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Slopeland Capability Classification As a Tool in Land Use Planning a. Taiwan
Chan, Lien-Chang
22, Yang-Ming Street,
Feng-Yuan City
Taichung County 420, Taiwan ROC, 2000-03-01

Abstract

The work of land capability classification (LCC) in Taiwan began in 1953. Forty-six years of valuable experience have now been gathered. In earlier years, the main goal of LCC was primarily so that land could be used efficiently for agriculture. Nowadays, classification involves the sustainable use and development of slopeland resources. The LCC system used in Taiwan has been modified over the years in response to social and economic changes. The scheme used to classify and manage slopeland in Taiwan can be applied in other countries. However, some adaptation is required, to correct for differences in social, economic and environmental needs. A classification sheme should also be integrated and extended on a regional basis, so that it is both effective and easy to implement.

Introduction

Taiwan is a mountainous island with steep terrain and fast-flowing streams. Land resources can be divided into 26% flatland, 27% slopeland, and 47% forestland. Slopeland is defined as land with an elevation of 100 m or more, or with a 5% gradient. This does not include national forest or other kinds of protected reserve.

The geology, topography and soils of Taiwan do not favor sustainable agriculture on slopelands. Rainfall is abundant, and is often concentrated in heavy downpours. This, combined with improper slopeland development, leads to frequent slopeland disasters. The government must pay a high remedial cost after such disasters, to restore the land.

As the result of population pressure, widespread deforestation occurred in Taiwan after the Second World War. Farmers planted crops on marginal land and forest reserves, using shifting cultivation methods. This often resulted in heavy losses of topsoil and productivity. According to a recent air reconnaissance report, of Taiwan's 1.3 million ha of hilly area, about 0.6 million ha are eroded and 0.3 million ha are severely eroded. This comprises about 75% of the total arable land.

Besides strengthening soil and water conservation and building the necessary infrastructure, the government has placed a strong emphasis on slopeland management. By this means, it hopes to protect slopeland soil and water resources, and minimize disasters created by heavy rainstorms associated with typhoons. Each block of slopeland must be used efficiently and economically, according to the slopeland capability classification scheme. This in turn is based on the results of field surveys.

Development of Slopeland Capability Classification

The classification of slopeland capability began in Taiwan in 1953. Since then, it has undergone several modifications. With the "Statute and Regulations on Conservation and Use of Slopeland in Taiwan" in 1976, slopeland capability classification became standardized. A field survey of all government and privately owned land was conducted.

Survey 1953 - 59

Between 1953 and 1959, the government spent six years studying land use on marginal agroforestry land at elevations below 1000 m. The total area was about 1,497,885 ha. The results of the survey are shown in Table 1(1282). Based on the survey, marginal land was classified according to its land use suitability, and the ease with which soil conservation could be implemented.

Survey 1961

In 1961, the Executive Yuan surveyed all land owned by the government which had been illegally developed by squatters. After the survey, the land was leased to the user, on condition that he completed the necessary soil and water conservation treatments. Six classes of slope steepness, four of soil depth, four of soil erosion and three of parent material (hard, soft, and sedimentary with a gravel layer) were used to classify land into three categories (arable, livestock production, and forest). The minimum land area for each arable block was about 0.05 ha, and for animal husbandry, 0.5 ha. Land used for groundwater storage, as a buffer zone, for trapping sediments or for windbreaks or tidal protection, was listed with forest land. Table 2(1320) shows the standards used with this classification.

Standard of 1976

In 1976, the government passed the "Stature and Regulations on Conservation and Use of Slopeland in Taiwan" and developed a standard for slopeland capability classification. This standard took effect from 1977, and has since been used throughout the island in all field surveys. A field survey was carried out, focusing on slopeland areas. Land classified according to the previous Marginal Land Classification remained in the same category. The classification and field survey parameters used are summarized in Table 3(1298).

Slopeland Capability Classification Standards

After examing the four classification parameters, each land unit was classified according to the land capability classification scheme described in Table 4(1162).

Field Surveys for Land Capability Classification

A field survey has both administrative and technical aspects. The administrative aspect involves collaboration between the central, provincial, county and township governments and land management agencies. They must together formulate programs to share information, to conduct the field survey, and to announce survey results to the public.

With regard to technical aspects, the methods used for the field survey are very important. Accurate results can only be obtained by an objective and detailed assessment.

Survey Procedure

Field Survey of Land Boundaries

Each land unit should be surveyed according to a land ownership map provided by the local government, as well as or air reconnaissance photos. Land boundaries must be confirmed by the landowner or land user. In Taiwan, a land administration officer must be present to confirm the exact boundary.

Average Slope Evaluation

Slope is usually measured along the slope or the direction of natural drainage. If the slope is irregular, the average gradient can be computed as follows (see Formula 1(1442) below).

  • Where, S = average slope (%),
  • A, B, C = area of each uniform sloping surface,
  • x, y, z = slope (%) of each uniform sloping surface.
Soil Depth Evaluation

Soil depth can be checked by a soil auger. On average, four to five sites should be sampled per hectare of land. Samples should be taken from the center, and at each compass point 50 m from the center. The average soil depth is then computed.

Soil Erosion Evaluation

At least four or five sampling sites are needed for one hectare. More sites are needed for erosion-prone areas. The rill depth, the amount of coarse sand on the surfaces, and the estimated rate of soil loss, must be evaluated for an area of 1 - 4 m 2 at each site. The soil erosion status of each sample is then used to calculate the average.

Parent Material Determination

The parent material can be determined by observing the soil profile, if this is available, or by excavation.

Classification Determination

Land capability classification is then determined according to the four parameters mentioned earlier.

Related Rules for Field Survey

Land used for residential purposes or other kinds of non-agricultural land use is not included in the field survey. The minimum land area suitable for crops and livestock is around 0.5 ha, or around 1.0 ha in the case of forest.

If a land unit has two or more land characteristics, each must be separately surveyed. The natural topography, as well as any conservation needs, can be used to subdivide land units for survey purposes, as well as any obvious topographic disruption line.

Compilation of Survey Results

The results of the survey must be plotted (using a color code) on a land ownership map, together with important features such as roads, streams and ridges. The completed map will be very useful in planning subsequent land use and management.

Supplementary Survey Work and Resolving of Disputes

After the survey is completed, additional work can be requested if data is missing or land holdings have been split. Farmers who disagree with the field survey result may file for a reclassification.

Application of the Results of the Field Survey

Survey Results

Taiwan's field survey program for slopeland capability classification lasted from 1961 to 1998, a total of 37 years. The total area surveyed was about 912 thousand ha, about 93.93% of the entire slopeland area. A survey of the remaining 6.07% is near completion. Results of the survey were as follows (see Table 5(1293)).

Application of the Results

Adequate Soil and Water Conservation Treatments

On land classified as suitable for crop and livestock production, soil and water conservation treatments can be used to reduce soil losses. Table 6(1323) lists the ideal treatments for such land. According to regulations, adequate soil and water conservation treatments must be completed within the time limit set by the County and City Governments. By 1996, such treatments had been carried out on 177,500 ha, about 42.08% of the sloping land classified as suitable for agriculture.

Delineation of Areas for Agricultural Development

The classification results are a useful guide in selecting areas (usually 100 - 300 ha) which have good potential for agricultural development. A total of 103 slopeland development areas for crop and livestock production have been selected in Taiwan. Regional agricultural development projects are implemented each year, to improve farm incomes and to protect natural resources in slopeland areas. Projects include soil and water conservation treatments, road construction, irrigation and farm management support.

Slopeland Management

Now that the results of the land classification survey and the land ownership map have been converted to digital form, both kinds of information can be retrieved instantly. Changes in land use can be detected by overlaying satellite pictures and the digitized land property map and its land capability classification information. An on-site visit can then determine whether the change is legal or not. Any illegal change in land use is recorded, and filed for further action.

Land surveyed as suitable for forest and reserves is considered overutilized if the area is no longer forested. According to government statistics, the total area of land overutilized in this way is 1985 was about 50 thousand ha. By 1998, this area had been almost halved to only 27 thousand ha as the result of strict government control, and effective extension and education programs. The major crop grown on overutilized land is betelnut, which is planted on 10,518 ha. Betelnut gives farmers a high return, but its shallow root system and lack of canopy cover make it a poor crop for erodible slopelands.

Overview and Recommendations

An Overview

Slopeland capability classification has been carried out in Taiwan for more than 46 years. The first stage had the aim of safe conversion of marginal land to agricultural use. The second stage was intended to prevent the deforestation of government-owned slopeland. Forested marginal land was classified as suitable for crops, livestock or forest. Farmers were educated in how to utilize slopeland wisely, in order to reduce soil losses. The third stage was to establish a slopeland capability classification system. Both government land and privately owned land were surveyed and classified.

Slopeland capability classification can guide farmers in proper land use, and in the need for soil and water conservation treatments. Statistics indicate that about 51% of the slopeland classified as suitable for crop and livestock production has now been reforested, while about 42.66% of the slopeland still used for agricultural production been given soil and water conservation treatments. The remaining 7.18% is not treated. Only 9% of the land suitable for forest and nature reserves is being overutilized.

Recommendations

The emphasis of slopeland capability classification should shift from agricultural production to the protection of environmental resources. Classification parameters should include topography, geology and land use for the entire region, and should be checked on a regional basis.

The unit classification area should be enlarged to the region, or even the watershed. This area could be classified as slopeland suitable for conservation or agriculture. Reforestation and protection of forest resources should be emphasized on slopelands suitable for conservation.

Agricultural production should be allowed on slopeland suitable for agriculture. However, soil and water conservation treatments, using appropriate technology and engineering measures, are necessary to prevent soil erosion problems. The reforestation of marginal agricultural land should be encouraged.

The work of slopeland capability classification work is near completion in Taiwan. To change classification standards at this point may impinge on farmers' rights. Any modification of relevant laws and regulations has to be done gradually. Even then, it may give rise to opposition.

Conclusion

Taiwan now has 46 years' experience of slopeland capability classification. This can be shared with many other countries. The classification standard used at each stage was based on social and economic criteria which have changed over the years. An early emphasis on agricultural production and farm incomes has given way to the current emphasis on resource management and conservation.

However, modifying the classification standards and relevant regulations may be difficult and take a long time. Therefore, the establishment of classification standards and their modification should be considered part of the national long-term social and economic development goal. For slopeland capability classification to have its maximum impact, the public has to follow and the government has to enforce the rules and regulations prescribed by the classification scheme.

References

  • Chang, S.C. 1960. Hillslope farming in Taiwan. Quarterly Taiwan Bank Bulletins 12, 4: 1-10. (In Chinese).
  • Council of Agriculture. 1987. Status and Regulations on Conservation and Use of Slopelands in Taiwan. The Executive Yuan, Taiwan ROC. (In Chinese).
  • Council of Agriculture. 1996. Technical Guide to Soil and Water Conservation. The Executive Yuan, Taiwan ROC. (In Chinese).
  • Huang, C. 1964. Mountain Protection and Flood Prevention. Taiwan Shin Song Pao (Newspaper), April 20 Commentary. (In Chinese).
  • Mountain Agricultural Resources Development Bureau. 1988. Handbook of Slopeland Capability Classification Field Survey. Taiwan Provincial Government. (In Chinese).
  • Soil and Water Conservation Bureau. 1998. Statistical Information on Slopelands in Taiwan. Taiwan Provincial Government. (In Chinese)
  • Wu, H.L. 1987. Soil Conservation on Slopelands in Taiwan. The Chinese Soil and Water Conservation Society. (In Chinese)
  • Yu, Y.S. 1985. Current emphases of soil and water conservation in Taiwan. Keynote Speech at Annual Meeting, Chinese Soil and Water Conservation Society. (In Chinese).

Index of Images

Formula 1

Formula 1

Table 1 Classification of Marginal Land in Taiwan (1953 - 59 Survey)

Table 1 Classification of Marginal Land in Taiwan (1953 - 59 Survey)

Table 2 Classification of Marginal Land Suitable for Crops, Livestock Production or Forest

Table 2 Classification of Marginal Land Suitable for Crops, Livestock Production or Forest

Table 3 Classification Parameters

Table 3 Classification Parameters

Table 4 Slopeland Capability Classification Standard

Table 4 Slopeland Capability Classification Standard

Table 5 Results of Survey of Land Capability Classification in Taiwan

Table 5 Results of Survey of Land Capability Classification in Taiwan

Table 6 Soil and Water Conservation Treatments for Slopeland Suitable for Crops and Livestock

Table 6 Soil and Water Conservation Treatments for Slopeland Suitable for Crops and Livestock

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