Hydraulic Report Content_01

PROJEK LEBUHRAYA PERSISIRAN PANTAI BARAT: MENAIKTARAF JALAN PERSEKUTUAN FR5 (TANJUNG KARANG-HUTAN MELINTANG) [“Project”]

-PRELIMINARY DRAINAGE REPORT-

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1. INTRODUCTION

The proposed “PROJEK LEBUHRAYA PERSISIRAN PANTAI BARAT: MENAIKTARAF JALAN

PERSEKUTUAN FR5 (TANJUNG KARANG-HUTAN MELINTANG) [“Project”], traverses through a

relatively flat terrains as well as within urban developed areas at the end chainage. The existing road is

two lane dual carriageways.

Total length of the proposed road at this package is about 50.000km from Persimpangan Jalan Mat

Rojak, Tanjung Karang to Jambatan Sultan Idris, Hutan Melintang, Selangor Darul Ehsan.

This report presents drainage design considerations and hydrological and hydraulics calculation for

culvert crossing from general catchments of the area and type of drainage system. The drainage system

for this project is consist of existing earth drains, box culvert, pipe culvert and bridge waterway. All

types of drainage are connected to existing earth drain or channel before discharging into Sg. Bernam.

2. EXISTING DRAINAGE SYSTEM

Based on site reconnaissance, the road is generally on flat terrain. The existing road is two lane dual

carriageways. Most of the existing earth drain along the road is discharged into existing river nearby.

The proposed road crossed many existing earth drains and also crossed one main (1) river, namely,

Sungai Bernam.

2.1 Drainage Scope of Works

Upgrade the drainage system

Earth drain improvement and relocations

Typical section detail of drainage



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3. DESIGN CRITERIA AND ASSUMPTION FOR THE PROPOSED DRAINAGE SYSTEM

Guidelines and design criteria established by Jabatan Pengairan dan Saliran (JPS) named MaSMA,

Jabatan Kerja Raya Malaysia (JKR) and Road Engineering Association of Malaysia (REAM).

The design criteria to be adopted will conform to the guidelines laid down in the Urban Strom water

Management Manual for Malaysia’ (Manual Saliran Mesra Alam Malaysia (MaSMA) which was

enforced in January 2001 by Cabinet and will be explained in detailed in Section: Design Calculations

and Urban Drainage Design Standards and Procedures No.1 for Peninsular Malaysia 1975 (DID No.1).

i. Drainage system shall be designed with regards to both operation and ease of maintenance.

Adequate gradients shall be provided to enable self-cleansing flow.

ii. Surface drain is design to cater for flood level of 10 years return period and shall cater for

efficient removal of storm water from road surface, erosion protection and slope stabilization.

iii. All culverts crossing shall be designed to cater 50 years ARI and to withstand traffic load based

on JKR standard.

iv. The river crossing is designed to cater for 100 years ARI with 1m freeboard from bridge soffit.

v. All drains shall be properly designed and constructed to give the best hydraulic features. There

shall be no flooding, ponding, and silted up either during construction or after completion of

this project.

vi. Minimum velocity of flow shall be 1.0m/sec in order to prevent rapid sedimentation and for

self-cleansing and the maximum velocity is 4.0m/sec.



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4. HYDROLOGICAL CALCULATION

There are 2 types of hydrological method used, which are Rational Method and Time Area Method.

Rational Method were used to determine the storm water runoff for catchments area less than 80ha

but catchments area more than 80ha, the Time Area Method were adopted.

4.1. Rational Method

The Rational Method was used to determine the storm water runoff. It is based on the

Rational Formula, which converts the rainfall intensity on a catchments area into peak

discharge of same ARI through a runoff coefficient. Experience has shown that Rational

Formula can provide satisfactory estimates of peak discharge on small catchments area up

to 80ha. The Rational Formula is as follows:

Qy= C.y It.A ______________________

360

Where,

Qy = y year ARI peak flow (m3/s)

yIt = y year ARI average rainfall intensity over time of concentration, tc (mm/hr)

A = drainage area (ha)

C = dimensionless runoff coefficient (Refer Design Chart 14.3 or 14.4 from Volume 4

(MaSMA).



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4.2. Hydrograph Method (Time Area Method)

The Hydrograph Method computes a flow hydrograph from a rainfall hyetograph after

subtracting losses and temporary storage effects. Time Area Method is one of the

methods available for Hydrograph Method. Time Area Method utilizes a complication of

the rainfall excess hyetograph with a time-area diagram representing the progressive area

contributions within catchments in a set time increments. Separate hydrographs are

generated for the impervious and pervious surfaces within the catchments. These are

combined to estimate the total flow inputs to individual sub-catchments entries to the

underground urban drain network.



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Figure 1.0 : Time Area Hydrograph

4.3 Hydrograph Ordinates

The translated inflow hydrograph ordinates qi for any selected design hyetograph can be determine

using equation as below:

qi = Ii.A1 + Ii-1.A2 + ………… +I1.Ai

where,

qi = the flow hydrograph ordinates (m3/s)

Ii = excess rainfall hyetograph ordinates (mm/hr)

Ai = time area histogram ordinates (ha)

I = number of isochrones area contributing to the outlet



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5. HYDRAULIC CALCULATIONS

5.1. Sizing of River Section

The Manning’s formula of open channel flow based on limitation on the velocity as follows:

a) Manning’s Formula:-

Q = (1/n) .A. R2/3.S1/2

Also,

Q = A.v

Where,

Q = discharge (m3/s)

v = velocity (m/s)

n = Manning’s Roughness Coefficient

P = wetted perimeter (m)

A = cross sectional area of channel (m2)

R = hydraulic radius

S = bed slope of channel



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Figure 2.0: Manning’s Coefficient

Figure 3.0: Values of Manning’s ‘n’ for Overland Flow

b) Velocity:- Lined Channels

Maximum velocity - 4.0 m/s (scouring prevention)

Minimum velocity - 1.0 m/s (self-cleansing velocity)



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6. EARTH DRAINS CALCULATION TO BE REALIGNED FROM CH2375.000 TO CH47600.000

Manning’s formula applied:-

Q = (1/n) .A. R2/3.S1/2 R = (A/P) 2/3

Where n = 0.011 (RC Precast U-Shape Drain)

n = 0.035 (Earth Drain)

Existing earth drain at site:-

Qexisting = (1/n) .A. R2/3.S1/2

Qexisting = (1/0.035). (10 x 2). [(10x2)/(2+2+10)]2/3. (1/250)1/2

Qexisting = 45.83m3

4 types of earth drains to be proposed at site:-

1. Existing earth drain to be realigned with min 2.0 wide channel and max 2.0 depth

2. Existing earth drain to be realigned with RC Precast U-shape drain 2 (W) x 2 (H)

3. Existing earth drain to be realigned with RC Precast U-shape drain 1.5 (W) x 1.5 (H)

4. Existing earth drain to be realigned with RC Precast U-shape drain 3 (W) x 2.4 (H)

1. Existing earth drain to be realigned with min 2.0 wide channel and max 2.0 depth

Q = (1/n) .A. R2/3.S1/2

Q = (1/0.011). (2x2). [(2x2)/(2+2+2)]2/3. (1/250)1/2

Q = 17.562m3 < 45.83m3

2. Existing earth drain to be realigned with RC Precast U-shape drain 2 (W) x 2 (H)

Q = (1/n) .A. R2/3.S1/2

Q = (1/0.011). (2x2). [(2x2)/(2+2+2)]2/3. (1/250)1/2

Q = 17.562m3 < 45.83m3



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3. Existing earth drain to be realigned with RC Precast U-shape drain 1.5 (W) x 1.5 (H)

Q = (1/n) .A. R2/3.S1/2

Q = (1/0.011). (1.5x1.5). [(1.5x.1.5)/(1.5+1.5+1.5)]2/3. (1/250)1/2

Q = 8.149m3 < 45.83m3

4. Existing earth drain to be realigned with RC Precast U-shape drain 3 (W) x 2.4 (H)

Q = (1/n) .A. R2/3.S1/2

Q = (1/0.011). (3x2.4). [(3x2.4)/(2.4+3+2.4)]2/3. (1/250)1/2

Q = 39.24m3 < 45.83m3

7. PROPOSED R.C PRECAST U-SHAPE CALCULATION SIZE 0.6m (W) X 0.6m (H), LENGTH 120.0m/G=1:200

FROM CH9125.000 TO CH9200.000

Q = (1/n) .A. R2/3.S1/2

Q = (1/0.011). (0.6x0.6). [(0.6x0.6)/(0.6+0.6+0.6)]2/3. (1/250)1/2

Q = 0.7078m3 < 45.83m3

8. PROPOSED R.C PRECAST BOX CULVERT CROSSING CALCULATION SIZE 3.0m (W) X 2.4m (H), FROM

CH44825.000 TO CH44925.000

Q = (1/n) .A. R2/3.S1/2

Q = (1/0.011). (0.6x0.6). [(0.6x0.6)/(0.6+0.6+0.6)]2/3. (1/250)1/2

Q = 0.7078m3 < 45.83m3



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9. PROPOSED PIPE CULVERT CROSSING 1500mm RCP CALCULATION LENGTH 10.0m FROM CH46975.000

TO CH47150.000

A= πr2 P=2πr

Q = (1/n) .A. R2/3.S1/2

Q = (1/0.011). (1.7674). (0.520)2/3. (1/250)1/2

Q = 5.284m3 < 45.83m3



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10. CONCLUSION

Total number of existing pipe culvert size 2m (W) x 2m (H) crossing main road at the existing

stream/earth drains to be maintained are 25 nos. The type of culvert proposed at CH46975.000 to

CH47150.000 is 1500mm dia Reinforced Pipe Culvert. The precast reinforced concrete box culvert is

proposed for size up to 3000mm x 2400mm.

Existing Sg.Bernam channel/earth drain under the existing bridge is maintained due to the capacity of

100 years ARI still sufficient.

The existing earth drains are to be maintained at site. The area that required road widening will require

existing earth drain to be realigned too. Referring to the calculation calculated above all proposed size

for R.C PRECAST U-SHAPE DRAIN, R.C PRECAST BOX CULVERT and PIPE CULVERT are sufficient.

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