The slope farmland of the whole country has a total area of 359 million Mu, which
accounts for 1/5 of the total farmland. The soil and water loss area of slope farmland
account for just 6.7% of the total soil and water loss area, but the erosion amount
accounted for 28.3% of the country's total erosion amount. The slope farmland is the main
source of soil and water loss. Among them, the basic soil characteristics of the rock-soil
mountainous region of north China, the rock-soil mountainous region of southwest China ,
southern red soil region of south China and the qinghai-tibet plateau are with thin soil layer.
Because of the thin layer, those slope farmland is not suitable for building a high standard
of level terrace, the traditional way to control soil and water loss of thin layer slope
farmland is using farming method , but those methods had some disadvantage such as low
standard, high casualness and poor effects. A kind of once for all engineering technology is
in urgent need to solve the difficult problem which had plagued China's for a long time.
According to the characteristics of development, evolution and harm of slope erosion
from surface erosion to gully erosion, we came out with the basic technical principle and
technical ideas to solve soil and water loss of thin slope farmland. Technical principle is
based on the development and evolution law of slope soil erosion from the occurrence of
splash erosion and surface erosion to gully erosion ( gully erosion of the soil erosion
amount is 2-3 times of surface and splash erosion amount, and it account for 50-70% of the
total slope erosion amount) and the basic characteristics of critical slope length, the field
engineering measures which allow surface erosion and reduce gully erosion were designed
to control soil erosion amount at a certain range. Technical ideas: (1) According to idea of
implementation of "block, filter, drainage " to the project slope runoff train, we designed
the field block and water soil discharge technology for wave-slope soil type and field block
and underground drainage technology for straight slope; (2) On the basis of slope type and combining with the characteristics of slope runoff implementation project of “cutting,
permeability(or cutting), drainage”, we put forward the rock wall cutting slope and
permeability of rainfall technology for straight slope type; (3) In order to overcome the
instability and maintenance difficulties of “filter” technology, we proposed the idea of
“block, sedimentation, drainage” and put forward the cement laid stone masonry block and
sedimentation and underground drainage technology.
The experimental runoff plots were set to evaluate the effect of soil and water
conservation, a comprehensive evaluation of all the technologies was made according to
the result of two years’ observation. The main conclusions are as follows:
1. As the field block and underground drainage technology for straight slope
designed, artificial high infiltration (gravel) layer and underground drainage facilities
(double-wall corrugated pipe) were set up at critical slope of straight slope field to safely
discharge runoff and ensure the security of the field. In 2012, the total runoff was 1.296 m 3 ,
it was 1.49 times of the conventional tillage annual runoff; Erosion amount was 99.02 kg,
it was 1.77 times of that in conventional tillage erosion; In 2013, the runoff was 3.58 m 3 , it
was 2.08 times of the conventional tillage; Erosion amount is 669.93 kg, it was 1.92 times
of conventional tillage. The measures were effective to intercept and discharge runoff and
reduce the erosion caused by the runoff at the beginning of the test, however, with the
passage of time, the gravel filter pore was blocked with silt, as results, the infiltration rate
was down and the runoff infiltration reduced sharply. This lead to a bigger erosion
intensity caused by runoff. So this measure is not successful and should be redesigned.
2. As the rock wall cutting slope and permeability of rainfall technology for straight
slope type designed, rock wall was set up at the critical slope of straight slope field and the
reverse slope was set up just below the rock wall to shape a capacity to contain runoff. This
can effectively reduce the formation of gully erosion and the erosion amount as well.
In 2012, the annual runoff volume was 0.538 m 3 , it was 61.69% of the conventional tillage.
The erosion amount was 99.02 kg, it was just 6.13% of conventional tillage erosion; In
2013, the runoff volume was 0.95 m 3 , it was 81.89% of conventional tillage, The erosion
amount was 21.23 kg, which is just 2.4% of conventional tillage. The technology can
effectively reduce the slope erosion which most of them were caused by super infiltration
runoff in the north of China, at the same time, in view of the slope erosion caused by filling up runoff in the south of China, we proposed the ditch drainage on the reverse slope
experiment design to solve the problem of suitability in different place in China.
3. The cement laid stone masonry block and sedimentation and underground drainage
technology for wave slope has a very good effect on water storage and sand block, it is an
engineering measure with good prospects. In 2012, the total runoff volume was 0.01 m 3 ,
which was just 2.73% of the control plot. The erosion amount was 0.03 kg, which was just
7.09% of the control plot; In 2013, the total runoff was 1.82 m 3 , which was 39.52% of the
control plot, the erosion amount was 126.21 kg, which was 49.16% of the control plot.
This technology can reduce the speed of runoff and the rate of erosion through block of
runoff. Most of the sand carried by runoff sediment before the cement laid stone masonry
wall and water flow was discharged out of field through underground drainage tubes after
filtered by gravel layer. As a result, the formation of runoff and erosion rate was both
4. The mortar-laid-stone interception was launched in critical slope length of
Waveform slope mortar-laid-stone works interception slope Precipitation and drainage
technique , pooling of water to reduced the water flow speed, leaving the sediment carried
by stream to precipitation, and then use the drain which is designed in different height of
inclined upward the supernatant fluid into soil drainage tubes, and the water discharge
slope, the sediment deposition in the cross wall directly. The runoff volume in 2013 is 0.18
m3, is 2.48% of the control plot, erosion amount is 0.89 kg, is 0.15% of the control plot.
The measures can effectively reduce the slope runoff erosion, precipitation and sediment,
5. The cost analysis of mature technology testing scheme was launched. The actual
construction of cross wall cut slope measures, such as slope grade 10 °, reverse slope 5 °,
the cost of the measure is ￥929 per acre, saved 78.74% compared to traditional rock ridge
terrace. When actually building waveform-slope slurry masonry precipitation and drainage
technology, distance calculated at 15 m, layout overall length of 44.4 m per acre, the
average cost is 1887 yuan per acre, save 56.81% compared to traditional rock ridge terrace.
Keywords: thin layered sloping farmland; soil and water loss; Engineering Measures;
Soil and Water Conservation Effect