Guideline Check Dams Complete Set

Title

Guidelines For Design and Construction Of Check Dams For Prevention and Control Of Peatland Fire

Type of Reference

Engineering Design Guides / Manual

Category

Structure

Author

Ng Kok Seng

Reference No.

EGM-STR-001

Date of Publication

August 2011

Serial No.

SS-TP-01-01-2011

Keywords

Check Dams, Peatland

Source

Design and Dam Division, DID Malaysia

Kementerian Sumber Asli Dan Alam SekitarKementerian Sumber Asli Dan Alam SekitarMalaysia

GUIDELINES FOR DESIGN AND CONSTRUCTION OF CHECK DAMSys

ia

CONSTRUCTION OF CHECK DAMSFOR PREVENTION AND CONTROL

OF PEATLAND FIRE

liran

Malay

iranda

nSa

latan

Peng

aiJab

August 2011Serial No: SSSerial No: SS--TPTP--0101--0101--20112011

Rev 0 (December 2010) - Guidelines for Design and Construction of Check Dams For

Prevention and Control of Peatland Fire i

FOREWORD

In the past decade, incident of peatland fires have been occurring frequently in Malaysia,

particularly during the prolonged dry weather which normally occurs between the month of

February to May and July to October each year. The associated haze and pollution have

resulted in severe consequences to the socio-economic, ecology, and environment especially

in term of their potential impact on public health of local residential population. Under the

Ministry of Natural Resources and Environment (NRE) Peat Fire Prevention and Control

Program, the provision of check dam structures has been identified as one of the key

components to combat the frequent occurrence of peatland wildfires and the associated

hazardous hazy conditions. Since 2008, Jabatan Pengairan dan Saliran Malaysia (JPS) has

been entrusted with the task of implementation of check dam structures in peat areas prone

to fires in various States such as Selangor, Johor, Pahang, Kelantan, Sarawak and Sabah.

This task includes the various aspects of planning, design, construction and operation and

maintenance of check dam structures.

The use of check dams has been proven to be an effective method in rising and maintaining

the water and moisture levels in the peatland, thus minimizing the risk of wildfires especially

during the prolonged drought periods. Various techniques and types of materials have been

used by JPS in the construction of these check dam structures which include sand/earth

filled bags, timber logs, stones/rocks, gabions and reinforced concrete either precast or cast-

in-situ. In view of these, it is hope that this Guideline would serve as a useful source of

information and knowledge as well as provides the best engineering practices for users

involved in the selection, planning, design and construction of check dam structures in

peatlands.

.

JABATAN PENGAIRAN DAN SALIRAN MALAYSIA (DEPARTMENT OF IRRIGATION AND DRAINAGE MALAYSIA) JALAN SULTAN SALAHUDDIN, 50626 KUALA LUMPUR


Prevention and Control of Peatland Fire ii

ACKNOWLEDGEMENT

This guideline is one of the many initiatives undertaken by JPS to improve its delivery

system and to achieve the mission of the Department in providing efficient and effective

services. It is made possible through the efforts by many JPS staff, in particular, Mr. Ng

Kok Seng (Senior Principal Assistant Director) who had prepared the Guideline, and the

following members of the Technical Committee in Bahagian Rekabentuk dan Empangan

(BRE) who had reviewed and provided valuable input:-

Ir. Lee Loke Chong, Director

Pn Rozaini Bt. Abdullah, Deputy Director

Mr. Ng Kim Hoy, Deputy Director

Pn. Rosilawani Bt. Sulong , Assistant Director

In addition, the Department is also grateful to JPS staff in the States of Selangor, Johor,

Pahang, Kelantan, Sarawak, and Sabah for their invaluable information, support and

contribution of ideas. Also, special thanks to Y.Bhg. Dato Ir. K. J. Abraham, Deputy

Director-General II (Specialist Sector), JPS Malaysia for his continuous support and

numerous useful suggestions in ensuring the successful completion of this Guideline.

Registration of Amendments Amend No Page No Date of

Amendment


Prevention and Control of Peatland Fire iii

PAGE

1.0 INTRODUCTION

1.1 Purpose And Scope

1.2 Limitation of Guidelines

1

2

2.0 DESIGN CONSIDERATION FOR CHECK DAM STRUCTURE

2.1 Purpose of Check Dam

2.2 Design Considerations

2.2.1 Location of Site

2.2.2 Control Water level

2.2.3 Durability of Check Dam

2.2.4 General Layout

2.2.5 Hydrology and Hydraulic of Peatland

2.2.6 Seepage Control

2.2.7 Cost

3

4

4

5

6

6

6

8

3.0 TYPICAL CHECK DAMS

3.1 Classification of Check Dam Structures

(a) Short-term (temporary)

(b) Medium-term (Semi-permanent)

(c) Long-term (Permanent)

3.2 Type of Check Dam Structure

3.2.1 Sand / Local Earth Filled Bags Check Dam

3.2.2 Timber Check Dam

3.2.3 Stones / Rocks Check Dam

3.2.4 Gabions Check Dam

3.2.5 Precast Concrete Stacked Blocks Check Dam

3.2.6 Precast Concrete Post-panel System Check Dam

3.2.7 Cast-in-situ Concrete check Dam

10

12

12

13

13

13

17

20

21

24

25

28

4.0 GENERAL MAINTENANCE GUIDELINES

30

TABLE OF CONTENTS


Prevention and Control of Peatland Fire iv

List of Figures

List of Tables

Appendix A

References


Prevention and Control of Peatland Fire v

LIST OF FIGURES

Page

Figure 2.1

Location of Series of check Dam Structures Along Waterway in Peatland

7

Figure 2.2 Cost comparison of Typical Check Dam Structures 8 Figure 3.1

Check Dam Structure Type Earth/Sand Filled Bags for Medium Term Application

16

Figure 3.2

Example of a Typical Timber logs Check Dam 17

Figure 3.3

Example of a Check Dam Structure Using Wood Board and Posts 19

Figure 3.4

Example of a Timber Check Dam with Rip-rap Protection Works (Plan View)

19

Figure 3.5

Minimum Design Requirements for Stacked Stones Check Dam. 21

Figure 3.6

Check Dam Structure Type Gabions with Gated Flow Control for Medium-Term Application

23

Figure 3.7

Precast Concrete Stacked Blocks Check Dam Structure

25

Figure 3.8

Check Dam Structure Type RC Post-Panel (with Flow Control) for Long-term Application

27

Figure 3.9

Example of a Check Dam Structure Type Cast-in-situ Reinforced Concrete for Long-term Application

29

Figure A2.1

Example of a Sand-Fill Bag Check Dam

33

Figure A2.2

Typical Sand-Fill Bag Check Dam Dam

33

Figure A2.3 Example of Timber board Check Dam

33

Figure A2.4 Example of Loose Stones Check Dam

34

Figure A2.5

Example of Loose Stones Check Dam 34

Figure A2.6 Figure A2.7

Example Gabion Type Check Dam Typical Gabion Type check Dam

34

35


Prevention and Control of Peatland Fire vi

LIST OF TABLES

Page

Table 3.1

Principal Characteristic of Check Dams

11

Table 3.2 Specifications of Geosynthetics Bag for Earth-filled Check Dam (Class: Medium Term Application)

15

Rev 0 (August 2011) - Guidelines for Design and Construction of Check Dams For

Prevention and Control of Peatland Fire Pg 1

INTRODUCTION

1.1 PURPOSE AND SCOPE

The purpose of this guide is to recommend a general standard of good practices in

planning, design and construction of check dam structures in existing waterway in

peaty areas to prevent and control peatland fires. It is developed to provide an

overview of some of the requirements, criteria and common practices in the design

and construction of these check dam structures. For the purpose of this guide,

waterways in peatland are regarded as having minimal discharge due to the

relatively large reservoir storage of the peatland which buffer the effects of rainfalls.

Generally, the main goal of this Guideline is to:-

a) Provide a general understanding and appreciation of the usage of check dams

gearing towards a sound, safe and effective design and construction

b) Provide a consistent guidance for practitioners involved in the provision of

check dam structures.

c) Provide some guides on the selection of the most suitable types of check dam

structures

The practices and standards set out here are not meant to be comprehensive but to

serve as a general guide due to the many uncertainties and wide variety of site

conditions as well as the many possible types of check dam structures that can be

used. It is aimed at practicing civil engineers and technical personnel in the

Department involved in providing check dams and who are also conversant with the

relevant engineering principles and practices in the field of hydraulic and

geotechnical engineering.

Section 2.0 outlined some the important considerations required in the planning and

design of check dam structures. However, detail design including the aspects of

hydrology, geotechnical, stability and seepage analysis requirements are not

discussed here as readers may refer to appropriate references.

Section 3.0 described and illustrated some of the common types of check dam

structures that can be used in the Department. It provided an insight into some of



the important design and construction requirements including materials

specifications, hydraulic and geotechnical considerations.

Section 4.0 provided some general guides on the operation and maintenance of

check dam structures. Personnel involved in the operation of check dams should

also refer to the operation procedure issued by the Ministry entitled Prosedur Tetap

Operasi Untuk Melaksanakan Program Pencegahan Kebakaran di Tanah Gambut

issued in May 2010.

1.2 Limitation of Guidelines

As mentioned above, this Guideline is meant to be used for check dam structures

located in peat areas where discharges during rainfalls in the waterways are at

minimal due to the attenuation effects of the large peatland storage. It is developed

based mainly on the information gathered from literature researches and the

Departments knowledge and experiences in the implementation of check dam

structures.

In view of the large variety of site and ground conditions, users must realize that

there is no possible way to cover all the various intricate aspects of check dams

structures design and construction. As such, sound engineering judgment from

experienced practicing personnel who are familiar with peat soil and knowledgeable

about the check dam structures design and construction are important in applying

the guidelines presented. Knowledge of local experiences can also be invaluable in

ensuring the success of the design of check dam structures.



2. DESIGN CONSIDERATIONS FOR CHECK DAM STRUCTURE

2.1 PURPOSE OF CHECK DAM

A check dam, sometimes known as ditch check, is a barrier constructed across

waterways such as open channel, swales, and ditch or drains. Check dam can either

be a temporary or permanent structure which is built to retain and maintain the

desired ground water level within the peatland. In this way, it reduces the possibility

of ignition of fire in the drying peat as well as prevents any fire from spreading

during any hot and dry spell.

In the context of fire prevention and control, check dams are specifically installed for

the following purposes:-

a) To maintain minimum water level in the peatland areas so as to avoid any fire

ignition on land surfaces.

b) To maintain high soil moisture levels so as to minimize fire in the peatland areas

from occurring and spreading especially during prolonged dry and hot season

c) To prevent over-drainage of the peat land which will lead to drying out of the

organic materials causing carbon release as well as land subsidence.

d) To conserve as much water as possible during and after the dry season that

would help to recharge ground water.

2.2 DESIGN CONSIDERATIONS

They are many different types of check dam structures utilizing various different

materials. Some of these check dams are

Local or imported sand/earth filled bags check dam - see Figure A 2.1 and A2.2

Timber logs check dam see Figure A2.3 and A2.4

Loose stones/rocks check dam - see Figure A2.5

Stacked stones/rocks in encasement (gabions) check dam - see Figure A2.6

and Figure A2.7

Concrete (either precast or cast-in-situ) check dams-see Figure 3.7, 3.8 and

3.9

Further details of these check dams can be found in Section 3 of this Guidelines.



In general, there are several important factors that need to be considered in the

design and construction of check dam structures. These factors are:-

Location of Site

Control Water Level

Durability of Check Dam

General Layout

Hydrology and Hydraulic of Peatland

Seepage control

Cost Effectiveness

Further details on these factors are discussed below.

2.2.1 Location of Site

The selection of the location of check dam is crucial as its will determine its

effectiveness in controlling the ground water table. Some of the considerations when

selecting the location are: -

a) The general topography of land so that the limited ground water can be stored

and the water level maintained over a longer duration. If possible, the site

selected should be able to provide a long length and large volume of stored

water

b) Existing drainage system so that water can be blocked effectively, and if

necessary a series of check dams is incorporated into the system

c) Percentage of potential fire hazard peat lands on either side of the length of

stored water should be high

d) Accessibility of site with regards to access to vehicles/machinery for

construction as well as operation and maintenance of structures

e) The risk of submergence to any cropped lands, residential areas and other

infrastructures during flash floods.

2.2.2 Control Water Level

The water level in the drain ponded by the check dam should be kept as high as

possible to prevent the peat from drying out and turn into a highly combustible

material. Some general requirements in the desired water level to be maintained by

the check dam are as follows:-



a) The ground water table in the peatland adjacent to the check dam structure

should not be more than 400 mm below the average peat ground level

b) The risk of submergence of any cropped lands or local residential population

during flash floods should be minimized

c) Check dams should never be placed in active and high flows waterways unless

they are designed to convey the required flows.

d) Freeboard for channel shall be site specific and take into consideration the

effects of any submergence to facilities such as roads, residential areas and

crops lands

2.2.3 Durability of Check Dam

Check dams can be built using various type of materials such as earth, sand (loose

or in bags), timber (sawn or log), stones/rocks (loose or stacked), or concrete (cast-

in-situ or precast form). In selection of the most appropriate materials to be used as

the main components of the check dam structure, designer should take into

consideration the following factors:

Size and dimensions of check dam

Site conditions (e.g. waterlogged, depth of peats)

Accessibility of site

Availability of local materials

Designed service life of the structure (short-term, medium term or long-term)

Cost of construction

2.2.4 General Layout

Some of the general layout requirements of check dam structures are:-

a) The centre of the dam should be at least 150 mm lower than either edge, so as

to form an outfall weir for any active flows. However, the actual freeboard to be

incorporated should be based on the risk and hazard of flooding to the

surrounding areas.

b) Stabilization works with channel lining or protection works (such as riprap or

gabion mattresses) should be provided immediately downstream of the check

dam to prevent any possible toe erosion and undercutting.



c) The embankment/barrier of check dam should be extended adequately into the

existing bank to prevent any excessive seepage and potential breaching of the

banks

d) If a series of check dams are required, the dams should be spaced so that the

difference in the water levels between any two dams do not fall below 300 mm

as illustrated in Figure 2.1 below.

2.2.5 Hydrology and Hydraulic of Peatland

For permanent check dam structure, it is advisable to evaluate the effects of check

dams on the designed water levels in the waterway and the necessary storage

volume analysed to efficiently meet its primary objective. Hydrological analysis on

effects of drought would be necessary to evaluate the availability of water during

prolonged dry weather condition via events and/or period-of-record of rainfall and

drought.

In peatland where any flooding has significant impacts on local residential population

and/or cropped land, a hydrologic analysis in peat areas including flood routing,

should be carried out to identify the risk and hazard of flooding.

2.2.6 Seepage Control

Seepage is to be anticipated in check dam structure either through its embankment,

bank or foundation. To control the desired water level in the waterway, excessive

loss of impounded water must be minimised. For this purpose, the design of check

dam structures should incorporate the following features,

a) Use of low permeability materials such as clayey soil for embankment and

foundation.

b) Incorporate an impermeable layer such as HDPE sheet in the embankment and

foundation

c) Remove highly porous peat soil under the foundation for the check dam

structures and replace with more impermeable materials

d) Install vertical cut-off such as interlocking sheet piles, if necessary



Figure 2.1: Proposed Location of Series of Check Dam Structures Along Waterway in Peatland

Spacing between check Dams

Existing Average Bank Level

Proposed Control Water Level

Existing Average Bed Level

Proposed Check Dam

W.L. below Bank Level < 400 mm

Max. Difference in W.L. between D/S

and U/S Check Dams = 300 mm



2.2.7 Cost

The actual cost of construction of check dam structures depends very much on the

type of core materials to be used (which is actually related to the required structures

durability and service life), conditions of site as well as the ease of construction.

Figure 2.2 below give some indications on the relative cost of the various typical check

dam structures compiled from the information provided by the various states. For the

purpose of cost comparison, the estimated cost of each type of structure indicated is

based on the assumed size of waterway shown and on site which is accessible to light

vehicles only.

(a) : Cost Estimate For Check Dam Structure - Assumed Cross-Section

Assumptions For cost Estimation: i) Dimensions of waterway as in Figure 2.2 (a)

ii) Site accessible to light vehicles only

(b) Cost comparison

Figure 2.2: Cost comparison of Typical Check Dam Structures

Gabions + Mattresses with Gated Flow Control (Figure 3.6)

RM 5,000 Bags filled earth materials (Low quality fabric bags (Figure A2.1 and A2.2)

RM40,000 Precast Concrete Stacked Blocks (Figure 3.7)

RM20,000 Loose rocks/stones (site accessible to light vehicles only (Figure 3.5)

3.9)

RM10,000 Timber logs/ Sawn Timber (Sarawak Rate Only (Figure 3.2)

RM65,000 Cast in situ Check Structures with Gated Flow Control (Figure 3.9)

~ 2.0 m

Check Dam Structure

~ 6.0 m Existing Ground Profile

RM27,000 Precast Concrete Post- Panel System with Flow Control (Figure 3.8)

Bags filled with imported earth (High Quality Geotextile Bags (Figure 3.4 )

RM25,000

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The above costs comparison served only as an overall guide on the relative cost of the

various types of check dams. The actual cost would very much depend on several factors

such as availability of materials, site accessibility, depth of peat, and design service life of

structures



3. TYPICAL CHECK DAMS

3.1 CLASSIFICATION OF CHECK DAM STRUCTURES

Check dams can be constructed using many different materials depending on factors

such as availability of embankment materials, ease of operation and maintenance,

site accessibility and most of all the desired service life of the structure. This

Guideline has classified the various types of check dams into three main categories

depending on the designed service life of the structure, namely:

Category of Check Dam Expected/Design Service Life (Before any major repair/ maintenance

is required)

(i) Short-term (temporary) < 2 years

(ii) Medium term 2 to 5 years

(iii) Long-term (permanent) > 5 years

Some basic criteria and characteristics of the above category of check dams are listed

in Table 3.1.



Table 3.1: Principal Characteristics of Check Dams

Characteristic

Type

Expected/

Designed Service Life

(years)

Main Material

Components Used as Embankment

Water retention Effectiveness

Frequency and

Cost of Maintenance

(RM)

Relative

Capital Cost (RM)*

Ease of Construction

1. Short-term < 1 years a) Earth/sand

- without bags Poor High Low Easy

- fill in bags Poor High Low Easy

< 2 years b) Timber logs

Poor

(Average if layer of impermeable sheet

is provided)

High Average Average

2. Medium-term

2 to 5 years

a) Loose stones/rocks

Poor (Average if layer of impermeable sheet

is provided)

High Average Easy

b) Stacked rocks or Gabion type

Poor (Average if layer of impermeable sheet

is provided)

Average Average Easy

3. Long-term > 5 years a) Precast Concrete Stacked Blocks

Good Low High Average

b) Precast Concrete Post-Panel System

Good Low High Difficult

c) Cast-in-situ Concrete Very Good Low High Difficult



a) Short-term (Temporary)

Very often check dam structures are constructed as a short-term measure to retain

and maintain the water level in the drain and surrounding areas due to reasons or

factors such as:-

Check dams are urgently required e.g. during prolong drought and imminent

occurrence of peat fire

Limited fund available for a more durable and expensive structure

Temporary in nature due to constraint of land ownership or other constraints

Inaccessibility of site which prevent the use of heavy equipment/machinery or

imported materials for construction

Owing to the temporary nature of the structures, local or light imported materials

are commonly used in the construction of the embankment of check dams which

include

(i) Locally excavated or imported earth materials (e.g. sand) either in their natural

state or put in bags (sand or earth filled bags) and stacked to act a barrier

across the waterway as shown in Figure 3.1

(ii) One or more rows of timber logs spaced and tied closely together, as illustrated

in Figure 3.2

A more detailed description on these type of check dam structures are discussed in

Section 3.1 and 3.2

b) Medium Term (Semi-permanent)

Medium term check dam structures are those designed for service life of between 2

to 5 years. For this purpose, relatively more durable materials such as stones and

rocks are used as ore material for the onstruction the check dams. The stones or

rocks used can either be in loose form or stacked (with or without encasement such

as wire cages gabions or mattresses) to the required height and size of check dam.

Normally a layer of impermeable sheet is incorporated within the rocks/stones

embankment to reduce the seepage losses through the structure as illustrated in

Figure 3.5 below



c) Long-term (Permanent)

For conditions where a more permanent check structure is required, durable

materials such as reinforced concrete, whether cast-in-situ or pre-cast units are

used. As concrete structures are relatively very much more durable than other

materials, it is envisaged that these structures could easily last more than 5 years

without any major repair required. Very often, these long-term check dam

structures are incorporated into existing or proposed drainage flow structures such

culvert and bridge crossing. Some examples of concrete check structure are shown

in Figure 3.7, 3.8 and 3.9

3.2 TYPE OF CHECK DAM STRUCTURES

There are many different types of check dam structures that can be used to control

and maintain the water level in the waterway in peatlands, depending on factors such

as the local site conditions and budget available. This section presented details of

some typical check dam structures together with some general design and

construction requirements. User should apply appropriate design procedures and

assessment of the various types of check dam structures to suit the particular

circumstances under consideration.

3.2.1 Sand/Local Earth Filled Bags Check Dam

a) General

Sand /Local Earth Filled Bags check dam is a series of earth-filled bags placed on a

level contour to intercept flows. It provides a relatively quick and effective way in

holding the water flow to create a pond. Some of the general requirements of earth

filled bags are:-

i) Bags should be made from durable, weather resistant fabric e.g. geotextile

(unless for short-term). The fabric pores must be tight enough to retain the filler

material. The bags usually measure about the standard size of 1 m x 2 m x 0.15

m or other size as required. Low quality polypropylene (PP) woven Sugar bags or

sacks, commonly used in check dams construction, are found to be not durable as

they are easily damaged by the flows and have low UV resistance. As such, these

materials are not recommended as they normally do not last longer than a years



and required regular maintenance, and as such are only suitable for short-term

check dam structure.

ii) On both side of the check dam structure, earth filled bags must be extended and

tightly abutted into the banks to prevent excessive seepage or breaching at the

banks of the check structure.

iii) The center of the check dam must be lower by at least 150mm (min) to allow

normal flows spilling to occur within the mid portion of the structure, as shown in

Figure 3.1 below.

iv) The earth-filled bags should be placed as deep as possible into the peat to

minimize any seepage through the foundation. Alternatively, the peat could be

removed and replaced with well compacted clayey soils.

b) Materials Specifications

i) Container Bags

They are many types of fabric bags available in the industry, varying both in term

of raw materials and their properties. However, selection of the types of bags

normally takes into consideration factors such as the service life required,

accessibility of site, ease of construction as well as relative cost of the structure.

Table 3.2 below provided a typical specification for a more durable earth or sand

filled bags (compare to PP woven Sugar bags mentioned above) that could be

used for construction of Medium-Term check dam structures.



Table 3.2: Specifications of Bag for Earth-filled Check Dam (Medium-Term Application)

Description Properties

1 Dimensions of container bag

1 m x 2 m x 0.3m (Typical) Dimensions may vary depending on manufacturers specification

2 Base Material

Non-woven polypropylene, polyethylene or

polyamide fabric, sewn with a special seam

3 Thickness (minimum) 4 to 5 mm

4 Max Tensile strength (DIN EN

ISO 10319)

- machine direction >25.5 kN/m - cross machine direction >25.5 kN/m

5 Elongation at max Tensile strength (DIN EN ISO 10319)

- machine direction > 50 %

- cross machine direction >30 %

6 Max tensile strength of the seam Geotextile container

>75%

7 Characteristic opening size 0.08 mm

ii) Filled Materials

Fill materials for earth-filled bags should be well graded non-cohesive material or

free from any deleterious materials. For short-term check dam where suitable

filled materials are not available, then local earth materials may be used.



Figure 3.1: Check Dam Structure - Type Earth/Sand Filled Bags for Medium-Term Application



3.2.2 Timber Check Dam

a) General

This type of check dam is constructed using timber logs piled (or in combination with

timber boards) and tied together across a waterway to serve as a barrier to back up

the water level. It is more suitable for site where timber logs are available readily

(such as in Sarawak where timber logs are commonly used for this purpose). Figure

3.2 and Figure 3.3 illustrated the general layout of typical timber log and wood board

check dam structures respectively.

The logs should be embedded sufficiently into the ground so as to withstand the

hydraulic forces of the flowing water. Normally the barrier has to be strengthened

and supported by strutting as illustrated in shown in Figure 3.2. The top of the logs

at the center portion of the barrier should be at least 150mm lower to cater for daily

overflow. To prevent scouring downstream, stacked rocks can also be placed on the

downstream side of the dam to prevent scour during high flows.

b) Material Specifications

i) Timber Log

Timber log check dams are normally constructed using 100 mm to 250 mm

average diameter logs and may vary based on locally available material and site

Figure 3.2: Example of a Typical Timber Logs Check Dam

Impermeable Sheet

(e.g. HDPE Sheet) Min 150 mm or as design

Timber struts for

Support

Actual Depth of Logs to be

determined on site

Timber Logs Tied together



requirement. Wire ropes are usually used to tie the logs together to increase its

stiffness and strength. Instead of logs, sawn timber posts and board can also be

used for construction of the check dam as shown in Figure 3.3 below.

To prevent downstream scouring, rip-rap of required size can be placed on the

bed and banks over a length of at least 1.5 times the height of the check dam

as illustrated in Figure 3.4.

ii) Impermeable Layer

A layer of impermeable materials such as HDPE sheet should be attached to the

timber logs barrier to prevent excessive loss of water through the log barrier as

shown in Figure 3.2 above



Figure 3.3 Example of Check Dam Structure Using Wood Board and Posts

Figure 3.4: Example of Timber Check Dam with Rip-rap Protection

Works (Plan view )

Rip-rap

extending to at

leat 1.5 X Height

of Dam

Rip-rap

extending into

Bank

Check Dam

Structure

(timber)

150 mm (min)



3.2.3 Stones/Rocks Check Dam

a) General

Stones or rocks placed on top of a blanket of engineering fabric either in loose form

or stacked tightly can also be used to block the water flows in the waterways to

create check dam structure in peatland. Hand or mechanical placement of stones or

rocks can be used depending on the accessibility of the site. Some general

requirements of stones/rocks check dams are discussed below and are as indicated

in Figure 3.5.

i) Maximum side slopes 1.5H : 1 V

ii) Center portion of the crest of the check dam should at least 150 mm lower than

the sides to prevent normal flows from going around the dam, and eroding the

sides of the channel.

iii) Adequate freeboard to be provided for annual flood flows

iv) Adequate scour protection downstream of check dam is to be provided for a

length at least 1.5 times the height of the check dam

v) Rocks or stones armouring layer of at least 400mm thick should be extended

into the banks of the waterway sides to prevent erosion and breaching of the

sides of the check dam

vi) To reduce the loss of water through foundation seepage, the underlying peat

soil below the check structure should be removed and replaced with highly

impermeable soils.

b) Materials

i) Stones / Rocks Size

All stones/rocks shall be dense, hard, durable broken or crushed granitic rocks.

They should be heavy enough to prevent the flows from pushing individual

stones downstream. For height of dam with flow velocity less than 1 m/s

maximum, the nominal stone diameter should be 100 mm to 350 mm. For flow

velocity higher than 1 m/s, the stones shall be sized in accordance standard

engineering practices.



3.2.4 Gabion Check Dam

a) General

Stacked stones in wire cages (gabions or gabion mattresses) are also commonly

used to construct check dams. Gabions check dams are essentially the same as

stacked stones/rocks check dam structure, except that the former is wrapped in wire

fence meshes for added stability and strength. A typical drawing of a gabion check

dam structure with flow regulating gate is shown in Figure 3.6. Some of the general

requirements for gabion check dam structures are:-

i) The gabions formed check dams are highly porous and as such a layer of

impermeable sheet such as HDPE need to be provided within the gabions to

reduce the seepage of water. Alternatively, highly impervious clayey soil can be

Figure 3.5 Minimum Design Requirements for Stacked Stones Check

Dam.



placed upstream of the gabions (together with a layer of geotextiles filter layer)

to retain the water in the channel

ii) A layer of gabion flexi-mattress is usually placed on the channel bed and banks

before the required gabions are placed. The mattresses would provide a better

sitting on the uneven ground of the channel bank/bed besides providing a more

stable support for the gabions block

iii) A layer of geotextile fabric filter is placed on the soil in contact with the gabions

mattresses to prevent ingress of soil into the gabions and washing away by the

water flows

iv) Proper foundation seepage cut-off needs to be provided to enable effective

control of water level upstream. This could be done by removing the peat soils

and replacing with less permeable soil (clayey) or embedding appropriate cut-off

barriers

v) Opening in the check dam structure may also be provided for passing flood

flows and can be gated (e.g. using timber drop boards) to raise the water level

during the dry weather.

Gabion check dams can provide a very cost-efficient alternative to those constructed

using concrete and are more resilient than concrete. They are also more durable

than sand/earth filled bags, timber logs or loose stacked stones / rocks check dams.

b) Materials

i) Gabions

Each stone-filled gabion usually measures about the standard size of 1.0m x

1.0 m x 1.0 m. Other size of up to 4.0 m x 1.0 m x 1.0 m are also available

The wire box cage or mattresses shall be made from galvanized wire or PVC

coated galvanized wire depending on whether they are to be used for

temporary or long-term installation

The stones in-filled shall be dense, sound and durable stones of size between

100 mm to 200 mm nominal diameter.

The gabion check dam should be designed based on the principle of mass

earth retaining walls against both the hydraulic as well as earth pressures.



Figure 3.6: Check Dam Structure - Type Gabion for Medium-Term Application



3.2.5 Precast Concrete Stacked Blocks Check Dam

a) General

Stacked precast concrete blocks can also be used for the construction of check dam

structures. An example of this type of check dam is as shown in Figure 3.7. Some

requirements for precast concrete block check dams are:-

i) Proper foundation has to be provided to prevent excessive deformation and

bearing capacity failure. If necessary the layer of soft and peat soils should be

replaced.

ii) The stacked precast concrete blocks should be stable and designed as mass

gravity wall that is able to resist both hydraulic and earth pressures.

iii) The dimensions of each individual precast block are to be decided based on

handling as well as stability requirements

iv) The precast blocks should be able to be removed swiftly in case of overtopping

and flooding problems

b) Materials

i) Concrete

The precast blocks can varied in size to suit ease of handling and lifting,

which depend very much on the site conditions and accessibility. Standard

size of 1.0m x 1.0 m x 1.0 m. is normally adequate for flow with velocity less

than 2 m/s. However, when stacked, the check dam must be stable against

foundation bearing failure and excessive deformation.

Grade of concrete used should be C25 or higher and can be reinforced or

unreinforced.

Properly designed lifting hook have to be provided for handling and lifting

Foundation of the check dam need to be properly leveled and if necessary,

any soft ground be removed and replaced or strengthened (e.g. piling or raft

footing) before placement of concrete blocks



3.2.6 Precast Concrete Post-Panel System Check Dam

a) General

For faster and easier construction, precast concrete retaining system comprising of

a series of regular soldier posts interspersed and connected with flat or curve slab

panels can be constructed across the waterway to retain and maintain the water

level upstream. A typical drawing of this system is detailed in Figure 3.8 which has

incorporated a flow regulating and water level control opening with timber

dropboards.

Figure 3.7: Precast Concrete Stacked Blocks Check Dam Structures

( Photo courtesy of JPS Klang)

a) Side View

a) Upstream View



Some of the general features of this type of check dam structure are:-

The regularly spaced precast concrete posts (piles) are embedded to

appropriate depth to serve as the main support for the dam and are inter-

connected with precast concrete slab panels.

Appropriate opening in the check structure with timber dropboards to control

the required water levels can be provided. These dropboards can be removed

to allow high flood flows whenever necessary. The length and elevation of

opening need to design for the necessary annual floods, thus minimizing the

need for frequent operation of the gate.

For stability of the check structure, the posts need to be embedded to the

required depth of penetration. In addition, potential seepage/piping problems

through the foundation also need to be addressed, and if necessary, the

permeable and soft peat layer is to be removed and replaced with more

suitable soil.

For downstream protection against scouring and erosion, proper lining of the

waterway should be provided e.g. using gabion mattresses or armour rocks.

To prevent breaching of the banks, the concrete post-slab panel barrier

should be extended adequately into the existing banks and protected against

possible erosion e.g. by laying armour rocks lining.

b) Materials

Grade A timber boards are to be used for slots

Grade of concrete used should be C40 or higher and minimum concrete

cover to be 30 mm



Figure 3.8: Check Dam Structure - Type Precast RC Post- Panel (with Flow Control) for Long-Term Application



3.2.7 Cast-in-situ Concrete Check Dam Structures

a) General

In waterway where long-term (permanent) check dam structures are required,

cast-in-situ reinforced concrete structures are preferred. Flows regulating gates and

sides spillway are normally provided to control the water level upstream as well as

discharging designed flood flows. An example of these JPSs drainage control check

structures is illustrated in the Figure 3.9

Some features of these drainage control check dam structures are:-

Consist of an inlet box structures with a upstream gated opening and two side

spillways

The length and elevation of the two side spillways are designed for the

necessary flood flows, thus minimizing the need for frequent operation of the

gate. Timber drop board are used to adjust the height of the side spillways

The gate itself can be opened in case of flood flows

The foundation of the structure need to be designed for bearing capacity and

settlement as well as potential seepage/piping problems. If necessary, the

highly permeable and soft peat layer is to be removed and replaced with better

soil or strengthened with bearing piles

These structures are usually located upstream of a bund or road culvert.

Proper access platform from the bund/road to the gate control device is also

provided for ease of operation and maintenance.

The reinforced concrete structure should be designed to the latest code of

practices for structural concrete

b) Materials

Grade A timber board are to be used for spillway slots

Grade of concrete used should be C25 or higher and minimum concrete cover

to be 40 mm

Timber or concrete piles can be used for bearing and/or settlement control

PFA cement is preferred for concreting works for resistance against acid attack



a) Typical Cross-Section

(b) Plan View

Figure 3.9: Example of Check Dam Structure-Type Cast-in-situ Reinforced

Concrete for Long-Term Application



4. GENERAL MAINTENANCE GUIDELINES

Check dam structures need to be properly operated and maintained so that they can

continue to operate and function effectively and efficiently. Some general guidelines

on the types of maintenance works required are as listed below. This list provides

some of the normal maintenance work required and may not be applicable to all the

various types of check dams as it depends on many factors such as the types,

materials used and site conditions and location of the check dam structures.

a) Inspect check dam structures periodically (once a fortnight) as required and after

each run-off producing storm, and throughout the dry season for any damages

where risk of peat land fire is high. Some of the possible damages include :

Damages or deterioration of the main embankment materials e.g. sand-bags

and timber logs

Excessive seepage resulting in weak water level control

Bank erosion or scouring

Undermining of base of structure e.g. due to seepage

Bed degradation and erosion especially immediately downstream of structure

Washouts of check dam materials

Accumulation of sediments and debris

Damages to concrete structure or gates (if provided)

b) Repair, replace or reshape damaged component of check dam immediately /

periodically especially those check dams using temporary materials such as sand

bags and timber logs

c) Remove any excessive sediments accumulation if necessary, as sometimes the

existence of sediments upstream actually helps to improve the impermeability of

the check dam. However, if the accumulated sediments have impaired the

effectively and safety of the structures, then works to clean and removed the

sediments will have to be carried out. Sediment removed shall be disposed of

properly.

d) Regular inspections should be made to insure that the center of the check dam is

lower than the edges

e) Erosion caused by high flows along the bed and around the edges of the dam

should be repaired immediately



f) Clear all debris along canals that impedes the water flow when water has reached

the optimum level. Regular monitoring of water levels especially during the dry

periods in accordance to Standard Operation Procedure. Constant surveillance for

fires in and around the site

g) Remove check dam structure when no longer needed



Appendix A:

Diagrams of Some Typical Check Dam Structures



Figure A2.1: Example of a Sand-Fill Bag Check Dam (Photo courtesy of JPS Johore)

Figure A2.2:Typical Sand-Fill Bag Check Dam Dam

(Photo courtesy of JPS Johore)

Figure A2.3: Example of Timber Log Check Dam (Photo courtesy of JPS MIRI)



Figure A2.4: Example of Timber Board Check Dam (Photo courtesy of JPS MIRI)

Figure A2.5: Example of Timber Board with Sandbags Check Dam (Photo courtesy of Jabatan Perhutanan, Sabah)

Figure A2.6: Example of Loose Stones Check Dam



Figure A2.7: Example Gabion Type Check Dam

Figure A2.9: Precast Concrete Block-Section Check Dam

Figure A2.8: Typical Gabion Type Check Dam



REFERENCES

1. Anderson, I. and Bowen, 2000. Fire Zones and the Threat to the Wetlands of

Sumatra, Indonesia. Report of European Union and Ministry of Forestry Forest Fire

Prevention and Control Project.

2. Appanah, S. Ismail H., Samsudin, M. and Sadali, S. 1999. Flora survey in North

Selangor Peat swamp forest. In sustainable management of Peat swamp Forest in

Malaysia. Forest Department , Kuala Lumpur.

3. BAPPENAS 1999. Final Report on Planning and Drought management in Indonesia

4. Chan, HT. 1989. A forestry action plan for the North Selangor Peat Swamp Forest.

AWB, Kuala Lumpur.

5. David Lee, T.Y. Chee and F. Parish. Smart Partnership in Fire Prevention and Peat

Forest Restoration: A Case Study

6. Parish, F. and Jamil H.(eds.) 2000. Management inventory of North Selangor Peat

Swamp Forest. Danced-Forest Department Kuala Lumpur.

7. Whitmore, TC. 1984 Tropical Rainforests of the Far East. Clarendon Press, Oxford.

8. Zulkifli, Y., Vily, K. and Baharuddin, K. 1999. Hydrological characteristics of the North Selangor Peat Swamp Forest. In Sustainable Management of Peat swamp Forest in

Malaysia. Forest Department, Kuala Lumpur

Documents

Guideline Check Dams Complete Set