JABATAN PENGAIRAN DAN SALIRAN (JPS) KEMENTERIAN SUMBER ASLI DAN ALAM SEKITAR (NRE)

MALAYSIA

NOTA KURSUS TAHUN 2006

DETENTION POND COURSE (CONCEPT, DESIGN & CALCULATION)

15 - 17 OGOS 2006

INSTITUT PEMBANGUNAN KOMPETENSI , IPS, KUALA LUMPUR

DISEDIAKAN OLEH

MOHD YAHAYA BIN AHMAD PEng

PRELIMINERIES POND DESIGN CONCEPT

1. SITE SELECTION

(a) Establish Land Owne~hip

structures

Secondary Outlet (Emergency Spillway)

PLAN

SECTION A-A

Figure 20.1 Typical Dry Detention Basin Components

(6) Assess Proximity to Flood-prone Areas

c Determine if site Size is Adequate

(d) Evaluate Topography and Likelihood of Gravity Flow

2. GENERAL DESIGN REQUIREMENTS

Outlet Control

(a) Primary Outlets

Primary outlets for detention basins shall be designed to reduce post-development peak flows to match pre- development peak flows for both the minor and major system design storm ARI in accordance with Section 4.5. Design storm ARIs for the minor and major drainage systems shall be selected in accordance with Table 4.1.

(6) Skcondary Outlets (Emergency Spi//wa ysf

A hazard rating for the basin should be determined and a secondary outlet design ARI selected in accordance with the Federal Government or relevant State Government dam safety guidelines and ANCOLD (1986) and shall be designed to safely pass a minimum design storm of 100 year ARI through the basin.

Bypass Flows

Provision should be made in a dry detention basin to bypass low flows through or around the basin. This is necessary to ensure that the basin floor, particularly if it is grassed, is not inundated by small storms or continually wetted by dry weather baseflow. The minimum amount of bypass should be one half the 1 month ARI flow.

3. DETENTION DESIGN CONCEPTS

The sizing of a detention facility requires an inflow hydrograph, a stage-storage curve, and a stage-discharge curve (sometimes called a rating curve). Inflow hydrographs for a range of design storm durations must be routed through the basin to determine the maximum storage volume and water level in the basin corresponding to the maximum allowable outflow rate.

The design storm duration that will produce the maximum storage volume in a basin will vary depending on catchment, rainfall, and basin outflow characteristics, and is typically somewhere between one and three times the peak flow time of concentration for the basin catchment. The design storm duration that produces the maximum storage volume is called the critical duration.

Inflow Hydrographs

Various method can be use such as Time Area Method, Non Linear Resevoir Method, Kinematic Wave Method and Rational Method Hydrograph Method.

Stage-Storage Relationship ( Stage vs Storage )

A stage-storage relationship defines the relationship between the depth of water and storage volume in the storage facility. The volume of storage can be calculated by using simple geometric formulas expressed as a function of storage depth.

storage (Ip

Figure 20.2 Typical Stage-Storage Curve

Stage-Discharge Relationship ( Stage vs Discharge)

A stage-discharge curve defines the relationship between the storage water depth and the discharge or oufflow from a storage facility. A single composite stage-discharge curve should be developed2for each design storm outlet arrangement, which requires consideration of the stage and discharge rating relationship for each outlet component.

Figure 20.3 Composite Stage-Discharge Curve

0 5 10 15 20 25 30

Discharge (curnec)

Storage Discharge - Discharge Relationship ( Storage Discharge Function vs Discharge)

4. BASIN CONFIGURATION

Classification

An embankment that raises the water level a specified amount as defined by the appropriate dam safety group (generally 1.5 m to 3 m or more above the usual mean low water height, when measured along the downstream toe of the embankment to the emergency spillway crest), is classified as a dam.

Maximum Pond Depth

The maximum pond depth within the basin should not exceed 3.0 m under normal operating conditions for the maximum design flow for which the primary outlets have been designed, i.e. the maximum design storm ARI flow that does not cause the emergency spillway to operate under normal design conditions.

Top Widths

Minimum recommended embankment top widths are provided in Table 20.1.

Table 20.1 Minimum Recommended Top Width for Earthen Embankments (USDA, 1982)

Height of Embankment (m)

Under 3

3 to 4.5

Top Width (m>

2.4

3.0

Side Slopes

For ease of maintenance, the side slopes of a grassed earthen embankment and basin storage area should not be steeper than 4(H):l(V). However, to increase public safety and facilitate ease of mowing, side slopes of 6(H): 1(V) (or flatter) are recommended.

Bottom Grades

The floor of the basin shall be designed with a minimum grade of l0/0 to provide positive drainage and minimise the likelihood of ponding.

Freeboard

The elevation of the top of the settled embankment shall be a minimum of 0.3 m above the water surface in the detention basin when the emergency spillway is operating at maximum design flow.

5. PRIMARY OUTLET DESIGN

Primary outlets are designed for the planned release of water from a detention basin. Basin outlets are ordinarily uncontrolled (i.e. without gates or valves), and may be a single stage outlet structure or several outlet structures combined to provide multi-stage outlet control.

(a) Pipe or Box Culvert (d) Weir Overflow Spillway

(b) Riser Structure Cross-section

(single and multi-level outlets)

-. . . . .. . . .. . . .. . . . . . . . .. .-

View from Downstream

(e) Slotted Outlet (c) Drop Inlet Pit

(surcharge pit or culvert outlet)

Figure 20.4 Typical Detention Basin Primary outlet^

Orifices

For a single circular orifice, illustrated in Figure 0.5(a), the orifice flow can be determined using Equation 0.1.

where,

Q = the orifice flow rate (m3/s) Cd = orifice discharge coefficient (0.40 - 0.62)

A, = area of orifice (m2), ~r 0 3 4 Do = orifice diameter (rn)

H, = effective head on the orifice measured from the centre of the opening (m) g = acceleration due to gravity (9.81 m/s2)

4 (a) Free Fall

(b) Single (Submergd)

(c) Multple

Figure 20.5 Definition Sketch for Orifice Flow

Weirs

(a) Sharp-Crested Weirs

Typical sharp-crested weirs are illustrated in Figure 20.6. Equation 20.2 provides the discharge relationship for sharp-crested weirs with no end contractions (illustrated in Figure 20.6(a)).

where,

Q = weir discharge (m3/s)

Cm= 1.81 + 0.22 (HIH,), sharp-crested weir discharge coefficient B = weir base width (rn) H = head above weir crest excluding velocity head (m)

(a) No end contractions (b) With end contractions

(c) Section (d) Section

Figure 20.6 Sharp-Crested Weirs

(b) Broad-Crested Weir

The equation typically used for a broad-crested weir is:

where,

Q = weirdischarge (m3/s)

CBCW= broad-crested weir coefficient B = weir base width (m)

H = effective head above weir crest (m)

(c) V-Notch Weir

The discharge through a V-notch weir is shown in Figure 0.7 and can be calculated using:

Q = 1.38 tan (: ) H

where,

Q = weir discharge (m3/s)

6 = angle of V-notch (degrees) H = head on apex of V-notch (m)

(d) Proportional Weir

Q = 2.PIa0.' b ( H -q)

Section A-A

Figure 20.7 V-Notch Weir

L 1

where,

Q = weir discharge (m3/s) H = head above horizontal sill (m) Dimensions a, b, x and y are as shown in Figure 20.8.

Figure 20.8 Proportional Weir Dimensions

Culverts

Pipe or box culverts are often used as outlet structures for detention facilities. The design of these outlets can be for either single or multi-stage discharges

Erosion Protection

(a) Primary Outlets

(6) Downstream Waterway

6. SECONDARY OUTLET DESIGN

The purpose of a secondary outlet (emergency spillway) is to provide a controlled overflow for flows in excess of the maximum design storm ARI for the storage facility.

flattening of the downstream embankment face armouring the embankment crest and downstream face using regulated floodplain delineation and occupancy restrictions downstream representative of conditions without the detention storage providing extra waterway capacity downstream using a wide embankment crest such as is common with urban roads and streets (where rapid failure seldom occurs due to modest overtopping depths) using non-eroding embankment material such as roller compacted concrete using small tributary basins, where the rate and volume of discharge involved are limited, resulting in overtopping flows of short duration and non-hazardous proportions

Overflow Weir

The most common type of emergency spillway used is a broad-crested overflow weir cut through original ground next to the embankment. The transverse cross-section of the weir cut is typically trapezoidal in shape for ease of construction.

Q = C, B H;.' (20.6)

Where,

Q = emergency spillway discharge (m3/s)

CSp = spillway discharge coefficient B = emergency spillway base width (m)

Hp = effective head on the spillway crest (m)

The discharge coefficient CSp in Equation 20.6 varies as a function of spillway base width and effective head. Design values for CSp are provided in Design Chart 20.2.

7. PUBLIC SAFETY

Retarding basins should be provided with signs that clearly indicate their purpose and their potential danger during storms. Signs should be located such that they are clearly visible at public access points and at entrances and exits to outlet structures.. Gratings or trash racks may be used to help prevent this happening. A pipe rail fence should be provided on steep or vertical drops such as headwalls and wingwalls at the inlet and outlet to a primary outlet structure to discourage public access.

8. LANDSCAPING

Aesthetics of the finished facility is therefore extremely important. Wherever possible, designs should incorporate naturally shaped basins with landscaped banks, footpaths, and selective planting of vegetation to help enrich the area and provide a focal point for surrounding development.

9. OPERATION AND MAINTENANCE

Consultation Planned Maintenance and Inspection Effect of Design on Maintenance Costs Grassed Areas and Embankments Waterways Primary Outlets Sediment Removal Structural Repairs and Replacement

STORM PAY

Quick Start Guide

Version 1.0 Feb 2006

Perunding Asnol Yahaya

Developing A Storm Pay Project

To develop a model, the user must complete the following steps:

Create a new project. Calculating a Precipitation.

The user must always start the storm pay and come back to main window after data input using a input box on colour and view a result using a output box by click &?%.

Main window The user can refer Urban Stormwater Management Manual, MSMA (2000) for further detail and description when using a Storm Pay.

Create a New Project

At How to use worksheet, create a new project by moving a mouse to a button box under Input in General information at Catchment as shown below.

Precipitation - - + - - - - - ~ - - - ~ F:- domain storm pay r e ~ proposd.xk - ~nput!~ l ) .

Enter a "project title", "state", "nearest hydrology station" and "area of development" in General Information at I n ~ u t worksheet as shown below.

ProJect tile. t I - -- - -- - POND 1

State : 1 Perak 1 I t I

Calculating a Precipitation

In calculating a precipitation, the user needs to: calculates a time of concentration calculates a intensity selection of intensity, and calculate a loss and excess rainfall

Time of concentration

At How to use worksheet, before calculated a precipitation at selected duration, td, the user must calculated tc pre and tc post by moving a mouse to a button box under Input in Time of concentrati~on at Precipitation as shown below.

Enter a "length", "slope", "n manning", "area" and "wetted parameter" in Time of Concentration at Input worksheet as shown below.

to, min - Length, m I 840 I Slope, % -- n manning P

-- M, min

Length, m

Either tc pre or tc post, to view the output, moving a mouse to a button box under Output in time of concentration at Precipitation as shown below.

The output as shown in tcpre and tcpost worksheet.

IS

6.01 1

2

6

Slope, W P -- n manning ----- Area, A (m2] ---.--

I

--- V- - - -----. --

Wetted parameter, P (ml I 1

Intensity

At How to use worksheet, to calculated a intensity at selected duration, td, for selected system, the user can moving a mouse to a button box under Input in Intensity at Precipitation as shown below.

Enter a "Fd", "AN at selected system", "a, b, c & d", and/ or "deduction factor" in Intensity at Input worksheet as shown below.

' For less than 2 ARC--+ 1 Deduction factor = 1

The output as shown in rfall insity minorari, rfall insity majorari and rfall insity emergency worksheet.

Selection of intensity

At How to use worksheet, the user can moving a mouse to a button box under Input in Intensity and temporal pattern at Selection of Intensity as shown below.

At Intenct temp petrn worksheet, for selection of intensity, the user must related to tc post. The selection of intensity must start from 0.5 tc post to 3 tc post. The value for selected tc and intensity for selected system must gain from rfall insity minorari, rfall insity majorari and rfall insity emergency worksheet. For values and referred table for temporal pattern, the user must refer to MSMA. Make sure the values represented selected tc (0.5 tc post to 3 tc post) as shown on Tables below.

Table 13.81 emo oral patterns - west coast of pemwxr m w i a I I i I i

FraGtion of Rainfall in Each lime Petiod I

Loss and excess rai~fall

The method used in calculating Loss and excess rainfall is Loss Method. At How to use worksheet, either for pre-development or post-development, at selected ART, the user can calculated loss and excess rainfall by moving a mouse to a button box under Input in Loss and excess rainfall at Precipitation as shown below.

Enter a "initial losses", "% pervious", "& impervious7', and "% propotional loss" in loss & excess rainfall Input worksheet as shown below.

Propotionctl loss . % I 20 I I o I Impervious, X -.--- ---- . - .- - 0 I \ so ' I

I "----

Propotional toss. % 20 0 I

1 Fram summary hydrogroph, ! -u !

-- I - i I

L

mlMhod

lime kea Method

A1

ARI P o r m d 0.5 tc t 2tc 3tc

"

Minor AR I tp [min] 25 25 40 &I .-

I QO fm31s) I 7.361 I 4- I Max. vol. estimated [m'l I 8341 1 ---t

llreo for pre dm., ma

-

0.5 tc

3461 S

A2 1 3461 .S

keo for port dew., mZ

tc

3461 .5

3461.5

0.5 1,

3461 .5

3461.5

- --- - - Major ARI

- tinergency ---. -- ---- --- -

--------- - -- -

t,

3461.5

3461.5

Max. vol. estimated [m')

ti (min)

tp [minl

F

ti [min]

tp [min)

Qo [m3/s]

Max. vol. estimated (m3]

2 k

3461.5

3461.5

7446

40, 25

40

25

8.251

8627

3t,

71 923.0

126730.0

55.

55

25

85

I

1 35

251 40

85

40

60

-

135

60 I

- -- - -- ---- --- -

pond parameter 1 I 1 I 1 ----- Stalt detention level 0.0 m

Start invert level i 31.00 m - i -

--- Max. bund high 32.50 m / Max. high when reach max. volume 32.10 m I

number cliameter

Area mmz

diameter

H

0.00

0.10

0.20

0.30

20

150

0.02

1 7673.75

0.15

0.075

Ho

0.000

0.025

0.125

0.225

rnM

m m

Q m3/s (basis)

0.000

0.153

0 343

0.4mf

I Time lndcx I Inflow l 1 Inflow l 1 Inflow l 1

APPENDIX

0.0.1 Polynomial Approximation of IDF Curves

Polynomial expressions in the form of Equation 0.1 have been fitted to the published IDF curves for the 35 main citiesltowns in Malaysia.

= a + b ln(t) + c(ln(t,l,I2 + d( l t~ ( t ) ) ~ (0.1)

where,

R4 = the average rainfall intensity (mm/hr) for ARI and duration t

R = average return interval (yti3n)

t = duration (minutes)

a to d are fmng constants dependent on ARI.

The design rainfall depth Pd for a short duration d (minutes) is given by, pd =&I -F~(P60 - 5 0 ) (0.2)

where Pso, PbO are the 30-minute and 60-minute duration rainfall depths respectively, obtained from the published design curves. FD is the adjustment factor for storm duration Equation 0.2 should be used for durations less than 30 minutes. For durations between 15 and 30 minutes, the results should be checked against the published IDF curves. The relationship is valid for any ARI within the range of 2 to 100 years.

Note that Equation 0.2 is in terms of rainfall depth, not intensity. If intensity is required, such as for roof drainage, the depth Pd (mm) is converted to an intensity I (mm/hr)'by dividing by the duration d in hours:

I , Pd d (0.3)

Table 0.1 Values of FD for Equation 0.2

~ u r a t i o 1 , P24h (, mm) I n West Coast East Coast

(minutes) 120 150 All

The following preliminary equations are recommended for calculating the 1,3,6-month and 1 year ARI rainfall intensities in the design storm, for all durations:

0.083 0.25 0.5 where, ID , ID , ID and 'I~ are the required 1,3,6-month and 1-year ARI rainfall intensities for any duration D, and 2 ~ D is the 2-year ARI rainfall intensity for the same duration D, obtained from IDF curves.

(a) Overland Flow Time The formula shown below, known as Friend's formula, should be used to estimate overland sheet flow times. The formula was derived from previous work (Friend, 1954) in the form of a nomograph (Design Chart O.Error! Bookmark not defined.) for shallow sheet flow over a plane surface.

where,

to = overland sheet flow travel time (minutes)

L = overland sheet flow path length (m) n = Manning's roughness value for the surface

S = slope of overland surface (Yo)

Note : Values for Manning's 'n ' are given in Table 0.2. Some texts recommend an alternative equation, the Kinematic Wave Equation. However this theoretical equation is only ,valid for uniform planar homogeneous flow. It is not recommended for practical application.

(b) Overland Flow Time over Multiple Segments Where the characteristics of' segments of a sub-catchment are different in terms of land cover or surface slope, the sub-catchment should be divided into these segments, and the calculated travel times for each combined.

Figure 13.3 V a b d 'pplh for lppe with Tat& 13.3 (source: HP 1,19821

Table 0.2 Values of Manning's 'n' for Overland Flow

Surface Type

ConcreteIAsphal t**

Bare Sand**

Bare Clay- Loam * * (eroded) Gravelled Surface* * Packed Clay**

Short Grass**

Light Turf*

Lawns*

Dense Turf*

Pasture* Dense Shrubbery and Forest Litter*

Manning n

7 Recommended Range

0.01-0.013

0.01 -0.06

0.012-0.033

0.012-0.03

0.02-0.04

0.10-0.20

0.15-0.25

0.20-0.30

0.30-0.40

0.30-0.40

0.35-0.50

* From Crawford and Linsley (1966) - obtained by calibration of Stanford Watershed Model.

** From Engman (1986) by Kinematic wave and storage analysis of measured rainfall runoff data.

However, it is incorrect to simply add the values of to for each segment as Equation 0.1 is based on the assumption that segments are independent of each other, i.e. flow does not enter a segment fiom upstream. Utilising Equation 0.1, the following method (Australian Rainfall & Runoff, 1998) for estimating the total overiand flow travel time for segments in series is recommended. For two segments, termed A and B (Figure 0.1):

t ~ o t a l = t ~ ( b ) + ~ B ( L ~ + L B ) - t ~ ( ~ ) (0.6a)

where,

LA = length of flow for Segment A

LB = length of flow for Segment 6

~ A W ) = time of flow calculated for Segment A over length LA

tBL..) =time for Segment B over the lengths indicated

For each additional segment, the following time value should be added: t~ = ~~(LT~I ) - ti(Lrota1 - 4 ) (0.6b)

where,

tadd = time increment for additional segment

LTotal = total length of flow, including the current segment i

L j = length of flow for segment i

t,( ...) = time for the segment i over the lengths indicated

Segment Segment

B

\ \ \ \ \ \ \

Travel Time

Figure 0.1 Overland Flow over Multiple Segments

This procedure must be applied iteratively because the travel time is itself a function of rainfall intensity.

(c) Roof Drainage Flow Time While considerable uncertainty exists in relation to flow travel time on roofs, the time of flow in a lot drainage system to the street drain, or rear of lot drainage system is generally very small for residential lots and may be adopted as the minimum time of 5 minutes (Chapter 23). However, for larger residential, commercial, and industrial developments the travel time may be longer than 5 minutes in which case it should be estimated using the procedures for pipe and/or channel flow as appropriate.

(d) Kerbed Gutter Flow Time The velocity of water flowing in kerbed gutters is affected by:

the roughness of the kerb, gutter and paved surface

the cross-fall of the pavement

the longitudinal grade of the kerbed gutter

the flow carried in the kerbed gutter

The flow normally varies along the length of a kerbed gutter due to lateral surface inflows. Therefore, the flow velocity will also vary along the length of a gutter. As the amount of gutter flow is not known for the initial analysis of a sub-catchment, the flow velocity and hence the flow time cannot be calculated directly. An initial assessment of the kerbed gutter flow time must be made. An approximate kerbed gutter flow time can be estimated from Design Chart O.Error! Bookmark not defined. or by the following empirical equation:

where,

t, = kerbed gutter flow time (minutes)

L = length of kerbed gutter b w (m)

S = longitudinal grade of the kerbed gutter (%)

Equation 0.2 should only be used for L < 100 metres. Kerbed gutter flow time is generally only a small portion of the time of concentration for a catchment. The errors introduced by these approximate methods of calculation of the flow time result in only small errors in the time of concentration for a catchment, and hence high accuracy is not required.

(e) Channel Flow Time

The time stormwater takes .to flow along a open channel may be determined by dividing the length of the channel by the average velocity of the flow. The average velocity of the flow is calculated using the hydraulic characteristics of the open channel. The Manning's Equation is recommended for this purpose:

1 V = - R 2 / 3 ~ 1 / 2

n (0.8a)

From which, n.L t,, = - ~ 2 1 3 ~ 1 / 2 60

(0.8b)

where,

V = average velocity (m/s)

n = Manning's roughness coefficient

R = hydraulic radius (m)

S = friction slope (m/m) L = length of reach (m)

tch = travel time in the channel (minutes)

Where an open channel has varying roughness or depth across its width it may be necessary to sectorise the flow and determine the average velocity of the flow, to determine the flow time.

(f) Pipe Flow Time

The velocity V in a pipe running just full can be estimated from pipe flow charts such as those in Chapter 25, Appendix 25.B where the flow, pipe diameter, roughness and pipe slope are known. The time of flow through pipe, t , , is then given by:

L t -- P - v (0.9)

where,

L =: pipe length (m) V = average pipe velocity (m/.s)

0.0.2 Time of Concentration for Natural Catchment

For natural/landscaped catchments and mixed flow paths the time of concentration can be found by use of the Bransby-Williams' Equation 0.10 (AR&R, 1987). In these cases the times for overland flow and channel or stream flow are included in the time calculated. Here the overland flow time including the travel time in natural channels is expressed as:

where,

t, = the time of concentration (minute)

F, = a conversion factor, 58.5 when area A is in km2, or 92.5 when area is in ha

L = length of flow path from catchment divide to outlet (km)

A = catchment area (km2 or ha)

S = slope of stream flow path (m/km)

0.0.3 Ratknal Formula

The Rational Formula is one of the most frequently used urban hydrology methods in Malaysia. It gives satisfactory results for small catchments only.

The formula is:

where,

Q, = yyear ARI peak flow (m3/s) C = dimensionless runoff coefficient

''1, = yyear ARI average rainfall intensity over time of concentration, tc, (mm/hr)

A = drainage area (ha)

Table 4.3 Design Storm ARIs for Urban Stormwater Systems

(See Note 1) Quantity

Type of Development

Open Space, Parks and Agricultural Land in urban areas

Average Recurrence Interval (ARI) of Design Storm (year)

Residential:

Low density

Medium density

High density

Commercial, Business and Industrial - Other than CBD

Commercial, Business, Industrial in Central Business District (CBD) areas of Large Cities

Quality

3 month ARI (for all types of development 1

Table 14.4 Recommended Loss Models and Values for Hydrograph

-

Condition

[mpervious Areas

Pervious Areas

Loss Model

Initial loss-Loss rate

-

Initial loss - proportional loss, or - Initial loss-Loss rate,

- Horton model

Initial loss: 1.5 mm

Recommended Values

Loss rate: 0 mrnkr

-

Initial loss: 10 mm

Initial loss: 10 mm for all soils

(i) Sandy open structured soil (ii) Loam soil (iii) Clays, dense structured soil (iv) Clays subject to high shrinkage and

in a cracked state at start of rain

~nitial Infiltration Capacity fo A. DRY soils (little or no vegetation) Sandy soils: 125 mmihr Loam soils: 75 mmihr Clay soils: 25 mmihr For dense vegetation, multiply values given in A by 2 B. MOIST soils Soils which have drained but not dried out: divide values from A by 3 Soils close to saturation: value close to saturated hydraulic conductivity Soils partially dried out: divide values from A by 1.5-2.5 Recommended value of k is 4hr

Proportional Loss: 20% of rainfall

Loss rate:

10 - 25 mmhr 3 - 10 mmhr 0.5 - 3 m d h r 4 - 6 mmihr

Ultimate Infiltration Rate fc (mmhr), for Hydrologic Soil Group (see Note) A 10 - 7.5 B 7.5 - 3.8 C 3.8 - 1.3 D 1.3 - 0

Note: Hydrological Soil Group corresponds to the classification given by the U.S. Soil Conservation Service. Well drained sandy soils are "A"; poorly drained clayey soils are "D". The texture of the layer of least hydraulic conductivity in the soil profile should be considered. Caution should be used in applying values from the above table to sandy soils (Group A). Source: XP-SWMM Manual (WP- Software, 1995).

Table O.Al Coefficients for the IDF Equations for the Different Major Cities and Towns in Malaysia

State Location

I / Highland

Pahang Kuantan

Terengganu Kuala Dungun I Terengganu

I Kuala I Terengganu

(30 5 t 5 1000 min)

Data Period ARI

(year)

Coefficients of the IDF Polynomial 1 Equations I

APPENDIX 0.A DESIGN TEMPORAL PATTERNS

Table O.B1 Temporal Patterns -West Coast of Peninsular Malaysia

n, 10 min Duration

Duration (min)

10 15 30 60 120 180 360

Time Period

1 2 3

Time Period

No. of Time

Periods 2 3 6

12 8 6 6

1 2 3 4 5 6 7 8 9 1 0 1 1 I 2

Time Period

Fraction of Rainfall in Each Time Period

0.570 0.430 - 0.320 0.500 0.180 - 0.160 0.250 0,330 0.090 0.110 0.060 - 0.039 0.070 0.168 0.120 0.232 0.101 0.089 0.057 0.048 0.031 0.028 0.017 0.030 0.119 0.310 0.208 0.090 0.119 0.094 0.030 - 0.060 0.220 0.340 0.220 0.120 0.040 - 0.320 0.410 0.110 0.080 0.050 0.030 -

180 minute Duration I

1 2 3 4 5

Time Period 1

l ime Per~od I 1 2 1 4

120 minute Durabon

0.5 r

1 2 3 4 5 6 7 8

Time Per~od

I 360 minute Duration

I 1 2 3 4 5 6

lime Period

No. of

(min) Periods

120 180 360

10 min Duration

Table 0.B2 Temporal Patterns - East Coast of Peninsular Malaysia '

Fraction of Rainfall in Each Time Period

I 2

Time Period

15 min Duratton

1 2 3

Time Jer~od

60 minute Durat~on

0.3 1

1 2 3 4 5 6 7 8 9 1 0 1 1 1 2

Time Period

180 minute Duration

1 2 3 4 5 6

Time Period

(# these patterns can also be used in Sabah and

30 minute Duration

1 2 3 4 5 6

Time Period

1 2 3 4 5 6 7 8 Time Per~od

360 minute Duration

1 2 3 4 6

lime Period

ak, until local studies are carried out)

CULVERT:

APPENDIX 27.A DESIGN FORM, CHARTS AND NOMOGRAPHS

I I H Conb-d hiornograph - COlXX* Pipe CuIvert

Inlet Contrd Nomograph -8ox C U M 27-24 - Irklet Corrtrd Nomograph - Cormgated Metal Pipe (CMP) Cuhrert 27-25

Rielathe Discharge, V e l o g and Hydraulic Radius in Part-full Pipe 27-26 Row

Relative Discharge, Velocity and Hydraulic Radius in Part-full Box 27-27 Culvert Flaw

Csitical Depth in a Circular Pipe 27-28 - Critical Depth in a Rectangular (Box) Sectjon 27-29

Outkt Control Nomograph - Concrete Pipe Culvert Rowing Full with 27-30 n = 0.012

-

Outfet Control Nomograph - Concrete Box Cutweft Rowing Full wlth 27-31 n = 0.012

Outkt Control Nomograph - Cr#Ngated Metal Rpe (CMP) Flowing 27-32 M I with n = 0.024 -

en-

REKABENTUK KOLAM TAKUNGAN MENGGUNAKAN MSMA Dari 15 Hingga 17 Ogos 2006

Di Institut Pembangunan Kompetensi JPS KL Bahagian Latihan & Kemajuan Kerjaya

JPS Malaysia

DETENTION POND COURSE (CONCEPT, DESIGN & CALCULATION)

15 - 17 OGOS 2006

INSTITUT PEMBANGUNAN KOMPETENSI , IPS, KUALA LUMPUR

DISEDIAKAN OLEH

MOHD YAHAYA BIN AHMAD PEng

'RELIMINERIES POND DESIGN CONCEPT

1. SITE SELECTION

(a) Establish Land Owne/sh@

PLAN

SECTION A-A

Figure 20.1 Typical Dry Detention Basin Components

(b) Assess Pro~inity to Flood-prone Areas

(c) Determine if Site Size 13 Adequate

(d) Evaluate Topography and Likelihood of Gram Flow

2. GENERAL DESIGN REQUIREMENTS

Outlet Control

(a) Primary Outlets

Primary outlets for detention basins shall be designed to reduce post-development peak flows to match pre- development peak flows for both the minor and major system design storm ARI in accordance with Section 4.5. Design storm ARIs for the minor and major drainage systems shall be selected in accordance with Table 4.1.

(b) Secondary Outlets (Emergency Spillways)

A hazard rating for the basin should be determined and a secondary outlet design ARI selected in accordance with the Federal Government or relevant State Government dam safety guidelines and ANCOLD (1986) and shall be designed to safely pass a minimum design storm of 100 year ART through the basin.

Bypass Flows

Provision should be made in a dry detention basin to bypass low flows through or around the basin. This is necessary to ensure that the basin floor, particularly if it is grassed, is not inundated by small storms or continually wetted by dry weather baseflow. The minimum amount of bypass shouid be one half the 1 month ARI flow.

3. DETENTION DESIGN CONCEPTS

The sizing of a detention facility requires an inflow hydrograph, a stage-storage curve, and a stage-discharge curve (sometimes called a rating curve). Inflow hydrographs for a range of design storm durations must be routed through the basin to determine the maximum storage volume and water level in the basin corresponding to the maximum allowable outflow rate.

The design storm duration that will produce the maximum storage volume in a basin will vary depending on catchment, rainfall, and basin oufflow characteristics, and is typically mewh here between one and three times the peak flow time of concentration for the basin catchment. The design storm duration that produces the maximum storage volume is called the critical duration.

Inflow Hydrographs

Various method can be use such as Time Area Method, Non Linear Resevoir Method, Kinematic Wave Method and Rational Method Hydrograph Method.

Stage-Storage Relationship ( Stage vs Storage )

A stage-storage relationship defines the relationship between the depth of water and storage volume in the storage facility. The volume of storage can be calculated by using simple geometric formulas expressed as a function of storage depth.

=rase (*

Figure 20.2 Typical Stage-Storage Curve

Stage-Discharge Relationship ( Stage vs Discharge)

A stage-discharge curve defines the relationship between the storage water depth and the discharge or oufflow from a storage facility. A single composite stage-discharge curve should be developed,for each design storm outlet arrangement, which requires consideration of the stage and discharge rating relationship for each outlet component.

Figure 20.3 Composite Stage-Discharge Curve

Storage Discharge - Discharge Relationship ( Storage Discharge Function vs Discharge)

4. BASIN CONFIGURATION

Classification

An embankment that raises the water level a specified amount as defined by the appropriate dam safety group (generally 1.5 m to 3 m or more above the usual mean low water height, when measured along the downstream toe of the embankment to the emergency spillway crest), is classified as a dam.

Maximum Pond Depth

The maximum pond depth within the basin should not exceed 3.0 m under normal operating conditions for the maximum design flow for which the primary outlets have been designed, i.e. the maximum design storm ARI flow that does not cause the emergency spillway to operate under normal design conditions.

Top Widths

Minimum recommended embankment top widths are provided in Table 20.1.

Table 20.1 Minimum Recommended Top Width for Earthen Embankments (USDA, 1982)

Under 3

Side Slopes

For ease of maintenance, the side slopes of a grassed earthen embankment and basin storage area should not be steeper than 4(H):l(V). However, to increase public safety and facilitate ease of mowing, side slopes of 6(H): 1(V) (or flatter) are recommended.

Bottom Grades

The floor of the basin shall be designed with a minimum grade of 1% to provide positive drainage and rninimise the likelihood of ponding.

Freeboard

The elevation of the top of the settled embankment shall be a minimum of 0.3 m above the water surface in the detention basin when the emergency spillway is operating at maximum design flow.

5. PRIMARY OUTLET DESIGN

Primary outlets are designed for the planned release of water from a detention basin. Basin outlets are ordinarily uncontrolled (i.e. without gates or valves), and may be a single stage outlet structure or several outlet structures combined to provide multi-stage outlet control.

(a) Pipe or Box Culvert (d) Weir Overflow Spillway

(b) Riser Structure Cross-section

(single and multi-level outlets)

(c) Drop Inlet Pit (surcharge pit or culvert outlet)

-. . . .. .. . . - . . :______.._..-

View from Downstream

(e) Slotted Outlet

Figure 20.4 Typical Detention Basin Primary Outlets

Orifices

For a single circular orifice, illustrated in Figure O.S(a), the orifice flow can be determined using Equation 0.1.

where,

Q = the orifice flow rate (m3/s) Cd = orifice discharge coefficient (0.40 - 0.62)

A, = area of orifice (m2), n 0 8 4 Do = orifice diameter (m)

H, = effective head on the orifice measured from the centre of the opening (m) g = acceleration due to gravity (9.81 m/s2)

(a) Free Fall

(b) Single (Submergd)

(c) Multple

Figure 20.5 Definition Sketch for Orifice Flow

Weirs

(a) Sharp-Crested Weirs

Typical sharp-crested weirs are illustrated in Figure 20.6. Equation 20.2 provides the discharge relationship for sharp-crested weirs with no end contractions (illustrated in Figure 20.6(a)).

where,

Q = weir discharge (m3/s)

CScw= 1.81 + 0.22 (H/H,), sharp-crested weir discharge coefficient B = weir base width (m)

H = head above weir crest excluding velocity head (m)

(a) No end contractions (b) With end contractions

(c) Section (d) Section

Figure 20.6 Sharp-Crested Weirs

(b) Broad-Crested Weir

The equation typically used for a broad-crested weir is:

Q =c- B (20.3)

where,

Q =

CBCW= B = H =

weir discharge (m3/s)

broad-crested weir coefficient weir base width (m) effective head above weir crest (rn)

(c) V-Notch Weir

The discharge through a V-notch weir is shown in Figure 0.7 and can be calculated using:

Q = 1.38 tan (; ) H

where,

Q = weir discharge (m3/s) B = angle of V-notch (degrees)

H = head on apex of V-notch (rn)

Section A-A

Figure 20.7 V-Notch Weir

(d) Proportional Weir

where,

Q = weir discharge (m3/s) H = head above horizontal sill (m) Dimensions a, b, x and y are as shown in Figure 20.8.

Figure 20.8 Proportional Weir Dimensions

Culverts

Pipe or box culverts are often used as outlet structures for detention facilities. The design of these outlets can be for either single or multi-stage discharges

Erosion Protection

(a) Primary Outlets

(b) Downstream Waterway

6. SECONDARY OUTLET DESIGN

The purpose of a secondary outlet (emergency spillway) is to provide a controlled ovefflow for flows in excess of the maximum design storm ARI for the storage facility.

flattening of the downstream embankment face armouring the embankment crest and downstream face using regulated floodplain delineation and occupancy restrictions downstream representative of conditions without the detention storage providing extra waterway capacity downstream using a wide embankment crest such as is common with urban roads and streets (where rapid failure seldom occurs due to modest overtopping depths)

using non-eroding embankment material such as roller compacted concrete using small tributary basins, where the rate and volume of discharge involved are limited, resulting in overtopping flows of short duration and non-hazardous proportions

Overflow Weir

The most common type of emergency spillway used is a broad-crested overflow weir cut through original ground next to the embankment. The transverse cross-section of the weir cut is typically trapezoidal in shape for ease of construction.

Q = C,, B H:.' (20.6)

Where,

Q = emergency spillway discharge (m3/s) CSP = spillway discharge coefficient B = emergency spillway base width (m)

H, = effective head on the spillway crest (m)

The discharge coefficient CSp in Equation 20.6 varies as a function of spillway base width and effective head. Design values for CSp are provided in Design Chart 20.2.

7. PUBLIC SAFETY

Retarding basins should be provided with signs that clearly indicate their purpose and their potential danger during storms. Signs should be located such that they are clearly visible at public access points and at entrances and exits to outlet structures.. Gratings or trash racks may be used to help prevent this happening. A pipe rail fence should be provided on steep or vertical drops such as headwalls and wingwalls at the inlet and outlet to a primary outlet structure to discourage public access.

8. LANDSCAPING

Aesthetics of the finished facility is therefore extremely important. Wherever possible, designs should incorporate naturally shaped basins with landscaped banks, footpaths, and selective planting of vegetation to help enrich the area and provide a focal point for surrounding development.

9. OPERATION AND MAINTENANCE

Consultation Planned Maintenance and Inspection Effect of Design on Maintenance Costs Grassed Areas and Embankments Waterways Primary Outlets Sediment Removal Structural Repairs and Replacement

STORM PAY

Quick Start Guide

Version 1.0 Feb 2006

Pcrunding Asnol Yahaya

Developing A Storm Pay Project

To develop a model, the user must complete the following steps:

Create a new project. Calculating a Precipitation.

The user must always start the storm pay and come back to main window after data input using a input box on colour and view a result using a output box by click -1,

Main window The user can refer Urban Stormwater Management Manual, MSMA (2000) for further detail and description when using a Storm Pay.

Create a New Project

At How to use worksheet, create a new project by moving a mouse to a button box under Input in General information at Catchment as shown below.

. . Precipitation .+--+---- -+ F:W domain storm pay new propcisal.xk, - Input!Al/

Enter a "project title", "state", "nearest hydrology station" and "area of development" in General Information at Input worksheet as shown below.

Calculating a Precipitation

In calculating a precipitation, the user needs to: calculates a time of concentration calculates a intensiw selection of intensity, and calculate a loss and excess rainfall

Time of concentration

At How to use worlcsheet, before calculated a precipitation at selected duration, td, the user must calculated tc pre and tc post by moving a mouse to a button box under Input in Time of concentration at Precipitation as shown below.

Enter a "length", "slope7', "n manning", "area" and "wetted parameter" in Time of Concentration at Input worksheet as shown below.

n manning

Slope, X n manning I I I 0.011 I Area, A (m') ----

Either tc pre or tc post, to view the output, moving a mouse to a button box under Output in time of concentration at Precipitation as shown below.

The output as shown in tcpre and tcpost worksheet.

Intensity

At How to use worksheet, to calculated a intensity at selected duration, td, for selected system, the user can moving a mouse to a button box under Input in Intensity at Precipitation as shown below.

Enter a "Fd", "ARI at selected system", "a, b, c & d", and/ or "deduction factors' in Intensity at Input worksheet as shown below.

For less than 2 ARC--+ 1 Deduction fuctor = 1 1 I

The output as shown in rfall insity minorari, rfall insity majorari and rfall insity emergency worksh.eet.

Selection of intensity

At How to use worksheet, the user can moving a mouse to a button box under Input in Intensity and temporal pattern at Selection of Intensity as shown below.

---5 F:bubUc domain storm pay-new proposal.xk - ' i i c t temp petrn'

At Intenct temp petrn worksheet, for selection of intensity, the user must related to tc post. The selection of intensity must start from 0.5 tc post to 3 tc post. The value for selected tc and intensity for selected system must gain from rfall insity minorari, rfall insity majorari and rfall insity emergency worksheet. For values and referred table for temporal pattern, the user must refer to MSMA. Make sure the values represented selected tc (0.5 tc post to 3 tc post) as shown on Tables below.

T a b k 13.B1 Temporal patterns - West Coast of Pensvlclr Malaysia

1 1 1 1 I 1 1 1 1

bction of Rdmfall in Each lime Period

Loss and excess rainfall

The method used in calculating Loss and excess rainfall is Loss Method. At How to use worksheet, either for pre-development or post-development, at selected A N , the user can calculated loss and excess rainfall by moving a mouse to a button box under Input in Loss and excess rainfall at Precipitation as shown below.

Enter a "initial losses", "% pervious", "& impervious", and "% propotional loss" in loss & excess rainfall Input worksheet as shown below.

Pervious, X - -- - 100

Propotional loss, 96 --- - -- ----- 20 -- imperv~ous. X -- -*-- -- - -- - - 0

I 80 1

Propotional k s s , % M 0 I

lllelhod

Time kea Melhod

A1

Meo tor pre dev., n2

0.5 tc 1 tc

3461.5 1 3461.5

kea tw pod dm., m2 0.5 1, 1 h. I 2t; I 3t,

3461.5 1 3461.5 3461.5 1 71923.0

I Start invert level 1 I 31.001m 1 bund high 1 high when reach max. vdvme

top surface area in 1

number

Area mm2 17613.75

diameter

-- --"

32.50

32.10

13818

Length,L

m m m2 I

76.W

Width, W I 1 181.82

I 1

APPENDIX

0.0.1 Polynomial Approximation of IDF Curves

Polynomial expressions in the form of Equation 0.1 have been fitted to the published IDF curves for the 35 main citieshowns in Malaysia.

ln(qt) = a + b ln(t) + c(ln(tjy2 + d(ln(t)13 (0.1)

where,

R& = the average rainfall intensity (mmfhr) for ARI and duration t R = average return interval (years)

t = duration (minutes)

a to d are fitting constants dependent on ARI.

The design rainfall depth Pd for a short duration d (minutes) is given by, ' d =40 - F~(P60 - 4 0 ) (0.2)

where P30, P60 are the 30-minute and 60-minute duration rainfall depths respectively, obtained from the published design curves. FD is the adjustment factor for storm duration Equation 0.2 should be used for durations less than 30 minutes. For durations between 15 and 30 minutes, the results should be checked against the published IDF curves. The relationship is valid for any ARI within the range of 2 to 100 years.

Note that Equation 0.2 is in terms of rainfall depth, not intensity. If intensity is required, such as for roof drainage, the depth Pd (mm) is converted to an intensity I (mm1hr)'by dividing by the duration d in hours:

Table 0.1 Values of FD for Equation 0.2

P24h (mm) West Coast East Coast

100 180

The following preliminary equations are recommended for calculating the 1,3,6-month and 1 year ARI rainfall intensities in the design storm, for all durations:

0.083 0.25 0.5 where, Z , I' , ID and 'ZD are the required 1, 3, dmonth and 1-year ARI rainfall intensities for any duration D, and 2~~ is the 2-year ARI rainfall intensity for the same duration D, obtained from IDF curves.

(a) Overland Flow Time The formula shown below, known as Friend's formula, should be used to estimate overland sheet flow times. The formula was derived from previous work (Friend, 1954) in the form of a nomograph (Design Chart O.Error! Bookmark not defined.) for shallow sheet flow over a plane surface.

where,

to = overland sheet flow travel time (minutes)

L = overland sheet flow path length (rn)

n = Manning's roughness value for the surface

S = slope of overland surface (YO)

Note : Values for Manning's 'n ' are given in Table 0.2. Some texts recommend an alternative equation, the Kinematic Wave Equation. However this theoretical equation is only .valid for uniform planar homogeneous flow. It is not recommended for practical application.

(b) Overland Flow Time over Multiple Segments Where the characteristics of segments of a sub-catchment are different in terms of land cover or surface slope, the sub-catchment should be divided into these segments, and the calculated travel times for each combined.

figure 13.3 V h of 2 ~ m for uer?. with Table X3.3 {source: HP 1,1982)

Table 0.2 Values of Manning's In' for Overland Flow

Surface Type

ConcreteIAsphal t**

Bare Sand**

Bare Clay- Loam** (eroded)

Gravelled Surface* * Packed Clay* * Short Grass* * Light Turf? Lawns*

Dense TurfF

Pasture*

Dense Shrubbery and Forest Litter*

Recommended Range

0.01-0.013

0.0 1-0.06

0.012-0.033

0.012-0.03

0.02-0.04

0.10-0.20

0.15-0.25 0.20-0.30

0.30-0.40

0.30-0.40

0.35-0.50

* From Crawford and Linsley (1966) - obtained by calibration of Stanford Watershed Model.

** From Engman (1986) by Kinematic wave and storage analysis of measured rainfall runoff data.

However, it is incorrect to simply add the values of to for each segment as Equation 0.1 is based on the assumption that segments are independent of each other, i.e. flow does not enter a segment from upstream. Utilising Equation 0.1, the following method (Australian Rainfall & Runoff, 1998) for estimating the total overland flow travel time for segments in series is recommended. For two segments, termed A and B (Figure 0.1):

trofd~ = ~ A ( L ~ ) + ~ B ( L ~ + ~ ) - f B(LA) (0.6a)

where,

LA = length of flow for Segment A

LB = length of flow for Segment 6 tNU) = time of flow calculated for Segment A over

length LA

tBc..) =time for Segment 6 over the lengths indicated

For each additional segment, the following time value should be added: tadd = t i ( L w ) - t i ( L , ~ a , - 4 ) (0.6b)

where,

t& = time increment for additi'onal segment

LTm = total length of flow, including the current segment i

Li = length of flow for segment i

t i ( ...) = time for the segment i over the lengths indicated

Segment Segment

B

\ \ \ \ \ \ \

Length b-~,+l~-l Travel Time

Figure 0.1 Overland flow over Multiple Segments

This procedure must be applied iteratively because the travel time is itself a function of rainfall intensity.

(c) Roof Drainage Flow Time While considerable uncertainty exists in relation to flow travel time on roofs, the time of flow in a lot drainage system to the street drain, or rear of lot drainage system is generally very small for residential lots and may be adopted as the minimum time of 5 minutes (Chapter 23). However, for larger residential, commercial, and industrial developments the travel time may be longer than 5 minutes in which case it should be estimated using the procedures for pipe and/or channel flow as appropriate.

(d) Kerbed Gutter Flow Time The velocity of water flowing in kerbed gutters is affected by:

the roughness of the kerb, gutter and paved surface

the cross-fall of the pavement

the longitudinal grade of the kcrbed gutter

the flow carried in the kerbed gutter

The flow normally varies along the length of a kerbed gutter due to lateral surface inflows. Therefore, the flow velocity will also vary along the length of a gutter. As the amount of gutter flow is not known for the initial analysis of a sub-catchment, the flow velocity and hence the flow time cannot be calculated directly. An initial assessment of the kerbed gutter flow time must be made. An approximate kerbed gutter flow time can be estimated from Design Chart O.Error! Bookmark not d e f i n d or by the following empirical equation:

where,

t, = kerbed gutter flow time (minutes)

L = length of kerbed gutter flow (m)

S = longitudinal grade of the kerbed gutter (%)

Equation 0.2 should only be used for L < 100 metres. Kerbed gutter flow time is generally only a small portion of the time of concentration for a catchment. The errors introduced by these approximate methods of calculation of the flow time result in only small errors in the time of concentration for a catchment, and hence high accuracy is not required.

(e) Channel Flow Time

The time stormwater takes to flow along a open channel may be determined by dividing the length of the channel by the average velocity of the flow. The average velocity of the flow is calculated using the hydraulic characteristics of the open channel. The Manning's Equation is recommended for this purpose:

1 V = - R 2 / 3 ~ 1 / 2

n (0.8a)

From which,

t - "'L ~ 2 1 3 s ' I 2

* -60 where,

V = average velocity (mls)

n = Manning's roughness coefficient

R = hydraulic radius (m)

S = friction slope (m/m)

L = length of reach (m)

td, = travel time in the channef (minutes)

Where an open channel has varying roughness or depth across its width it may be necessary to sectorise the flow and determine the average velocity of the flow, to determine the flow time.

(f) Pipe Flow Time

The velocity V in a pipe running just full can be estimated from pipe flow charts such as those in Chapter 25, Appendix 25.B where the flow, pipe diameter, roughness and pipe slope are known. The time of flow through pipe, t , , is then given by:

L t,, =V (0.9)

where,

L = pipe length (m)

V = average pipe velocity (mls)

0.0.2 Time of Concentration for Natural Catchment

For natural/landscaped catchments and mixed flow paths the time of concentration can be found by use of the Bransby-Williams' Equation 0.10 (AR&R, 1987). In these cases the times for overland flow and channel or stream flow are included in the time calculated. Here the overland flow time including the travel time in natural channels is expressed as:

where,

tc = the time of concentration (minute)

F, = a conversion factor, 58.5 when area A is in krn2, or 92.5 when area is in ha

L = length of flow path from catchment divide to outlet (krn)

A = catchment area (km2 or ha)

S = slope of stream flow path (m/km)

0.0.3 Rational Formula

The Rational Formula is one of the most frequently used urban hydrology methods in Malaysia. It gives satisfactory results for small catchments only.

The formula is:

where,

Qy = y year ARI peak flow (m3/s) C = dimensionless runoff coefficient

YIt = yyear ARI average rainfall intensity over time of concentration, tc , (mm/hr)

A = drainage area (ha)

Table 4.3 Design Storm ARIs For Urban Stormwater Systems

Type of Development

(See Note 1)

Open Space, Parlts and Agricultural Land in urban areas

Residential:

Low density

Medium density

High density

Commercial, Business and Industrial - Other than CBD

Commercial, Business, Industrial in Central Business District (CBD) areas of Large Cities

Average Recurrence Interval (AN) of Design Storm (year)

Quantity Quality

3 month ARI (for all types of development 1

Minor System

Major System (see Note 2 and

3)

Table 14.4 Recommended Loss Models and Values for Hydrograph

Condition

[m~ervious 4reas

Pervious Areas

Loss Model

Initial loss-Loss rate

Initial loss - proportional loss, or

Initial loss-Loss rate,

Horton model

Initial loss: 1.5 mm

Recommended Values

Loss rate: 0 mmlhr

Initial loss: 10 mm

Initial loss: 10 mm for all soils

(i) Sandy open structured soil (ii) Loam soil (iii) Clays, dense structured soil (iv) Clays subject to high shrinkage and

in a cracked state at start of rain

Initial Infiltration Capacity fo A. DRY soils (little or no vegetation) Sandy soils: 125 mmhr Loam soils: 75 mm/hr Clay soils: 25 mmhr For dense vegetation, multiply values given in Aby2 B. MOIST soils Soils which have drained but not dried out: divide values from A by 3 Soils close to saturation: value close to saturated hydraulic conductivity Soils partially dried out: divide values from A by 1.5-2.5 Recommended value of k is 4hr

Proportional Loss: 20°/0 of rainfall

Loss rate:

10 - 25 mmhr 3 - 10 mmhr 0.5 - 3 mmhr 4 - 6 mmhr

Ultimate Infiltration Rate fc (mmhr), for Hydrologic Soil Group (see Note)

Note: Hydrological Soil Group corresponds to the classification given by the U.S. Soil Conservation Service. Well drained sandy soils are "A"; poorly drained clayey soils are "D". The texture of the layer of least hydraulic conductivity in the soil profile should be considered. Caution should be used in applying values from the above table to sandy soils (Group A). Source: XP-SWMM Manual (WP- Software, 1995).

Table O.Al Coefficients for the IDF Equations for the Different Major Cities and Towns in Malaysia

State

Pahang

Terengganu

Terengganu

Location

Kaub

Cameron Highland

Temerloh

Kuala Dungun

Kuala Terengganu

(30 I t < 1000 min)

Data Period

APPENDIX 0.A DESIGN TEMPORAL PATTERNS

Table O.B1 Temporal Patterns - West Coast of Peninsular Malaysia ,

0,6 10 min Durahon

Duration (min)

10 15 30 60 120 180 360

1 L

Time Period

15 min Duration

No. of Time

Periods 2 3 6 12 8 6 6

Time Period

Fraction of Rainfall in Each Time Period

0.570 0.430 - 0.320 0.500 0.180 - 0.160 0.250 0.330 0.090 0.110 0.060 - 0.039 0.070 0.168 0.120 0.232 0.101 0.089 0.057 0.048 0.031 0.028 0.017 0.030 0.119 0.310 0.208 0.090 0.119 0.094 0.030 - 0.060 0.220 0.340 0.220 0.120 0.040 - 0.320 0.410 0.110 0.080 0.050 0.030 -

- -

60 mlnute Duration 0.3 ,

1 2 3 4 5 6 7 8 9 1 0 1 1 1 2

Time Period -

180 minute Duration I

1 2 3 4 5

Trne Period 1

30 mlnute Duratton

0.4

1 2 3 4 5 6

Time Period

120 minute Duration

1 2 3 4 5 6 7 8

Time Pertod

360 minute Duration

1 2 3 4 5 6

Tiwe Period

Table 0.B2 Temporal Patterns - East Coast of Peninsular Malaysia '

10 min Duration I 1 15 mln Durat~on

Duration

(min)

10 15 30 60 120 180 360

1 2 3 4 5 6 7 8 9 1 0 1 1 1 2

Time Period

180 minute Duration

No. of Time

Periods 2 3 6 12 8 6 6

1 2 3 4 5 6

Time Period

Fraction of Rainfall in Each Time Period

0.570 0.430 - 0.320 0.500 0.180 - 0.160 0.250 0.330 0.090 0.110 0.060 - 0.039 0.070 0.168 0.120 0.232 0.101 0.089 0.057 0.048 0.031 0.028 0.017 0.030 0.119 0310 0.208 0.090 0.119 0.094 0.030 - 0.190 0.230 0.190 0.160 0.130 0.100 - 0.290 0.200 0.160 0.120 0.140 0.090 -

30 minute Durahon

Time Perrod

1 2 3 4 5 6 7 8

Time Period

1 360 minute Duration

1 2 3 4 5 6

Time Period

(# these patterns can also be used in Sabah and Sarawak, until local studies are carried out)

CULVERT:

APPENDIX 27A DESIGN FORM, CHARTS AND NOMOGRAPHS

1 27.2 1 Entrance ~oss~oef~c ien ts 1 27-22

Ir~let Wef Nomograph - Cormgated Metal Pipe (OIP) Culvert 27-25

Relative Discharge, Velodty and Hydraulic Radius in Pwt-full Pipe 27-26

I -- -

27.7 1 -

Wative Discharge, Velodty and Hydraulic Radius in Part-full Box C~ulwrt Row

27-27

27.8

27.9 1 27.10 1 Outlet Cmtrd Nomograph -Corn& Pipe CUM flowing Full with n = 0.012

aiticai Depth in a Circular Pipe

Oitical Depth in a Rectangular (Box) Section

27-30

Outlet Contrd Normgraph - Cmmte f3ox Cukrt Rowing Full with n = 0.012

27-28

27-29

27-3 1

Control Nwnograph - Cormgated Metal Rpe (CMP) flowing Full with n = 0.024

27-32

CASE STUDY . I _I- j -

USING MSMA CONCEPT TO SOLVE FLOOD PROBLEM

FOR SG. KERAYONG - SRI JOHOR POND Lllu.lOlb- i

-II-"" !

i k. Chin Cbong Wing

Penganh

i P S Wayah Perukutwn

Klang River Basin

Banfir Di Kg. C h e m bw, Sun@ Kenyong

p d a a uur row

Jab" I(bng LIrm 4 'h

Butiran Kontrak -

Nama Kontraktor : Kettrade Sdn. Bhd. j Nilai Kontrak : RM 95.150.000.00 1 LOA : 28 Nov 2005 Tarikh Mula : 3 Jan 2006 Tarikh Siap : 2 Julai 2008

&$c JPS U'IMYAH PERSEKUnANi RTB LEMBAH SUNGAI KL4NG

LOKASI PROJEK

r 5.rr .=A I

Organisasi Projek

DESIGN PEAK FLOW

POND EFFECT OF THE INFLOW AND OUTFLOW FLOW HYDROGRAPH

FLOOD HYDROGRAPH

Flow Distribution at Diversion Modelled by HECR4S

Elevation-Area-Storage Curves of Seri-Johor Pond

Diversion1 Inlet Works A I

- Doenion n o r k flood r l o r l g paad Pond iolct and oullrl works Outlet channel Other ancillary works

Bed level 30 50 rn

.- < - - 18 m

500 mm drop

14 m Constriction across Sg Kcrajong in Reference Design - Plan

Outlet Channel Works @ I

1 PREFER CO.YSTHI<:TIO.U AS CONTROL

---pa ~ -..---.-- ~ - ~ -

50m Length W e i r across Diversion C a n a l - Section

r *

Study Objectives I Physical Hyddraulie Model Study I

To determine effectiveness of reltrence (original) design in diverting the requisite proportion of inflow to detention pond Based on test findings on reference design, to recommend design modifications where necessary for further testing To determine final dimensions of inlet configuration to achieve the desired diversion To study the effects of a nearby DBKL drain, and a log boom, on the flood diversion

Test Series Carried Out

Test Series Carried Out

FINDINGS

I Modified Design I1

The design is able to divert over 170 m3/s flow to the diversion drain at the peak discharge of 350 m3/s

The 9 rn constriction appears excessive to client

FINDINGS

Reference Design

The design is not able to divert > I70 11131s to the detention pond

Modified Design 1

The design is able to divert over 170 mYs flow to the diversion drain at the peak discharge of 350 m31s Not in favour of a constriction located upstream of LRT bridge crossing

FIXDINGS Modified Design 1x1 I

The design is able to divert about 170 m3/s to the detention pond during peak flood discharge of 350 m31s for both the nose shapes tested Flood water starts to overflow into detent~on pond when flood discharge exceeds about 35 m3/s

Modified Design I11 is preferred for its wider 12 m constriction and con~paratively better flo\v conditions.

Other fmdings

Maximum measured water fwd d& apstream of Sg Kerayong was 3494 when ModifbDd Desigd 1 was tested Maximum measured water level dong ajetrem of Sg Kerayong in Modified Design I11 was 34.67 m instailation of the log boom, aad varying flow conmitition from DBKL drain (up to 10% of total) have little impact on the flow d i s t n i o n at the bifurcation

POND DESIGN

CH ZOOB - CH350B

PELBAGAI ISU LAIN I

I POND - Relocation Of Trees

Prov. Sum I . UTILITIES 4LLOCATION

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PENGAUHAN SETXNGGAN

,- DESIGN PEAK FLOW