Murphy 1999;Al Bakri 2001).

Quaternary alluvium (Qa)This LG unit is associated with the most recent deposits inthe catchment; they consist of alluvial sand, silt, and clay.It was also ranked number 2, but its RIS (41.2) was mar-ginally lower than those of the other two LG units thatreceived a similar ranking. One would, normally, expectthat alluvial deposits offer the best potential in terms ofagricultural use and land productivity. The RIS of this unitwas ultimately due to the geological and geomorphic set-ting. The alluvial deposit in this area has been primarilyderived from granite and felsic volcanic rocks, which leadsto the development of sodic soil (enriched with sodium).Consequently, the area tends to be prone to serious gullyand stream-bank erosion and related land-degradationproblems. This inherent limitation reduced the potential ofthis biophysical system (Tables 1 and 2).

Ordovician volcaniclastic sandstone (Okt, Ocr, Ocrc)The Okt component of this LG unit, which is part of theOrdovician Kenilworth Group, is the second-oldest for-mation in the catchment. It comprises mafic volcaniclasticsandstone, with metabasalt, slate, schist, chert, andquartzite. The Rockly Volcanics (Ocr, Ocrc), which areconstituents of the Ordovician Cabonne Group, comprisemainly mafic volcaniclastic sandstone and siltstone, withsome chert and rare conglomerate. This unit has areasonably productive and resilient ecosystem and wasranked number 3, with an RIS of 37.7 (Tables 1 and 2).This unit did not attain a higher ranking because of therelative abundance of the metasediments and metamor-phic rocks, which tend to produce a poorer and lessproductive biophysical system than that developed onthe mafic volcaniclastic sandstone (Al Bakri 2001).

Devonian deepwater deposit (Dc, Dcd, Dca)The Devonian Crudine Group (Dc) conformably overliesthe Mumbil Group and was deposited in a deepwaterenvironment (the Hill End Trough sequence). It ischaracterized by massive, medium–coarse-grained quartzo-feldspathic crystal or lithic sandstone of intermediate tofelsic volcanic origin, interbedded with siltstone and

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Environmental Geology (2002) 42:588–596 591

Tab

le1

An

alys

iso

fla

nd

scap

ege

nes

isu

nit

so

fth

eB

enC

hifl

eyC

atch

men

t

Lan

dsc

ape

gen

esis

un

its

Lan

dat

trib

ute

s

Soil

typ

e(%

)L

and

use

(%)

Lan

dca

pab

ilit

y(%

)Su

rfac

eer

osi

on

(%)

Gu

lly

ero

sio

n(%

)Sl

op

e(%

)

Po

or

Fai

rG

oo

dC

rop

Pas

ture

Tim

ber

1–3

4–5

67–

8Se

vere

Min

or

No

ne

Seve

reM

ino

rN

on

e0–

1011

–20

>20

Ter

tiar

yb

asal

t(T

b)

427

6916

795

4536

136

059

410

010

087

121

Ord

ovi

cian

mu

dst

on

e(O

a,O

ac)

595

000

100

026

659

00

298

10

9998

20

Ord

ovi

cian

mafi

cin

tru

sio

ns

(Om

)0

100

00

100

00

964

00

397

00

100

991

0

Qu

ater

nar

yal

luvi

um

(Qa)

1783

01

963

4348

72

036

6433

760

982

0

Ord

ovi

cian

volc

anic

last

icsa

nd

sto

ne

(Ok

t,O

cr,

Ocr

c)

293

50

929

1262

215

041

596

1282

9010

0

Dev

on

ian

dee

pw

ater

dep

osi

t(D

c,D

cd,

Dca

)

3462

40

964

777

115

063

377

885

936

1

Silu

rian

silt

sto

ne

and

met

ased

i-m

ent

(Sm

c)

786

71

7524

455

306

059

416

886

215

83

Car

bo

nif

ero

us

gran

ite

and

gran

od

iori

te(C

lg–

Co

g)

793

04

7818

165

1420

037

6310

1476

8710

3

Ord

ovi

cian

sch

ist

and

met

avo

lca-

nic

s(O

cru

,O

crs)

1481

50

919

539

3917

195

441

3722

6928

3

Silu

rian

gran

ite

(Svg

)an

dli

mes

ton

e(S

mck

)

8019

12

7127

153

2224

069

3136

2737

6924

7

Silu

rian

met

afel

sic

volc

anic

s(S

ml,

Smls

)

3565

00

3466

021

4435

591

414

878

5534

11

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592 Environmental Geology (2002) 42:588–596

fine-grained sandstone, together with minor tuff and da-citic lava and intrusions. The Dunchurch Formation (Dcd)conformably overlies the Campbells Formation. It ischaracterized by massive, coarse-grained, feldspathic andquartzo-feldspathic sandstone interbedded with shale andsiltstone beds, and rare conglomerate and breccia. TheAdderley Formation (Dca) conformably overlies theDunchurch Formation and is unconformably overlain bythe Lambie Group. This formation comprises a sequenceof felsic (rhyolitic and dacitic) volcaniclastic conglomerateand sandstone with rare slate (Pogson and Watkins 1998).This LG unit was also ranked number 3 with an RIS of 36.This favorable rating reflects the dominance of fine-grained sediment deposited in a deepwater environment.However, the rhyodacitic to dacitic volcaniclastic origin ofthe deposit, enriched with sodium plagioclase, led to thedevelopment of a relatively fragile and rather vulnerablesystem, which in turn reduced the inherent carryingcapacity and resilience of the unit (Tables 1 and 2).

Silurian siltstone and metasediment (Smc)This undifferentiated Campbells Formation (Middle Silu-rian), a unit of the Mumbil Group (Sm), comformablyoverlies the Bells Creek Volcanics (Sml). It consists ofshale and siltstone overlain by interbedded slate, fine- tocoarse-grained meta-feldspathic sandstone, and limestone.This unit was ranked 4 because the relatively high inherentpotential of siltstone and shale, in terms of resilience andcarrying capacity, was reduced by the presence of me-tasediments, metamorphic rocks and limestone (Table 2).

Carboniferous granite and granodiorite (Clg–Cog)These Carboniferous plutons are characterized by medium-to coarse-grained, equigranular to porphyritic biotite–hornblende granite to granodiorite. Albite and oligoclaseare present, and sometimes oligoclase is displaced by albite(Pogson and Watkins 1998). As expected, the ranking of thisunit was relatively low (4), exhibiting limited carryingcapacity and a moderately degraded biophysical system(Table 1). LG units associated with granitic areas arenormally characterized by fragile, dispersing, and unstablesoils, with severe gully and streambank erosion, and sandyand infertile topsoil. Sodicity, acidity, salinization, andrelated resource degradation are also common. The rootcauses of these problems are due to the presence ofhigh-sodium plagioclase of albite and oligoclase (Gray andMurphy 1999; Al Bakri 2001).

Ordovician schist and metavolcanics (Ocru, Ocrs)These two geological units, which are part of the RocklyVolcanics, are dominated by actinolite–talc schist,metabasalt, amphibolite, peridotite, pyroxenite, serpente-nized peridotite, and minor volcaniclastic sandstone andmetasiltstone. The low–moderate grade regional

Table 2Ranking of the landscape genesis units of the Ben Chifley Catchment in terms of carrying capacity and sustainability. Rating scores and theirequivalent ranking index of sustainability (RIS) are listed in Table 3

Landscape genesis(LG) units

Rating score RIS Area % of thecatchment

Soil type Land use Landcapability

Soil erosion Slope Total score

Tertiary basalt (Tb) 10 10 10 8.5 9 47.5 1 7.1Ordovician mudstone

(Oa, Oac)6.5 8.5 9.5 10 10 44.5 2 4.7

Ordovician maficintrusions (Om)

6 8.5 9 10 10 43.5 2 0.5

Quaternary alluvium (Qa) 7 8.5 10 5.7 10 41.2 2 3.8Ordovician volcaniclastic

sandstone (Okt, Ocr, Ocrc)6 8 7.5 7.2 9 37.7 3 31.9

Devonian deepwater deposit(Dc, Dcd, Dca)

4.5 8.5 7 6.5 9.5 36 3 7.2

Silurian siltstone andmetasediment (Smc)

6 6 6 7 8 33 4 15.1

Carboniferous granite andgranodiorite (Clg–Cog)

5 6.5 5.5 6 8 31 4 3.5

Ordovician schist andmetavolcanics (Ocru, Ocrs)

5 8 3 2 5 23 6 14.7

Silurian granite (Svg) andlimestone (Smck)

1 6 3 3 4 17 7 4.6

Silurian metafelsic volcanics(Sml, Smls)

3 1 1 4 1.5 10.5 8 4.4

Table 3Total rating scores and their equivalent ranking index of sustain-ability (RIS) listed from RIS = 10 (lowest carrying capacity and sus-tainability) to RIS = 1 (highest carrying capacity and sustainability)

Total rating score RIS

<5 105–9.99 910–14.99 815–19.99 720–24.99 625–29.99 530–34.99 435–39.99 340–44.99 245–50 1

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metamorphism, evident in the area, reduced the carryingcapacity of the unit and increased its vulnerability todegradation by making the terrain steeper and, in part,more prone to erosion, particularly gully and streambankerosion. The erosion and associated land degradation weredue to the albitization of the Ca-plagioclase in basalt andother mafic and ultramafic parent rocks. In this process,sodium content in the metamorphosed rocks increases,which in turn increases weathering and erosion potential.As shown in Tables 1 and 2, this LG unit exhibits thehighest level of erosion in the catchment, with a ratingscore of 2. If not for the fact that the unit is dominated byrocks derived from mafic and ultramafic parent material,the designated ranking of 6 would have been even lower.

Silurian porphyritic granite (Svg) and limestone(Smck)

The limestone unit is the upper part of the differentiatedCampbells Formation (Smc), which consists of fossilifer-ous limestone, felspathic sandstone, and minor conglom-erate and slate. The Svg unit consist of intrusions classedas Late Silurian–Early Devonian (Davies Creek) Granite.The plutons comprise S-type granophyre dikes and stocksconsisting of pink, fine- to medium-grained, equigranularleucogranite, containing orthoclase and microcline andquartz. Porphyritic granite with albite and alkali-feldsparphenocrysts is common (Pogson and Watkins 1998). ThisLG unit was ranked as the second-least productive andsustainable system in the catchment. The designated lowranking of 7 reflects the limitation of the biophysicalsystem underlain by felsic, porphyritic plutons, andchemical and arenaceous sedimentary rocks (Gray andMurphy 1999; Al Bakri 2001).

Silurian metafelsic volcanics (Sml, Smls)These Lower Silurian geological units are constituents of theBells Creek Volcanics, which are part of the Mumbil Group(Sm). The undifferentiated unit (Sml) consists of metadaciteand metarhyolite. These rocks have been intensely foliatedand metamorphosed to greenschist facies, and the originalphenocrysts recrystallized to andesine. Quartz is commonas phenocrysts in some localities. The lower unit of the BellsCreek Volcanics (Smls) is dominated by volcaniclasticsandstone and tuff, with slate and mudstone of rhyolitic anddacitic origin (Pogson and Watkins 1998).This LG unit gave rise to the least-productive and most-degraded biophysical system within the catchment. It wasranked 8 with an RIS of 10.5. The area scored low to verylow on all five land attributes (Tables 1 and 2). This LGunit was not only unsuitable for most agricultural uses, butit has suffered serious resource degradation in spite of thedominance of relatively passive land-use activities. Acursory assessment of the geology indicates that this LGunit, being dominated by volcanic rocks, should provide amuch better potential. There are, however, two main rea-sons for rendering this unit as having the lowest carryingcapacity and sustainability in the catchment. First, sodiumcontent in the dacite, rhyolite, and other felsic–interme-diate igneous rocks, which tends to be normally high, wasincreased further due to albitization associated with

metamorphism. Second, the intensive foliation and meta-morphism of the area increased the steepness and relief ofthe terrain. As discussed earlier, this type of geology leadsto the development of a biophysical system inherentlyprone to serious erosion and degradation.

Conclusions

The Ben Chifley case study demonstrated that there arestrong links between geology and the soil, land capability,erosion, slope, and land use. Furthermore, the lithologiccomposition and topographic characteristics were effectivein establishing a genetic basis for classifying the catchmentinto unique landscape units. The LG model provided auseful insight into the biophysical properties, carryingcapacity, and response of the catchment to various land-use activities and management practices. Consequently,the LG model provides a rational basis to better under-stand the impact of the anthropogenic activities, which isessential for the development of sustainable catchmentand resource management strategies.As the catchment is dominated by a biophysical systemunderlain by parent material derived mostly from felsic–intermediate igneous rocks that have undergone low tomoderate regional metamorphism, the study area has in-herent genetic constraints that limit its carrying capacityfor the development of an intensive agricultural system.Although the existing land use was mostly restricted tofairly passive agricultural activity, such as grazing andsoftwood plantation, the catchment has suffered seriousland and water degradation because its biophysical systemis fragile. Judicious conservation measures and consider-able chemical inputs are necessary to sustain this modestagricultural-production system.To illustrate the role of geoscience in catchment andresource management, a conceptual multi-layered andmulti-disciplinary approach is presented in Fig. 2. In thisapproach, four interrelated stages are envisaged:

• Stage 1: This focuses on conducting a geoscientific in-vestigation to develop a LG model to predict the in-herent opportunities and constraints of the biophysicalsystems. The investigation relies largely on commonlyknown geological principles, models, and geoscienceinformation from readily available sources, such asgeological and geomorphic maps and reports. A fieldreconnaissance will be necessary to verify and updateexisting information. An initial socio-economic inputwill also be necessary early in the study to establish thepurpose and direction of the overall project.

• Stage 2: Aspects of all or some of the five biophysical systems(Fig. 2) will need to be assessed. The scope and depth of theassessment will depend on the outcome of stage 1.

• Stage 3: Assessment of the other two important elementsof the approach, the socio-economic systems and thetechnological factors, will be carried out to complementthe findings from the biophysical assessment. An inte-grated assessment of results from the three systems will

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594 Environmental Geology (2002) 42:588–596

need to be used for problem diagnosis and definition ofcause-and-effect relationship. As the biophysical sys-tems and resources influence the socio-economic andtechnological development, it is imperative that the as-sessment of the latter two systems should be undertakenat or about the completion of the biophysical assess-ment (stage 2). This will be critical for ensuring a rel-evant and focused assessment.

• Stage 4: Based on the outcome of stage 3, appropriateland use and development for each LG unit, togetherwith a holistic management plan and relevant mitigationstrategies, need to be formulated at this stage. Tocomplete the sustainability and holistic managementloop, a monitoring program and feedback mechanismwill need to be integrated in this stage.

Although this new approach is still in its infancy, the BenChifley Catchment case study, and other recently pub-lished research (Al Bakri 2001) have demonstrated that thegeoscience-based approach has several advantages interms of promoting the goal of sustainability efficientlyand effectively because it:

• Offers a rational process to undertake an integratedholistic assessment. The process can be implementedwithin a single project or within a number of projects,

each addressing one or part of the four stages, providedthat the designated pathway was correctly followed. Forinstance, the present case study has focused mainly onstage 1 and part of stage 2 of the process due to time andresource constraints. Other stages of the process will beaddressed later.

• Employs genetic (LG) models to understand theintrinsic properties and predict the inherent carryingcapacity of different landscape units under a range ofland-use scenarios.

• Establishes a diagnostic basis to define root causes andcause-and-effect relationships, which are essential fordetermining preferred land use and developing appropri-ate solutions to mitigate against anthropogenic impacts.

• Offers the potential to develop global and quantitativelybased models and geoindicators that can be applied atdifferent catchment scales, climatic regions, and land-use scenarios.

Acknowledgements I would like to thank Dr R. Raman of theUniversity of Sydney, Orange, for reviewing the manuscript andproviding a valuable feedback and Ms M. Carlson for assisting inthe GIS analysis.

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