“technical standards” river act article 13. (structural standards for

“Technical Standards”Groyne and Revetment in Japan and the World

1Niyodo River, Japan

Presentation 2 24 March 2014 Dr. Matsuki Hirotada: JICA Expert for Disaster Risk Reduction

River Act

Article 13. (Structural Standards for River Facilities)

River facilities must be safe structurally inconsideration of river conditions of water level,discharge, topography, geology and others andanticipated loads of itself, water pressure andothers.

2 Technical standards necessary for river facilitiessuch as dams, dykes and other major facilitiesshall be stipulated in Governmental Decree.

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Decree on Structural Standards for River Facilities Chapter 3. Dyke ----- Governmental decree

Article 17. (Scope of application)The provisions of this chapter shall apply to dykes and

unconnected dykes to prevent outflow.

Article 18. (Principle of structure)Dyke, as a unit with revetment, groyne and other facilities,

shall be safe against ordinary flow lower that design high-water level.

Article 25. (Revetment)Revetment shall be built to cover river-side slope and

berms if it is necessary for protecting the dyke from actionsof flowing water.

Article 26. (Groyne)Groyne shall be built at appropriate positions if it is

necessary for adjusting flow direction or buffering flowenergy in order to protect the dyke from actions of flowingwater. 3

Technical Standards for River Works (Planning) ----- MLIT regulation

7.2 Revetment planningRevetment is built to protect dyke or bank from erosion of flowing water in

combination with flood plain and other structures. Revetment shall bedesigned to have necessary position, alignment and extension with fullconsideration for cross-sectional profile including width of flood plainchannels, alteration of thalweg, etc. Revetment shall be planned tocontribute conservation and restoration of habitat for plants and animalsbecause it much affects river environment.

7.3 Groin planningGroyne is built to protect dyke or bank from erosion of flowing water in

combination with flood plain and other structures. It is also build to maintaina navigation channel or to improve and conserve river environment. Groyneshall be planned taking much account of habitat of plants and animals,landscape, channel capacity, impact on upstream, downstream andopposite bank, etc. considering plain configuration, longitudinal and cross-sectional profiles, channel characteristics and environmental issues of theriver.

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― Commentary on Revetment ―

1. Structure of revetmentRevetment consists of slope protection, foundation and foot protection. Revetment is different form coating

or groyne. Coating, such as grassing, also protects dyke but it is less durable than revetment. Groyneprotects dyke indirectly by adjusting or buffering flow which is far from functions of revetment.

Slope protection is a safe structure covering river-side surface of dyke to prevent contact with and scour byflowing water.Foundation supports slope protection.Foot protection is built to keep foundation stable by preventing frontal scour of riverbed which is exposed to

severe scouring action of flood flow.

2. Location of revetmentRevetment is built if it is necessary for protecting the dyke from flow impact. This means that location of

revetment is almost exclusively confined on eroding banks.

3. Plan of revetmentDyke is embankment of soil commonly so that it needs revetment. However revetment has heavy impact

on waterfront environment, so that it must be planned carefully confirming followings:- Revetment must be verified its necessity.- Revetment must work together with flood plain and groynes to provide better habitat for plants andanimals, comfortable connection to people, etc.

- In accordance with characteristics of the river, revetment must be built by creative efforts both forenvironmental enhancement and cost saving.

- Revetment must be designed taking account for frontal flow velocity, width of the flood plain channels,thalweg change over time, etc.

- Revetment often shifts the eroding bank downward.

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Revetment has a set of structures namely;(1)slope protection,

(2) foundation and (3) foot protection.

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― Commentary on Groyne ―

1. Variation of groyneGroyne is classified by structure, purpose and material into followings;a) by structure: permeable or impermeableb) by purpose: flow deflector or flow retarderc) by material: concrete block, riprap, timber skeleton, triangular crib, A-frame crib, wooden mattress,

lying groyne, pile groyne, vegetation like willow, etc.

Groyne produces a variety of currents which can vitalize river environment. Groyne must be installedobserving its impact to upstream, downstream and opposite banks and also to natural environment.

2. Groyne and revetmentGroyne is different from revetment on points below;

1) Revetment covers bank directly so that it is easier to prevent erosion instantly.2) Groyne protects bank indirectly as a deflector or a retarder so that it is insufficient if it has inappropriate

location and structure.3) Well-designed groyne makes channel of ordinary flow narrower and deeper.4) Root section and downstream bank of groyne is likely to be eroded by complex currents while flood,

which needs attention.5) Interspace of groynes provides sediment on which vegetation can grow up and habitat in which fish can

feed, breed and evacuate.

As described above, because of the multiple functions to protect riverbank differently from revetment, toregulate water flow and to form waterfront, groyne must be designed with sufficient consideration forprotective effects and environmental impacts.

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Groynes are effective for control river flowas a series of short structures.

Groynes

Ichi River, Japan

River facilities must be safe and also

easy-to-maintain within the lowest cost.

River bank protection

= combination of flow control and dyke protection

= groyne+ foot protection + foundation + slope protection

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Point 1: Total planning

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Standing groyne to attract flow to invite thalweg to its tip.

Low-lying groyne to reduce velocity to welcome sediment.

Point 2: Groyne

Scouring(by faster flow)

Low water level

High water level

Revetment

Slide down

Natural riverbank

Scouring(to be monitored)

Low water level

High water level

Slope protection,foundation andfoot protection

Extra foot protection(as maintenance)

Natural riverbank

Foot protection for long-term sustainability within the lowest cost

Point 3: Foot protection

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Slope protectionwith “flexibility” to avoid severe damage

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Water flow sucks out soil behind a slope protection.

Flood water scours river bed in front of bank protection.

Flexibility avoids significance to enable to repair damages.

A flexible slope protection can fit bank depressions due to suction stress.

A flexible foot protection can follow bed scour during peak-level flood water.

ScourSuction

to be repaired

to be repaired

Point 4: Slope protection

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Oregon Study

The recession flows for arunoff hydrograph are likelyto transport bed material intothe scour hole to deposit whilethe streambed armor layer in redeveloping upstreamand clearwater flow conditions are being reestablished.

This study make it clear that rockfill structures (dike, groin and weir) canbe used to manipulate sediment scour and deposition. In most existingapplications, such manipulation has been undertaken for “defensive” orpreventative reasons of protecting river banks or river structures. Scourmanipulation in the “offensive” or positive sense of encouraging scour tooccur has been an uncommon application. Yet there are many situationswhere the intentional encouragement of scour may be desirable.

(Streambank erosion protection and channel scour manipulation using rockfill dikes and gabions; 1984)

Trend 1: Oregon Study

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Australian GuidelinesThis guidelines is intended as a guide for experienced engineers with an

understanding of basic hydraulics and fluvial processes.It should nor be used as a ‘cookbook’ nor as asubstitute for individual training and local experience.

Retards are long low vertical fences constructed inthe stream bed normally projecting from thestream bank across the line of flow.

Groynes are short, tall fences or structuresconstructed in the stream bed projecting fromthe stream bank into the flow.

Maintenance and monitoring notes- Check for accumulations of debris which may either overload the

structure or reduce its permeability. Clear debris if necessary.- Check for evidence of scour at the structure which may indicate that the

structure is not sufficiently permeable. Adjust if necessary or placescour protection.

- Check for signs of abutment failure and correct as necessary.- Encourage vegetation in embayments between structures.

(Guidelines For Stabilising Waterways; 1991)

Trend 2: Australian Guidelines

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Delft ReviewClassification according to the action on the stream flow:Groynes may be classified as attracting, deflecting or repelling groynes.

Attracting groynes point downstream, they serve to attract the streamflow towards themselves and do not repel the flow towards theopposite bank.

Deflecting groynes are generally short ones and used for local protection.They serve to change the direction of flow without repelling it.

Repelling groynes point upstream. They serve to repel the flow awayfrom themselves.

(The Effect of Groynes on Rivers; 2002)

(Waar River, Nederland) Trend 3: Nederland Review

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Japanese Reconsidering

In recent years, river management has beenreconsidered to provide

- warm relationship with riparian people- sound habitat for aquatic plants and animals- capacity to minimize damages

against unexpected-scale.

After the end of 19th century, Japan eagerlyinstalled modern engineering with concrete materials.Generations of Japanese, however, have cultivatedflood-prone areas and created wisdom to manageand utilize river resources. This is called as traditional river engineering.

It is time to combine modern and traditional engineering and to leveragethem in a balanced manner. Traditional river engineering is not an oldtechnique but a source of application to the latest demands of thechanging society.

(River Committee’s Report “Progression of River Culture”; 1999)

(Nagaike River, Japan)

(Tsurumi River, Japan)

Trend 4: Japanese Reconsideration

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Flood Fighting

Introduction:- Farmers have been in charge of dykes, banks and irrigation since

ancient era. - Maintain dykes, banks and irrigation every year, otherwise our next

generations will suffer from flood disasters.

River Dyke:- Dykes are built to defense our paddies and houses.- Excellent engineers build anti-breaching dykes against an over-dyke

flood.- Don’t build a dyke at an eroding band but do it at a slackwater bank.

Bank protection:- Bank protection is facilities and activities to prevent dyke breaches.- Patrol and repair facilities along water flowing routes, or waste budget.- Prevent dyke breaching while a flood with all you have.

from “Flood Fighting (Hyakusho Denki)”; 168017

J-Traditional River Engineering 1680

River Management

Never win out but never lose out:- River management is not to defeat flood flow.- River management is not to be conquered by flood flow. - River management is to reduce conflict with the river.

Flatten and straighten:- River maintenance is to flatten the bank and straighten the thalweg. - Groynes enable to reduce flow energy and flow velocity so that they

remove the main flow away and welcome deposition into scour holes.

On-site planning:- Survey kilometers of the river in upstream and downstream.- Observe behavior of flood flow and movement of thalweg.- Draw a river management plan for years in the future.

from “River Management (Kawayoke Shiyocho)”; 1720


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Decree on Dyke Management

1) Small damage repair and severe damage prevention

2) Daily patrol and flood fighting

3) Yearly maintenance of irrigation and drainage

4) Integrated flood management plan

5) Stockpile of materials and equipments for emergency

6) Procurement of wood material

7) procurement of earth material

8) Budgetary assessment

9) Tender of contractor

10) Community alliance and cost saving

from “Decree on Dyke Management (Kyoho Shuchiku Reiki)”; 173219


Standards of Groyne Works

Key concept- 水以防水: Water prevent water(Water cushion protect riverbank form water attack.)

Groyne standards- 川除防水多種多様: There are best-functioning structures site by site. It

is impossible to copy a groyne.

- 短出直出潜水留砂: A groyne should be short and right-angle orientedto the flow. Submerged groynes can promote deposition.

- 固頭埋脚滅身安岸: A groyne should have a head concreted bygabions and a foot buried into the bank. However it should get damagein order to secure safety of the bank.

- 顔前導流上頰迎流: A series of groynes guide the main flow in front oftheir heads. Only at a bend, groynes should receive the main flow onthe upper faces.

from “Standards of River Management (Chika Yoroku)”; 1800s20

J-Traditional River Engineering 1800s

TIÊU CHUẨN VIỆT NAM TCVN 8419 : 2010CÔNG TRÌNH THỦY LỢI - THIẾT KẾ CÔNG TRÌNH BẢO VỆ BỜ SÔNG ĐỂ CHỐNG LŨ

Technical Standards for Riverbank Protection structures

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★ VN Technical Standards ★

from TIÊU CHUẨN VIỆT NAM, TCVN 8419; 2010

Scope 1. Phạm vi áp dụng

General 2. Một số quy định chung và phân loại công trình bảo vệ bờ song

general rules 2.1. Một số quy định chung

classification 2.2. Phân loại công trình bảo vệ bờ sông để chống lũ

Conditions 3. Tài liệu phục vụ thiết kế công trình bảo vệ bờ

Topography 3.1. Tài liệu địa hình

Geology 3.2. Địa chất công trình

Navigation 3.3. Thủy văn công trình và thủy lực

Tech-standards 4. Cấu tạo và các tiêu chuẩn kỹ thuật của công trình bảo vệ bờ song

Revetment 4.1. Thiết kế kè lát mái

Groyne 4.2. Thiết kế kè mỏ hàn

Non-hard type 4.3. Thiết kế kè mềm

4.1. Thiết kế kè lát mái (Revetment)

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Hình 1 - Cấu tạo kè lát mái

Hình 7 - Kết cấu rồng

Hình 8 - Chống xói chân kè bằng rồng hoặc bè chìm


4.2. Thiết kế kè mỏ hàn (Groyne)

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Loại mỏ hàn Góc lệch (độ)Xuôi (following) < 90o

Thẳng góc (right angle) = 90o

Ngược (reverse) > 90o

Bảng 2 - Phân loại kè theo góc lệch

Khu vựcTừ chân kèvào thân kè

Từ chân kè rasong

Tổng chiềudài rồng

Phía mũi 1 m đến 2 m 8 m đến 9 m 10 mPhía thượng lưu 1 m đến 2 m 8 m đến 9 m 10 m

Phía hạ lưu 1 m đến 2 m 6 m đến 7 m 8 m

Bảng 4 - Quy định bố trí lớp đệm chống xói bằng rồng đá

Hình 11 - Bố trí đệm chống xói bằng bè chìmHình 10 - Mặt cắt ngang điển hình kè mỏ hàn

24Onga River, Japan

“Technical Standards”

should nor be used as a ‘cookbook’ nor a substance for individual training and local experience. (AUS)

Rivers can be maintained within the minimum cost using local materials and creative efforts of engineers. (JPN)

One suggestion is how to control river flow using deposition and erosion of river itself. (USA)

A country, rich in rainfall, sediment and techniques, can develop advanced river engineering. (VN)

“technical standards” river act article 13. (structural standards for

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