APPENDIX DESIGN DATA & REFERENCES

1.0 REFERENCE

1.1 The design is based on the Urban Stormwater Management Manual for Malaysia 2nd Edition from

Department of Irrigation and Drainage (DID) Malaysia hereinafter referred to as MSMA. The

following formulas and tables are used in the design report.

2.0 DESIGN CONSIDERATION AND CRITERIA

2.1 Table 12.16: Sediment Basin Types and Design Considerations, MSMA 2nd Edition.

Category

Soil Description

Hydrological

Soil Group

Basin

Type Design Considerations

I Coarse-grained sand, sandy loam: less

than 33%

APPENDIX DESIGN DATA & REFERENCES

2.3 Table 12.18: Dry Sediment Basin Sizing Criteria, MSMA 2nd Edition.

Parameter Time of Concentration of Basin Catchment (minutes)

10 20 30 45 60

Surface Area (m2/ha

Total Volume (m3/ha)

333

400

250

300

200

240

158

190

121

145

2.4 Table 12.19: Wet Sediment Basin Sizing Volume (m3/ha) , MSMA 2nd Edition.

3.0 TIME OF CONCENTRATION

3.1 Overland flow time is estimated by the use of Friends Equation (Table 2.1, MSMA 2nd Edition).

Typical values of Hortons roughness n* for various land surfaces are taken from Table 2.2, MSMA

2nd Edition.

Table 2.1: Equations to Estimate Time of Concentration (QUDM, 2007), MSMA 2nd Edition

Travel Path Travel Time Remark

Overland Flow

to = Overland sheet flow travel time (minutes)

L = Overland sheet flow path length (m)

for Steep Slope (>10%), L 50 m

for Moderate Slope (

APPENDIX DESIGN DATA & REFERENCES

Densely Grassed 0.060

4.0 DESIGN RAINFALL INTENSITY

4.1 Adopted from Hydrological Procedure (HP) No. 1 revised in 2010 expressed in Equation 2.2, MSMA

2nd Edition:

where,

i = average rainfall intensity (mm/hr)

T = average recurrence interval ARI (0.5 T 12 months & 2 T 100 years)

d = storm duration (hours), 0.0833 d 72

, K, , = fitting constants dependent on the raingauge location (Table 2.B1 in Appendix 2.B)

5.0 STAGE DISCHARGE RELATIONSHIP

5.1 For a single orifice, orifice flow is estimated by the use of Equation 2.6, MSMA 2nd Edition.

Q = Co Ao (2gHo)0.5

where,

Q = orifice flow rate (m3/s)

Co = discharge coefficient (0.60)

Ao = x-sectional area of orifice (m2)

Ho = effective head of the orifice measured from the centroid of the opening (m)

G = gravitational acceleration (9.81 m/s2)

If orifice discharges as a free outfall, effective head is measured from the centerline of the orifice to the

upstream water surface elevation

If orifice discharge is submerged, effective head is the difference in elevation of the upstream and

downstream water surfaces.

5.2 Broad-crested emergency spillway flow is estimated by the use of Equation 2.10, MSMA 2nd Edition.

where,

Q = emergency spillway discharge (m3/s)

CSP = spillway discharge coefficient (m0.5

/s)

B = spillway base width (m)

Hp = effective head on the spillway weir crest (m)

The discharge coefficient CSP in Equation 2.10 varies as a function of spillway base width and

effective head (Table 2.7).

APPENDIX DESIGN DATA & REFERENCES

Table 2.7: Broad-Crested Weir Coefficient CSP Values as a Function of Weir Base Width and Head

(FHWA, 1996), MSMA 2nd Edition

Head

Hp (m)

Weir Base Width B (m)

0.15 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.25 1.50 2.00 3.00 4.00

0.10 1.59 1.56 1.50 1.47 1.45 1.43 1.42 1.41 1.40 1.39 1.37 1.35 1.36 1.40 1.45

0.15 1.65 1.60 1.51 1.48 1.45 1.44 1.44 1.44 1.45 1.45 1.44 1.43 1.44 1.45 1.45

0.20 1.73 1.66 1.54 1.49 1.46 1.44 1.44 1.45 1.46 1.48 1.48 1.49 1.49 1.49 1.45

0.30 1.83 1.77 1.64 1.56 1.50 1.47 1.46 1.46 1.46 1.47 1.47 1.48 1.48 1.48 1.45

0.40 1.83 1.80 1.74 1.65 1.57 1.52 1.49 1.47 1.46 1.46 1.47 1.47 1.47 1.48 1.45

0.50 1.83 1.82 1.81 1.74 1.67 1.60 1.55 1.51 1.48 1.48 1.47 1.46 1.46 1.46 1.45

0.60 1.83 1.83 1.82 1.73 1.65 1.58 1.54 1.46 1.31 1.34 1.48 1.46 1.46 1.46 1.45

0.70 1.83 1.83 1.83 1.78 1.72 1.65 1.60 1.53 1.44 1.45 1.49 1.47 1.47 1.46 1.45

0.80 1.83 1.83 1.83 1.82 1.79 1.72 1.66 1.60 1.57 1.55 1.50 1.47 1.47 1.46 1.45

0.90 1.83 1.83 1.83 1.83 1.81 1.76 1.71 1.66 1.61 1.58 1.50 1.47 1.47 1.46 1.45

1.00 1.83 1.83 1.83 1.83 1.82 1.81 1.76 1.70 1.64 1.60 1.51 1.48 1.47 1.46 1.45

1.10 1.83 1.83 1.83 1.83 1.83 1.83 1.80 1.75 1.66 1.62 1.52 1.49 1.47 1.46 1.45

1.20 1.83 1.83 1.83 1.83 1.83 1.83 1.83 1.79 1.70 1.65 1.53 1.49 1.48 1.46 1.45

1.30 1.83 1.83 1.83 1.83 1.83 1.83 1.83 1.82 1.77 1.71 1.56 1.51 1.49 1.46 1.45

1.40 1.83 1.83 1.83 1.83 1.83 1.83 1.83 1.83 1.83 1.77 1.60 1.52 1.50 1.46 1.45

1.50 1.83 1.83 1.83 1.83 1.83 1.83 1.83 1.83 1.83 1.79 1.66 1.55 1.51 1.46 1.45

1.60 1.83 1.83 1.83 1.83 1.83 1.83 1.83 1.83 1.83 1.81 1.74 1.58 1.53 1.46 1.45