Design of canal cross section in alluvial soils

 

 

(A)      Branch Canals

1.          General

 

1.1             Design of irrigation channels involve the condition of steady and uniform flow which inter-alia means that flow characteristics at any given point as well as at any given time remain same.

 

1.2             Alluvial tracks are one of the most common among the different types of terrain through which the canal may pass. This is particularly so in case of Utter Pradesh. Regime flow conditions govern the design needs of canal cross section in alluvial soils. The flow of water in an open channel is generally defined by Chezy’s equation

 

V = mean velocity of flow in m/sec

C= a coefficient, its value depends upon the shape and surface of the channel

R = Hydraulic mean depth in m

S = Slope of channel

 

1.3             With a view to arrive at stable channel dimensions attempts have been made from time to time by various authors in the field of open channel flow to define the value of C in the above equation. The most widely accepted values are those suggested by Kutter and Manning as given herein below:

 

1.                 Kutter’s Equation

 

 

2.                Manning’s  Equation

 

 

1.4             In the above equations ‘n’ is the roughness coefficient and is identical for both the equations within practical ranges. This is generally referred to as rugosity coefficient and varies according to the physical roughness of sides and bed of the channel apart from other factors viz (i) channel curvature (ii) changes in size and shape of cross section, (iii) obstructions and vegetation etc.

 

1.5             R.G. Kennedy established a relation between non scouring, non silting velocity, termed as “critical velocity” of flow and the stage of flow on the basis of experimental work done by him on the upper BARI-DOAB canal system in Punjab. For any given channel having a particular soil condition, the critical velocity ratio which is a function of silt charge and grade and rugosity coefficient is uniquely fixed. Kutter’s equation was used for the calculation of mean velocity in the channel. Though the use of Kutter’s equation by Kennedy in theory of channel design made the design procedure tedious and complicated, Garret had given graphical solutions in the form of charts for relatively easy design procedures. The design procedures still involved trial and error.

 

The reasons behind selection of Kutter equation for determination of mean velocity instead of Manning’s equation is not available, however, hydraulic engineers have now started preferring Manning’s equation in determining the mean velocity of flow. Manning’s roughness coefficient and Kutter’s rugosity coefficient are generally identical within practical ranges, the Manning’s roughness coefficient is better known, therefore, the use of Manning’s equation which is much simpler in application is suggested for determing the mean velocity flow in a channel.

 

Kennedy had suggested a general form of equation for critical velocity              V0=CmDn. The value of m depends upon the silt charge and silt grade. The coefficient C and the power index n are not constant and change from site to site. The most prevalent values of C and n as worked out by Kennedy are 0.546 and 0.64 respectively. The popular form of Kennedy’s equation for regime channel designs is

 

V0 = 0.546 m D0.64

 

For design of stable channel in alluvial soils graphical solutions by developing hydraulic diagram using Kennedy theory with Manning’s equation is suggested for general application. Taking a trapezoidal section, the area, wetted perimeter and hydraulic mean depth can be described in terms of bed width and depth of flow. The mean velocity of flow can be written in terms of rugosity coefficient n, bed width, depth and slope parameter. Equating the velocity obtained from Manning’s equation to the critical velocity as per Kennedy theory a chart can be developed between  and depth of flow for various values of B/D and Q/m. These hydraulic charts can be used for design of channels.

 

 

1.6             Bureau of Indian Standards have recommended criteria for design of cross section for unlined canals in alluvial soils vide IS 7112:2002. IS 5968:1987 (reaffirmed 1998) and IS 4701:1982 (reaffirmed 1995) provide the guidelines for planning and layout of canal systems for irrigation and code of practice for earthwork in canals respectively are other relevant references to the criteria for design for deciding the hydraulic parameters and construction guidelines.

 

1.7             IS 7112:2002 which details the criteria for design of cross section of unlined canals in alluvial soils provides details about the data required, design including side slopes, free board, bank width, radii of curvature, berms, dowels, bed width, depth and slopes, falls, hydraulic gradient lines, catch water drainage etc. Whereas majority of the above design features are suggested to be decided on location specific conditions and standard approaches, the bed width, depth and slope features are required to be analytically designed for various reaches to carry the required discharge according to the best prevalent practices as per details given herein below:

 

1.8             A number of methods for design of unlined canals in alluvium are prevalent in the country but all of them have some limitations. The use of such a method which gives good results under similar conditions is the best solution.

 

I.                   For design of alluvial channels, Lacey’s regime equations have been in use for nearly four decades. The method of design according to Lacey’s equation is given in Annexure A of IS 7112:2002.

 

II.                Though the Lacey’s equations have been in common use in the country, it has been long realized that these equations are not perfect and suffer from certain limitations. The major difficulty experienced in the use of Lacey’s equations is about its applicability for the design as it is for incoherent alluvium of infinite extent and the appropriate value of silt factor. Moreover, the divergence from dimensions given by Lacey’s equation in existing stable canals has been found significant in many cases. In view of the necessity for evolving formulae more accurate than Lacey’s but without sacrificing the simplicity of regime equations, regime type-fitted equations were evolved which are given in Annexure B of IS 7112:2002. Within the range of data tested, these equations are anticipated to give channel dimensions which would be nearer to regime conditions. The regime type-fitted equations recommended for application are not considered the last work on the subject. It should be fully realized that further modifications in the equations are possible and necessary as and when more field observations of stable sites on the canal systems become available. Till then, the use of these equations is recommended since they are expected to yield more accurate results than Lacey’s and other regime formulae.

 

Lacey modified his equations so as to include sediment concentration  (X in parts per million) and size and density of the sediment as definded by its fall velocity (Vs in m/s) as additional parameters affecting the regime dimensions of a stable channel. These are given in Annexure C of IS 7112:2002.

 

III.             Another method of design is by tractive force approach which is given in Annexure D of IS 7112:2002.

 

1.9             Criteria for Design of Hydraulic Profile

 

The Haidergarh and Jaunpur branch canals are existing channel, to be redesigned under the UPWSRP rehabilitation initiative.

 

The details of the existing design cross sectional parameters and bed slope of the two branches in their different reaches are given in the tables below:

 

Haidergarh Branch:

 

Sl.No

Chainage

from-to km.

Discharge cumec

Bed width metre

Water depth metre

Slope

cm/ km

1.

0.0 to 4.0

165.5

55.5

3.0

9.1

2.

4.0 to 7.4

165.5

51.8

3.0

10.6

3.

7.4 to 15.4

163.2

50.9

3.0

10.6

4.

15.4 to 16.4

163.2

50.0

3.0

10.6

5.

16.4 to 22.98

159.7

50.0

3.0

10.6

 

Jaunpur Branch:

 

Sl.No

Chainage from-to km.

Discharge cumec

Bed width metre

Water depth metre

Slope

cm/ km.

1.

0-16.32

123.204

28.87

3.485

12.2

2.

16.32-22.52

121.195

28.565

3.485

12.2

3.

22.52-27.42

99.648

28.346

3.180

12.2

4.

27.42-35.00

97.742

28.041

3.180

12.2

5.

35.00-41.60

94.07

27.431

3.140

12.2

6.

41.60-44.18

92.762

27.431

3.109

12.2

7.

44.18-58.40

77.819

23.774

3.048

12.2

8.

58.40-66.80

69.064

21.64

2.987

12.2

9.

66.80-76.25

59.207

21.335

2.743

12.2

10.

76.25-100.00

52.612

20.726

2.59

12.2

11.

100.00-110.00

47.236

19.202

2.59

12.2

12.

110.00-116.20

32.991

16.459

2.256

12.2

13.

116.20-119.45

28.688

14.630

2.256

12.2

 

The hydraulic design methods for the redesign of Haidergarh branch are describe herein below.

 

(i)                Both the Haidergarh and Jaunpur branches were highly silted. This is due to (i) heavy silt load entering the branch at its head and (ii) relatively flat bed slope of the branch canal. As per the profile of the existing canal cross section, determined on the basis of survey’s provided by PACT. The accumulated silt volumes in Haidergarh and Jaunpur branches were about 0.94 million cubic metre and 2.0 million cubic metre respectively. The Haidergarh branch is not drawing its authorized (designed) head discharge and accordingly the Jaunpur branch and the distribution system have reduced conveyance efficiencies.

 

(ii)             The branch canals and distribution network are unlined channels constructed in alluvial soils. Bureau of Indian Standard vide code no -IS 7112:2002 “Criteria For Design Of Cross Section For Unlined Channels In Alluvial Soil.” out lines four different approaches for design of canal sections in alluvial soils. An attempt has been made to design the Haidergarh branch based on these approaches.

 

The design sheets giving the hydraulic parameters by use of the four methods suggested in IS 7112:2002 are given in Annexure 1, 2, 3 and 4 of the IS 7112:2002. Due to the constraints of existing bed slope of the system, the results as obtained for the design of Haidergarh branch do not match the existing parameters in any of the methods.

 

(iii)          A review of the designed longitudinal and cross section of the branches indicates that the canal parameters seems to have been designed using Garret Diagram. From a study of channel design as given in Annexure 1 to 5, it is apparent that the exiting section of Haidergarh branch canals is very much close to that determined by using Manning’s equation. Therefore the design of channel have been done by use of Manning’s equation for velocity calculations assigning a value of 0.02 for rugosity coefficient. The longitudinal bed slope has been adopted as per the maximum available country slope along the canal alignment, which is 9.1 cm/km between km 0.0 to km 4.0 of the Haidergarh Branch.

 

As discussed in Para (iii) above, the existing design parameters were determined using Garret diagrams and the existing bed slope of the channel as guided by the general ground feature. Redesign of the canal cross section using Manning’s equation with a value of n=0.02 is given in Annexure 5.

 

(iv)           An attempt was also made to assess the value of ‘n’ from analysis of proto type canal running data for observations on 11.7.03, 16.8.04, 21.9.04 and 3.1.05. In practice because of the changed regime of the canal due to large silting, the values do not replicate the original ground conditions and was therefore not considered a rational value for adoption in the redesign. The revised sectional profile based on the Manning’s equation and using the existing bed width and slope parameters gives a water depth of 3.06m instead of 3.0m for passing the design discharge of 165.5 cumec.

1.10         The canal parameters as determine by use of the various methods described in para 1.9(ii) are at large variance with the existing canal parameters. Notwithstanding the fact that a regime channel as determined by the above methods is a possibility within the limitations of general country slope, the existence of the branch canals and their vast distribution networsk with numerous control and other structures will not permit such an intervention. The redesign of the branch canals therefore has been done keeping in view this fact in mind and Manning’s equation has been used for velocity parameter. For mitigation of silt problem in the branch canal a silt trap arrangement has been proposed to limit the entry of silt in the branch canal and thereby ensuring its conveyance capacity.

 

(B)      DISTRIBUTARY AND MINOR CANALS

2.          GENERAL INFORMATION

 

2.1             Haidergarh branch off-takes from left bank of the Sarda Sahayak Feeder Channel at its km 171.5. The head discharge capacity of this branch canal is 165.5 cumec. The reach between head to km 23.0 of the Haidergarh branch and the distributary and minor canal systems in this reach along with the entire Jaunpur branch, which is a sub system of Haidergarh branch, with its distributary and minor canal networks from head to km 119.54 is the defined project area. The Haidergarh and Jaunpur branches, Dy and minor networks were mostly constructed / remodelled in phases between year 1970 to 1980. The head discharge capacity of Jaunpur branch is 123.2 cumec. The culturable command of the Haidergarh branch in its reach from head to km 23.00 is 17,567 ha and that of the Jaunpur branch system is about 2,75,000 ha. The proposed intensity of irrigation as per Sarda Sahayak Project stipulations for the above mentioned canal systems is 115% (Kharif 67%, Rabi 48%).

 

2.2             The Haidergarh branch canal in its reach from km 0.0 to 23.0 has 3 distributaries and 8 directly off-taking minors. Similarly, Jaunpur branch canal has 13 distributaries and 52 directly off-taking minor canals. The distributary canals serve their respective commend area through sub distributaries and minor canals. The direct off-take minors serve their respective command area. The distributary canals also serve a part of their command area through direct outlets.

 

2.3             Due to constraints in delivery of design discharge in the feeder channel and consequently non availability of design discharge in the branch canal, the distributary and minor systems do not receive their authorized discharge. The branch canal full supply levels are below the design levels and this causes problem in feeding the distribution network. In-fact the entire system is performing sub-optimally, resulting in problems not only in water management but also in providing services, which situation is reflected in comparatively low irrigated areas as compared to design stipulations.

 

2.4             In reaches of comparative high ground level, along the distributary or minor canal, the design water surface elevation is not likely to command such areas. No doubt the cultivators are expected to make their arrangement for lifting the water at such locations, the general practice however, is to artificially jack-up the water surface elevation by putting obstructions in the canal. This adversely affects the canal operation.

 

2.5             Transfer of operation, maintenance and management of minor canal systems to duly constituted WUAs’ is one of the stepping stones towards the modernized irrigation management systems. In this perspective the supplies at the head of the minor canal shall be measured and delivered to the WUAs’ according to a pre-determined and accepted schedule. The WUAs’ in turn will manage the distribution in the respective command of the outlets. This operation system will enable introduction of volumetric measurement and billing for water by the department and will replace the presently in vogue system of measurement on irrigated area basis.

 

2.6             The present design practices adopted by the department do not generally incorporate the views / suggestions of the water user, farmers or other stakeholders. In view of the proposed management transfer to WUAs’, the process of design / redesign has been based on community participation and discussions / deliberations with the WUAs.

 

3.          DESIGN CRITERIA

 

3.1             Equity of Allocation

 

Promotion of “equity and social justice” among individuals and groups of users in water resource allocation and management is one of the main features of the objectives of “State Water Policy”. The contract assignment also stipulates reliable and equitable distribution of water in the farmland as a basis for the program of rehabilitation and modernization of the system, which will establish prerequisite conditions for farmer’s participation through the WUAs’, in the entire process of various project elements of planning implementation, operation, maintenance and management, to ensure success of the program.

 

The project area command is presently served by the surface irrigation systems associated with Haidergarh and Jaunpur branches and their vast distribution network. Any exploitation / use of ground water is only in private domain with some subsidies provided by the State. The “State Water Policy” having recognized the unitary nature of both the surface and ground water resources, their exploitation and use to the extent of availability has to be in an equitable manner. This will ultimately realize the objective of the rehabilitation initiative under the UPWSRP.

 

In view of the present perennial rights of the users on the surface waters and very minimal exploitation of the ground water resource, due t6o the present socio economic condition of the farmers, the approach is to, in the first phase; equitably distribute the surface waters in the command. Use of ground water in head reaches where the ground water tables are generally high shall provide opportunity for higher allocation of surface water to the lower reaches. With the large scale rehabilitation and modernization of the systems under the UPWSRP it is expected that ground water exploitation will increase many fold and the equitable distribution of both surface and ground water as one resource will be possible. The canal capacity factor have been optimized for equity, based on the net available water after deducting the losses and the CCA. As the gross availability of water is limited to the present design capacities, the changes in the agriculture by way of cropping intensity have been suggested by use of ground water. As a precaution for likely higher deliveries in the tail reaches when ground water is exploited, sufficient free board has been provided in the canal systems.

 

A review of the existing hydraulic design features of the distributary and minor canals has revealed that the allocation of discharges to the canal systems is highly variable in relation to the command area served by them. The redesign approach for rehabilitation and modernization of the distributary and minor systems, in view of the above is to ensure equity of the available supplies in proportion to the CCA served for each system.

 

The CCA of the Jaunpur branch sub basin has been assessed to be about 2,72,000 ha. The branch canal head discharge is 123.2 cumec. Based on various empirical formulas, being used for assessment of conveyance loss in earthen channel, the total conveyance loss in Jaunpur branch sub basin is estimated to be of the order of 33% (branch canal 8%, distributaries 10% and minors 15%). The water rights per unit area for the Jaunpur sub branch basin command area works out to as follows;

 

1. Head discharge capacity – 123.2 Cumec

2. Conveyance losses 33% of (1) above – 40.565 Cumec

3. Water available for irrigation at outlet head – 82.635 Cumec

4. Total CCA – 2,71,853 ha

5. Available equitable discharge per unit area – 0.3 l/sec/ha

 

The corresponding equity at minor and distributary head works out to 0.37 l/sec/ha and 0.42 l/sec/ha after accounting for losses at the head of the distributary and minor canals.

 

The proposal for equitable and uniform allocation of the available water resource in proportion to the CCA served was presented  in the Review Committee meeting on the Draft Second Interim Report for Package ‘B’ Canal systems and was approved.

 

The allocation of discharge to the distributary head and minor head for the purpose of designing, the hydraulic profile of the canal systems has been worked out according to the proposed criterion of equity and reassessment of the CCA from the GIS data provided by PACT. This will meet of objective of the State Water Policy as well as the public participation in redesign process through the Water User’s Association.

 

3.2             Canal Design

 

The following IS codes shall be referred for planning and layout and hydraulic    profile design of the distributary and minor canal systems.

 

IS 5968 : 1987 (reaffirmed 1998) - Guide for Planning and Layout of Canal System for Irrigation.

IS 7112:2002 – Criteria for Design of Cross Section for Unlined Canal in Alluvial Soils.

IS 4701 : 1982 (reaffirmed 1995) – Code of Practice for Earthwork on Canals

IS 4839 (Part 1) : 1992 (reaffirmed 1998) – Maintenance of Canals Code of Practices – Silt Disposal

 

3.3             The distributary and minor canal systems in the present case are an existing system. The redesign and rehabilitation proposals while following the above design standards and any other relevant standard that may be necessary, have to take into consideration, the limits of possibilities of hydraulic and structural changes. This is all the more essential because of the constraints on the presently allocated flow quantities in the system, which cannot be altered much. The design process shall be oriented in such a manner that an economical and efficient system is put in place both in respect of water deliveries as well as management processes. The redesign process would broadly comprise the following :

 

(i)                 Determination of hydraulic parameters.

 

(ii)              Defining longitudinal and cross sectional profiles.

 

(iii)            Arrangement for control of water surface elevation over a wide ranges of discharges in distributary and minor canal system to enable proper system control and operation.

 

(iv)            Design of new canal head regulator, cross regulator, bridges, deck slab, tail wall and other structures.

 

(v)               Possibilities of clubbing of direct outlets on distributary canals.

 

(vi)            Outlet system to ensure reliable and timely deliveries and their operation by farmers – semi module outlets.

 

(vii)          Orifice modules near minor heads for regulation and measurement of discharge.

 

(viii)       Redefined location of outlets, delineation of their command and fixing layout of field channels for proper water distribution with a view to ensure equity of supplies.

 

3.4             Design Option

 

The data on distributary and minor canal systems i.e. long section of canals, received from the field divisions show that the existing canal systems have been designed using Manning’s equation for velocity parameters-

 

           

 

where V =  Velocity of flow,

            n  =  Rugosity coefficient

            R =  Hydraulic mean depth

            S = Canal bed slope.

 

The canal bed width and water depth are thereafter worked out from the design discharge values. The value of rugosity coefficient ‘n’ has been adopted as 0.0225, which normally fits well for the system. The regime type fitted equations have been generally recommended as a suitable option for channel designs within the range of data tested            [IS 7112:2002]. The limitation of canal bed slope, however, is a major constraint in use of this method. Other methods recommended for canal design also suffer from limitations of assigning suitable values to the variables.

 

 

 

4.          DESIGN PROCEDURE AND CANAL DIMENSIONAL PARA-METERS FOR DISTRIBUTARIES

 

4.1             Canal section 

 

The canal section shall be trapezoidal, having the following internal side slopes-

 

·               Canals in cutting    -       1:1

·               Canals in filling      -       1.5:1

 

4.2             Free board

 

Free board above the water surface up to the top of the bank (ignoring daula height) shall be provided as follows –

 

·               0.3m    Up to 1 m3/s

·               0.5m    1 to 10 m3/s

·               0.75m    10 to 30 m3/s

 

4.3             Bank width

 

The minimum top width of bank shall be adopted according to the parameters given in Table-1:

 

Table-1 : Canal Discharge and Bank Width Parameters

 

Sl. No.

Discharge (m3/s)

Minimum Bank Top Width

 

 

Inspection Bank

Non- Inspection Bank

1

2

3

4

(i)

< 0.30

1.5

1.5

(ii)

0.3 to 1.0

3.0

1.5

(iii)

1 to 7.5

5.0

2.0

(iv)

7.5 to 10.0

5.0

2.5

(v)

10.0 to 15.0

6.0

2.5

(vi)

15.0 to 30.0

6.00

3.5

 

The canal cross sectional profile shall, however, be accommodated within the available land width.

 

4.4             Hydraulic gradient

 

For embankments less than 5 m height, which is generally the case in distributary canals the hydraulic gradient shall be kept with in the following range.

 

 

·               For silty soils          4:1

·               For silty sand                   5:1

·               For sandy soils        6:1

 

A hydraulic gradient of 5:1 is proposed to be adopted for design of distributary and minor canals. In case the embankment height is more than 5 m at any specific location, its stability shall be checked by appropriate design procedures. The embankment height in specific cases of the present canal systems are all less than 5.0 m. Stability analysis is therefore not recommended. The hydraulic gradient line shall, in all cases, be provided with a minimum cover of 0.3 m. Appropriate counter berm shall be provided as found necessary.  

 

4.5              Radii of curvature

 

The radii of curvature for canals in its curved reaches shall usually be 3 to 7 times of water surface width subject to the minimum values given in Table-2.

 

Table-2 : Canal Discharge and Radii of Curvature Parameters

 

Discharge [m3 / s]

Radius, Min. [m]

(1)

(2)

80 and above

1,500

Less than 80 to 30

1000

Less than 30 to 15

600

Less than 15 to 3

300

Less than 3 to 0.3

150

Less than 0.3

90

 

4.6             Berms

 

Berms along earthen canal are usually provided to reduce bank loads which may cause sloughing of earth into the canal section and to lower the elevation of the service road for easier maintenance. Berms have to be provided in all cuttings when the depth of cutting is more than 3m. Berms width varying between 2D to 3D (D = water depth) have been recommended in IS 7112:2002 for different situations of canal bank formation i.e. completely in cutting, infilling or in partial filling and cutting. The depth of cutting in distributaries and minors under consideration is less than 3m. It is proposed to provide a berm width of only 0.5 D at FSL with minimum width of 0.2m.

 

4.7             Daula

 

A 0.5 m high Daula above the bank level shall be provided on the service bank. The top width of the Daula shall be 0.5 m and the side slopes shall be 1.5:1.

 

4.8             Catch Water Drainage

 

An affective system of catch water drainage shall be provided to prevent damage of the bank. For this purpose suitably designed chutes shall be provided at locations where the canal is in complete or partial filling.

 

5.                DESIGN PROCEDURE & CANAL DIMENSIONS FOR MINOR   CANAL

 

5.1             Canal Section

 

In the existing minor canal systems, water to the minor service area is distributed through a network of outlets serving individual chak area through water course and turnouts. The minor canal head discharge as well as the location of outlet and their ventage shall generally be adopted from the relevant details made available by UPID/ PACT for designs. The location of outlet and layout of field channel have been finalized in consultation with Stakeholders and Culaba Samiti members. In view of the fact that any appreciable change in the system deliveries is not practicable except in some isolated cases, the deliveries to outlets are not proposed to be converted into delta and duty functions but it shall be provided as an instrument to ensure method of equitable supplies to the system and the agriculture practices shall have to match these deliveries. Large variation in water drawl in different reaches of the minor canal system, have generally resulted in failure of equity of distribution. However, now that WUAs’ are in position and they shall manage the distribution of water among the users; equity of distribution to the extent of available surface waters can be ensured. As the gross availability falls short of the demand (intensity of irrigation in each crop season being less than 100%) any supplemental requirements of water for increasing intensity of agriculture shall have to be conjuncted from ground water systems. The present design section for minor canals shall be trapezoidal and  shall be limited to the following :

 

(i)            assigning the head discharge,

(ii)         assessment of losses,

(iii)       rehabilitation of intake, profile designs,

(iv)       provision of gate and arrangements of flow control / regulation and measurements,

(v)          rationalisation of outlet discharges and command areas,

(vi)       finalization of location of outlets,

(vii)     type of outlet.

 

 

 

Item (i), (ii), (iv), (v) have been considered as part of basic input for design and the relevant details are presented with the design calculations. Regarding the rationalization of intake designs, provision of gates and arrangements for control regulation and measurement of flow volumes to the minors, the details are described in respective sections. 

 

The design equity has been calculated according to availability of maximum canal water in Kharif season after deducting 33% total cumulative losses in the entire system dividing by total CCA. Discharge of 0.3 l/sec/ha has been taken as equity for design canal sections. For design purposes, a combined figure for evaporation and seepage losses has been taken as 8 cusec per million on sq. ft. of wetted area.

 

Free Board

        

It shall be kept equal to 0.3 m.

 

Bank Width

 

For discharge more than 0.3 m3/s, inspection bank 3.0 m wide shall be provided if canal land width is available. In all other cases, both the banks being non inspection banks, their widths shall be kept as 1.5 m.

 

Berm

 

Berm shall be provided as per Para 4.6 with a minimum dimension of             0.20 m.