construction and refurbishment of earthen irrigation channel banks

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Thus channels are usually designed to avoid erosion at maximum discharge, andprovision made to remove or exclude the sediment at the intakes or periodicallyremove it from the channel system.In earthen channels, sediments generally enter at the intakes, or are eroded from thebed and banks. Large particles eroded from the banks usually settle along thechannel bed, where they tend to prevent bed erosion. Small particles eroded frombanks are carried downstream, since scouring velocities are high enough tomaintain transportation.Fine sands and silts that can be carried in suspension are not normally as much of aproblem as the heavier materials. Coarse sand and gravel should be kept out ofchannels as much as possible by sediment-control works, either at the intake oralong the channel.Where channels flows carry silty water, minimum velocities should be high enough,wherever practicable, to keep the silt moving. The velocities required in particularchannels depends on quantities and qualities of silt transported. Velocities of 0.45to 0.6 metres per second are usually high enough to keep small quantities of finesand and silt in motion. Velocities of 0.8 metres per second or more are required toinhibit growth of aquatic plants. In areas where these velocities cannot be achieved,the minimum channel velocity should be kept above 0.3 metres per second whenever possible.Where the silt content of water is significant and velocities high enough to preventserious silting can not be maintained, silt-control works at the intakes would berequired. The design of such works is outside the scope of this Manual.12.12 Channel ControlThe two basic systems of channel control are defined by the location of the controlledwater surface relative to the control structure:• upstream – supply orientated operation• downstream – demand orientated operationUpstream Control refers to a system where the water level being controlled or maintainedconstant, is immediately upstream of the regulating point. Most manually controlled dropboard systems in Australia have been designed on this basis. Drop bars are removed orreplaced, or gates opened or closed to maintain a steady level upstream of a regulatingpoint.The opposite mode of operation, defined as Downstream Control, is where the control isoperated so the level on the downstream side of the regulating structure remains constant.Because it reacts to changes downstream, it is user-oriented. This control mode whichwas introduced to Australia in the 1970’s, can operate automatically since demand signalscan be passed up the system. If individual outlets turn on, the change in that pool levelcauses a change in the regulator to change the flow to re-establish the prior setpoint. Achange in any pool will cause a sequence of proper compensating actions to be made inthe upstream structures, all the way back to the source. A secondary benefit is theincreased distribution efficiency since the system is essentially closed at the downstreamend. Downstream control systems are always automated; upstream control systems maybe manual or automatic.Construction and Refurbishment of Earthen Channel Banks August 2002 - Edition 1.0 12-20
Figure 12-4 illustrates the principals of each control system with relevant features markedshowing the essential differences. The most important characteristic is the operationalstorage wedge, defined as the difference between the volume in a channel reach at zeroflow and that at full flow. For upstream controlled systems the wedge characteristic isnegative and represents a limit on the speed of propagation of changes through thesystem. That is, the operational storage must be made up before the flow in any reach canbe increased. Flows are therefore normally adjusted in a downstream direction.ControlStructureBank ElevationOperational StorageDesign Flow LevelQ=maxBank ElevationOperational StoragePool ElevationQ=0ControlStructurePool ElevationQ=0BedDesign Flow LevelQ=maxBedUpstream ControlDownstream ControlFigure 12-4Upstream and Downstream ControlFor downstream controlled systems, this wedge characteristic is positive and representsthe limitation to automatic operation. If the response time of the regulations is shortenough so that flow changes can be met from the operational storage volume, the systemcan theoretically operate automatically. That is, changes in demand will be fed back upthe system progressively back to the source of supply. System responds to demandchanges rather than supply changes.This gives rise to the flat top channels in downstream controlled systems, compared to thesloping top channels in upstream controlled systems. In downstream control the channelbanks and structures have the same elevation over the entire channel pool.The decision-making criteria for upstream control mode versus downstream control modecan be complex, involving a range of technical and economic parameters. The differentcontrol methods cannot be mixed within a channel system unless a buffer storageseparates the different segments. These issues are outside the scope of this manual andreaders should consult other technical references on the subject.Construction and Refurbishment of Earthen Channel Banks August 2002 - Edition 1.0 12-21
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Your comments on the format and con
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During the course of this project,
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AcknowledgmentsThese Guidelines rep
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FundingFunding of this project was
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Table of ContentsBook 1SubjectPage
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1. Introduction1.1 GeneralGood asse
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(iv) provide proven practice approa
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3. Research Procedure3.1 Terms of R
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4. How to use these Guidelines4.1 W
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6. Units of MeasurementQuantity Uni
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8. Earthen Irrigation Channels8.1 D
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8.3 ReferencesAustralian National C
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9.1 IntroductionA key input to adva
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Data from Goulburn-Murray Water’s
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General 1 2 3 4 5 6DescriptionRisk
Page 33 and 34: Channel BankSequential Deterioratio
Page 35 and 36: 9.2 ReferencesGutteridge Haskins &
Page 37 and 38: 10.2.3.1 Dispersive layer of materi
Page 39 and 40: Causes ofSpecific factorDeteriorati
Page 41 and 42: 10.1.2.5 BendsA bend in the channel
Page 43 and 44: 10.1.4.1 Construction techniqueIrri
Page 45 and 46: 10.1.5.4 Overtopping of banksIn ade
Page 47 and 48: In the past maintenance techniques
Page 49 and 50: Maintenance is a continuing require
Page 51 and 52: 10.1.7.4 Yabbies/fresh water crayfi
Page 54 and 55: Direct removal ofmaterial by entrai
Page 56 and 57: Figure 10.10 shows longitudinal cra
Page 58 and 59: 10.2.3.3 Irregular compaction - bri
Page 60 and 61: 10.3 ReferencesEmerson W (1996), pe
Page 62 and 63: 11.1 GeneralThe Investigation and P
Page 64 and 65: iv) Available fill materials and, w
Page 66 and 67: 12.15 Radius of Bends .............
Page 68 and 69: There are several ways a channel ca
Page 70 and 71: • Land acquisition extent and typ
Page 72 and 73: The investigation should generally
Page 74 and 75: • Backfill: 10% compaction factor
Page 76 and 77: 1. Flow Area, A, is the cross-secti
Page 78 and 79: after ageing and weed growth. If an
Page 80 and 81: elationships may be the controlling
Page 82 and 83: These maximum velocities should be
Page 86 and 87: Some of the design issues that shou
Page 88 and 89: 12.12.1.3 Best PracticeEither of th
Page 90 and 91: 12.13.2 Channel MaintenanceIncrease
Page 92 and 93: along a channel. The depth of the w
Page 94 and 95: 12.13.4.7 Change of AlignmentThe in
Page 96 and 97: 12.15 Radius of Bends12.15.1 Flow A
Page 98 and 99: 12.16 Channel Cross SectionThe cros
Page 100 and 101: Some irrigation authorities use one
Page 102 and 103: 12.16.2 BanksChannel cross sections
Page 104 and 105: Unless the bank is very high, the s
Page 106 and 107: The stability of channel batters ca
Page 108 and 109: drop bars become difficult and time
Page 110 and 111: Both the height above the bed and t
Page 112 and 113: • enable maintenance of the chann
Page 114 and 115: - Access agreementsA description of
Page 116 and 117: 13/08/02 19:2012.20 Channel Tenure
Page 118 and 119: 13/08/02 19:20As with the damage to
Page 120 and 121: 13/08/02 19:20Advantages of Protect
Page 122 and 123: - gates provide a better deterrent
Page 124 and 125: 13/08/02 19:20When considering expo
Page 126 and 127: 13/08/02 19:20A typical design draw
Page 128 and 129: 13/08/02 19:20Sinclair Knight Merz
Page 130 and 131: 13.1 IntroductionIn many irrigation
Page 132 and 133: For example, the initial constructi
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13.2.6 When to use Life Cycle Analy
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The timing of the life-cycle costin
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• assess cost of collecting missi
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Microsoft Excel has quite a good pr
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The costs used in these methods sho
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Life CyclePhaseInvestigationDesignC
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Life CyclePhaseMaintenanceRehabilit
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ReplacementProject managementInvest
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Residual valueLegal feesInsuranceAd
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13.4.6.2 Recurring CostsChannel con
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$1.00.80Percent ofValue of$1.00.60.
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13.4.11 Evaluate ResultsThe results
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13.6 Tipsthe way open to incur sign
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14. Risk AnalysisTable of ContentsS
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Consequences for irrigation authori
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15. Material Selection and TestingT
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c) Shrinkage - will the bank crack
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depth. For this reason, the soils o
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Natural moisture content should als
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The study identified some confusion
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15.4.2 Determination of the plastic
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1. Preparation of PatTake approxima
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EmersonClass No.Degree ofDispersion
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15.7.1 Coarse grained soilsIn this
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sufficient gravel for erosion resis
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GroupSymbolsSuitability for Earthen
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The uniform application and thoroug
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essential that the chemical is thor
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Where laboratory testing facilities
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Clays are the plastic fines. They c
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etween the soil sample and the wate
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16. Compaction ControlTable of Cont
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16.1 PurposeDuring this research pr
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All compaction equipment utilises s
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The soil density required for a cha
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In the past, a method specification
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Low permeability and high stability
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16.10.1.1 Tamping Foot RollerTampin
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16.10.1.5 Non-Circular Impact Rolle
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16.10.3 Compactor OperationsAfter t
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16.11.4 Moisture Content ControlBef
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16.12 Density Control Tests and Pro
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Correlation with local materials an
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The main advantages of the Nuclear
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Figure 16.4Hilf Density Ratio Repor
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The location and test results for e
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16.14.3 Reporting and RecordsTest r
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16.16 Tests for small projectsThe s
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The advantages of the Drop Test are
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AS1289.6.3.2-1997AS1289.6.3.3-1997A
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17. Protective CoverTable of Conten
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The bank dries and cracks from the
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17.5 Specifications17.5.1 GravelPar
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17.6 Establish Vegetation CoverTops
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Species Growing Conditions Establis
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17.7.2 Rope Wick ApplicationMuch of
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There are a number of fibre mats or
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17.10 Australian StandardsAS1289.3.
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18.1 IntroductionFor many earthen c
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When re-shaping the batters of exis
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LifeCrestOld bank lineBattered bank
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Photos\inside batter\CG7channel2arm
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4. To help place the rock material
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False ToeFigure 18.8Protective laye
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The confinement system would be adv
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• Able to survive during non-oper
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18.6 ReferencesHutchison D & Locke
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19.20 Guidelines on Field Quality C
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Construction and Refurbishment of E
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• Figure 19.2)3. Temporary Bench
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The capabilities and limitations of
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19.3.1 Construction EquipmentThe ba
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construction. The aim of scarifying
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Whether or not a front-end loader o
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The thickness of each layer will va
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distribution. The use of alternativ
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19.8 Construction RecordsAdequate r
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19.12 Protective Cover on Crest and
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19.21 Australian StandardsAS 1726-1
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20.1 ScopeAustralia’s earthen irr
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Bank re-construction normally requi
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•meter outlet locations and type
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In the case of channel bank refurbi
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20.4.1.1 StrippingWith outside bank
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All public roads to be used by truc
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5. Material is delivered by trucks
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Need to drain and de-waterEBM befor
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significantly and a more conservati
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Aim for crest width ofabout 2 metre
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Refer to Section 18, Inside Batter
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21.8.10 Re-alignment ..............
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Seepage is a complex hydrologic phe
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2. Seepage losses increase as the d
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Refer also to the following section
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21.4 Channel Seepage ConsequencesSe
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Channel seepage is one of the sever
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Seepage is proportional to soil per
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Methods based on vertical flow meas
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ainfallPumpingevapotranspirationIrr
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Flow NetsA flow net is a system of
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Data from indirect measurement proc
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(ii) EM SurveyElectro-magnetic (EM)
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The volume of waterloss from the dr
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21.7.3.2 Inflow-Outflow Method (Dyn
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Imperfect seal will cause the meter
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The groundwater level can then be d
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Stable IsotopesThe basis of testing
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To be most successful, there needs
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21.8.6 Surface interception drainag
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KeyWatertable before tree plantingW
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• The preparation of a best pract
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21.11 ReferencesAustralian National
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22. Channel LiningTable of Contents
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22.1 IntroductionThe conservation o
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The different types of channel lini
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Table 22-1Unlined Earthen Channels
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Lining of channels will not elimina
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To supply a given discharge, the cr
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22.4.5 Structural SafetyThe stabili
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soil pressures and under-drainage i
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Concrete linings are suitable for b
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22.5.12 Availability of Constructio
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esistance to erosion. To improve th
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Construction and Refurbishment of E
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22.7.1.2 General Design Considerati
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22.7.1.4 Lining ThicknessThe thickn
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particular problems, but in smaller
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Where the earth lining finishes abo
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control where the channel material
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sand requires about 5% cement by we
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22.7.6 Soil SealantsSoil sealants a
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22.7.7 Cost of Earth LiningsThe cap
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Although they can assist with shear
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22.8.2 Membrane Liner TypesGeomembr
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Polyethylene has also appeared in m
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FPP resistance to common chemical e
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The base coat and seal coat rates m
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A common and misleading argument is
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These thermal expansion and contrac
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Another factor is the ability to ha
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Some lining methods expand and cont
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22.8.9.1 Geomembrane ThicknessThe t
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Cover typeThickness ofEarth fill(m)
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22.8.9.5 Cover MaterialGeomembranes
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As well, velocities which are permi
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22.8.11 FencingWhen livestock, part
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22.10 ReferencesAlther GR (1987), T
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23. Measures to Reduce the Rate ofD
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Channel DesignBank MaterialDeterior
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Stock and VerminAdjacentlandholders
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To ensure that a channel bank has a
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Advantages of Draining• Allows fo
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To efficiently maintain a channel,
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Compared with other countries where
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23.4.7 LeaksTransverse cracks are t
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23.5 Reduction of Deterioration due
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Photo 23-1Channel bed showing mumbl
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Thus, control of carp by draining c
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The disadvantages of a biological c
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Carp have been blamed for erosion o
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Management Groups gives guidelines
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Organisation Contact Details Aims/A
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Chemical treatment is often recomme
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23.7 Reduction of Deterioration due
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Grey Parrot Pea - Dillaynia cineres
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Lodge G (1998), Review on Fish Barr
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cation exchange capacity (CEC) a me
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fetch the distance over which the w
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plant term used for construction eq
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supply level the supply level is a
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