Land Evaluation Procedures

Land evaluation procedures

1. General

Land comprises the physical environment, including climate, relief, soils, hydrology and vegetation, to the extent that these influence potential for land use. It includes the results of past and present human activity, e.g. reclamation from the sea, vegetation clearance, and also adverse results, e.g. soil salinization. Purely economic and social characteristics, however, are not included in the concept of land; these form part of the economic and social context.

A land mapping unit is a mapped area of land with specified characteristics. Land mapping units are defined and mapped by natural resource surveys, e.g. soil survey, forest inventory. Their degree of homogeneity or of internal variation varies with the scale and intensity of the study. In some cases a single land mapping unit may include two or more distinct types of land, with different suitabilities, e.g. a river flood plain, mapped as a single unit but known to contain both well-drained alluvial areas and swampy depressions.

Land is this a wider concept than soil or terrain. Variation in soils, or soils and landforms, is often the main cause of differences between land mapping units within a local area: it is for this reason that soil surveys are sometimes the main basis for definition of land mapping units. However, the fitness of soils for land use cannot be assessed in isolation from other aspects of the environment, and hence it is land which is employed as the basis for suitability evaluation.

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.

2. Initial consultations

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 data and assumptions on which the evaluation is to be based

- The extent and boundaries of the area to be evaluated

- The kinds of land use which appear to be relevant for consideration

- Whether a two-stage or parallel approach is to be followed

- The type of suitability classification to be employed

- The intensity and scale of the required surveys

- The phasing of activities in 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.