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Chapter 4: Land evaluation procedures
4.1 General
4.2 Initial consultations
4.3 Kinds of land use and their requirements and limitations
4.4 Description of land mapping units and land qualities
4.5 Comparison of land use with land
4.6 Economic and social analysis
4.7 Land suitability classification
4.8 Synopsis of procedures
4.9 Presentation of results
This chapter describes how to carry out a land evaluation. The activities undertaken and the order in which the work is done depend in part on the type of approach adopted, whether parallel or two-stage (Section 1.5.2).
The main activities in a land evaluation are as follows:
- Initial consultations, concerned with the objectives of the evaluation, and the data and assumptions on which it is to be based
- Description of the kinds of land use to be considered, and establishment of their requirements
- Description of land mapping units, and derivation of land qualities
- Comparison of kinds of land use with the types of land present
- Economic and social analysis
- Land suitability classification (qualitative or quantitative)
- Presentation of the results of the evaluation.
A schematic and simplified representation of land evaluation activities is given in Fig. 3.
It is important to note that there is an element of iteration, or a cyclic element, in the procedures. Although the various activities are here of necessity described successively, there is in fact a considerable amount of revision to early stages consequent upon findings at later periods. Interim findings might, for example, lead to reconsideration of the kinds of land use to which evaluation is to refer, or to changes in boundaries of the area evaluated. This cyclic element is indicated on Fig. 3 by the arrows labelled "iteration", and should be kept in mind throughout the following description of procedures.
FIG. 3 SCHEMATIC REPRESENTATION OF ACTIVITIES IN LAND EVALUATION
Within the Framework, considerable freedom exists in choice of the approach and procedures that are most appropriate in any set of circumstances. This choice is made on the basis of the objectives and assumptions of the study.
Consultation between the planning authorities that have initiated the study and the organization which will carry it out is an essential first stage in all cases. Such meetings are not simply briefings, but a two-way interchange of ideas on the objectives of the survey and the kind of evaluation that will achieve these objectives. Terms of reference should be flexible, permitting iterative modification during the course of the survey in the light of its interim findings.
Among matters to be decided at this stage are:
- The objectives of the evaluation
The general assumptions can be divided into those referring to the physical, economic and social context of the area, and those underlying the evaluation process itself. In addition to these general assumptions, there may be assumptions specific to particular kinds of land use (e.g. size of landholdings, minor land improvements, techniques of farming); these latter assumptions are given in the descriptions of the respective uses.
4.2.1 Objectives
The first requirement is to establish the objectives of the proposed development or adjustment, constraints to change, other assumptions, and thus the forms of land use that must be considered. This requires discussions between resource surveyors, experts in land use technology (e.g. agriculturalists, foresters), engineers, economists, sociologists, planners, government officials and representatives of the local population likely to be affected.
It is necessary to identify the broad aims of the proposed changes and to formulate general and specific proposals designed to fulfil these aims. A broad aim might be, for example, self-sufficiency in food production; general proposals to achieve this might include increased wheat production, increased livestock production and expansion of irrigation. These in turn could be broken down into more specific proposals, such as the location of a mechanized food farm, or the irrigation of a particular valley. Other examples of broad aims might be providing land for settlement, evaluating land liable to be lost to rural uses through urban development or, the most general case, making a resource inventory of a country or region for overall planning and development purposes. At the opposite extreme there may be some specific objective, such as establishing a forestry plantation to supply firewood, or providing recreational land for an urban population.
Either the broad aims or the general or specific proposals can form the objectives for land evaluation: broad aims in the case of reconnaissance surveys for resource inventory and identification of development possibilities, more specific proposals in semi-detailed and detailed surveys.
The objectives serve to define, at least as a first approximation, the relevant kinds of land use. This in turn limits the range of information needed and hence the types of surveys necessary. Where the objectives are very specific, e.g. land for smallholder tea production, survey activity is concentrated on the type of information relevant to this use and the land surveyed and personnel engaged are correspondingly limited.
Experience has shown that a suitability classification for only one use may be misleading. It is nearly always desirable to classify for at least one alternative form of use. This need not necessarily involve change but could be a continuation of the present use, with management practices either modified or unchanged. In the case of uninhabited land, it is possible, as a basis for comparison, to assess the benefits deriving from the present non-use.
4.2.2 The Context of the Study Area
Some data and assumptions are so obvious under the physical, economic, social and political conditions of a country or region that they are not always specified. Examples are aridity in a desert region, and either a high or a low level of living. However, to assist in the transfer of information from one area to another, these assumptions should be recorded.
In order to avoid an excessive list, or pages of obvious statements, this requirement can be met by an initial description of the context of the study area. This will include the following:
- Location and accessibility
Not only is it possible to infer some of the obvious assumptions from such a description, but also the significance of the suitability classification is dependent on the physical, economic and social context. Since economic and social conditions are continuously changing, the classification will eventually become obsolete and this background information will assist in judging the relevance of an evaluation some time after it has been made.
4.2.3 Data and Assumptions underlying the Evaluation
Besides the general context, there are also assumptions used as a basis for evaluation, which affect the interpretation and the spatial and temporal applicability of the results. Such assumptions should be listed as such. Some examples, by no means covering the full range of possibilities, are as follows:
- Limits to information utilized (e.g. only the soil conditions shown on a given map have been used)
- The reliability and applicability of data available from within or outside the studied area (e.g. rainfall measured x km away is applicable)
- Location is, or is not, taken into account (see below)
- Demography (e.g. present rates of population increase will continue, or will decrease)
- Infrastructure and services (e.g. repair services, credit facilities, agricultural extension services etc. will remain as at present, or will be improved)
- Level of inputs (e.g. recurrent inputs by users of land will remain at present levels, or will be increased)
- Land tenure and other institutional conditions (e.g. continuance of private freehold, or customary communal tenure is assumed, or farmers will co-operate within communal villages to be set up)
- Demand, markets and prices (e.g. existing prices in the region have been assumed, or, since no market for the projected crop exists in the region, world prices have been assumed; the effects of the expected large supply of produce from the project on the market price have, or have not, been taken into account)
- Land improvements; where a classification of potential suitability is to be made, the extent and nature of the land improvements are described
- Basis for economic analysis (e.g. amortization costs of capital works have not, or have, been partly or wholly included; family labour by smallholders has, or has not, been included in costs; discount rates used in cost-benefit analysis).
Irrespective of whether land improvements are major or minor, their cost (or the magnitude of the effort required) should be considered in a land evaluation. This applies to the maintenance costs of the improvements as well as to the non-recurrent capital costs. If the costs cannot be assigned to specific areas of land (as is sometimes the case in multi-purpose improvements, e.g. irrigation and hydro-electric power projects), then the degree to which recurrent and capital costs have or have not been taken into account must be specified.
Location in relation to markets and supplies of inputs, may affect land suitability. Especially in less developed countries, there may be areas which in other respects would be suitable for some form of productive use, but which cannot presently be put to that use because of difficulties of access to markets and supplies of inputs (e.g. fertilizers). This may be caused by distance alone or because the areas lie amid difficult terrain or lack good roads.
In surveys of relatively small areas, the location factor may be effectively uniform throughout the area studied. In such circumstances, location can be treated as part of the economic context. \}here large areas are being considered however, transport costs may vary considerably with location. In these circumstances, location can be treated as a land quality.
Location should be taken into account in evaluations where possible. In qualitative surveys this may not be the case, owing to lack of sufficient information on costs. In quantitative surveys, road construction and transport costs can be estimated and therefore included. Depending on the objectives, accessibility may be assessed either with respect to the present situation or to the position following improvements under consideration, e.g. a new road, railway or harbour works. It is open to exclude the costs of the improvements themselves (on grounds that their benefits extend beyond the land under consideration), to include maintenance costs but not amortization of capital, or to include both.
4.2.4 Planning the Evaluation
Other matters discussed during the stage of initial consultations involve the nature and planning of subsequent activities in the evaluation.
i. The extent and boundaries of land to be evaluated
ii. The kinds of land use which appear to be relevant for consideration
These are selected on the basis of the objectives of the evaluation and the physical, economic and social background of the area. The objectives indicate whether a wide range of kinds of land use are to be included, or whether the study is directed towards one specific use. In most cases the physical background, e.g. features of climate found over the whole area under consideration, will substantially reduce the range of uses of land which are relevant. There will also be constraints set by economic and social factors, e.g. levels of living or a requirement that a particular type of land tenure, individual or communal, be employed.
iii. Whether a two-stage or parallel approach is to be followed
This depends on the purposes, scale and intensity of the study and also on the times when the specialists are available.
iv. The type of suitability classification to be employed
Selection of a qualitative or quantitative classification, and one of either current or potential suitability, is made on the basis of the objectives, scale and intensity of the evaluation. Qualitative classifications are normally employed on reconnaissance surveys for general planning purposes, quantitative for more specific proposals. Where major land improvements, such as drainage, reclamation or irrigation schemes, are contemplated, classifications of potential suitability are necessary; in such cases it may be desirable additionally to classify the land on the basis of its current suitability, or order that benefits with and without the proposed development can be compared.
v. The scope, intensity and scale of the required surveys
This is decided by means of comparison between the data required, as determined by the purposes of the evaluation, and that which is already available. The nature of the data required is greatly influenced by the kinds of land use being considered (e.g. soil survey for agricultural use, ecological survey for grazing of natural pastures). It is first necessary to review the existing information e.g. topographic maps, air photograph cover, soil maps, river discharge data, population, production and other statistical data, projections of demand. This is compared with the requirements for an evaluation of the given type and intensity. Decisions made will include, for example, whether new air photograph coverage is required, whether a soil survey is necessary and if so at what scale and density of observation, and what economic data must be collected.
vi. Phasing of the activities
Having made initial decisions on the aspects detailed above, it is then necessary to estimate the time to be allotted to each of the subsequent activities and their relative phasing.
The initial consultations are an essential part of any land evaluation study. Through a clear understanding of the objectives and assumptions it is possible to plan the subsequent activities so that they are directed towards producing information relevant to the purposes of the evaluation and, conversely, to avoid activities, particularly time-consuming and costly field surveys, which will yield information of an inappropriate type or level of intensity.
Some of the decisions made during the initial consultations may later be modified, by iteration, during the evaluation. Such decisions should therefore be left flexible. Where a written agreement is involved e.g. between clients and consultants, provision should be made for its subsequent modification, by further discussion and agreement.
The following sections outline subsequent activities in an evaluation, including surveys, analysis, classification and presentation of results.
4.3 Kinds of land use and their requirements and limitations
4.3.1 Description of Kinds of Land Use
The identification and description of the type" of land use which are to be considered is an essential part of the evaluation procedure. Some restrictions to the range of uses relevant for consideration will have been set by the objectives and assumptions. Two situations may be distinguished:
- The kinds of land use are specified at the beginning of the evaluation procedure.
- The kinds of land use are broadly described at the beginning and subject to modification and adjustment in accordance with the findings of the evaluation procedure.
The first situation can arise in qualitative surveys aimed at evaluation in terms of major kinds of land use. It can also occur in studies aimed at locating land for only one or for a limited number of land utilization types, e.g. sites for irrigated fruit growing or for a forest reserve; in such circumstances the kinds of land use to be considered are largely defined by the objectives.
The second situation occurs, for example, in land development projects which are likely to include arable farming of several kinds, livestock production and forestry. Initially the land utilization types are described in general terms, e.g. arable farming by smallholders. As the evaluation proceeds, such details as crop selection, recommended rotations, required soil conservation measures and optimum farm size are progressively determined, so that at the end of the study the land utilization types are described in detail.
In the first situation, the kinds of land use are described prior to the land suitability classification. In the second, they are modified during the classification. In practice the distinction is not sharp as some adjustment or reconsideration of uses may take place in the first situation.
Attributes of land utilization types to be included in the description have been given in Chapter 2.
4.3.2 Identification of Requirements of the Use and Limitations
After, or concurrently with the description of kinds of land use, their requirements are determined (Section 2.5). Each kind of land use needs different environmental conditions if it is to be practiced on a sustained and economically viable basis. For example, most perennial crops require available moisture within root range throughout the year, irrigated rice culture requires land which is level or can be made level at acceptable cost, and forestry requires a certain foothold for roots although it is usually tolerant of steep slopes.
The limitations (2.5) for each type of land use are determined at the same time as the requirements. These requirements and limitations indicate the types of data which are required for evaluation, and thus condition the nature of the surveys needed.
It should be noted that the description of kinds of land use and the identification of their requirements and limitations are operations requiring studies in the field. These are likely to include visits to sites where production data (e.g. crop yields, cattle carrying capacity, rates of tree growth) are available, and comparison of these data with environmental conditions and methods of management. These sites need not be confined to the area being evaluated. Fieldwork of this nature may constitute a major activity in the evaluation in terms of time and manpower, perhaps equalling or exceeding that spent on the survey of basic resources.
Further information relevant to the identification of land use requirements and limitations is discussed below under Diagnostic procedures (4.5.2), and examples are given in Chapter 5.
4.4 Description of land mapping units and land qualities
Most land evaluation studies require physical resource surveys, although occasionally there may be sufficient information already available. The surveys will frequently include a soil or soil-landform survey, and sometimes such work as pasture resource or other ecological surveys, forest inventory, surveys of surface-water or groundwater resources, or road engineering studies. The objects of such surveys are to define and determine boundaries of the land mapping units and to determine their land qualities.
The delineation of land mapping units will be based in part on land characteristics most readily mapped, frequently landforms, soils and vegetation. However, at the stage of resource survey, the land qualities believed to have significant effects on the types of land use under consideration have already been provisionally identified; consequently, special attention should be given to those qualities during field survey. For example, in surveys for irrigation projects, particular attention is given to the physical properties of the soil, to the quality and amount of available water and to the terrain conditions in relation to methods of irrigation considered.