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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
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
Keywords: field survey, over-utilized, marginal land, slopeland, Taiwan
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survey are shown in Table 1. 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 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.
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.
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.
Table 1. Classification of marginal land in Taiwan (1953 - 59 survey)
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Table 2. Classification of marginal land suitable for crops, livestock production or forest
Table 3. Classification parameters
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Table 4. Slopeland capability classification standard
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 below).
Where, S
A, B, C
x, y, z
= average slope (%),
= area of each uniform
sloping surface,
= slope (%) of each uniform sloping surface.
Soil Depth Evaluation
Soil depth can be checked by a soil auger.
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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 m2
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).
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 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
Table 5. Results of survey of land capability classification in Taiwan
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construction, irrigation and farm management support.
OVERVIEW AND RECOMMENDATIONS
An Overview
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.
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.
Table 6. Soil and water conservation treatments for slopeland suitable for crops and livestock
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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).
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