Geomorphological indicators for environmental impact assessment: consumable and non-consumable geomorphological resources

Geomorphology 18 (1997) 169-182

GeomoNrphological indicators for environmental impact assessment: consumable and non-consumable geomorphological resources V. Rivas a, K. Rix b, E. Fran&s b, A. Cendrero b, D. Brunsden a a Dept. of Geography, King’s College, Strand, London WC2R2LS, UK b DCITIMAC, Ciencias de la Tierra, Fat. Ciencias, Uniuersidad de Cantabria, Auda. de 10s Castros s/n,

39005 Santander, Spain

Received 6 June 1995; accepted 19 June 1996

Abstract A methodological approach is proposed for the incorporation of geomorphological features into environmental impact A series of quantitative indicators and indices are proposed, so that impacts on both consumable and assessments. non-consumable geomorphological resources can be objectively determined. Impact can thus be expressed by means of magnitudes with specific dimensions, or at least as fractions of a maximum theoretical value. Procedures for the integration of individual indices into general impact assessments are also proposed. Keywords: geomorphological resources; environmental impact assessment; geoenvironmental indicators

1. Introduction Geomorphological features are an essential part of the environment and they represent an important conditioning factor for the development and distribution of certain biological assemblages, as well as for a variety of human activities. However, geomorphology usually receives very limited or no attention at all in the process o-F Environmental Impact Assessment (EIA). This is the case both for legal norms and for existing practices (Rivas et al., 1994, 1995a; Gonzllez et al., 199.5). This situation is probably due to a great extent to the fact that the geomorphological community has not developed methods and criteria for the incorporation of geomorphological characteristics into the process of EIA which are comparable to those developed in other fields.

A general conceptual framework concerning the role of geomorphology in environmental impact assessment has been presented by Cavallin et al. (1994). The aim of the work presented here is to go further and define a series of indicators and indices which can be used for the assessment of impacts on some geomorphological components of the environment, at different phases in the process of project development, so that meaningful comparisons between projects or alternatives can be made. The proposal presented here deals only with geomorphological resources in the wide sense of the term. That is, static geomorphological features but not active processes. The idea is to develop a series of numerical indices and to express them, whenever possible, in specific magnitudes, so that assessments can be more objectively and quantitatively expressed. This should

0169-555X/97/$17.00 Copyright 0 1997 Published by Elsevier Science B.V. All rights reserved. PI1 SO169-555X(96)00024-4

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also help to improve the reproducibility of results when assessments are made by different operators.

18 (19971169-182

Identification

of significant geomorphological elements/ comuonents

1 2. Methodology 2.1. General The methodological approach proposed here (Fig. 11, follows the classical Cartesian method; a complex reality or problem (the environment) is conceptually divided into different parts or aspects, each one of them simpler and easier to analyse, describe and assess. Geomorphological components of the environment can be grouped, for EIA purposes, into three main categories: _ Geomorphological resources (consumable); construction and other materials. - Geomorphological assets (non-consumable resources); including other geomorphological resources, the use of which does not imply the direct extraction and consumption of materials: * Landforms as a geomorphological component of the landscape. * Sites of geomorphological interest (SGI), from the scientific, educational or recreational points of view. * Geomorphological units as a support of other, geomorphologically conditioned elements of the environment (mainly certain ecosystems which are linked to some geomorphological environments). - Geomorphological processes, which can represent hazards and/or contribute to environmental degradation, i.e. weathering, soil erosion/sedimentation, mass movement, fluvial, glacial, periglacial, coastal, karst, subsidence, groundwater, and aeolian processes. The nature of the interactions between human activities for different types of projects and those categories of geomorphological features is very different, and so are the parameters which can be used to express such interactions in a way which is meaningful for the process of EIA. Therefore, the different categories should be treated separately. In the discussion that follows indicators are proposed for EIA on consumable and non-consumable geomorphological resources.

Definition of the types of interactions

with human activities

Identification of relevant parameters/qualities to describe interactions

1 Proposal of indicators to “measure” impacts and to establish impact categories

Integration

procedure

GIA ---+ EIA

Fig. 1. Methodological

flow diagram.

A description and inventory of environmental components is the first step for EIA (Rivas et al., 1994). In the case of geomorphological features, this is best done through the use of maps. These maps can be prepared at two levels: descriptive and interpretative or diagnostic. Examples of the former are surfacial deposits maps, landscape units and SGI maps, general geomorphological and process maps, geotechnical maps, etc. Examples of the latter are hazards maps, resources maps, landscape quality maps, etc. (Cendrero et al., 1992). The interactions between geomorphological features and human activities range from loss of geomorphological resources with a market value to changes in the quality of the landform units, to modifications of the rates and/or magnitude of processes, leading to increased hazards or to degradation of soil, water and biota. For each of those interactions some parameters must be indentified to describe the possible impacts, and indicators must be defined so that the impacts can be measured. 2.2. Impact on resources Surface deposits (sand, gravel, clay, peat) can be considered as geomorphological resources, because they are often consumed as construction or raw materials or as a source of energy. Any human

V. Riuas et al. / Geomorphology 18 (1997) 169-182

activity which consumes, sterilises or degrades these resources, would represent a negative impact on the geomorphological environment. The following kinds impacts can be considered: consumption as a consequence of direct extraction (this would bl: actually, the logical use but it nevertheless represents the loss of the resource). sterilization as a .result of activities which make the resource unusable (permanently or temporarily). The net effect is, in any case, the permanent or temporary loss of a resource with a market value which can, therefore, be expressed as an actual or potential monetary loss. To quantify the impacts on these type of geomorphological resources., the following parameters have been considered: V: Volume affected by the project [m3]. U: % of useful material in the deposit. P: Price [$ . m-3 11.The price of these resources is usually directly related to its quality, abundance and exploitability. R: Reversibility of action [Dimensionless: 0 to - 11. Obviously, the degree of reversibility depends on the type of project. We have considered the minimum reversibility ( - 1) for those projects which imply construction on top of the deposit for an unlimited time (nuc.lear power station, urbanisation, roads, dams, etc.); (- 0.5) for legal limitations, such as National Parks, etc.; reversibility near 0 corresponds to activities such as forestry, agricultural uses or holiday villages, where the technical measures for decommissioning are simple. if a limitation affects a resource for more than 100 years reversibility can be taken as - 1; therefore, it can be expressed as 0.01 X t, where t = No. of years the limitation remains. when the project ‘does not limit the use of the resource, the value of reversibility is 0. a: Relative abundance. It can be expressed as the volume of the deposit affected divided by the total resource volume in the area of reference [dimensionless]. The geographical area used as reference could be the country, province, municipality, the study area or the area within a certain distance of the project. A: Accessibility, defined as the ratio between the number of potential users (inhabitants) within a certain radius from the resource and the distance (D, in m or km) from the resource to the nearest road

171

(H/D). The quotient Apre/Apost will always be I 1 as accessibility after a project will never be smaller than before. The negative impact on consumable geomorphological resources (I,) can be expressed, for each outcrop affected, as a potential monetary loss by means of the following expression: 1, = V. u . p . R . a .

A

pre-project A post-project

Thus, the maximum possible negative impact will be equivalent to the total market value of the resource. The total impact on resources (Zrr) would be: n

‘Tr=

C

i=

'Ii

1

where n is the number of outcrops or deposits. Detailed geomorphological information conceming the geometry, size and composition of the deposits in the area should be gathered to obtain a precise measure of the impact (planning and design phase). This impact would express in monetary terms the geomorphological resource loss to be expected. Comparisons between alternatives (locations, projects) will be simple and straightforward. At the reconnaissance level the same indicator can be applied but it will be much less precise. If exact data on volumes and percentage of useful material (V,u) are not available, reasonable estimates can be made. In the case of relative abundance (a), areas occupied by the different outcrops can be used instead of volumes. The use of these indicators to determine post-project impacts (audits) is also simple. An example of the type of geomorphological information which could be used for the assessment of impacts on resources is shown in Fig. 2. Thresholds to define impact categories can easily be defined using this index. For instance, it could be established that when the total “value” of the impact is greater than X, the impact is not acceptable; or that an impact equivalent to 1% of the value in the area of reference is not acceptable, etc. 2.3. Impact on assets Other geomorphological which are not connected

resources have values to their direct use and

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et al ./Geomorphology

18 (1997)

169-182

V. Rivas et al./Geomorphology 18 (1997) 169-182

consumption as materials and, therefore, cannot easily be expressed in monetary terms. These include, as mentioned above: geomorphology as a component of landscape; geomorphological sites of interest from the scientific, educational or recreational point of view; geomorphological features as an essential support of other components of the environment. In this case, the interactions with human activities which can result in impacts on the resource include any action which diminishes the aesthetic quality of a unit, the scientific-cultural character or usefulness of a site or the productivity or character of biologic assemblages supported by certain geomorphological units. In order to evaluate the geomorphological components of the landscape, it is necessary to define landscape units which can be mapped, the parameters for the description of such units and their interaction with human activities. The perception of the landscape depends on a variety of factors, such as topographic complexity, relief, colours, shapes, human intervention, presence of water, uniqueness of the elements present, etc. (Claver, 1991). Several such factors depend ‘on geomorphological characteristics. For the evaluation of landscape, the relevant components can be assessed separately and then integrated (Cendrero et al., 1992). The method proposed here takes into consideration the geomorphological components of the landscape, but it also provides the basis for the integration of other components, following a similar procedure. Geomorphology is considered as a factor which determines both quality and visual incidence of the landscape. The quality (Q) of each landscape unit can be considered to depend on two main characteristics: intrinsic value (V) and degree of naturalness (N) of the unit as a result of human interventions. The quality of one unit is not only determined by the characteristics of the unit itself, but also by those of the surrounding landscape units: n No . V, + c N, . V,

Q=

e=l

n+l

where N, = degree of naturalness of unit 0 (ranging from 0 to 4, see below), V, = intrinsic value of unit 0 (ranging from 0 to 4, see below), N, = degree of

173

naturalness of the adjacent units, V, = intrinsic value of the adjacent units, and n = number of adjacent units. The degree of naturalness of a unit depends on the intensity and extent of human activities in it and may vary as a result of the project. It can be expressed by means of a O-4 scale, on the basis of the percentage covered by different types of land-use activities. Intrinsic value can be defined, from the geomorphological point of view, using a series of parameters which are related to the perceptual factors mentioned above. The following expression is proposed: V= W,.S+

W,.D+

W,,.CX+

W,.R+

W;w

where W = weights of the different parameters established, for instance, by means of the Delphi method (Balkey, 1969; Ervin, 1974; Eckenrode, 1975); CW = 1, S = geomorphological singularity, uniqueness, or relative abundance of the unit type in the area of reference (see Table l), D = geomorphological diversity, a measure of homogeneity, defined by the number of morphodynamic units per km2 (see Table l), CX = geomorphological complexity, equal to the number of slope units per km’, which in a way reflects shapes (see Table 11, R = relief energy, expressed as maximum minus minimum altitude, which is related to the size of landscape features (see Table 11, and w = water (presence of different types of water bodies, as described in Table 1). The superposition of a geomorphological map and a landscape units map allows the determination of the number of important geomorphological features in each landscape unit in order to obtain singularity values; geomorphological diversity can be obtained through a map of morphodynamic units, on the basis of the morphodynamic systems map (Cendrero and Diaz de TerBn, 1987) (Fig. 3); terrain complexity and relief energy can be determined using topographic maps. Table 1 shows the criteria which could be applied. If Q is divided by 16, landscape quality will be expressed by a O-l scale; that is, fractions of a maximum theoretical value. Other, non-geomorphological factors affecting landscape quality which should be added to the expression above are, for instance; vegetation, fauna and historical/symbolic significance, or type and intensity of human activities/use.

4 5

Coast from Laredo to Punta Yesera Slopes to the south of Laredo

Atlantic Ocean

Karst complex (Candina)

terrace

units are denoted by large digits. SGI are denoted by numbers inside from Rivas et al. (1995b).

@Marine

@ Bamhans (Sonabia)

@ Diapir (San Julian)

@ Karstic-structural depression (Liendo)

01

B,: Outlet beach (OriiUn) B,: Pocket beach (Sonabia) B,: Pocket beach (S. Julian) D,: Dune field (Oriii6n) D,: Climbing dunes (Sonabia) C,: Cliff on limestones with very active erosion processes C,: Cliff on limestones with scree deposits (very active erosion) C,: Retreating cliff on marls I,: Main intertidal channel I,: Sandflats I,: Mudflats 14:Isolated former intertidal areas Is: Drained former intertidal areas I,: Filled former intertidal areas T,: Marine terrace on marls T,: Marine terrace on limestones with lapiez and dolines T+ Marine terrace on limestones with lapiez covered with vegetation T.,: Marine terrace on limestones with lapiez without vegetation T,: Marine terrace on limestones with residual clays at the bottom F,: Small plain bottom fluvial valley

nt Coast from Cercdig0 to Castro 1W of Agiiera valley Liendo 10 Penfnsula of Sonabia

Fig. 3. Map of landscape units, morphodynamic units and SGI in the area represented in Fig. 2. Landscape ctrcles. Limtts of SC;1 shown by dashed lines. The morphodynamic units are denoted by letters. Modified

0

f-l-

K,: Alochtonous karst depression with sink hole 6: Karstic depression with surface lapiez and dolines Ks: Karstic towers

S,: Guilied slopes S,: Strong gullied slopes S,: High erosive slopes KSD: Karstic-structural depression Ka: Slopes on limestones K,: Slopes with partly covered lapiez and dolines Ks: Slopes with surface lapiez and dolines K,: Slopes with covered lapiez and dolines K.,: Karstic depressions Ks: Karstic depression with residual clays at the bottom

s,: Slopes

V. Rivas et al. /Geomorphology Table 1 Parameters proposed for the determination landscape in an area of northern Spain

of the intrinsic value of

Parameters

Value

Class

Geomorphological singularity (Sk 1/number of units of the same type in the area of reference

1 0.75 0.50 0.25 < 0.05

4 3 2 1 0

Geomorphological diversity ( D): number of morphodynamic: units/km*

>4 3-4 2-3 l-2
4 3 2 1 0

I8 (1997) 169-182

parameters suggested. The Pp value can be computed for individual units or for “bands” or “rings” along or around the structure/unit considered. A weight can be assigned to perceptibility as a function of distance to the structure. Impacts on landscape (I,) could thus be expressed, for each landscape unit, as: 1, =

- Qpre) .VI (Qpost

and the total impact on landscape

‘Tl = i

i=

>8 6-8 4-6 2-4 <2

4 3 2 1 0

Relief energy CR): difference in altitude (m)

> 1000 500- 1000 300-500 50-300 < 50

4 3 2 1 0

Presence of water ( W) in or adjacent to unit

Sea Lake(s) Rive&) Small stream(s) No water

4 3 2 1 0

Geomorphological complexity number of slope units/km*

CC):

The visual incidence (V,) of projects depends essentially on their degree bf visibility (V) from surrounding areas (a function of landform and relief; Fig. 4) and perceptibility can be expressed, for instance, in terms of total person-hours per day of viewing of a certain structure or unit. Different assumptions or detailed surveys can be carried out to determine the

175

(IT,) as:

‘li 1

where IZ is the number of landscape units. At the end of this process landscape categories will be expressed by a magnitude which has specific dimensions (for instance, visual incidence in km2 * person-hours) multiplied by a dimensionless factor which depends on the intrinsic value of landscape units and on the degree of human modification of such units, before and after the project. When the quality of a unit is not affected by the project (Qpre = Qpost) the impact is obviously nil. If visual incidence (Vi) is expressed as percentages or fractions of one, with respect to an established threshold considered as a maximum, the overall impact is also dimensionless. Alternatively, impacts on landscape could be expressed by quality loss and visual incidence taken separately, and thresholds could be defined for both parameters independently. Thus, the significance of geomorphology as a conditioning factor of visual impacts can be incorporated. Geomorphology is included in the definition of landscape quality; landform and relief are used to establish the effect of landscape modifications on human beings, through the consideration of visibility. Mitigation measures can affect the visibility of the project and the degree of naturalness, but not the value of units, as defined above. Therefore it is possible to calculate the impact during the construction phase, considering the visibility and degree of conservation without mitigation, and the impact during the functioning phase, considering all possible mitigation measures. The index proposed can be applied at both the reconnaissance and detailed levels. The only differ-

176

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I8 (1997) 169-182

Atlantic

Ocean

V 0

Ikm

Fig. 4. Visibility map for a motorway (modified from-Rivas et al., 1995b).

built in the area shown in Figs. 2 and 3. Areas from which the motorway

ence would be the scale of the maps to be used and the precision in the values obtained for the different parameters. It can also be used to determine postproject impacts for audits. As in the former case, it is possible to define thresholds or limits between impact categories. It must be mentioned that, although the definition of thresholds is simple at the conceptual or theoretical level, it may be more difficult to establish and apply them at the practical level, depending on the nature of the impacts and of the area considered. Sites of Geomorphological Interest (SGI). These sites are defined on the basis of scientific, educational and recreational interest, from the geomorphological point of view. The value of a SGI can be expressed by means of a dimensionless index such as: ” ,=

WQ+P)

Sk?1

48 (where C = state of conservation of the SGI (from 0 to 4; Table 21, Q = quality of the SGI (O-41, P = potential for use of the SGI (O-4), and V,,; = value of the SGI, which will range from 0 to I) with quality defined as (Table 2): Q= W,.A+ W,.E+ W,.K+ W,;Ex+W,.D

is visible are shown in white

(where W = weights of the different parameters (Delphi method), A = relative abundance, E = extent of the SGI with respect to the largest SGI of the same kind, K = degree of knowledge, Ex = good example for processes, and D = diversity of elements of interest: mineralogical, geomorphological, palaeontological, stratigraphical, structural, etc.) and potential for use (Table 2): P=W,;Ac+

W,.O+

W,-S+

W,.H+

W,,,

. Act where W = weights of the different parameters (Delphi method), AC = activities which can be carried out, such as specimen collecting, field experimentation, recreation, etc., 0 = conditions for observation, S = availability of services, H = inhabitants in the area, and Act = accessibility. Weights add up to 1 in both cases. Division by 48 is used to normalise V& values to a theoretical maximum value of 1. The expression for V& shows that the most relevant parameter is the state of conservation (Cl since the destruction or near destruction of a SGI leads to values near 0. On the other hand, we have considered quality twice as important as potential for use

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Table 2 Values of the different parameters potential for use of XX’s

Table 2 (continued) used to express the quality and

Value Description Potential for use

Value Description

E 4 3 2 1 0

state

AC: activities 4 5 types of activities 3 4 types of activities 2 3 types of activities 1 2 types of activities 0 1 type of activity

of conservation

Well preserved, no deterioration. Some deterioration with loss of some minor elements. Deteriorated through some human actions which destroy or hide part of the features. Numerous human actions which deteriorate the character of the site. Character of the site destroyed.

H: number of inhabitants 4 > 100000 inhab. in a radius of 25 km 3 50-100000 inhab. in a radius of 25 km 2 25-50000 inhab. in a radius of 25 km 1 10-25000 inhab. in a radius of 25 km 0 < 10000 inhab. in a radius of 25 km

Q: quality of the SGI A: relative abundance Only one example in the region 4 2-4 examples 3 5 - 10 examples 2 IO-20 examples 1 > 20 examples 0 D: diversity 5 or more 4 4 elements 3 3 elements 2 2 elements 1 1 element 0

S: availability of services 4 2 0

Act: accessibility Direct access 4 Direct access 3 Direct access 2 < 1 km from 1 > 1 km from 0

elements of interest of interest of interest of interest of interest

E: extent > 90% of the greatest SGI of the same kind 4 70-90% 3 30-70% 2 lo-30% 1 < 10% 0 Ex: good example for processes 4 Present, active processes clearly defined Erosion/accumulalion features of present processes not 2 clearly defined or fi3ssil forms clearly defined Fossil forms arid/c’‘’ deposits whose use for extrapolation 0 past processes is difficult K: degree of knowledge More than a Ph.D. thesis and numerous articles in refereed 4 national and international journals. At least one Ph.D. thesis and/or more than one article in 3 refereed international journals and/or various in national journals. Some articles in refereed national journals and/or one 2 article in an international journal. Some brief notes in national journals or some articles in 1 regional-local journals. No existing publications. 0

Good services within 1 km Incomplete services within 5 km Absence of services within 10 km

via national/regional via local roads via tracks a vehicle path a vehicle path

roads

0: conditions of observation Public property of land, no limitations of access, no visual 4 obstructions Limitation of access or partial visual obstructions 2 Private property or view obstructed by fences, vegetation, 0 etc.

of

because the former reflects the intrinsic interest of the site and is essentially permanent while potential for use is more subject to changes. Finally, the impact on a SGI (&) can be defined as follows: ‘sgi = Vsgi(post) -

Vsgi(pre)

and the total impact on SGI (ZTsgi): i: ITsgi

=

‘sgij

j=1

n

where n Thus, fractions possible

is the number of SGI. impacts on SGI can also be expressed as of the maximum theoretical value. It is to have a positive impact if the project

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improves the characteristics which determine potential for use, thus resulting in a post-project value higher than the pre-project value. If the project causes the total destruction of the SGI, the impact is the total value of the SGI; that is VP,,. Impacts as defined above are also dimensionless. Obviously, a precise assessment of this type of impact requires a detailed knowledge of the geomorphology of the area, including a good inventory of valuable geomorphological sites. Geomorphological units as a support of other components of the environment include: - high-productivity ecosystems (for instance, high quality soils, estuaries and coastal wetlands, etc.) _ valuable biotopes (a heathland on a dune field, a karst massif which supports a particular forest formation, etc.) The application of the concept of morphodynamic units for the definition and mapping of biotopes (Frances, 1987) has shown that the most important factor which determines the distribution of the relict green oak (Quercus ilex) forest and some rare and endangered species of fauna, in northern Spain, is the presence of carbonate massifs and karst morphology, followed by height and orientation as secondary factors. The importance of geomorphology for ecosystems such as dune fields or coastal wetlands is obvious. In the case of high-productiuity ecosystems, impacts can be expressed, in a first approximation, by the absolute loss in productivity (in calories . year- ’) or in monetary terms, translating kcal year-’ into weight of food products with a market price, through different food chains (Cendrero et al., 1981; Rivas and Cendrero, 1991). In a second approximation that value could be corrected using a series of coefficients dependent on the reversibility of the action, the percentage of the unit affected and the relative abundance of such units in the study area.

where Z, = impact on ecosystems [calories +year-l], S = area affected [m*], Pr = theoretical productivity [calories m-* year- ’1, R = reversibility [dimensionless, 0 to - I], s = proportion of unit affected [fractions of 1, dimensionless], and I = importance, defined as [I - Rarity], that is 1 - (surface of similar units)/(surface of reference area).

18 (19971 169-182

The total impact on geomorphological units which support high-productivity ecosystems would be: w

be=

CL

i=

I

where rz is the number of units affected. Thus, all impacts on high-productivity environments could be added up, regardless of the type of unit/ecosystem considered, as impacts are expressed in the same productivity or monetary units. In the case of geomorphological units which support valuable biotopes, the impact can be expressed by means of:

I, = impact on biotopes [m2], S = affected surface [m2], R = reversibility [dimensionless, 0 to - 11, s = proportion of unit affected by the project [fractions of 1, dimensionless], I = importance, defined as [l - Rarity], that is 1 - (surface of similar units)/(surface of reference area>, and K = factor representing the quality or significance of the biotope (to be determined by the appropriate specialists). As in the former case, impacts on units supporting valuable biotopes can also be added, as they are expressed in m2. The impacts described here can be assessed for both geomorphological units which actually support valuable ecosystems and those which do not presently have them but represent their potential domain. For instance, a precise map of the area covered by carbonate rocks with karst morphology in northern Spain reflects the maximum potential area for the Cantabrian green oak forest. Thus, some actual and potential environmental consequences of projects or plans could be assessed on the basis of geomorphological characteristics. According to the method described above, impacts on geomorphological assets are expressed either by magnitudes with specific dimensions (km’ . persons, calories . year- ‘, m2> or as fractions of a maximum theoretical value. The establishment of impact categories can thus be simple and straightforward; it would only require the definition of certain criteria. For instance, as in the case of air or water quality standards, impacts above a certain value, on landscape or on units supporting productive ecosys-

V. Rivas et al./Geomorphology

terns or valuable biotopes, could be considered as not acceptable. In other cases the standard would not be expressed in absolute terms, but as the acceptable proportion with respect to the maximum theoretical value. The numerical values proposed for the parameters involved in the different indicators described are not necessarily acceptable for every possible situation. The characteristics of each area, the nature of the project, the scale of the analysis and the degree of detail of the assessment may require the use of different values. Nevertheless, once a set of values is accepted, the level of objectivity of the assessment can be very high and, consequently, also the degree of reproducibility of the results obtained by different operators.

2.4. Impacts on processes The establishment of indicators for the assessment of impacts on processes (and the hazards related to them) is more comphcated, because predictions have to be made with respect to dynamic rather than static qualities of the environment. Very often, the state of the art with respect to the study of different geomorphological processes does not enable making precise predictions with respect to the evolution of those processes if certain changes are introduced. Moreover, the response of natural systems may occur far away, in time and/or in space. The assessment of impacts on geomorphological processes requires the definition of ‘‘geoindicators’ ‘, of magnitudes, frequencies, defined as “measures rates and trends of geological-geomorphological processes occurring over periods of 100 years or less, at or near the e.arth’s surface, that are subject to variations of significance for understanding rapid environmental change” (Berger, 1996; McCall, 1996). If these indicators are to be useful for environmental impact assessment, it should be possible to identify the natural and human contributions to the changes they may experience. Also, it should be possible to make forecasts concerning the changes that would take place as a result of certain actions (projects>. This, in turn, requires baseline studies to determine the initial or present condition of the system.

18 (1997) 169-182

179

When it comes to impacts on hazards related to different processes, the definition of a conceptual framework and a general methodological procedure may be possible (Panizza, 1990; Cendrero, 1992; Cavallin et al., 1994), but the application of the methodology to specific problems in real-world situations is normally very difficult. For all these reasons, proposals for impact indicators for geomorphological processes are not presented here. 2.5. Integration To obtain a measure of the overall geomorphological impact some procedure for integrating individual impacts must be found. The main difficulty for arriving at a satisfactory integration is that the different impacts are expressed in different “units” or “magnitudes”. If an integrated index of geomorphological impact has to be obtained, those heterogeneous units must be transformed into homogeneous ones. One possibility is to express the different impacts in monetary terms, using a series of clearly defined criteria and assumptions. In some cases this is immediate (resources) and in others it can be done in a reasonably acceptable way (high-productivity ecosystems). However, to express in monetary terms impacts on the landscape or on sites of geomorphological interest requires the application of complex and expensive socio-economic survey methods (Lopez de Sebastian, 1975; Krutilla and Fisher, 1975; Cendrero et al., 1981) and it is not clear to what extent the monetary values thus obtained are comparable to the former ones. Nevertheless, this procedure would make it possible to add individual impacts and to obtain a value for geomorphological impacts (and, similarly, for EIA adding other types of environmental impacts) expressed in monetary units. Although this would not be an absolute and objective measure of impacts, it would certainly provide the means to make useful comparisons between different alternatives, on the basis of criteria clearly expressed in numerical terms. Another possibility is to transform individual impacts and to express all of them on a scale of O-l or O-100, by means for example of “value functions”, as in the Batelle method (Batelle Columbus Labora-

180

V. Rims et al./Geomorpholog~~

tory, 19721, or normalizing the values obtained as proposed above. If all impacts are expressed in values between 0 (no impact) and - 100 (maximum possible impact), values can be considered as “ points” or as measures of “environmental quality loss” and added up, with or without the use of weights (Ervin, 1974; Eckenrode, 1975; Cendrero and Diaz de Terln, 1987; Claver, 1991; Cendrero et al., 1993). A third possibility is to express impacts graphically, showing on a map the simple graphical superposition of individual impacts (Diaz de Teran et al., 1992; Rivas et al., 1995b). This is illustrated in Fig. 5. A somewhat more refined approach is to correct the above values, taking into account the intensity of impacts. Three levels (or more) of impact intensity (defined, as indicated above, on the basis of fractions of maximum theoretical impact) can be defined for each individual impact and coefficients can be assigned to them, such as: high = 1; medium = 0.5; low = 0.1. But of course, even if they have similar “intensities” impacts on SGI’s may be more (or less) significant than impacts on geomorphological

A

Atlantic

Ocean

18 (1997) 169-182

resources or on geomorphological units which support valuable biotopes. To take this into account, weights can be assigned to impacts on the different environmental components (using the Delphi or some other weighting method). In this case, Geomorphological Impact (GI) can be expressed by means of two indices:

GIx=

[(xs01%1%01) +(xoR~4iR*~oR) +(xo,~~o,~~o,)+(xo,~~o,~~o,)l

/rwso,+WOR+ Ki, GI, = 5,.

+ WOE 1

I,

where X represents linear kilometers affected by the different types of impacts, Z the intensity of such impacts and W their weights. S, and I,_ represent, respectively, the area and intensity of landscape impacts. GI is thus expressed by a double index: GI, (km); GI, (km*). The higher those values the greater the combined impact. A similar procedure can be used to integrate other types of impacts, on geomor-

B

A

td

B

V

1

.

2

?? 3

Fig. 5. Map of integrated geomorphological impacts. 1: impact on geomorphological resources, 2: impact on SGI, 3: impact on geomorphological units which support valuable biotopes, 4: impact on geomorphological units which support high-productivity ecosystems. Impact on landscape: A: high, B: medium, C: low. Modified from Rivas et al. (1995b).

V. Riuas et al./Geomorphology

phological features or on other components of the environment, so that a final EIA can be expressed in quantitative terms and comparisons can be made among alternatives.

3. Conclusions The figures obtained for the different impacts on geomorphology using the indices proposed, although expressed quantitatively, do not always represent “absolute measures” of specific magnitudes. Some impacts can indeed be expressed in strict quantitative terms (on geomorphological resources or on geomorphological units supporting ecosystems of high productivity); others, although expressed in magnitudes with well-specified dimensions (landscape impacts), are obtained on the ‘basis of parameters which are described in part in relative terms; finally, other impacts (on SGI’s) are expressed in relative terms with respect to a maximum theoretical value. EIA is a tool which must be applied to enact existing legislation and it is meant to provide the means to make decisions concerning the approval of projects or to select “the best” among different alternatives (locations and/or designs). Thus, it is desirable to establish procedures with the maximum possible degree of objectivity, so that the ambiguity of the assessments made by an expert or a group of experts can be reduced to a minimum. The methodology described above represents a possible approach to obtain that kind of assessment. It establishes a set of clearly defined parameters and criteria for the evaluation of impacts on geomorphological features. The choice of parameters or the criteria used (contained in the tables and in the expressions used for the calculation of the various indices) may not be. considered the best or even adequate by other geomorphologists, but once they are accepted and applied, any person studying the same area or project should derive the same or very similar results. The application of the method must rely, of course, on a good knowledge of the geomorphology of the study area. One of the more subjective aspects of the methodology presented is the choice of the “area of reference”, which is necessary to determine the relative abundance (rarity, singularity, importance) of differ-

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ent features. The choice of the area of reference should probably depend on the nature and magnitude of the project, the natural and socio-economic character of the region affected and the types of impacts considered. Examples of possible reference areas include administrative divisions (municipality, province, state, nation), natural physiographic units or environments (a mountain chain, a segment of the coastal fringe, a river basin, a forest), visual basins, the area within a specified distance from the project, etc. We believe that the kind of approach proposed here could facilitate the incorporation of geomorphological considerations into the process of EIA, thus contributing to a better understanding and preservation of the geomorphological environment.

Acknowledgements Critical review by Andrea Patrono, Hans Veldkamp and two anonymous referees helped to improve the original manuscript. The research described in this paper was funded by the Human Capital and Mobility programme of the European Union (Project ERBCHRXCT 930311) on Geomorphology and EIA: a network of researchers in the EU, publication No. 26. A. Cendrero had a grant from the DGICYT, Spain (Project PR 94-036, Prog. Sabaticos).

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