drainage design criteria

Drainage Design Criteria

DRAINAGE DESIGN CRITERIA

Drainage.

- Design Manual of Road Drainage System, Departemen Pekerjaan Umum, 2005

- Guidelines of Surface Drainage Design on Road, SNI 03-3424-1994.

- Hydrology of Open Channel, Ven Te Chow, Erlangga-Jakarta.

- Analisa Hidrologi, Gramedia Pustaka Utama, Jakarta 1993.

- Banjir Rencana untuk Bangunan Air, Yayasan PU, Jakarta 1992

- Calculation for Discharge Flood Method, SNI-03-2415-1991.

Hydrology and Drainage

Concept Design of Hydrology

Collecting Data

Design more attend to compiled highest maximum flood in happen and compared with output from analysis rainfall data, and will calculated design using flowed evaluation. The data getting from ;

a. Rainfall data from Badan Meteorologi dan Geofisika

b. Surface map from Bakosurtanal

c. Study on site location

Distribution Frequency / Statistic of rainfall

Distribution frequency necessary used formula as follow ;

a) Distribution of Gumbel.

Calculation of Gumbel used formula as below :

. . . . . . . . . . . . ( 1 ).

. . . . . . . . . . . . . . . . . . . ( 2 )

Where ,

= Maximum daily rainfall on “ T ” years repeat period ( mm )

= Average sample of rainfall cumulative aritmatic ( mm )

= Reduce private in probability function, table. A

= Value of reduce private mean function of monitoring, table B

= Reduce private of standard deviation from ‘n” function, table C

= Standard deviation

= Rainfall intensity ( mm/hr )


= Years repeat period

Where ;

= Maximum average daily rainfall ( mm/hr )

= Maximum daily rainfall ( mm/hr )

= Time of monitoring

Table 5.6.1. Vary of YT

Return Period ( years ) Vary of reduce value

2 0.3665

5 1.4999

10 2.2502

25 3.1985

50 3.9019

100 4.6001

Table 5.6.2. Yn Valuen 0 1 2 3 4 5 6 7 8 9

10 0.4952 0.4996 0.5035 0.5070 0.5100 0.5128 0.5157 0.5181 0.5202 0.5220

20 0.5225 0.5252 0.5258 0.5283 0.5296 0.5309 0.5320 0.5332 0.5343 0.5353

30 0.5362 0.5371 0.5380 0.5388 0.5402 0.5409 0.5410 0.5418 0.5424 0.5432

40 0.5436 0.5442 0.5448 0.5453 0.5458 0.5463 0.5468 0.5473 0.5477 0.5481

50 0.5485 0.5489 0.5493 0.5497 0.5501 0.5504 0.5508 0.5511 0.5519 0.5518

60 0.5521 0.5524 0.5527 0.5530 0.5533 0.5535 0.5538 0.5540 0.5543 0.5545

70 0.5548 0.5552 0.5555 0.5556 0.5557 0.5559 0.5561 0.5563 0.5565 0.5567

80 0.5569 0.5570 0.5572 0.5574 0.5576 0.5578 0.5580 0.5581 0.5583 0.5585

90 0.5586 0.5587 0.5589 0.5591 0.5592 0.5593 0.5595 0.5596 0.5598 0.5599

Table 5.6.3. Sn Valuen 0 1 2 3 4 5 6 7 8 9


10 0.9496 .9676 0.9833 0.9971 1.0095 1.0206 1.0316 1.0411 1.0493 1.0565

20 0.0628 1.0696 1.0696 1.0811 1.0864 1.0915 1.0961 1.1004 1.1047 1.1086

30 0.1124 1.1159 1.1159 1.1226 1.1255 1.1285 1.1313 1.1339 1.1363 1.1388

40 0.1413 1.1436 1.1436 1.1480 1.1499 1.1519 1.1538 1.1557 1.1574 1.1590

50 0.1607 1.1623 1.1623 1.1658 1.1667 1.1681 1.1696 1.1708 1.1721 1.1734

60 0.1747 1.1759 1.1759 1.1782 1.1793 1.1803 1.1814 1.1824 1.1834 1.1844

70 0.1859 1.1863 1.1863 1.1881 1.1890 1.1898 1.1906 1.1815 1.1823 1.1930

80 0.1938 1.1945 1.1945 1.1959 1.1967 1.1973 1.1980 1.1987 1.1994 1.2001

90 0.2007 1.2013 1.2020 1.2025 1.2032 1.2038 1.2044 1.2049 1.2055 1.2060SNI 03-3424-1994/P16

b) Distribution of Pearson

Calculation of Pearson used formula as below ;

Where ;

= Denation factor for repeat period with using fixed

Table 5.6.4. Y value as T functionT Y T Y

1.01 -1.53 20 2.97

1.58 0.00 50 3.90

2.00 0.37 100 4.60

5.00 1.50 200 5.30

10.00 2.25 - -

Table 5.6.5. Frequency Factor for Extreme value ( K )

nRepeat Period ( years )

10 20 25 50 75 100 1000

15 1.703 2.410 2.632 3.321 3.721 4.005 6.265


20 1.625 2.302 2.517 3.179 3.563 3.836 6.006

25 1.575 2.235 2.444 3.088 3.463 3.729 5.842

30 1.541 2.188 2.393 3.026 3.393 3.653 5.727

40 1.495 2.126 2.326 2.943 3.301 3.554 5.476

50 1.466 2.086 2.283 2.889 3.241 3.491 5.478

60 1.446 2.059 2.253 2.852 3.200 3.446

70 1.430 2.038 2.230 2.824 3.169 3.413 5.359

75 1.423 2.029 2.220 2.812 3.155 3.400

100 1.401 1.998 2.187 2.770 3.109 3.349 5.261SNI M-18-1989-F

c) Distribution of Haspers ;

Calculation of Haspers formula based on maximum daily rainfall data with principle as below ;

Where ;

XT = RT Maximum rainfall on “ T “ years repeat period ( mm )

n = Total monitoring data

SD = SX Standard deviation

SV** = Standard variable

UT = Standard variable repeat period

m = Number level of data

TR = Probability

Result calculation of design rainfall therd distribution comparation shall be used a high rainfall. The three distribution compare will get high result calculation of rainfall design to used after evaluate with coefficient of skewness and curtosis.

Rainfall Intensity.

From several formulae for calculated the rainfall intensity one of them is Mononobe formula. In this analysis, time of rainfall intensity certain by assumption rainfall distribution during in 6 hours per day and used based on Mononobe formula.


Where ;

It = Average of rainfall intensity start point to t hours ( mm/hr )

R24 = Maximum rainfall design in 24 hours ( mm )

24 = Standard presentation in 1 day ( R24 = 100 % )

t = Duration of rainfall ( hours )

Effective Rainfall Intensity

Intensity of rainfall depend from effectively water flow and type of surface. The effective rainfall intensity calculated with formula as follow ;

Where ;

Ief = Effective rainfall

I = Rainfall intensity

α = Coefficient of flowed as shown at table

Table 5.6.6. Coefficient of Flowed

No. Type of surfaceCoefficient

( α )

1 Asphalt Road 0.70 – 0.05

2 Shoulder 0.70 – 0.85

3 Concrete Road 0.70 – 0.95

4 Embankment 0.40 – 0.65

5 Urban 0.70 – 0.95

6 Inter Urban 0.60 – 0.70

7 Resident 0.40 – 0.60

Drainage will be design with adequate capacity to accommodate storm run off and to avoid drainage to the fly over arterial road and surrounding properties and to maintain traffic safety.

Table 5.6.7. Design Period of Life Time :

Type of drainage Life time period

In let 25 years

Box Culvert 25 years

Side ditch 10 years


River Q < 200 m3/sec 50 years

River Q ≥ 200 m3/sec 100 years

Design Discharge

a. Rational Method

Design discharge calculated with Rational Method, if the catchments area smaller than 500 km2 ( SNI ) used formula as follow ;

Where ;

Q = Design discharge ( m3/sec )

f = Conversion factor ( f = 0.278 )

α = Coefficient of flowed

I = Rainfall intensity have same duration with time concentrated in repeat rainfall time ( mm/hr ).

A = Catchments area ( km2 ).

Formula rational used to calculated the side ditch capacity and drainage which replaced surrounding main road corridor. Based on site visit design alignment crossing rolling area expected every 1 km can be installed 2 or 3 channels.

b Regression Method.

Regression Method used to estimated discharge of top debit at flow river area with minimum data, parameter can used as follow ;

1. Area ( A ), map with scale 1 : 25,000

2. Average daily rainfall ( )

3. Slopping river ( S ), minimal S = 0.1 %

4. Flowed area (Al )

Equation regression from above parameter have formula to decided design average per year as follow :

Where ;

V = 0.02 – 0.0275.log A

Discharge debit based on repeat period as follow :

Where ;

QN = Design discharge debit ( m3/sec )

C = Coefficient factor as shown at table

Table 5.6.8. C - Factor

Repeat Reduction Variable “ C “ factor


( T )

5 1.50 1.28

10 2.25 1.56

20 2.97 1.88

50 3.90 2.35

100 4.60 2.78SK SNI M-18-1989-F/P21

Coefficient of Average Flow

Where ;

C = Coefficient of flow appropriate the type of surface condition

A = Wide area of flowed (Catchments area)

Table 5.6.9. Coefficient of Flow

Type of SurfaceCoefficient of Flow

( C )

1 Concrete Road and Asphalt 0.70 – 0.95

2 Earth and Granular Stone 0.40 – 0.70

3 Shoulder :

- Soil with small granular 0.40 – 0.65

- Soil with rock granular 0.10 – 0.20

- Soft massive stone 0.70 – 0.85

- Hard massive stone 0.60 – 0.75

4 Urban 0.70 – 0.95

5 Inter Urban 0.60 – 0.70

6 Industry 0.60 – 0.90

Discharge of Ditch water

Where :

Q = Discharge of water ( m3/sec )

C = Coefficient of flow


I = Rainfall Intensity

A = Wide area of flow/catchments area ( m2 )

Design Dimension of Drainage

Sloping Control for existing area

One of the other provision during design drainage is breaking water flow,

Where ;

il = Sloping the existing area ( % )

elev1 = Upper elevation the existing area

elev2= Lower elevation the existing area

Drain Capacity.

Design of side ditch based on uniform flow shall be continue and calculated with formula as follow ;

Where ;

Qs = Drain capacity ( m3/sec )

F = Catchments Wet area ( m2 )

V = Velocity of flow ( m/sec )

Velocity of flow calculated by Manning formula :

Where ;

nd = Coefficient Manning friction.

So = Slopping of channel

R = Hydrolic radii channel ( m ).

Where :

F = Catchment wet area ( m2 )

P = Circumference wet area ( m )

Concentration Time

Flowing time to drainage or time of inlet used formula as follow ;


Where ;

t1 = Time inlet ( minute )

t2 = Time outlet ( minute )

l = Maximum length flowing

nd = Manning Coefficient of friction

So = Drainage Slopping.

V = Average velocity of ditch

Manning’s Coefficient

Value of Manning’s coefficient for design analysis shown at table.

Table 5.6.10. Manning Coefficient

No. Type of Surface Drain nd

1 Cement and Asphalt concrete 0.013

2 Slip and water proof 0.020

3 Slip and strong 0.010

4 Earth with small grass 0.020

Slopping of Drainage

Slopping of drainage shall be calculated with formula as follow ;

Where ;

v = Velocity of flow

R = Hydraulic radii of drain

nd = Coefficient of friction

Slopping of Drainage Wall

Usually slopping of drainage wall valuated according to safety, economic and have sloping 1 : 1 ~1.5

Free board

Distance vertical freeboard from top of drainage to surface of water design refer to formula as follow :

Where :

W = High of Freeboard ( m )

D = Depth of Drainage ( m )

Design of Drainage / Channel

Design type of drainage ( pipe or box ) shall be decided after maximum flood of water founded also to easy build on site.


Slopping of drainage 0.5 ~2.0 % will condition freefall, for open drainage/channel freefall shall be calculated with formula as follow ;

a) Outlet not flowed, if h = depth of water, D = diameter of channel

b) Outlet flowed, if

c) Freeboard for open drainage

Box Culvert

The box culvert have been functioned to water side drain catchments and to continued flowing to the ditch which have 3 main section :

Main Pipe

Head wall of box culvert and

Apron

Minimal life time design of box culvert 10 years, sloping of box culvert design provision from 0.5 – 2.0 % with consider other function because sedimentation in inlet or outlet drainage.

Box Culvert Dimension

Dimension of box culvert shall be used formula as below ;

Where ;

= Wide area ( m2 )

Q = Debit of water ( m3/sec )

v = Flow velocity ( m/sec )

R = Hydraulic radii of drain ( m )

I = Rainfall intensity

A = Wide area of flow ( m2 )

C = Coefficient of flow

n = Coefficient of friction

Pipe Culverts Dimensions

Place of underground culvert minimum = 60 cm in depth, with maximum length of culvert = 300 m.

Dimension of Pipe Culvert were shown as below :


→

Where :

∅ = Angle wet surface of water in pipe ( rad )

d = high of water in pipe ( m )

F = Channel wet area ( m2 )

D = Diameter of pipe ( m )

P = Circumference wet area in pipe ( m )

r = Radii of pipe culvert ( m )

R = Hydraulic radii of drain ( m )

Details dimension of Pipe Culvert based on standard drawing were shown as below :

Table 5.6.11. Pipe DetailsDiameter D (mm)

Wall Thickness T (mm)

Length L (mm)

Weight W (kg)

Rubber Ring Thickness

400 55 1250 470 16

600 65 1250 825 18

800 84 12500 1400 18

1000 108 2500 2200 24

Table 5.6.12. Depth of Over Fill ( H )Diameter D (mm)

Type - A Type - B

400 500 < H ≤ 3000 300 ≤ H ≤ 500 or 3000 < H

600 500 < H ≤ 3000 300 ≤ H ≤ 500 or 3000 < H

800 500 < H ≤ 3000 300 ≤ H ≤ 500 or 3000 < H

1000 500 < H ≤ 3000 300 ≤ H ≤ 500 or 3000 < H

Simple Design for Size of Side Ditch

Design size of side ditch for at grade road have function to water catchments rainfall from fly over and auxiliary road decided used the RC square side ditch.

Dimension of side ditch as follow :


Minimum wide size of side ditch is 0.5 m2

Minimal highest of wall side ditch ( T ) 70 cm.

Dimension of side ditch with minimum highest of wall 70 cm, used the value as shown at table :

Table 5.6.13. Vertical Wall of Side Ditch with MasonryDitch sloping

i ( % )L = 100 m L = 200 m L = 300 m L = 400 m

0 – 1High ( cm ) 70 80 90 100

Wide ( cm2 ) 4,900 5,600 6,800 7,000

1 – 2High ( cm ) 70 70 80 90

Wide ( cm2 ) 4,900 4,900 5,600 6,300

2 – 5High ( cm ) 70 70 70 70

Wide ( cm2 ) 4,900 4,900 4,900 5,600

5 - 10High ( cm ) 70 70 70 70

Wide ( cm2 ) 4,900 4,900 4,900 4,900

Note ; T = High

P = Width

Table. 5.6.14. Vertical Wall of Side Ditch without Masonry ( bottom width of ditch D= 50 cm)

Ditch sloping i ( % )

L = 100 m L = 200 m L = 300 m L = 400 m

0 – 1High ( cm ) 50 60 70 80Wide ( cm2 ) 5,000 6,600 8,400 10,400

1 – 2High ( cm ) 50 50 60 70Wide ( cm2 ) 5,000 6,600 6,600 8,400

2 – 5High ( cm ) 50 50 50 50Wide ( cm2 ) 5,000 5,000 5,000 6,600

5 - 10High ( cm ) 50 50 50 50Wide ( cm2 ) 5,000 5,000 5,000 5,000

Where : L = Length of ditch


Fly over Drainage

Inlet box shall be used provided and spacing for depress fly over will be design based on a 25 years frequency storm. The longer of concentration due to turfed swales in medians will result in fewer inlets. Inlets in medians shall be grates or a curb opening inlet turned directly into the flow. Grates have larger opening than gutter inlet.

Drainage for fly over ordinary used the following types as :

a) Deck Drainage

b) Culvert with catch basin.

The deck drainage shall be accommodate of the rainfall in the fly over catchments area with minimum a half of carriageway in maximum available length within transversal and longitudinal drainage.

Culvert with catch basin are used to carry out the water through fly over or embankments road. The type of culvert is pipe, and cross culvert should be to take all the water out of the gutter.

Design of Deck Drainage and Culvert with catch basin as shown below :

drainage design criteria

Documents

years repeat

repeat period

side ditch

wide area

regression

vertical wall

rainfall intensity

catch basin