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Evaluation of Bioengineering Soil Erosion

Control Techniques in Standard USLE Plots

M.S.M. Amin, H.L. Yong and M. Rashidi BakarDepartment of Biological and Agricultural Engineering

Faculty of Engineering

Universiti Putra Malaysia

43400 Serdang, Selangor DE

Abstract

An erosion control study on Serdang series soil

was conducted in standard USLE plots at DBAEField Station, UPM. The bioengineering erosion

control techniques include vetiver (Vetiveria

zizanioides), legume ( Arachis pintoi), spotturfing and close turfing with cowgrass

(Axonopus compressus), hydroseeding and fewcombinations of hydroseeding with biomats. A

plot was left bare as a control. Close turfing

gave better soil protection than the other grass

species, reducing soil loss by 99% compared to

the bare plot. The addition of "fibromat" to the

hydroseeding plot resulted in significantly lower

soil loss. All hydroseeding plots overlaid with biomats gave better protection, resulting in Cfactor lower than 0.004. Close turfing produced

C factor of 0.004, compared to 0.017 for spotturfing, 0.021 for hydroseeding only, 0.122 for

vetiver and 0.213 for legume. From statistical

correlation results, soil loss from the bare plot

was better correlated with KE>25 thanraindepth, EI30 andAIm.

1.0 Introduction

Looking briefly into the history of land use, it

seems that human interference by clearing of

natural vegetation covers result in serious soil

erosion. Excessive runoff generated from

logging activities, golf courses and highway

constructions usually moves directly from

drainage structures into waterways and cause

considerable sedimentation in nearby streams

and lakes. Tropical countries like Malaysia has

a climate which is abetted by monsoon. Without

taking proper mitigation, high intensity rainfall

strike on denuded slope causing a spate of

landslides in the country. Traditional methods

have been devised to combat erosion such as

retaining wall, sheet piles and concrete

embankments. However, such solutions may

not be acceptable mainly due to the costimplications. An alternative approach is

bioengineering, a method using life plants alone

or combined with dead or inorganic materials to

arrest and prevent slope failures and erosion

(Franti, 1996). Advantages of bioengineering

solutions are 1) less expensive and lower

maintenance than structural measures; 2)

environmental compatibility with landscape and

limited access sites; 3) strengthen the soil by

binding action of vegetation roots; 4)

environment friendly of wildlife habitat, water

quality improvement and aesthetics; 5) use ofnatural by-products such as rice straw, jute,

coconut fibres etc.

2.0 Bioengineering Techniques

Bioengineering control measures have been

applied to highway construction to improve

slope stability and minimise slope erosion.

However, most estimates of soil erosion

emphasised on agricultural land. Soil loss

equations have been developed using data fromstudies conducted on cropland. Little

information on bioengineering characteristics

and performances has been obtained.

There are numerous studies where runoff and

soil losses under natural and artificial rainfall are

measured. Sulaiman (1989) documented soil

loss from isolated land use in Peninsular

Malaysia and soil loss was much greater in

urban development area. He also pointed out an

alarming increase in the rate of soil loss

following a greater intensity of the land use.

Evidence shows that tropical soils erode more

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quickly when disturbed and that the impact of

erosion is greater than in temperate counterparts

(Edwards, 1983; El-Swaify, 1977). Ahmad

(1990) highlighted the problems of soil erosion

on the North-South Expressway. Unprotectedand improperly installed measures on cut slopes

exposed the soil surface to rills and gullies

erosion. Effective erosion control depended on

fast initial vegetation growth and cover.

Biodegradable mulch has been used for erosion

for many years and there are extensive literature

confirming its effectiveness (Lal, 1977a; Jenning

and Jarrett, 1985; Cazzuffi, 1994; Mostaghimi et

al., 1994). Mulch encourage plant growth by

protecting seeds and seedlings, slow down

runoff, protect the soil from raindrop impact and

increasing soil moisture. The effect of surface

cover types, their combinations and percentage

ground cover on soil loss were studied by Grace

et al. (1998). They found that erosion mat

treatment with grass seedling gave better

percentage of cover and hence, effective in

mitigating erosion losses with a 98% and 88%

reduction in cut slope and fill slope sediment

yield respectively. Biodegradable mat and

hydroseeding (a combination of seeds, fertiliser,

tackifier and mulch) are commonly used on

construction sites. However, hydroseeding onlydid not give good protection on bare slope.

Non-germinated seeds are transported down the

slope with the runoff. Low percentage of grass

cover encourages concentrated flow and gullies

erosion (Ahmad, 1990; Mostaghimi et al., 1994).

Vegetation intercepts the kinetic energy of the

raindrops and inhibits sediment detachment and

soil erosion. Elwell and Stocking (1976)

suggested that about 60% of vegetation cover

are sufficient to cope with erosive forces. In a

study on Mediterranean shrub cover in Valencia,

Spain, Andrew and associates (1998) found thatpercentage vegetation covers play important role

in soil loss and effective with covers higher than

30%. This is in agreement with the study

conducted by Thornes (1990). Vetiver

(Vetiveria zizanioides) has been applied forerosion control and slope stabilisation on

highway projects in Malaysia. It is planted as a

hedge across the slope, which acts as a natural

barrier that slows down the runoff and allow

sediments to be deposited behind the barrier.

As a result, natural terraces built up behind the

hedge, which further reduces water velocity andsoil and water losses. Koon and Lim (1991)

showed that vetiver was able to reduce runoff

and soil loss to 73% and 98%, respectively

compared to the bare soil.

The literature clearly indicates that careful planning and implementation of slope

construction minimise soil erosion. Additional

information is needed to properly select

appropriate vegetation measures from currently

available alternatives. The selection varies in

cost and erosion control efficiency. The

objective of this study was to quantify the effect

of commonly used bioengineering slope erosion

control techniques. The effect of biodegradable

mat on vegetation growth and development was

examined. The initial costs of the erosion

control techniques were also considered to

provide a comparison of cost-benefit.

3.0 Materials and Methods

Experimental Design

The site selected for the study is located at the

Biological and Agricultural Engineering

Department Field Station, UPM. The site

consists of ten standard Universal Soil LossEquation (USLE) plots, which measure 1.8 m

wide by 22 m long, on 9 % slope. The soil was

classified as Serdang Series (sandy-clay). These

plots were provided with 25 cm deep, 10 cm

wide reinforced concrete partition to form the

perimeter on three sides, with 10 cm depth

extended into the ground. At the downslope end

was placed a series of metal roof covered with

lids to prevent the direct entry of rainfall. The

metal roof acts as a divisor, which divided the

runoff into equal portions and passed one part or

one-fifteenth through the central slot of themetal roof, into a calibrated, covered divisor

tank, while the remaining 14/15 flowing to

waste. The excessive runoff from the divisor

tank was then subdivided further where one-

fourth of the flow was collected in a second

calibrated, covered tank. The weight of soil in

both tanks was adjusted in accordance with the

proportion of the total runoff passing into the

tanks. Thus, the total soil loss from each plot

was fifteen times the weight of soil in the divisor

tank plus sixty times the weight of soil in the

second tank. Both tanks were carefully emptiedand cleaned after each measurement.

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The plots were given the following ten

treatments:

1. Vetiver (Vetiveria zizanioides), the leaf was

trimmed monthly to about 40 cm height;2. Legume (Arachis pintoi);

3. Bare (control);

4. Hydroseeding after laying coco-rice straw

mat ("coco-fibromat" + hydroseeding);

5. Hydroseeding before laying rice straw mat

(hydroseeding + "fibromat");

6. Hydroseeding after laying rice straw mat

("fibromat" + hydroseeding);

7. Hydroseeding;

8. Hydroseeding after laying geojute ("geojute"

+ hydroseeding);

9. Spot turfing with cowgrass (Axonopus

compressus);

10. Close turfing with cowgrass.

Vetiver, legume and cowgrass were planted on

1/1/1998. Vetiver and legume were planted 15

cm and 25 cm apart between the clumps

respectively. The vertical interval between rows

for both grasses was one meter. In close turfing,

23 cm square sod was laid close together and

compacted to an even thickness on the surface of

the soil. While in spot turfing, the sods werepegged down about 20 cm apart side by side on

the soil. The hydroseeding was done by a local

contractor on 21/4/1998 and applied at

recommended rates with a high pressure sprayer.

The hydroseeding contained a mixture of 50 kg

of limestone, 50 kg of 15-15-15 NPK, 80 kg of

paper mulch, 50 kg rock phosphate, 50 kg of

aerolite, 25 kg of Japanese millet (Echinochloacrusgalli) seed, 50 kg of Ruzi grass (Brachiariaruziziensis) seed, and enough water to fill 3/4volume of the container. It was applied at a rate

of 27 kg/m2.

Sample Analysis

The total surface runoff was measured and

stirred after each runoff-producing storm. The

volume of runoff collected was calculated from

the knowledge of depth of runoff in the tanks.

500 ml of water sample was taken by grab-

sampling technique. Gravimetric analysis was

carried out to determine the sediment

concentration on a storm or daily basis. Soil

loss was calculated by the product of the

sediment concentration (g/l) and volume of

surface runoff (l), and expressed in kilogram per

hectare (kg/ha). The total soil loss was obtained

by summing up the stormwise losses for each of

the runoff plots. Vegetation cover was

quantified each month during the study using avisual assessment method. A rod with 20 fixed

observation points was placed at 20 random

locations in hydroseeding plots. Each

observation point was classified as either

covered or bare.

Rainfall Erosivity Index

Rainfall was measured with tipping bucket

pluviometer, which was located at the head of

the plots. A laptop computer was used with data

loggers to record and download the precipitation

depth and intensity data. The data obtained

from this record for kinetic energy and rainfall

erosivity computations as EI30, KE>25 and AIm.The EI30 is the product of the kinetic energy ofthe storm and its maximum 30-minute intensity

(I30). The SI metric-unit version of the energy-intensity equation is (Foster et al, 1981):

E= 0.119 + 0.0873log10I I 76 mm/h [1]

E= 0.283 I>76 mm/h [2]

whereEis expressed in MJ.mm/ha.h and Iis inmm/h. AIm (Lal, 1976) is defined as the productof the amount of rainfall per storm, A (cm) andits maximum 7.5 minutes intensity, Im (cm/h).

The index has the unit cm2/h. Kinetic energy

(KE) computed by Hudson (1971):

KE = 29.8 I

5.127 I >25 mm/h

[3]

where KE is in J/m2, and I is the rainfallintensity in mm/h. The erosivity index is the

totalKEcaused by the storm at intensities above25 mm per hour.

Cover Management Factor (C)

Cover management factor, C in the USLE wasevaluated by summing soil loss and rainfall

erosivity index (Mutchler et al., 1994) from the

following equation:

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RKLSP

AC= [4]

where,

C= cover management factor.A = soil loss (t/ha).

R = rainfall erosivity index (MJ.mm/ha.h).K= soil erodibility factor Mg.ha.h/ha.MJ.mm)

LS= slope length and steepness factor.P= support practise factor.

The standard plots were managed so Pequalled1 and topographic factorLS is unity for each

plot. TheKvalue computed from the same fieldwas 0.02 Mg.ha.h/ha.MJ.mm (Yong, 1998).

Upon substitution of these values, C in the

USLE was computed by the ratio below:

R

AC 05.0=

[5]

Statistical Analysis

Two statistical tests were used to analyse

erosion data, correlation analysis and ANOVA.

Simple correlation were computed to determine

the relation between soil loss (kg/ha) from

control plot for each storm with variouserosivity indices including raindepth, EI30,

KE>25 andAIm. The runoff and soil loss meansof individual treatment were compared for

significant differences using Duncan's multiple-

range test.

4.0 Results and Discussion

Rainfall Characteristics

Table 1 gives the monthly rainfall distribution

for the study site in 1998. Average 30-minutes

intensity, I30 and three erosivity indices such as

EI30,KE>25 andAIm are also included. The 10-year average monthly rainfall distribution from

UPM station over the years 1988 to 1997 was

compared to the monthly rainfall distribution for

1998 as shown in Fig. 1. The total annual

rainfall for 1998 was 1587.5 mm, which can be

considered as a dry year because it was less than

the 10-year average annual rainfall in UPM,

2400 mm. The Elon

~Ni

SouthernOscillation occurred at the beginning of the

study year reduces the rainfall and the

phenomena was more severe in March. The

1998 monthly rainfall distribution showed that

the highest rainfall occurred in August,

indicating the necessity for provision of good

vegetation covers, while the lowest rainfall wasin October. The average monthly 30-minutes

intensity were generally high (>12.72 mm/h)

(Soong et al., 1980), except for July, October

and November, indicated by lower erosivity

indices.

Runoff and Soil Loss

Figures 2 and 3 show total runoff depth and soil

loss of each plot. The data were analysed

separately according to the study period. Over

the entire 1-year study period, statistical analysis

showed that there were no significant

differences on soil loss among the treatments

(Table 1). The bare plot had significantly

greater soil loss and runoff than all of the other

treatments. However, there were no significant

differences in runoff between the plots with

legume and vetiver, vetiver and spot turfing and

finally spot turfing and close turfing. Close

turfing had 99.4% and 90.0% less soil loss and

runoff respectively compared to bare plot (Fig.

2). Spot turfing was the next most effectivetreatment with a 97.3% and 76.9% less soil loss

and runoff with respect to the bare plot. Both

plots used cowgrass which covered well the soil

surface. The grass intercepted raindrops and

decreased the drops impact pressure. The

raindrop energy was dissipated before it struck

the ground, causing less erosion. Runoff was

also greatly reduced by infiltration into the root

systems. Vetiver gave 81.2% and 61.8% less

soil loss and runoff. Vetiver planted as hedges

across the plot slowed down the runoff and

sediments deposited behind the hedges. As aresult, it reduces water velocity, soil and water

losses. The legume was least effective with

67.0% and 41.4% reduction in soil loss and

runoff, respectively to the bare plot. This may

be due to poor propagation of the legume with

less fertiliser input. The bare plot produced

170.3 t/ha/y of soil loss during the study period,

which was far greater than the acceptable limit,

13 t/ha/y (Morgan, 1979). Plots treated with

legume and vetiver also gave soil loss above the

permissible value with 56.1 t/ha/y and 32.0

t/ha/y, respectively. Soil loss from the spot andclose turfing, which were the better protection

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among the treatments, produced 4.5 t/ha/y and 1.0 t/ha/y, respectively, were lower than the

acceptable limit.

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No significant differences were observed during

the 8-months study among the hydroseeding

plots with biomats. Hydroseeding alone had

significantly greater soil loss than all other

treatments.

However, the runoff depths among all

treatments were not significantly different. Both

hydroseeding + "fibromat" and "fibromat" +

hydroseeding plots were the most effective

treatments, represented 98.3% and 98.0%

reduction in soil loss, respectively as comparedto "control" plot (hydroseeding only) (Fig. 3).

Runoff were reduced in both treatments by

48.0% and 39.8%, respectively. Both results

showed no significant difference either

hydroseeding was done before or after laying the

"fibromat". "Coco-fibromat" + hydroseeding

reduced soil loss and runoff by 95.9% and

40.0%, respectively. The increased in soil loss

in this treatment may be due to poor germination

of seeds at the downslope, as "coco-fibromat"

was not placed in close contact with the ground.

"Geojute" + hydroseeding gave 82.1% and

12.6% less soil loss and runoff, respectively,compared to the control plot. It was least

6

Table 1: Rainfall characteristics, runoff and soil loss of different treatments for the study period.

January February March April May Jun July August September October November December Total Mean*

Rainfall (mm) 65.0 143.0 88.0 162.5 199.5 123.5 134.0 240.0 149.0 36.8 75.8 170.4 1587.5 -

Intensity I30(mm/h) 14.4 21.6 16.6 21.9 22.5 22.4 11.8 14.9 22.2 4.6 7.1 15.0 - -

Erosivity EI30 (MJ.mm/ha.h) 326 1503 549 1310 2249 1367 613 1190 2317 44 178 1533 13178 -

Indices KE>25 (J/m2) 1305 3748 1600 3257 4056 2261 1616 3117 2974 32 499 2621 27086 -

AIm (cm2/h) 39 82 56 95 148 96 51 102 109 3 14 94 891 -

Runoff (mm) Control 32.5 72.9 64.8 74.6 92.4 66.3 44.5 66.2 58.5 9.1 7.9 78.0 666.7 55.6A

Legume 25.5 53.9 27.7 55.7 43.1 26.4 22.9 51.1 44.7 3.6 2.8 33.9 391.3 32.6B

Vetiver 23.5 39.9 23.5 42.8 19.5 14.8 33.2 44.6 8.8 1.0 0.7 2.9 255.2 21.3BC

Spot Turfing 15.0 16.0 14.5 22.3 29.5 14.3 14.0 15.4 7.4 1.0 1.1 3.7 154.2 12.9CD

Close Turfing 5.0 7.6 2.7 7.1 11.4 5.4 8.7 9.9 3.6 0.9 0.8 3.4 66.5 5.5D

CMH - - - - 22.9 9.3 8.3 13.6 7.6 1.1 0.7 4.1 67.6 8.5a

HM - - - - 20.8 6.5 10.7 9.8 5.5 1.1 0.9 3.3 58.6 7.3a

MH

- - - - 20.9 6.7 12.0 15.2 8.1 1.1 0.8 3.1 67.9 8.5a

HB# - - - - 26.9 14.2 11.9 28.1 25.1 1.9 1.6 3.0 112.7 14.1a

GH - - - - 23.4 15.6 12.6 17.4 22.0 2.2 0.7 4.6 98.5 12.3a

Soil Loss Control 8750 29587 13833 31254 57184 8697 3872 3002 4984 512 395 8235 170305 14092A

(kg/ha) Legume 4875 18699 6878 17729 3657 1925 523 1097 538 17 10 190 56138 4678B

Vetiver 4595 7187 3320 13470 914 1190 593 701 38 2 1 3 32014 2668B

Spot Turfing 1885 409 278 1435 343 141 16 10 11 1 1 0 4530 378B

Close Turfing 945 25 6 13 8 2 2 3 6 0 1 0 1011 84B

CMH - - - - 109 30 10 5 6 0 1 2 163 20b

HM - - - - 47 8 5 3 3 0 1 2 69 6b

MH - - - - 54 10 5 3 3 0 1 2 78 7b

HB#

- - - - 1046 937 519 764 712 3 1 2 3984 332a

GH - - - - 349 207 30 42 81 2 1 2 713 59b

= - = "Coco-fibromat" + hydroseeding Hydroseeding + "fibromat" "Fibromat" + hydroseeding# Hydroseeding only

"geojute" + hydroseeding

* Means with same letter are not significantly different ( = 0.05)

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effective compared to other "fibromat"

treatments, possibly due to the 25 mm woven

open mesh of "geojute" allows high intensity

storms to wash away a part of the seeds.

0

50

100

150

200

250

300

January

Febr

uary

March Ap

rilMa

yJune Ju

ly

August

Septe

mber

Octob

er

Novemb

er

Decemb

er

Month

Rainfall(mm)

0.0

5.0

10.0

15.0

20.0

25.0

I30(mm/h)

1988-97 1998 I30

Figure 1: Monthly rainfall distribution at UPM

0

50000

100000

150000

200000

Bare LegumeVetiver S.

Turfing

C.

Turfing

Treatment

SoilLoss(kg/ha)

0

200

400

600

800

Runoff(mm)

Soil Loss Runoff

Figure 2: Total soil loss and runoff for each

treatment over one-year study period.

0

1000

2000

3000

4000

5000

CMH HM MH HB GH

Treatment

SoilLoss(kg/ha)

0

20

40

60

80

100

120

Runoff(mm)

Soil Loss Runoff

Figure 3: Total soil loss and runoff for each

treatment over eight-months study period.

All biomat treatments had greater amount of

vegetation cover compared to the control plot

without biomat. This would result in greater

interception, decreased raindrop energy, and

decreased runoff due to increased canopy. As

shown in Fig. 3, hydroseeding alone did not give

good protection on soil erosion although its soil

loss, 4.0 t/ha, was much lower than the

acceptable limit.

Figure 4 shows the soil loss ratio for each

treatment during the one-year study period. The

data were plotted with a best-fit polynomial

equation. The results indicate that the soil

erosion - time relationship were curvilinear. The

soil losses were high in the initial study period

and decreased with time. In Fig. 4, close and

spot turfing gave better protection after one and

two months, respectively. Cowgrass is a fast

growing stoloniferous perennial and quickly

forms a dense mass and ground-hugging turf.

Vetiver required 8 months to form dense and

tight hedges, which blocked the movement of

soil. Least effective cover was found from the

legume which took 10 months due to poor

propagation as was mentioned earlier.

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"Fibromats" and "geojute" treatments gave good

protection immediately after installation.

Legum

y =0.3103x2 - 9.654x + 72.82

R2 =0.7384

020406080

100

Month

SoilLossRatio(%)

Spot Turfing

y =0.3389x2 - 5.7891x +23.055

R2 =0.83810

20406080

100

Month

SoilLossRatio(

Vetiver

y =0.2585x 2 - 7.2142x +49.498

R2 =0.6446

020

40

60

80

100

Month

SoilLossRatio(

Close Turfing

y = 0.147x 2 - 2.3282x + 8.11

R2 = 0.50650

20406080

100

Month

SoilLossRatio(%

Figure 4: Monthly distribution of soil loss ratio for each treatment.

y = 0.0004x 3 - 0.0845x 2 + 4.4322x +11.832

R2 = 0.9824

0

20

40

60

80

100

0 20 40 60 80 100

% Cover

SoilLoss(kg/ha)perEI30(%)

Hydroseeding Poly. (Hydroseeding)

Figure 5: Effect of percentage of cover on soil loss perEI30on hydroseeding only.

The biomats offered nearly 100% coverage and

protected the soil surface from raindrop impact,

hence reduced soil detachment. The Millet and

Ruzi grasses from plots overlaid with biomats

appeared to establish more quickly compared to

the hydroseeding only. The high water retention

capacities provided by the biomats encourage

the growth of the grasses. Interception was

increased by grass development and detachmentwas reduced as the root network develops.

Hydroseeding alone only gave good protection

in October, after 6 months in which Ruzi grass

covered about 90% of the plot (Fig. 5). The

increase of soil loss (kg/ha) perEI30 from 0% -30% cover was due to the formation of rill

erosion which diverted the concentrated flow to

the centre of the divisor. This demonstrates that

hydroseeding alone allows the formation of rill,

hence the occurrence of rill erosion.

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Correlation coefficients, rrelating soil loss frombare plot to various erosivity indices including

the raindepth are show in Table 2. There was no

strong correlation between the erosivity indices

and soil loss. EI30 had a lower correlation whenstudies conducted in the tropics (Lal, 1977:

Balasubramanian and Sivanappan, 1981).

Hudson (1971) observed that erosion is entirely

caused by rainfall at intensities above a

threshold level, 25 mm/h. At intensities lower

than this level, soil erosion is negligible. By

leaving out the energy of the non-erosive rain, a

better correlation was obtained between the

KE>25 and soil loss from bare plot.

Table 2: Correlation of soil loss from bare plot

with erosivity indices.

Erosivity index r

Raindepth 0.41

EI30 0.56

KE>25 0.70

AIm 0.64

Costs

Table 3 shows the cost per square meter of each

treatment, including costs of labour, fertiliser,

seed application and mulching. Vetiver and

Arachis pintoi are more expensive than turfing,but the latter gave better protection. The cost of

hydroseeding depends on the landscape. Often,

overlaying with "fibromat" and "geojute", are

more costly but they are very effective erosion

control measures.

Cover Management Factor

Cover management factor, C for varioustreatments are given in Table 4. Hydroseeding

overlaid with "fibromat" was found to give the

best protection with C value lower than 0.001(0.0004) as compared to 0.004 treated with

"geojute" and 0.021 treated with hydroseeding

only. Meanwhile, close turfing gave good

protection with C value 0.004, followed by

0.017 for spot turfing, 0.122 for vetiver and

0.213 for the legume. Two assumptions were

made in the computation of the Cfactor. First,the slope length and steepness factor, LS is

always unity. The second assumption was that

the soil erodibility factor,Kwas constant duringthe study period whereas in reality the Kfactorcan vary because of the effect of soil loss. For

instance, the bare plot was exposed for too longuntil the topsoil deteriorated from excessive

erosion and this significantly changed the Kvalue. As a result, we obtained a value of 0.646

for bare soil instead of the theoretical value of

1.000.

Table 3: Contract cost of each treatment.

Treatment RM/m2

Vetiver 10.50

Legume (Arachis pintoi) 8.00

Spot turfing 2.00

Close turfing 4.00

Hydroseeding 2.00 - 3.00

Geojute 1.60

Fibromat 2.50

Table 4: Cfactor of each treatment.

Treatment Cfactor

Bare 0.646

Legume 0.213

Vetiver 0.122

Spot turfing 0.017

Close turfing 0.004

Hydroseeding 0.021

Geojute + hydroseeding 0.004

Coco-fibromat + hydroseeding 0.001

Fibromat + hydroseeding

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during a one-year study period. Bioengineering

soil erosion control techniques were found to

have significant effect on reducing soil loss.

The following conclusions can be drawn from

this study:1. In one-year study period, close turfing with

cowgrass was the best treatment, reducing

soil loss by 99% compared to the bare plot.

2. Hydroseeding + "fibromat" gives better

protection among the plots treated with

hydroseeding. This technique reduced soil

loss by a factor of fifty-seven compared to

hydroseeding only. Hydroseeding overlaid

with "fibromat" gave the best protection

with a Cfactor of 0.0004.3. The "fibromat" can be considered to be the

most reliable erosion control technique since

it provides a more secure cover to protect

the soil surface from raindrop impact and

enhance the growth and development of

vegetation.

4. Without biomat, hydroseeding alone

required 6 months to form about 90% cover

in order to have effective protection.

5. The KE>25 can be considered as a better

erosivity index than any other commonly

used indices.

6. A combination of control measures usuallyimprove protection from erosion

Acknowledgements

This work is a part of IRPA Project 51350. The

financial support of MPKSN is acknowledged.

The authors are also indebted to all staff of the

DBAE Field Station. Their help in this project

is greatly appreciated.

References

Ahmad, A. K. Z. (1990). Erosion of Slopes. In:

C. H. Chin, M. J. D. Dobie and R. A. Nicholls

(Eds.), Seminar on Geotechnical Aspects of the

North-South Expressway, PLUS Projek

Leburraya Utara-Selatan Bhd., Malaysia, pp

283-292.

Andreu, V., J. L. Rubio and R. Cerni (1998).

Effects of Mediterranean Shrub Cover on Water

Erosion (Valencia, Spain). J. Soil and WaterCons. 53(2): 112-120.

Balasubramanian, G. and R. K. Sivanappan

(1981). Effect of Degree of Slope and Rainfall

Erosivity on Soil Erosion and the Influence of

Mulching on Runoff and Soil Loss. Proceedings

of the South-East Asian Regional Symposiumon Problems of Soil Erosion and Sedimentation,

January 27-29, 1981, Asian Institute of

Technology, Bangkok, pp 29-36.

Cazzuffi, D., F. Monferino, R. Monti and P.

Rimoldi (1994). Experimental Evaluation of the

Erosion on Bare and Geosynthetically Protected

Slopes. In: R. J. Rickson (Ed.), Conserving Soil

Resources, Cranfield, pp 413-421.

Edwards, K (1983). Analysis of Runoff and Soil

Loss from Long-term Plots. In: S. A. El-Swaify,

W. C. Moldenhauer and A. Lo (Eds.), Soil

Erosion and Conservation of America, Ankeny,

pp 472-479.

Elwell, H. A. and M. A. Stocking (1976).

Vegetal Cover To Estimate Soil Erosion Hazard

in Rhodesia. Geoderma 15: 61-70.

El-Swaify, S. A. (1977). Susceptibilities of

Certain Tropical Soils to Erosion by Water. In:

D. J. Greenland and R. Lal (Eds.), Soil

Conservation and Management in the Humid

Tropics, John Wiley & Sons, London, pp 71-77.

Foster, G. R., D. K. MCcool, K. G. Renard and

W. C. Moldenhauer (1981). Conversion of the

Universal Soil Loss Equation To SI Metric

Units. J. Soil and Water Cons. 36(6): 355-359.

Franti, Thomas G. (1996). Bioengineering for

Hillslope, Streambank and Lakeshore Erosion

Control. Cooperative Extension, Institution of

Agriculture and Natural Resources, Universityof Nebraska-Lincole.

Grace, J. M. III, B. Rummer, T. A. Dillaha and

R. A. Cooke (1994). Evaluation of Erosion

Control Techniques on Forest Roads. Trans. of

the ASAE 41(2): 383-391.

Hudson, N. W. (1971). Soil Conservation. Bt

Batsford Ltd., London.

Jenning, G. D. and A. R. Jarrett (1985).

Laboratory Evaluation of Mulches in ReducingErosion. Trans. of the ASAE 28(5): 1466-1470.

10

8/3/2019 msmebs (1)

11/11

Koon, P. K. and F. W. Lim (1991). Vetiver

Research in Malaysia - Some Preliminary

Results on Soil Loss, Runoff and Yield. In:

Vetiver Newsletter no. 5, March 1991. Vetiver

Information Network, ASTG, World Bank,Washington D.C.

Lal, R. (1976). Soil Erosion on Alfisols in

Western Nigeria, III. Effect of Rainfall

Characteristics. Geoderma 16: 389-401.

Lal, R. (1977a). Soil - Conserving Versus Soil -

Degrading Crops and Soil Management for

Erosion Control. In: D. J. Greenland and R. Lal

(Eds.), Soil Conservation and Management in

the Humid Tropics, John Wiley & Sons,

London, pp 81-86.

Lal, R. (1977b). Analysis of Factors Affecting

Rainfall Erosivity and Soil Erodibility. In: D. J.

Greenland and R. Lal (Eds.), Soil Conservation

and Management in the Humid Tropics, John

Wiley & Sons, London, pp 49-56.

Morgan, R. P. C. (1979). Soil Erosion,

Longman, London.

Mostaghimi, S., T. M. Gidley, T. A. Dillaha and

R. A. Cooke (1994). Effectiveness of Different

Approaches for Controlling Sediment and

Nutrient Losses from Eroded Land. J. Soil and

Water Cons. 49(6): 615 - 620.

Mutchler, C. K., C. E. Murphree and K. C.

McGregor (1994). Laboratory and Field Plots

for Erosion Research. In: R. Lal (Ed.), Soil

Erosion Research Methods, 2ed., SWSS-ISSS,

Ankeny, pp 11-37.

Soong, N. K., G. Haridas, C. S. Yeoh and P. H.Tan (1980). Soil Erosion and Conservation in

Peninsular Malaysia. A Monograph, Rubber

Res. Inst. Malaysia.

Sulaiman, W. W. H. (1989). Fighting Erosion in

the Humid Tropics. In: O. Van Cleemput (Ed.),

Soil for Development. ITC - Ghent, Publication

series no. 1, Belgium, pp 85-107.

Thornes, J. B. (1990). The Interaction of

Erosional and Vegetational Dynamics in Land

Degradation: Spatial Outcomes. In: J. B.

Thornes (Ed.), Vegetation and Erosion, John

Wiley & Sons, Chichester, pp 41-55.

Yong, H. L. (1998). Comparison of Four

Agronomic Erosion Control Measures. BachelorDegree Project, UPM, Serdang.

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