Object 452 PDF English

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Biotechnical Riverbank Restoration: A Sustainable

Alternative to Traditional Engineering in the Tropics

Primary Presenter: Kwok Wing Leong

Company: CHT-NATURAL SOLUTIONSAddress: 16 Jalan PJU 1A/10

City: Petaling Jaya State: Selangor Zip: 46050 Country: Malaysia

Learning Obj 1 : Discover Biotechnical Engineering approaches applied to

Riverbank Restoration solutions.

Learning Obj 2 : Elucidate Sustainable Alternatives to Traditional Engineering.

Learning Obj 3 : Share techniques used to overcome tropical rainstorm challenges.

Key words : Sustainability, Soil migration, best management practices(BMP)techniques, erosion & sediment control, sustainable slope

and river channel rehabilitation & vegetation, bioengineering,erosion control & permanent turf reinforcement mattress.

Academic :

BSC in Civil Engineering (California State University Sacramento)

Professional licenses :

i) Professional Civil Engineer (PE 1981) in the State of California, USA.

ii) Certified Professional Erosion & Sediment Control (CPESC 2001) specialist USA.

iii) Certified Professional Storm Water Quality (CPSWQ 2003) specialist USA.

Professional Associations/Affiliations :

i) Member ASCE American Society of Civil Engineers since 1983.

ii) Member IECA International Erosion Control Association since 1992.

iii) Vice President IECA Malaysian Chapter 2003-5.

Work Experiences :

Worked for over 15 years in State of California Department of Transportation and Department of

Parks and Recreation with experience in design, development & construction supervision, ofhighway, geotechnical foundation, water & sewerage systems, park systems & trails, storm water

management, river channel & shoreline protection Since 1992, responsible for the marketing,

design and construction in Asia of Alcoa-Prestos Geoweb Cellular Confinement System forslope protection, geotechnical soft soil heavy load design, green retaining walls, river

embankments & shoreline protection systems. Since 2000, established joint venture in Malaysia

to research & develop biotechnical solutions as alternative to traditional engineering withreusable natural resources of Malaysia. Biotechnical solutions include slope rehabilitation &

river restoration techniques.

Teaching :

Lectured and taught BMPs for erosion & sediment control methods and storm management to

Department of Environment senior officers at EiMAS (July 2004), Department of Drainage &


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Irrigation senior officers & engineers for IECAM-JPS(Pahang) at Bukit Tinggi (August 2004)

and IECAM-JPS(Federal) at Port Dickson (October 2004).

Drainage & Irrigation Dept(JPS) program:

JPS-ESCP program (Johore) at Johor Bahru (December 2004),

JPS-ESCP program (Pinang) at Seberang Jaya (May 2005),JPS-ESCP program (Trengganu+Kelantan) at Cherating (June 2005),

JPS-ESCP program (Sarawak) at Kuching (November 2005),

JPS-ESCP program (Sabah) at Kota Kinabalu (December 2005),JPS-ESCP program (Federal Territory) at Labuan Island (April 2006)

Paper on BMP Techniques in construction sites @ Singapore Public Utility Board(PUB) &Institute Engineers Singapore (IES) jointly organized Erosion & Sedimentation Control at

Construction Sites (IES-PUB) on 8th

April 2004

Paper on Site Solutions & Management of Erosion & Sediments @ Singapore (PUB) &

Singapore Contractors Association (PUB-SCAL) on Earth Control Measures at ConstructionSites on 1st

Oct 2004

Institute Engineers Singapore (IES) organized: The Singapore Construction Industries Joint

Committee (CIJC) & Singapore Public Utility Board(PUB) (CIJC-PUB) on Erosion &

Sedimentation Control on 20th

April 2005.

Short course for Singapore (PUB) field inspectors on Feb. 2006.

ABSTRACT : The combination of climatic and geological conditions account for much of the

slope and riverbank erosions here in the tropics, Malaysia, which is located 4 off the equator.

The problem is further exacerbated with rapid development integrated with constructionpractices resulting in steep embankments, striping of natural vegetation and heavy earth

movements leading to soil laden rivers, downstream scouring and sedimentation at riverestuaries.

This paper presents bio-technical engineering techniques developed in Northern America and

Europe to naturally heal eroded riverbanks, modified and reinforced to meet the local tropicalchallenges.

Case history of several projects with before & after results shall be presented exemplifyinggreen solutions on river channel rehabilitation as a viable and sustainable alternative to

traditional hard core solutions.


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Biotechnical Riverbank Restoration: A Sustainable

Alternative to Traditional Engineering in the Tropics

1. INTRODUCTION

Biotechnical engineering has been extremelysuccessful over the past decade as a

compliment and in certain situations, an

alternative to traditional engineering. Thedesign and applications has been described

by many distinguish engineers and

professors in papers at Civil Engineeringand Erosion Control (IECA) Conferences

and Seminars worldwide in recent years.The applications were initially focused on

slopes with recent integration into riverembankment repairs.

This paper presents the authors observationon the several technical benefits of

biotechnical techniques when applied to

stabilize river embankments in the tropicalrainforest environment. Three riverbank

repair projects at different locations in

Malaysia with different soil and climaticchallenges shall be shared to exemplify the

above described benefits.

As integral part of these research projects,

we shall highlight The Malaysian Drainage

and Irrigation Department(DID)s verycomprehensive drainage manual (MASMA)

of 2001, which describes alternative design

procedures that encourages the use ofnon-hard surfaces in the design, repair and

stabilization of riverbanks.

It is a major paradigm shift from the

traditional rapid discharge concept where

rainwater is quickly & efficiently

transported via smooth concrete drains toriver channels and discharged to ocean. The

latter method has accounted for much

downstream scouring, riverbank erosion andirrevocable damage to aquatic and wildlife.

The pilot projects described exemplifiesDIDs lead-by-example policy and

reflexes a combination of several techniques

adopted from the MASMA Manual andbio-engineering used in USA and Europe.

The primary goal is to :

a) Stabilize and repair riverbanks andestablish vegetation

b) Reduce both flow and runoff velocitiesc) Reduce downstream sedimentationd) Sediment trap and retain organicse) Increase water infiltration and filtrationThe secondary goal :

a) Increase natural aestheticsb)

Improve water quality and fish habitat

1.1 SITE LOCATION @ SUNGAI

(RIVER) JENDERAM

The project site is located at the lower

reaches of River Jenderam, flowing through

rural countryside of Sepang municipality inthe State of Selangor. Drainage basin

includes watersheds of surroundingJenderam vicinity and upper stream ofbordering State of Negri Sembilan. Local

animal life includes the local lizards, wild

fowl, heron, king fisher, some migratory

birds, fishes and domestic cows. Soil istypically sandy clay, very erosive, river

cross-section is 2-benches trapezoidal.


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1.2 SITE CONDITION @ SUNGAI(RIVER) JENDERAM

The local DID has been given the task of

de-silting River Jenderam periodically tomaintain hydraulic flow capacity. Dredged

tailings are placed on both sides of the

riverbank while a backhoe trims theembankment back to its 2-bench trapezoidal

river cross section. No riverbank protection

method was employed and within months of

the rainy season, severe rills and gullieswere experienced with sediments

re-depositing back to the river bed.

Photo-Leong

1.3 DESIGN SOLUTION @ SUNGAI

(RIVER) JENDERAM

Design objective: Protect riverbank from

runoff and flow erosion. The traditionalsolution would be reinforced concrete slabs

or wire gabions and reno mattresses

however DID broke from norm and

approved a biotech solution.

Design: Leong-Perunding Azman, Rao & Ooi

The riverbank is protected by a system of

specially engineered High Strength ErosionControl Mattress (ECM), Turf Reinforced

Mattress (TRM) and Roll Mattress Logs

(RML) :

i) Lower berm slope @ higher flowvelocity,

ii) High Strength ECM ecomix (coir :

polymer fibre mix) used

iii) Upper berm slope @ moderate

velocity, regular ECM ecomix isapplied.

Riverbank Toe Scour Protection @ high

scouring forces, RML was secured intotoe-trench @ riverbed.

Drawing: Perunding Azman, Rao & Ooi

The mattresses were made of re-use coconut

coir and polymer fibre @ 70:30sandwiched within PP nettings and

reinforced high tensile strength geogrids for

high velocity flows.

1.3 IMPLEMENTATION @ SUNGAI(RIVER) JENDERAM


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Photo-Leong

The riverbanks were re-trimmed, whilst asecond team followed behind and installed

according to design.

Site Preparation :

Grade, fill-in eroded gullies and level with

top-soil mixture ;

Scour Protection :

RML placed into riverbank toe trench and

secure with J-rebars criss-cross tied-downwith coated tie-wires.

Photo-Leong

Bank Protection :

High Strength Reinforce ecomix mattresswas used at the lower bench whilst ecomix

mattress was use at upper bench.

Photo-Leong

Installation :

The mattress were laid parallel to river flow,

the ends were hand-stitched together,

secured with J-rebars @ 12mm x 500mm

at 1m laterally and longitudinally andkey-in at anchor trenches (200W x

300D)mm. TRM method of installation waschosen where top-soil mixture with

microbs were installed onto the installedmattress before hydroseeding applied. Live

staking of bamboo and scrub cuttings were

installed at riverbank, anchored through the

installed surfaces.

1.5 CHALLENGES @ SUNGAI

(RIVER) JENDERAM

Rain struck at the midst of construction with

bank discharge. The water level stayedat the upper reaches of the lower bench for

over 12 hours. Upon receding, minimal

damages were observed. It appears that themattress allows water to flow-out but

retained the soil from eroding from the bare

surface. The installed mattress acted as a

one-way filtration mechanism. Some

top-soil had to be replenished as it waswashed away before grass seeds could

germinate and establish rooting.Second challenge learnt here is the

voracious appetite of local animal life. It

appears that both the herds of local cows andwild fowl took a liking to the newly

germinated grass !


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1.6 RESULTS AND OBSERVATIONS@ SUNGAI (RIVER) JENDERAM

The local District Engineer Ir. Nordin is

very satisfied with the outcome and theyhave been closely monitoring the progress

for over a year. According to Engineer

Nordin, this riverbank section has withstoodan ARI 50yrs storm event with no problems

where concrete U channels less than 500m

upstream has failed. Both the hydroseededvegetation and live stakes has grown and

flourishing well. The soft and green

armour are performing well.

Fully restored and vegetated Sg.Jenderam, very natural, 1+ yrs.

2.1 SITE LOCATION @ SUNGAI(RIVER) DCA (DEPARTMENT

OF CIVIL AVIATION)

Drawing by Perunding Azman, Rao & Ooi

The project site is located within the vicinityof Subang Town and airport. It drains across

Department of Civil Aviation property

connecting into major tributarySungai(River) Damansara. Increase

development adding to high impervious

pavement of Subang Airport with no newwater holding capacity has resulted indrainage flow rising 5m within 23 minutes

of rain falling at Subang Town.

Soil is typically fill material of silty-sandy-clay. Riverbank is built probably from

dredgings during construction of Subang

Airport and drainage channel 40yrs ago.

Eroded riverbank w/settlement

2.2 SITE CONDITION @ SUNGAI(RIVER) DCA

Riverbank at DCA has been eroding and

settling over the years with critical areasapproaching their septic system. The whole

DCA complex will have to shut down if

the septic system fails. DID headquarterscame to the rescue of DCA and took up the

challenge of repairing the banks

biotechnically.


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Design by Leong- Perunding Azman, Rao & Ooi


(RIVER) DCA

The traditional solution would typically

include some piling, rubble pitching,concrete work, gabions and reno mattresses

or a combination.The Green Riverbank Rehabilitationproposal includes a combination of specially

engineered high strength P-TRMs and

RMLs with high tensile strength deep tie-back anchors(3.5m) for fast scouring

conditions:

i) Riverbank Toe Scour Protection @

high scouring forces, HS-RML wassecured to riverbed with HS deep tie-

back anchors for uplift restraints.

ii) Lower bench slope @ higher flowvelocity, special HS P-TRM was

used.

iii) Upper bench slope @ moderate

velocity, HS ECM is applied.

Design by Leong- Perunding Azman, Rao & Ooi

The 3-D matrix is made from re-use coconutcoir and polymer fibre @ 70:30

sandwiched within PP nettings and

reinforced with high tensile strength

grids(40kN/m @ each direction).

2.4 IMPLEMENTATION @ SUNGAI(RIVER) DCA

The riverbanks were trimmed one-side-at-a-time. One team installed the high strength

deep anchors at toe trench before securing

the HS RMLs while another installed

HS P-TRM and HS ecomix mattresses.

Photo-Leong

Site Preparation :

Clear and grub, fill-in all gullies and level.

Scour Protection :

Riverbank toe trench, drive-in high strengthdeep anchors (3.5m), set and lock, seat

HS-RML onto toe trench and securewith J-rebars criss-cross tied-down with

coated tie-wires.

Driving 3.5m deep high strength tie-back anchors

Bank Protection :


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Secure HS P-TRM with J-rebars at the lowerbench.

Secure HS Ecomix mattress with J-rebars at

upper bench.

Water level rises 5m within 23mins rain-storm

Photo-Leong

Installation :

The mattress were laid parallel to river flow,

the ends were hand-stitched together,

secured with J-rebars @ 12mm x 500mm

at 1m laterally and longitudinally andkey-in at anchor trenches

(200W x 300D)mm. TRM method of

installation was chosen where top-soilmixture with microbs were installed onto

the installed mattress before grass turf was

installed. Live staking of flowering scrubcuttings were planted at top bench.

2.5 CHALLENGES @ SUNGAI

(RIVER) DCA

Challenges: bank failure@ rain-storm 9-9-06

Mother-Nature :

Due to delays, project started at thebeginning of the rainy season. Heavy rain-

storm bombarded the excavated riverbanks

before the system was fully installed onSeptember 9

thevening. The damages were

severe and unprecedented. The side that had

mattress protection (left bank) survived theturbulent flow well while the unprotected

riverbank (right bank) suffers bank failures

with much toe-scouring. The project had just

escalated from hydraulic to hydraulicw/geotechnical problems combined.

The action plan formulated to address thefollowing situation :

Installing re-directive vanes.

Buying time Technique :

Whilst the left bank damage is being sortedout and designed, 2 biotech vanes (learnt

from John McCullah, Salix Corp, USA) at

15m apart were built at the damaged banktoe with 3 High Strength Roll Mattress Logs

strapped together and secured into the bank

with deep J-rebars driven to riverbed andcovered with stone-boulders. They were


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placed facing up-stream at 30 to flow-line.The vanes were able to re-direct the flow

scouring energy thalweg away from the

damaged riverbank, hence buying time for

stabilization work to be done in-betweenrain-storms.

Left Bank Scoured Toe :

3 rows of wooden piles(3.5m) were driven-

to-bearing,

Left Bank Slope :

Shorter wooden stakes (1.5m) were drivenperpendicular to the original slope gradient,

gunny sacks were filled with dislodged

soil and installed between pile heads andstake ends to build-up slope to original

grade. HS P-TRM were then installed and

vegetated.

2.6 RESULTS AND OBSERVATIONS@ SUNGAI (RIVER) DCA

The local District Engineer Ir.Azmi and

team is happy with the biotech installationand closely observing the dynamic

challenges that the riverbank is subjected to

with every rain-storm event, as water risesin-a-flash.

The local District Engineer Ir.Azmi andteam is happy with the biotech installation

and closely observing the dynamic

challenges that the riverbank is subjected towith every rain-storm event, as water rises

in-a-flash.

Riverbank naturally repaired, withstood several 2006-7

monsoon rain-storms

3.1 SITE LOCATION @ SUNGAI

(RIVER) SURA

The project is located in the fishing town ofDungun at the north-eastern state of

Trengganu. Coastal state enjoys great sun-

sizzling beaches with servings of crystal

blue waters however during the monsoonseason, its rain and more rain. Good

drainage system is critical in these areas inorder that areas are not isolated by flood

waters.

3.2 SITE CONDITION @ SUNGAI

(RIVER) SURA

River Sura is heavily concrete-canalizedthrough the town. Certain sections have

seen better years with concrete slabscracking and banks settling. The debris fromthese bank failures causes flow restriction

and major constriction during high flows

undermine the integrity of pedestrian bridgeabutments and possible flooding during the

monsoon period.

Fail concrete slabs & bank failure, public hazard & flow restriction


(RIVER) SURA

DID Urban Drainage division in

coordination with the Trengganu DID office

took this opportunity to repair and replacefailed concrete slabs with a bio-engineered

solution, exemplifying the principles

described in the MASMA manual.


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A bio-engineered section was proposed withhigh strength reinforce mattress and roll

mattress logs for scour protection.

Design by Leong-Perunding Azman, Rao & Ooi

3.4 IMPLEMENTATION @ SUNGAI

(RIVER) SURA

The eroded bank was trim-back-to-grade.

The surface was protected by a layer of highstrength ecomix mattress secured into

embankment with J-rebars at 1m laterally

and longitudinally and vegetated with closeturf cow grass. The bank toe is protected

with a longitudinal roll of Roll Mattress

Logs(RML) secured with 4 pairs of 1.3m J-rebars driven to bed and strapped with

coated tie-wire criss-cross connecting the

hooks.

The surface is infilled with top-soil and

microbs before close turf cow grass layer

is installed.3.5 RESULTS AND OBSERVATIONS

@ SUNGAI (RIVER) SURA

This is the first time that a direct repair on adilapidated concrete channel is replaced

with a bioengineered soft solution in

Malaysia. The system has been through onemonsoon season and fared well.

Photo-Leong

4.0 CONCLUSIONS

Although traditional river embankment

repair methods (semi & hard solutions) have

benefits, their future applications arelimited. The alternative solutions with their

proven sustainability in Northern America,

Europe and now Malaysia has given a good


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opportunity for the engineering communitya viable alternative and can play a major role

in future river channel restorations.

BRIEF SUMMARY

Acknowledgements and References :

Manual Saliran Mesra Alam Malaysia Malaysia Dept. Drainage & Irrigation: Hj. Fuad, Dr. Nasir & Ir. Azman PAOR Salix Applied Earthware Erosion & Sediment Control Manual, CA, USA, by J. McCullah Dr. J. Fifield Designing for Effective Sediment & Erosion Control on Construction

Sites Certified Professional in Erosion & Sediment Control Workbooks, CPESC USA by J.

Scherer, C. Forrest, D. Lake, M. Harding, Dr D Walker, D. Ward D.H. Gray and A.J. Leiser Biotechnical Slope Protection and Erosion Control Wendi Goldsmith and Lothar Bestmann An Overview of Bioengineering for Shore

Protection

J.J. Armstrong and G.J. Wall Comparative Evaluation of the Effectiveness of ErosionControl Materials.

P. Raymond and D.J. Putt Biotechnical Stabilization of A Landslide- A Case Study ofSheep Creek, British Columbia, Canada.

J. Suarez-Diaz Erosion Control Basics in Tropical Areas G. Dallaire Cost-Effective Erosion Control with Blankets and Mats

Manufacturers :

Polyfelt, Maccaferri, Risi Stone Systems, Presto Products Company, CHT-NaturalSolutions, TEI Tighter Engineering, North American Green, Synthetic Industries a and.

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