06 Urban Drainage - Universiti Sains Malaysia

transcript

IntroductionLined DrainsComposite DrainsGrassed SwalePipe DrainsEngineered Waterways

ContentsContents

Introduction

Existing Drain

Rigid Boundary ChannelRigid Boundary Channel

Rigid Boundary ChannelRigid Boundary Channel(Dry Period)(Dry Period)

Trunk Drain During Dry Period

Wet PeriodWet Period

Trunk Drain - Wet Period Rigid Boundary ChannelRigid Boundary Channel

Feasibility Study On Drainage Improvement in PraiIndustrial Complex, Seberang Perai Tengah, Penang

Study Area

Legend:Primary DrainExisting Pump StationRailway

Pump House A

Pump House B

Existing Primary Drains

Pump House A

Pump House B

Existing Primary Drains

Pump House A

Pump House B

Existing Trunk Drains

Pump House A

Pump House B

Existing Trunk Drains

B-2EL-6B

Rubber Pitching :Rubber Pitching :Top Width = 30’ - 46’

Depth = 5’ – 13’

Rectangular :Rectangular :Width = 5’ – 8’

Depth = 16’

Feasibility Study and Detail Design of Flood Mitigation and Drainage Improvement in Taman Sentul, TamanSentul Jaya, Taman Pinang & Taman Mangga, Juru,

S.P.T, Penang

Study Area

TolJuru

Lebuhraya Utara-Selatan

ParitNo. 5

Perkampungan Juru

KawasanPerusaha

anRingan

TamanSentulJaya

Mangga

Sentul

Pinang

Precast Concrete Drain900mm

Precast Concrete Drain1200mm

Precast Concrete Covered Drain

1200mm

PrecastConcrete

Drain3000mm

Feasibility Study of Flood Mitigation and Drainage Improvement in Kampung Tersusun, Juru, Seberang

Perai Tengah, PenangStudy Area

Primary Drain

Secondary Drain

Trunk Drain

Natural Waterway

Parit No. 5

Sungai Juru

Existing Problems

Feasibility Study of Flood Mitigation and Drainage Improvement in Kampung Tersusun, Juru, Seberang

Perai Tengah, Penang

Flooding occurs along the roads of the study areas due to improper drainage design, where roadside drains are not

provided.

Normal conditionNormal condition Flood condition on 6th October 2003

Flood condition on 6th October 2003

provided.

Flooding caused by lack of maintenance and undersized secondary drain.

Flooding caused by overflow of trunk drain.

Open Drains Volume 10 (Chapter 26)

Design Criteria

(a) Grassed Swale

Drainage Reserve

0.5 m Design flow width + freeboardmin min

1.5 m minimum 1.0 m

Drainage Reserve

(b) Lined Open Drain

Reserve Width for Open Drain

321. SRnAQ =

Manning’s Equation

nQBYv.s

Manning’s Roughness Coefficient, n (Design Chart 26.1)

0.0150.012Precast Masonry Blockwork

0.0180.012 Brickwork

0.0300.025Rock Riprap

0.0350.020Random stones in mortar or rubble masonry

0.0170.015Dressed stone in mortar

Stone Pitching

0.0180.013Off form finish

0.0150.011Trowelled finish

Concrete

MaximumMinimum

Suggested n valuesSurface Cover or Finish

Solution to Manning Equation for Lined Open Drains

Longitudinal Grade, S0 (%)

1 20.4

(m3 /s

Use 'vee' shaped section

Base width, B (m)

Swale reserve width, R (m)( including required freeboard )

Base width, B (m)

Flow depth, y (m)

0.1 0.90.5

Flow Depth, y (m)

0.2 0.3 0.4 0.6 0.7 0.8

Z = 5.5

Z = 4.5

Swale reserve width, R (m)( including required freeboard )

'Vee' shaped Section

Lined Drains Volume 10 (Chapter 26.3)

Design Criteria

Uncovered Open Lined Drain (Minor System – Chap. 26)

H max = 0.5 m

B = 0.5 – 1.0 m 1.5 m minimum1.0 m

Drainage Reserve Width

Covered Open Lined Drain (Minor System – Chap. 26)

H = 0.5 m – 1.0 m

B = 0.5 – 1.0 m 1.5 m minimum1.0 m

To prevent sedimentation and vegetative growth

Min Average Flow Velocity = 0.6 m/s

Velocity Limitation (Minor System – Chap. 26.3.6)

To prevent Channel Surface Erosion

Max Average Flow Velocity = 4.0 m/s

Note: Average Flow Velocity > 2.0 m/s, drain provided with a handrail fence, or covered with solid or grated cover

Composite Drains Volume 10 (Chapter 26.4)

Design flow width + freeboard

14 min

Qminor

50 mm freeboard

4 min1

Grassed Section

Lined drain

Recommended Composite Drain

• Provided in locations subject to dry-weather base flows which would otherwise damage the invert of a grassed swale, or in areas with highly erodible soils.

•The lined drain section is provided at the drain invert to carry dry-weather base flows and minor flows up to a recommended limit of 50% of the 1 month ARI.

Grassed Swale Volume 10 (Chapter 26.2)

Constructed Swale

Perimeter Perimeter SwaleSwale

Bio-Ecological Drainage SystemUSM, Engineering Campus

Type CType C

Type BType B

Type AType A

Design Criteria

4 min1 1

Qminor

(a) ' Vee' Shaped

300mm freeboard

4 min14 min

Batter BatterBase

Qminor

(b) Trapezoidal Shaped

C 300mm freeboard

Velocity Limitation (Minor System – Chap. 26.2.5)

Max Average Flow Velocity < 2.0 m/s

Freeboard (Minor System – Chap. 26.2.4)

Min freeboard of 50 mm above the design stormwater level

Manning’s Roughness Coefficient, n Design Chart 26.1

0.0500.035Tall grass cover

0.0350.030Short grass cover

Grassed Swales

MaximumMinimum

Suggested n valuesSurface Cover or Finish

Worked Example(Application of Bio-Ecological

Drainage System (BIOECODS) in Malaysia)

Perimeter Swale

Study Area – BIOECODS, USM Engineering Campus

Recommended Grassed Swale Cross-Sections: Side slope = 1:4 min (batter); 1:50 (base)

Figure 26.2

The average flow velocity in a grassed swale shall not exceed 2 m/s.

26.2.5

The depth of a grassed swale shall include a minimum freeboard of 50 mm above the design storm water level in the swale.

26.2.4

In new development areas, the edge of a grassed swale should generally be located 0.5 m from the road reserve or property boundary.

26.2.2

Design CriteriaReference

a) Overland flow time:Overland sheet flow path length = 35mSlope of overland surface = (3.60-2.40)/35 = 3.5%Design Chart 14.1, overland flow time, to = 12 minute

b) Flow time in channel:

- Reach length of perimeter swale = 130m

- The estimated average velocity = 0.25m/s

- Flow time in ecological swale , td = (130/0.25)/60 = 8.7 minutes

c) Time of concentration

Time of concentration, tc = to + td = 12 + 8.7 = 20.7 minutesAssume : tc = 20 minit

d) Design Storm

Minor Storm : 10 year ARIMajor Storm : 50 year ARITable 13.A1 Lacation : Pulau Pinang and equation 13.2 for tc = 20 minute,

Table 13.A1 Coefficients for the IDF Equations for the Different Major Cities and Towns in Malaysia (30 ≤ t ≤ 1000 min)

0.0341-0.56102.24172.7512100

0.0335-0.54692.14562.842950

0.0286-0.47031.76893.325520

0.0241-0.40231.43933.727710

0.0180-0.32401.12843.95995

0.0118-0.23110.67294.514021951-1990

PenangPulauPinang

Coefficients of the IDF Polynomial EquationsARI (year)

Data Period

LocationState

0.000.000.000.000.0030

0.480.320.360.420.4720

0.740.540.620.720.8015

1.030.860.991.131.2810

1.391.401.621.852.085

All≥ 180150120≤ 100(minutes)

East CoastWest Coast

2P24h (mm)Duration

Table 13.3 Values of FD for Equation 13.3

Where, 10I30 = 3.7277 + (1.4393) [In(30)] + (-0.4023) [In(30)]2 + (0.0241) [In(30)]310I30 = 136.65 mm/hr

P30 = 136.65/2 = 68.32 mm

And, 10I60 = 3.7277 + (1.4393) [In(60)] + (-0.4023) [In(60)]2 + (0.0241) [In(60)]310I60 = 92.83 mm/hrP60 = 92.83/1 = 92.83 mm

32 ))t(ln(d))t(ln(c)tln(ba)Iln( tR +++=

Thus, P20 = 68.32 – (0.42) (92.83 - 68.32) = 56.80 mm

10I20 = 56.80 (60) / 20 = 170.41 mm/hr

(13.2)

)( 306030 PPFPP Dd −−= dPI d=(13.3) (13.4)

Minor Storm: 10 year ARI:

Where, 100I30 = 2.7512 + (2.2417) [In(30)] + (-0.5610) [In(30)]2 + (0.0341) [In(30)]3100I30 = 186.35 mm/hr

P30 = 186.35/2 = 93.17

And, 100I60 = 2.7512 + (2.2417) [In(60)] + (-0.5610) [In(60)]2 + (0.0341) [In(60)]3 100I60 = 129.75 mm/hr

P60 = 129.75 /1 = 129.75

Thus, P20 = 93.17 – 0.47 (129.75 - 93.17) = 75.99

100I20 = 75.99 (60) / 20 = 220.96 mm/hr

(13.2)

)( 306030 PPFPP Dd −−= dPI d=(13.3) (13.4)

Major Storm: 100 year ARI:

e) Runoff Coefficient

Design Chart 14.3 (Landscape: Category 7),

C for minor storm = 0.58I= 170.41 mm/hr

C for major storm = 0.67I= 220.96 mm/hr

Rainfall Intensity, I (mm/hr)

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180

0190 200

8Impervious Roofs, ConcreteCity Areas Full and Solidly Built Up

Urban Residential Fully Built Up with Limited Gardens

Surface Clay, Poor Paving, Sandstone RockCommercial & City Areas Closely Built Up

Semi Detached Houses on Bare Earth

Bare Earth, Earth with Sandstone Outcrops

Bare Loam, Suburban Residential with Gardens

Widely Detached Houses on Ordinary LoamSuburban Fully Built Upon Sand Strata

Park Lawns and Meadows

Cultivated Fields with Good GrowthSand Strata

*I = 200mm/hr, C = 0.63I = 400mm/hr, C = 0.90

(Pavement: Category 1),C for minor & major storm = 0.91

f) Average Runoff Coefficient

000,3600AIC t

Q ××=

g) Peak flow

By using Rational formula (equation 14.7)

Minor storm,Cavg = [(0.58x4600) + (0.91x1900)] / 6500 = 0.68

Major storm,Cavg = [(0.67x4600) + (0.91x1900)] / 6500 = 0.74

Qminor /2* = C.I.A/ (3600,000) (2) = 0.68 (170.41) (6500) / (3600,000) (2)= 0.10m3/s

Qmajor /2* = C.I.A/( 3600,000) (2) = 0.74 (220.96) (6500) / (3600,000) (2)= 0.15m3/s

* There are two perimeter swale in the catchment area to cater the peak flow.

∑∑

g) Perimeter Swale SizingLongitudinal slope = 1:1000; Side slope 1:6 (batter), 1:50 (base); Bottom width, B = 1.8m; Depth, D = 175mm; Manning’s, n = 0.035; Area, A = 0.50 m2,; Wetted Perimeter, P = 3.93m;Hydraulic radius, R = A/P = 0.13m;Average velocity, V = 0.23m/s (<2.0 m/s) …OKQ = 0.11m3/s (> Q10) ... OK

0.1460.240.144.230.604.200.20061.80.001

0.1130.230.133.930.503.900.17561.80.001

0.0840.210.113.620.413.600.15061.80.001

0.0600.190.103.320.323.300.12561.80.001

0.0400.170.083.020.243.000.10061.80.001

0.0240.140.062.710.172.700.07561.80.001

0.0120.110.042.410.112.400.05061.80.001

0.0040.070.022.100.052.100.02561.80.001

0.0000.000.001.800.001.800.00061.80.001

(cumec)(m/s)(m)(m)(sq.m)(m)(m)(m)(m)

QVRPATWDepth, DSide Slope, ZBWSLOPE

Freeboard = 300mm; Depth, D = 1200mm; Area, A = 11.64 m2;

Wetted Perimeter, P = 17.10m; Hydraulic radius, R = A/P = 0.68m;Average velocity, V = 0.27m/s (<2.0 m/s) …OKQ = 0.19m3/s (> Q100) ... OK

0.2760.290.185.150.955.100.27561.80.001

0.1910.270.164.540.714.500.22561.80.001

0.1460.240.144.230.604.200.20061.80.001

0.1130.230.133.930.503.900.17561.80.001

0.0840.210.113.620.413.600.15061.80.001

QVRPATWDepth, DSide Slope, ZBWSLOPE

Pipe DrainsVolume 10 (Chapter 25)

Design Criteria

Table 25.5 Minimum Pipe Diameters

Diameter

450For a non-self draining underpass, the pipe shall be sized for 10 year ARI and shall not be less than

375Any other pipe

300Pipe draining a stormwater inlet and crossing a footpath alignment *

Diameter (mm)Application

Note: * 300 mm diameter pipes are permitted in this situation only, in order to provide more space in the footpath alignment for other utility services.

Minimum Design Service LifeStormwater pipelines shall be designed for a minimum effective service life of 50 years.

Pipe Grades

(a) Maximum Grade

Pipeline grades shall be chosen to limit the pipe full flow velocity to a value less than or equal to 6.0 m/s.

(b) Minimum Grades

Stormwater pipelines shall be designed and constructed to be self cleansing. The desirable minimum grade for pipelines shall be 1.0%.

An absolute minimum grade of 0.5% may be acceptable where steeper grades are not practical.

Table 25.7 Pipe Roughness Values (average condition)

0.060.011UPVC

0.150.013Fibre Reinforced Cement

0.30.013Spun Precast Concrete

k (mm)nPipe Material

Pipe Roughness Values

n = Manning roughness coefficientk = Pipe roughness height for Colebrook-White equation

Worked Example(Proposed Tuanku Heights Mixed Development of Daerah Seremban,

Negeri Sembilan)

System System Layout Layout

Forebay

Mini Wetland

RockBaffle

Community Detention Pond

Engineered Waterway

Pipe DrainEngineered WaterwayEcological Drain

Natural Waterway

SCHEMATIC LAYOUT OF NEW SCHEMATIC LAYOUT OF NEW DRAINAGE SYSTEM, TUANKU DRAINAGE SYSTEM, TUANKU

HEIGHTHEIGHT

Subcatchment : 1

Area = 6770m2

Qp1 = 144.39 l/s

k = 0.3 mmTable 25.7

n = 0.013Table 25.7

Minimum grade = 1.0%Sec. 25.3.3 (b)

Maximum Grade : Velocity < 6 m/s.Sec. 25.3.3 (a)

φmin = 375mmTable 25.5

Calculation for Underground Drain Pipes Sizing

From Design Chart 25.B3 (k = 0.3 mm),

With D = 375 mm

Hydraulic gradient 1 %

Q = 230 l/s (> Qp1 …OK)

V = 2 m/s (< 6m/s…OK)

(Major System)

Engineered WaterwaysVolume 11 (Chapter 28)

Engineered Waterways

W VariesVaries

300 mm

Recommended Waterway Reservefor Maintenance Access

To prevent sedimentation and vegetative growth

Min Velocity = 0.8 m/s

To prevent Channel Surface Lining Erosion

Max Velocity = 4.0 m/s (Lined Channel / Low flow invert)

= 2.0 m/s (Floodways and Natural Waterway)

Minimum Longitudinal Slope

0.2 % - Lined Channel0.5 % - Grassed floodways and natural waterway

Suggested Values of ManningSuggested Values of Manning’’s s Roughness Coefficient, Roughness Coefficient, nn

0.1200.100Medium to dense

0.0500.040Scattered

Tree cover

0.1600.100Medium to dense

0.0700.050Scattered

Shrub cover

0.0500.035Tall grass

0.0350.030Short grass

Grass cover only

Grassed Floodways

MaximumMinimum

Suggested n valuesSurface Cover

0.2000.110Dense growth of trees

0.1600.070Medium to dense brush

0.0800.040Light brush and trees

0.0500.030Long pasture grass, no brush

0.0350.025Short pasture grass, no brush

Overbank flow areas

0.1000.035Irregular and rough cross-section

0.0600.025Regular cross-section with no boulders or brush

Large streams

0.0700.030Steep mountain streams with gravel, cobbles, and boulders

0.0800.050Sluggish weedy reaches with deep pools

0.0450.035Clean, winding with some pools and shoals

0.0330.025Straight, uniform and clean

Small streams

Natural Channels

MaximumMinimum

0.0300.025Rock Riprap

0.0350.020Random stones in mortar or rubble masonry

0.0170.015Dressed stone in mortar

Stone Pitching

0.0250.020Unfinished

0.0250.018Trowelled, wavy

0.0230.016Trowelled, not wavy

Shotcrete

0.0180.013Off form finish

0.0150.011Trowelled finish

Concrete

Lined Channels and Low Flow Inverts

MaximumMinimum

0.0240.02014 mm stone

0.0190.0177 mm stone

Flush Seal Pavement

0.0170.015Rough

0.0140.012Smooth

Hotmix Pavement

0.0150.011Kerb & Gutter

Roadways

MaximumMinimum

I. Composite Waterways(With Increased Capacity - Chap 28)

where,n* = equivalent Manning’s roughness coefficient for the whole

cross-sectionni = Manning's roughness coefficient for segment iAi = flow area of segment i (m2)P = wetted perimeter of segment i (m)m = total number of segments

(28.1)

Estimate the Overall Roughness Coefficient

II. Natural Waterways

To prevent Channel Erosion

Max Velocity = 2.0 m/s

Critical Velocity

Minimum Longitudinal Slope0.5 %

Velocity Limitation (Major System - Chap 28)

To prevent Channel Erosion

Max Velocity = 2.0 m/s

Critical Velocity

Minimum Longitudinal Slope0.5 %

Critical Velocities, (m/s) for various conduit materials

III. Grassed Floodways

Batter BatterBase

C Low FlowProvision

Figure 28.3 Typical Grassed Floodway Cross-Section

Qmajor

Qminor

C Terracing

BatterTerrace Base

Figure 28.4 Typical Grassed Floodway Terracing

Low Flow Provision:Minimum capacity of 50% of the 1 month ARI flow.

Design Chart Design Chart 28.228.2

Floodway Base Width –Preliminary Estimate(Manning's n = 0.035,

Average Velocity = 2 m/s)

Worked Example(Application of Bio-Ecological

Drainage System (BIOECODS) in Malaysia)

Ecological Swale

Study Area – BIOECODS, USM Engineering Campus

Low flow inverts and pipes shall be sized for a minimum capacity of 50% of the 1 month ARI flow

28.10.4

Side slopes = 1:6 min (batter); 1:50 (base)Side slopes = 1:4 may be provided in special circumstance

28.10.2

Longitudinal grades shall be chosen such that the design storm average flow velocity will not exceed 2 m/s in grassed floodways and natural waterways

28.7.2

The minimum longitudinal grade for engineered waterways = 0.5% for grassed floodways and natural channels;Longitudinal grades shall not produce velocities less than 0.8 m/s if low flow inverts flowing full

28.7.1

The freeboard above the design storm water level shall be a minimum of 300 mm.

Minimum requirements for maintenance access = 3.7m (One side) and 1.0m (Other Side) for top width of waterway ≤ 6m or Both sides = 3.7m for top width of waterway > 6m

Table 28.1

a) Overland flow time:Overland sheet flow path length = 35mSlope of overland surface = (3.60-2.40)/35 = 3.5%Design Chart 14.1, overland flow time, to = 12 minute

b) Flow time in channel:

-Reach length of ecological swale = 920m

- Average velocity for ecological swale is given by Manning equation. The estimated average velocity = 0.35m/s

-Flow time in ecological swale , td = (920/0.35)/60 = 43.8 minutes

c) Time of concentration

Time of concentration, tc = to + td = 12 + 43.8 = 55.8 minutesAssume : tc = 56 minit

d) Design StormMinor Storm : 10 year ARIMajor Storm : 100 year ARITable 13.A1 Lacation : Pulau Pinang and equation 13.2 for tc = 56 minute,

Table 13.A1 Coefficients for the IDF Equations for the Different Major Cities and Towns in Malaysia (30 ≤ t ≤ 1000 min)

0.0341-0.56102.24172.7512100

0.0335-0.54692.14562.842950

0.0286-0.47031.76893.325520

0.0241-0.40231.43933.727710

0.0180-0.32401.12843.95995

0.0118-0.23110.67294.514021951-1990

PenangPulauPinang

Coefficients of the IDF Polynomial EquationsARI (year)

Data Period

LocationState

Minor Storm: 10 year ARI:

10I56 = 3.7277 + (1.4393) [In(56)] + (-0.4023) [In(56)]2 + (0.0241) [In(56)]310I56 = 96.99 mm/hr

Major Storm: 100 year ARI:

100I56 = 2.7512 + (2.2417) [In(56)] + (-0.4023) [In(56)]2 + (0.0241) [In(56)]3100I56 = 135.48 mm/hr

32 ))t(ln(d))t(ln(c)tln(ba)Iln( tR +++= (13.2)

e) Runoff CoefficientDesign Chart 14.3 (category 5),

Minor storm:(I=96.99mm/hr,)C for = 0.61

Minor storm:(I=135.48mm/hr,)C for = 0.70

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180

190 200

000,3600AIC t

Q ××=

Qminor = C.I.A/3600,000 = 0.61 (96.99) (256,000) / (3600,000) = 4.21m3/sQmajor = C.I.A/3600,000 = 0.70 (135.48) (256,000) / (3600,000) = 6.75m3/s

f) Peak flow

By using Rational formula (equation 14.7), peak flow for minor storm = 4.21 m3/s and peak flow for major storm = 6.75 m3/s

g) Ecological Swale SizingLongitudinal slope = 1:1000; Side slope 1:6 (batter), 1:50 (base); Bottom width, B = 2.5m; Depth, D = 900mm; Manning’s, n = 0.035; Area, A = 7.12 m2,; Wetted Perimeter, P = 13.46m;Hydraulic radius, R = A/P = 0.53m;Average velocity, V = 0.59m/s (<2.0 m/s) …OKQ = 4.21m3/s (= Q10) ... OK

5.3290.630.5814.678.5014.501.0062.50.001

4.1910.590.5313.457.1113.300.9062.50.001

3.2150.550.4812.235.8412.100.8062.50.001

2.3910.510.4311.024.6910.900.7062.50.001

1.7090.470.379.803.669.700.6062.50.001

1.1590.420.328.582.758.500.5062.50.001

0.7290.370.277.371.967.300.4062.50.001

0.4090.320.216.151.296.100.3062.50.001

0.1880.250.154.930.744.900.2062.50.001

0.0530.170.083.720.313.700.1062.50.001

0.0000.000.002.500.002.500.0062.50.001

QVRPATWDepth, DSide

Slope, ZBWSLOPE

Freeboard = 300mm; Depth, D = 1200mm; Area, A = 11.64 m2;

Wetted Perimeter, P = 17.10m; Hydraulic radius, R = A/P = 0.68m;Average velocity, V = 0.70m/s (<2.0 m/s) …OKQ = 8.13m3/s (> Q100) ... OK

8.1280.700.6817.1011.6416.901.2062.50.001

5.3290.630.5814.678.5014.501.0062.50.001

4.1910.590.5313.457.1113.300.9062.50.001

2.3910.510.4311.024.6910.900.7062.50.001

1.7090.470.379.803.669.700.6062.50.001

1.1590.420.328.582.758.500.5062.50.001

0.7290.370.277.371.967.300.4062.50.001

0.4090.320.216.151.296.100.3062.50.001

0.0530.170.083.720.313.700.1062.50.001

0.0000.000.002.500.002.500.0062.50.001

QVRPATWDepth,

Slope, ZBWSLOPE

Low Flow Provision: Design Capasity for 1 Month ARI

Design Storm : 2 year ARITable 13.A1 Lacation : Pulau Pinang and equation 13.2 for tc = 56 minute,

2I56 = 69.94 mm/hr

2I56 = 4.5140 + (0.6729) [In(54)] + (-0.2311) [In(54)]2 + (0.0118) [In(54)]3

1 month ARI rainfall intensity = 0.4x69.94 = 27.98 mm/hr

DD II 2083.0 4.0 ×= 13.5a

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180

190 200

e) Runoff CoefficientDesign Chart 14.3 (category 5), C for 1 month ARI = 0.30

360AIC t

Q ××=

f) Peak flowBy using Rational formula (equation 14.7), peak flow = 0.60 m3/s

Qlow flow = C.I.A/3600,000 = 0.30 (69.94) (256,000)

/ (3600,000) = 0.60m3/s

Ecological SwaleDrainage capacity for low flow = 0.30 m3/s.

Thus, no. of module needed = (0.60-0.30) / 0.038 = 8

06 Urban Drainage - Universiti Sains Malaysia

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