Geographic Information System (GIS)
As A Tool for Land Evaluation and Land Use Planning

ABSTRACT

The need for optimum use of land has never been greater than at present, when rapid population growth and urban expansion are turning land into a relatively scarce commodity for agriculture.

Sustainable productivity of lands in Vietnam can be only achieved by implementing soil conservation programs which will maintain soil fertility and minimize adverse environmental impacts. A determination on how to use best the lands in our country for sustainable agriculture, forestry and environmental protection is urgent. In order to solve the above mentioned problem, land evaluation and land use planning is necessary for the whole country in general, and for provinces and districts in detail. Geographic Information Systems (GIS) is one effective tool for land evaluation and land use planning.

During the last decade of this century, the land evaluation works in Vietnam have achieved significant results thanks to the advantages of GIS which have promoted sustainable agriculture production and environmental protection.

This paper presents the research results of land evaluation in the Doan Hung mountainous District, Phu Tho Province as a case study which was carried out in 1998 using GIS as an effective tool.

INTRODUCTION

The increasing demand for intensifying cultivation as well as opening up new areas of land in the Doan Hong District may be possible to meet without causing damage to the environment, but only if the land is properly classified according to its suitability for different kinds of use. It is known that Geographic Information Systems (GIS) deal with information related to spatial distribution of features on the earth’s surface, and is designed to efficiently capture, store, update, manipulate, analyze and display all forms of geographically referenced information. Thus, nowadays, GIS is used widely as an effective tool for land evaluation throughout the world – including in Vietnam.

The Doan Hung District has land that could potentially be developed for agriculture and forestry, but these lands had not been evaluated. Consequently, the need to evaluate land for the district became quite urgent. In doing so, the standard FAO methodology and approaches were broadly adopted, albeit with modifications to suit local conditions.

In order to evaluate lands of district, the following maps have been compiled: soil map, present land use map, land unit map and land suitability map. All maps at scale 1: 25,000 have been digitized and printed using computer and plotter.

USING GIS FOR LAND EVALUATION OF THE DISTRICT

Background of the District

Doan Hung is one of ten districts in Phu Tho province, situated between 21^°00’ - 21°30’ N Latitudes and 105°00’ - 105^°17’ E Longitudes. The total area of the district is 30,400 ha and supports a population of 99,587 which includes seven minorities. The topography of the district is commonly undulating to rolling and mountainous with narrow valleys between the hills and mountains which make the district higher from Southeast to Northwest. Main soil forming parent materials are metamorphic, clay shale and sedimentary. Two rivers flow throughout the district, Lo and Chay, as well as a number of small streams. Some meteorological features are as follow: Mean summer and winter temperatures are 23^°7C to 24^°3C and 15^°2 to 16^°3 C respectively. Annual rainfall is 1,641 mm, which is concentrated in June, July and August, while evaporation is 824 mm. Humidity is rather high, more than 80%; total solar radiation is around 100-110 Kcal/cm²/year.

Compiling soil map

In order to conduct a planned land evaluation in the Doan Hung district, a soil map was required. The mapping exercise that resulted was based on the FAO-UNESCO soil classification system. Soil survey and soil sample analysis were conducting following FAO methods. The completed soil map (scale 1: 25,000) divides the soils into six major groups, thirteen soil units and fifty two soil subunits and lower levels. Of the major soil groups, Acrisols cover the largest area (accounting for 20,104.17 ha), followed by Fluvisols (4,131.88 ha); Ferralsols (1,573.05 ha); Leptosols (920.34 ha); Gleysols (693.33 ha) and Arenosols (55.81 ha); the percentages of total area are: 73.16%; 15.04%; 5.72%; 3.35%; 2.52% and 0.20%, respectively. Each soil subunit and lower level has been expressed in the soil map

Soil characteristics in general can be described as follows: soil texture commonly clay (Acrisols and Ferralsols) to loamy silt (other soils); soils are acid and very acid (pH KCl varied from 3.5 to 5.0 with a central point between 4.2-4.3); decline of soil organic matter (on average, organic carbon in the cultivated soils represents only 40-60% of that found in the soils under forests); low cation exchangeable capacity (CEC) and base saturation (BS); poor in nutrients.

Present land use map

The current district level land use map was compiled using the land use map of 1995 as well as satellite images and aerial photos. The structure of main land use types, agriculture land and forestry in 1997 are expressed in tables 1 and 2.

Land unit map

The following land characteristics have been used for compiling the land use map:

- Soil Types:

There are 13 soil units have been chosen:

There are sixty nine land units have been identified and expressed in the land unit map. Some land units are expressed in table three.

Land suitability map

In accordance with the FAO Land Evaluation Framework, land suitabilities for each land use type/crop or group of crops have been identified. In order to assess suitabilities, seven land use types have been used:

Matching of land use requirements with land qualities and further factors such as land improvement, environmental impact, economic and social analysis... the map of land suitability for the district has been compiled at the scale of 1: 25,000. At this level, land suitabilities are expressed in category Subclass. The obtained research results in land suitabilities of crops in Doan Hung district are summarized and expressed in table 4.

CONCLUSION:

In Vietnam, land evaluation for land use planning and decision making in sustainable agriculture has benefited considerably from the effective use of GIS. Together with the adoption of FAO’s methodology and approaches of land evaluation, Vietnam’s land evaluation process in Vietnam has progressively improved and developed.

The set of maps, notably the land suitability map, completed for the Doan Hung District are proving a helpful database not only for decision-makers but also for farmers to help select the best crops for their lands.

REFERENCES

Bo N.V, Duc H.Q. et al. 1998. Land Evaluation for Doanhung District (Phutho Province) Following FAO Methods. (In Vietnamese). Research results of National Institute for Soils and Fertilizers (NISF). Hanoi.

FAO. 1976. A Framework for Land Evaluation. Soils Bulletin No 32. Rome.

FAO. 1983. Guidelines: Land Evaluation for Rainfed Agriculture. Soils Bulletin No 52. Rome.

FAO. 1984. Guidelines: Land Evaluation for Forestry. Soils Bulletin No 48. Rome.

FAO. 1985. Guidelines: Land Evaluation for Irrigated Agriculture. Soils Bulletin No 42. Rome.

FAO. 1996. Guidelines for Land Use Planning. Reprinted. Rome.

National Institute for Soils and Fertilizers (NISF). 1997. Land Evaluation for Dongnai Province Following FAO Methods. (In Vietnamese). Agricultural Publishing House. Hochiminh City.

Table 1. Structure of main land use types

Table 2. Structure of agriculture and forestry land

Table 3. Some land units and characteristics of Doan Hung district

Table 4. Recommended land suitabilities of Doanhung District

Note: S1- Highly Suitable;

S2- Moderately Suitable;

S3- Marginally Suitable.