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Journal of Environmental Management (2002) 66, 239±247
doi:10.1006/jema.2002.0574, available online at http://www.idealibrary.com on
1
Erosion risk analysis by GIS in
environmental impact assessments:
a case studyÐSeyhan Ko
ÈpruÈ Dam
construction
SË. SË ahin*and E. Kurum
Ankara University Faculty of Agriculture, Department of Landscape Architecture,
06110 Ankara, Turkey
Received 11 July 2001; accepted 8 March 2002
Environmental Impact Assessment (EIA) is a systematically constructed procedure whereby environmental impacts
caused by proposed projects are examined. Geographical Information Systems (GIS) are crucially ef®cient tools for
impact assessment and their use is likely to dramatically increase in the near future. GIS have been applied to a wide
range of different impact assessment projects and dams among them have been taken as the case work in this article. EIA
Regulation in force in Turkey requires the analysis of steering natural processes that can be adversely affected by the
proposed project, particularly in the section of the analysis of the areas with higher landscape value. At this point, the true
potential value of GIS lies in its ability to analyze spatial data with accuracy. This study is an attempt to analyze by GIS the
areas with higher landscape value in the impact assessment of dam constructions in the case of Seyhan-Ko
Èpru
È
Hydroelectric Dam project proposal. A method needs to be de®ned before the overlapping step by GIS to analyze the
areas with higher landscape value. In the case of Seyhan-Ko
Èpru
ÈHydroelectric Dam project proposal of the present work,
considering the geological conditions and the steep slopes of the area and the type of the project, the most important
natural process is erosion. Therefore, the areas of higher erosion risk were considered as the Areas with Higher
Landscape Value from the conservation demands points of view.
#2002 Published by Elsevier Science Ltd
Keywords: GIS, EIA, erosion risk, dams.
Introduction
The use of GIS for impact assessment
GIS have been applied to a wide range of different
impact assessment projects. The most common GIS
applications for the impact evaluation are the roads,
pipelines, housing developments, coast and ¯ood
protection works, dams, tourism related projects,
ports and power lines. GIS is also widely used by
environmental consultancies for all impact assess-
ment stages (Joa
Äo, 1998).
Many of the GIS applications for impact assess-
ment use basic GIS functions such as measurement
of lengths and areas, map production, buffering,
and the classic overlay operation (Joa
Äo, 1998).
Recognizing the spatial nature of many environ-
mental impacts, overlay mapping in the manner of
ecosystem analysis was pioneered by McHarg (1969)
who is both a landscape architect and a city planner.
Compared with the cumbersome manual process of
overlaying transparencies, the overlay analysis is
made much more powerful through the use of GIS
(Smith, 1993). Arithmetic and logical overlay opera-
tions are part of all GIS software packages.
Arithmetic overlay includes such operations as
addition, subtractions, division, and multiplication
0301±4797/02/$± see front matter #2002 Published by Elsevier Science Ltd
of each value in a data layer by the value in the
* Corresponding author. Email: sahin@agri.ankara.edu.tr
corresponding location in a second data layer.
A logical overlay involves ®nding those areas
where a speci®ed set of conditions do or do not
occur (Aronoff, 1991). Those abilities of overlay
mapping by GIS technology make it an ef®cient
tool for the assessment of incremental changes in an
environment; the site selection for a project pro-
posal; the comparison of the alternatives; the exam-
ining and visually displaying the spatial nature of
the impacts in an EIA work.
The areas with higher landscape value:
problem description and target
formulation
The analysis of the areas with higher landscape
value is a requirement of the current EIA regulation
in Turkey within the content of General Format of
EIA Report (Section IV.2.14). This practice is among
the responsibilities of landscape architects, however
there is still room for improvement for a widely
accepted common approach. From the view point of
the landscape architecture discipline, in determin-
ing of `the areas with higher landscape value', the
ecological, cultural and visual characteristics of the
area in question are examined with an holistic
approach considering Conservation Demand and
Development Demands. Human welfare and the
quality of life in many ways depend directly and
indirectly on the availability of environmental goods
and services, thereby on the natural process and
ecosystem that provide them (Vellinga et al., 1994).
This means that the conservation demand of the
area, and accordingly the interrelations among the
components of the bio-physical environment should
be analyzed, and the section of determining the
areas with higher landscape value of the EIA process
presents an opportunity for this purpose. In prac-
tice, however, the assessment of mentioned natural
processes, what is also called ecological impact
assessment in literature, is not executed properly
in formal EIA studies in Turkey. The more import-
ant purposes of this paper are to disclose this
de®ciency of EIA studies, to present the way in
which this problem can be overcome, and to conduct
a case study to prove the crucial outputs of the
analysis of the areas with higher landscape value.
Another equally important purpose is to show
indispensability of GIS in such cases.
At the present article, erosion risk analysis is
recommended to determine the value of natural
landscape taking into account the characteristics of
the environment and the nature of the dam con-
struction as a development demand.
Erosion risk mapping
Investigations on the evaluation of water erosion
and soil loss started in the beginning of 1900s, but
more signi®cant studies were conducted after the
1940s. Initially soil loss was predicted in accordance
with empirical equations. After the 1950s para-
metric models have been developed. This parametric
models rely on statistical relationships between
soil-loss and various parameters derived from larger
sets of data such as rainfall, soil erodibility, slope-
length, slope gradient, crop management, etc. The
most common and widely used parametric model
for the prediction of soil losses is the well known
`Universal Soil Loss EquationÐUSLE' (MAPA/
ICONA, 1983; MOPU, 1985), developed in the
USA as an aid for conservation considering agricul-
tural activities. In general, the methods to measure
soil loss can be divided into two: Quantitative (such
as USLE, MUSLE) and Qualitative Methods (such
as ICONA, CORINE).
Quantitative methods usually involve the meas-
urement and quanti®cation of various components.
Qualitative methods, on the other hand, rely more
on the judgments and responses of the analyst.
However it is important that this professional
judgment takes place in the context of a systematic
and structured approach (NRA, 1993). In practice,
a more accurate prediction of erosion risks can be
achieved by the integration of the qualitative and
quantitative methods considering long-run land
conservation strategies, management and monitor-
ing (Gardi et al., 1996).
PAP/RAC (Priority Actions Program/Regional
Activity Center) of the MAP (Mediterranean Action
Plan)ÐUNEP in corporation with FAO prepared
the Guidelines for Erosion and Deserti®cation Con-
trol Management. This Guidelines, dealing with
management related issues of erosion/deserti®ca-
tion control are a logical and thematic follow up of
the guidelines on mapping and measurements by
PAP/RAC in 1997 (UNEP/MAP/PAP 2000).
Determining the areas with
higher landscape value: a case
Dams may have a series of environmental conse-
quences that can or can not be anticipated. Some of
these are dealt with in greater detail elsewhere,
such as subsidence, earthquake triggering, the
transmission and expansion in the range of organ-
isms, the build-up of soil salinity, changes in
ground-levels creating slope instability, logging
240 SË . SË ahin and E. Kurum
and sediment load reduction of the river down-
stream (Goudie, 1995). Otherwise dams can be
effected by the physical environment where they
are built. The life span of a dam is very strongly
related with the soil erosion caused by rainfall
runoff. Hence one of the steering natural processes
that may have an impact on proposed project and
which in turn may be affected by the project itself is
`erosion process'. Vegetation cover and accordingly
fauna, river sedimentation, dam life span can be
affected by this process as well. Thus, the `erosion
process' is considered in the analysis of `the areas
with higher landscape value' at present work. In
this paper this process is analyzed in the case area.
The project area
In the present work proposed Seyhan-Ko
ÈpruÈ
Hydroelectric Power Station to be constructed
over Go
Èksu Brook is taken as the case study. In
the analysis of natural processes that form a land-
scape, the natural boundaries should be taken as the
study area limit, for this reason, the catchment of
the dam lake was determined (Map 1). Impact areas
related to the proposed project were divided into two
regions within the entire catchment of the dam lake.
First degree impact areas are the slopes, which feed
directly the dam lake by rainfall run-off. Second
degree impact areas are the rest of the catchment in
which the tributaries of the Go
Èksu Brook are loaded
by sediments at ®rst, than those tributaries carry
whole sediment loads into dam lake.
Method
In this study ICONA erosion risk method developed
by the Directorate General for the Conservation of
Nature (DGCONA, previously ICONA) in Spain was
used and adopted to the study area. The method
integrated with the Guidelines for Mapping and
Measurements of Erosion prepared by UNEP/MAP/
PAP (2000), particularly in order to use a standar-
dized mapping legend (Annex IV of the Guidelines)
and to recommend the follow up steps of erosion risk
analysis.
Map 1. Study area: Dam lake catchment over Seyhan-Go
Èksu Brook.
GIS Environmental Impact Assessments 241
The Directorate-General for the Conservation of
Nature (DGCONA) executed a project called
LUCDEME (Lucha Contra la Deserti®cacio
Ân en el
Mediterr
aneo/Combat with Deserti®cation in
Mediterranean) at the South-East of Spain between
the years of 1981±1984, and developed a method in
order to de®ne erosion risk (MOPU, 1985). Figure 1
illustrates the steps of the method. For the elabor-
ation of the present method, conventional maps (at
1/25 000 scale) of topography (for slope analysis),
vegetation cover (for soil protection grades), geology
(for erodibility analysis) were transferred to the
computer media by the AutoCAD R.14 software.
The recti®cation of the transferred data was per-
formed by ERDAS Imagine 8.3. Slope analysis was
made by LANDCADD R.12 software. Then all the
data were transferred into a GIS engine that is
ArcCAD R.14. This software provided the ability to
create, manipulate, analyze and display topological-
ly correct geographic data in digital form.
Slope
In accordance with MAPA/ICONA (1983), following
slope gradients were used: 0±12, 12±18, 18±24,
24±35, 35±60 and >60%.
Vegetation cover and soil
protection grades
Vegetation cover is the variable controlling ero-
sional activity that is most affected by human mani-
pulation and is therefore an important component
of any predictive model (Trimble, 1990). Each
vegetation cover type has its own soil protection
grade, which depends upon land-use differences,
current soil management practices, and other
environmental parameters. In this case study, for
the de®nition of soil protection grades the follow-
ing table developed by IFIE-Seccio
Ân de Hidr
aulica
Torrencial del Antiguo Instituto Forestal de
Investigaciones y Experiencias in 1968 (MAPA/
ICONA, 1983) was used (Table 1).
The vegetation cover map to be used in this study
was re-coded from the `Vegetation Cover Map of
Turkey' by OB-Directorate General of Forestry in
accordance with the following classes de®ned from
Table 1:
Bare areas;
Dense woodland;
Loose woodland;
Degraded woodland;
Agricultural areas.
In the next step, the geographical data (slope
condition and vegetation cover) of the site were
interpreted by the indices given Table 1 in order to
produce site speci®c composite indices. `The soil
protection grades' being qualitative values were
then assigned to these composite indices in the
following fashion: 10: very high (VH), 09±08: high
(H), 07±06: moderate (M), 04±03: low (L), 02±00:
very low (VL). Accordingly, The map of `Soil
Protection Grades' was produced with the aid of
GIS by the superimposition of soil condition and
vegetation cover data in accordance with these
qualitative values shown in Table 2.
Geology and erodibility
Physical and chemical characteristics of bedrocks
have signi®cant in¯uence over erosion process.
Geological structure map to be used in this study
was re-coded from the `Geological Resources Map of
Turkey' by MTA, Directorate General of Mineral
QUALITATIVE EROSION
ANALYSIS
VEGETATIONSLOPEGEOLOGY
SOIL PROTECTIONERODIBILITY
EROSION RISK
Figure 1. Method: MOPU (1985), MAPA/ICONA (1983), and MAPA/ICONA (1991).
242 SË . SË ahin and E. Kurum
Research and Exploration in accordance with the
classi®cation of erodibility by MAPA/ICONA 1983.
Igneous rocks;
Well cemented calcareous rocks;
Compacted siliceous rocks;
Slightly consolidated rocks;
Soft formations;
Alluvial deposits.
After this interpretation, it was observed that
there exist only the following two geological classes
Table 1. Soil protection indices by vegetation cover by IFIE (MAPA/ICONA 1983).
Vegetation type Statement Slope Protection index
Forest Dense woodland cover (07 density) for any slope gradient 10
Woodland cover with less than 07
density and non-degraded bushes
and herbaceous plant cover
for any slope gradient 10
Woodland cover with less than 07
density and degraded bushes and
herbaceous plant cover
3 04
2 08
1 10
Non-degraded bush cover for any slope gradient 10
Degraded bush cover 3 02
2 02
1 08
Well-conserved pasture 530% 09
>30% 06
Degraded pasture for any slope gradient 03
Agriculture Agriculture without conservation practices 3 00
2 05
1 09
Agriculture with conservation practices 1 and 2 10
3 03
Bare-land 3 00
2 05
1 09
1. Slope inferior than the gradient of erosion initiation.
2. Slope between the gradient of erosion initiation and total dragging.
3. Slope superior than the gradient of total dragging.
Table 2. Soil protection grades and Erodibility (Adopted from MAPA/ICONA 1983, MAPA/ICONA/1991), Atucha et al.,
1993; Gardi et al., 1996.
Slope
0±12 12±18 18±24 24±35 35±60 >60
Type of vegetation cover
Soil protection grades
Bare-lands V V V V V V
Dense woodland VH VH VH VH VH VH
Loose woodland VH H M M V V
Degraded busy areas H M V V V V
Agricultural areas M V V V V V
Material
Erodibility
Compacted siliceous rocks EN EL EL EM ES ES
Slightly consolidated rocks EL EM EM ES EV EV
Soil protection grades: VH, Very High; H, High; M, Moderate; L, Low; VL, Very Low.
Erodibility classes: EN, erodibility from none to low; EL, erodibility from low to moderate; EM, erodibility from moderate to severe;
ES, erodibility from severe to very severe; EV, erodibility from very severe to total dragging.
GIS Environmental Impact Assessments 243
in the study area:
well cemented calcareous rocks;
siliceous rocks.
The inherent characteristics of these re-coded
geological structure were then interpreted with
slope gradients to come up erodibility classes
shown in Table 2 and superimposed to produce the
map of `Erodibility'.
Result
The `Erosion Risk Map' which is one the main goals
of this article was produced by the superimposition
of two critical attributes of the site `Soil Protection
Map' (produced by the superimposition of the map
of vegetation cover and slope) and `Erodibility Map'
(produced by the superimposition of the maps of
geology and slope).
The superimposition of the two attributes was
achieved according to the criteria presented in the
Table 3, and Map 2 was produced as a result. Table 3
enumerates the degrees of erosion risks in accord-
ance with Annex IV on Mapping Legend of the
Guidelines for Erosion and Deserti®cation Control
Management of UNEP/MAP/PAP (2000): These
numbers denote the following: 1: very severe; 2:
severe; 3: moderate; 4: slight; 5: very slight.
As it is seen on Map 2, the signi®cant coverage
of the study area including the surroundings of
the dam lake presents very severe risk of erosion.
When analyzed by conventional indices, such as
Map 2. Erosion risk.
Table 3. Criteria for erosion risk (Adopted from MAPA/
ICONA 1983, MAPA/ICONA/1991), Atucha et al., 1993;
Gardi et al., 1996.
Erodibility Soil protection grades
VH H M L VL
EN 1 1 1 2 2
EL 1 1 2 3 4
EM 1 2 3 4 4
EV 2 3 3 5 5
EE 2 3 4 5 5
244 SË . SË ahin and E. Kurum
percentages (Figure 2), the picture of the distribu-
tion reveals a clear pattern of gravity as far as the
erosion risk is concerned.
The areas at severe and very severe level of
erosion risk excluding rocky areas are those in
high landscape value from conservation point of
view. For the sustainability of natural landscape,
such activities that can accelerate erosion should
not be permitted in those areas. Therefore, to
improve the conditions of land in order to provide
resistance against the potential erosion problem re-
vegetation practice needs to be improved in par-
ticular on the ®rst degree impact areas around the
dam lake to be able to both extend the dam life-span
as well as to decrease the potential risk of rainfall
erosion. As it is stated before in the section of project
area de®nition, ®rst degree impact areas are the
slopes that feed directly to the dam lake by rainfall
surface runoff. The conservation value of these
areas is very high.
The more rational and effective impact mitigation
measures can be achieved by the combination of
erosion risk map with existing land-use types
and socio-economic structure. The further steps
of ICONA method provide an opportunity for this
purpose with its erosive landscape classi®cation.
Discussion
The results of this study might be discussed in two
aspects.
Methodological aspects
Erosion in Turkey is one of the most important
ecological problems threatening natural resources.
According to the sediment measurements made on
26 large basins, the amount of sediment transported
to seas and lakes is about 500 million tons per year
(Dog
Æan et al., 2000). In this end environmental
management practices such as EIA have to take into
consideration properly this severe problem in their
contex. One of the main contributions of this paper
is to propose a method how to carry out erosion risk
analysis in an EIA work under the section of the
analysis of the areas with higher landscape value
toward internationally appreciated standards.
There are some commonly known soil erosion risk
estimation and mapping methods such as ICONA,
CORINE,
1
USLE, etc. In this present work
ICONA method was used and integrated with
the Guidelines for Erosion/Deserti®cation Control
Management which were prepared by UNEP/MAP/
PAP (2000) in corporation with FAO. All these
methods have their own merits and the paper does
not aim to make an argument in favor of the ICONA
method. In the countries where the problem of soil
erosion is very severe and the dearth of detailed and
upgraded data have been signi®cant and the avail-
ability of data is very expensive and time consum-
ing, the design of data processing within the
framework of a method carries a crucial importance.
In this sense the ICONA method presents an
opportunity for rapid evaluation of potential erosion
risk in large areas. Other methods can be easily
incorporated with the results as the complimentary
part of it taking into account mainly the areas where
the erosion risk is severe.
Technological and practical aspects
The de®nition of the areas with higher landscape
value can be considered as an Ecological Impact
Assessment (EcIA) work of the EIA in respect to
ecological concerns. Brie¯y, EcIA is a formal process
of identifying, quantifying and evaluating the
potential impacts of de®ned actions on ecosystem
(Treweek and Hankard, 1998). At the same time the
effects of ecological phenomena over the proposed
projects is the question of EcIA. Treweek (1999)
states that GIS can be used as a tool in scooping or
conceptualizing the EcIA, deriving suitable study
limits and generating appropriate impact scenarios
and mitigating strategies as well as simply handling
Erosion risk degree
Very severe
82.26%
Very severe
Severe
Moderate
Slight
Very slight
Severe
0.10%
Moderate
0.11%
Slight
6.75%Very slight
10.78%
Figure 2. The area portion of erosion risk degrees.
1
CORINE Method in erosion mapping analyses the following
factors for the determination of potential and actual erosion risk;
soil texture, soil depth, stoniness, Modi®ed Fournier Indices and
Bagnouls-Gaussen Draught Indices and slope for the potential
erosion risk, and also vegetation cover for the actual erosion risk
(Dog
Æan et al., 2000; GencËler et al., 2000).
GIS Environmental Impact Assessments 245
the relevant data and making them accessible. GIS
can therefore play an important part in managing
the EcIA process. GIS holds much promise for
supporting numerical modeling of spatially distrib-
uted ecosystem processes. There are a number of
ways that GIS and ecosystem models can be inte-
grated for ecological studies (Stow, 1993). This
paper presents an example for its potential uses.
The further step of the erosion risk analysis
executed in this article as a part of EIA (or being
the possible requisite of an other environmental
management activity) should be integrated with the
recommended procedures by UNEP/MAP/PAP
(2000) for erosion control management as:
Integration of mapping outputs with socio-
economic and land-use features;
De®nition of the negative impacts of the risk
areas over proposed project and vice versa,
identi®cation of priority areas, formulation of
remedial;
Formulation of the strategy and the program for
management of erosion control, and implemen-
tation;
Environmental impact monitoring and auditing.
This evaluation practice of the erosion risk levels
and the higher landscape values for dam projects
has to be started at more strategic levels before
project level EIA, when the policies, programs and
master plans for dam constructions are being devel-
oped over a stream. This study also shows that the
environmentally determinative factors and proces-
ses may extend beyond of the legal and political
boundaries. For the success of the overall project in
any EIA practice the responsibility area of the
developer should not be limited by the legal and
political boundaries but include naturally effective
areas. The neighboring parties and the share-
holders need to be acknowledged, and be given
responsibilities for the well-being of the project
and the nature itself.
References
Aronoff, S. (1991). Geographical Information Systems:
A Management Perspective. WDL Publications,
Ottowa, 294pp, Canada.
Atucha, J. L., Ben Dadj Ali, H., Echeverria, J. L.,
Kristensen, M. J., Rios, J., Rozpide, M. and SËahin, SË.
(1993). `Nuevas Orientaciones para el Uso Integrado
de los Recursos Naturales en la Comarca del Moncayo',
Volume I, pp. 31±44, Instituto Agronomico Mediterra-
neo del Zaragoza-EspanÄa.
Dog
Æan, O., KuÈcËuÈkcËakar, N.,
Ozel, M. E. and Yõldõrõm, H.
(2000). Erosion Risk Mapping of Dalaman Basin
Located in West Mediterranean Region Using Corine
Method. In International Symposium on Deserti®ca-
tion, Konya, Turkey.
Gardi C., Pisa, P. R., Rossi, M., Kurum, E. and SËahin, E.
(1996). Qualitative Analysis of Land Degradation by
Erosion in Centonara River Basin, Bologna, Italy.
In Proceedings of 1st International Conference on Land
Degradation, pp. 204±216, Adana, Turkey.
GencËler, G., Azdiken, S. and Altan, M. (2000). Prepara-
tion of Soil Erosion Risk Map of Middle Sakarya Valley
by Using Remote Sensing (RS) and Geographical
Information Systems (GIS). In Proceedings of 2nd
International Conference on GIS for Earth Science
Applications, on CD, I
Çzmir, Turkey.
Goudie, A. (1995). The Human Impact on the Natural
Environment. Blackwell Publisher Ltd, 454pp, UK.
Joa
Äo, E. M. (1998). Use of Geographical Information
Systems in Impact Assessmet. In Environmental
Methods Review: Retooling Impact Assessment for the
New Century (A. L. Portae and J. F. Fittipaldi, eds.),
pp. 154±170, AEPI, IAIA.
MAPA/ICONA (1983). Paisajes Erosivos en el Sureste
Espan
Äol: Ensayo de Methodologõ
Âa para el Estudio de su
Cuali®cacio
Ân y Cuanti®cacio
Ân. Proyecto LUCDEME,
66p, EspanÄa.
MAPA/ICONA (1991). Metodologia para el Disen
Äo
de Actuaciones Agrohidrologias en las Cuencas
del Ambito Mediterraneo. Proyecto LUCDEME,
pp. 1±31, EspanÄa.
McHarg, I. (1969). Design with Nature. Doubeday:
Garden City, NY.
MOPU (1985). Methodologõ
Âa para la Evaluacio
Ân de la
Erosio
Ân Hõ
Âdrica. Direccio
Ân General del Medio Am-
biente, EspanÄa.
NRA (1993). River Landscape Assessment: Methods and
Procedures. Conservation Technical Handbook No. 2,
National Rivers Authority, UK.
SËahin, SË. and ve CËabuk, A. (1998). Cog
Æra® Bilgi
Sistemlerinin CËevresel Etki Deg
Æerlendirmesinde
Kullanõmõ (Use of Geographical Information
Systems in Environmental Impact Assessments).
UlasËilabilir GIS Semineri, Sayõsal Gra®k, 16 Aralik,
Ankara.
Smith, L. G. (1993). Impact Assessment and Sustainable
Resource Management. Longman Group, p. 21, UK.
Stow, D. A. (1993). `The Role of Geographical Informa-
tion Systems for Landscape Ecological Studies'. In
Landscape Ecology and Geographical Systems
(R. Haines-Young, D. R. Green and S. Cousins, eds.),
pp. 11±19, Taylor &Francis Ltd.
Treweek, J. and Hankard, P. (1998). Ecological Impact
Assessment. In Environmental Methods Review:
Retooling Impact Assessment for the New Century,
(A. L. Portae and J. F. Fittipaldi eds.), pp. 262±272,
AEPI, IAIA.
Treweek, J. (1999). Ecological Impact Assessment. Black-
well Science Ltd., 352pp.
Trimble, W. S. (1990). Geomorphic Effects of Vegetation
Cover and Management: Some Time and Space
Considerations in Predicting of Erosion and Sediment
Yield. In Vegetation and Erosion (J. B. Thornes ed.),
John Wiley and Sons Ltd, UK.
UNEP/MAP/PAP (2000). Guidelines for erosion and
deserti®cation control management with particular
246 SË . SË ahin and E. Kurum
reference to Mediterranean coastal areas. Split, Priority
Action Programme.
Vellinga, P., R. S. de Groot, R. J. T. Klein Rudolf de Groot
and Richard Klein (1994). An Ecologically Sustain-
able Biosphere. In The Environment: Towards a
Sustainable Future (Dutch Committee for Long Term
Environmental Policy ed.), pp. 317±346, Environment
and Policy-series Vol. 1, Kluwer Academic Publ.,
Dordrech, The Netherlands.
GIS Environmental Impact Assessments 247
