Project Detailed Information:
Company Name: Perunding
MOBD Sdn Bhd
File No.:
Description: Drainage-Jln Yahya Designer: Aween Checker:
Awal Date: 4 September, 2019 Date:
Reference Calculation Output
1. Design Criteria
Design Manual : MSMA 2nd Edition (SUStoM)
Design Type : Dry Sediment Basin
Outlet Design Storm ARI : 10 years
2. Determination Time of Concentration
a) Overland Flow Time, to (minutes)
Table 2.1 Friend's Equation
Table 2.2 to = (107 × n* × L1/3)/S1/5
= (107 × 0.028 × 100.0001/3)/2.5001/5
= 11.37 min
Hence, standard storm duration = 15 min
3. Determination Type of Soil
Table Soil Type = Coarse-grained sand, sandy loam; less than 33%<0.02mm
12.16 Dry Sediment Basin is selected
4. Determination of Basin Dimension
Table The Surface Area is 291.50 m2/ha and the Total Volume is 350.00 m3/ha. Required
12.18 surface area =
The Required Surface Area for the site = 291.50 × 1.90 = 553.85 m2(Note: 553.85 m2
This is the Average Surface Area for the Settling Zone Volume) Required Total
Basin Volume
The Required Total Basin Volume for the site = 350.00 × 1.90 = 665.00 m3 = 665.00 m3
a) Settling Zone
Table The Required Settling Zone, V1 = 332.50 m3 (half of the Total Volume) and
12.17 the Settling Zone Depth y1 = 1.00 m
Settling Zone Average Width, W1 = 10.00 m
Settling Zone Average Length
L1 = V1/(W1 × y1)
= 332.50/(10.00 × 1.00)
= 33.25 m
2
Minimum L1 = V1/(W1 × y1) = 332.500/(1.00 × 10.00 = 55.39 m
Maximum L1 = y1 × 200.00 = 200.00 m
Provided L1 = 56.00 m
Check Settling Zone Dimensions:
L1/y1 ratio = 56.00/1.00 = 56.00 56.00<200.00
OK
L1/W1 ratio = 56.00/10.00 = 5.60 5.60>2.00 OK
b) Sediment Storage Zone
The required Sediment Storage Zone Volume, V2 = 332.50 m3
For a Side Slope Z = 2(H): 1(V), the dimensions at top the Sediment Storage
Zone are,
W2 = W1 - 2 × y1/2 × Z
= 10.00 - 2 × 1.00/2 × 2
= 8.00 m
L2 = L1 - 2 × y1/2 × Z
= 56.00 - 2 × 1.00/2 × 2
= 54.00 m
The required Depth for the Sediment Storage Zone, which must be at least
0.3m, can be calculated from the following relationship,
V2 = Z2y23 - Zy22(W2 + L2) + y2(W2L2)
Which gives. y2> 0.3 m
332.50 = 4y23 - 124.00y22 + 432.00y2 V2>332.50 m3
OK
For y2 = 1.20m, V2 = 346.75 m3
c) Overall Basin Dimension Total Basin
Dimension
Top Water Level:
Top Width = W1 + 2 × Z × y1/2 WT = 12.00 m
= 10.00 + 2 × 2 × 1.00/2 = 12.00 m
Top Length = L1 + 2 × Z × y1/2 LT = 58.00 m
= 56.00 + 2 × 2 × 1.00/2 = 58.00 m
Base
Bottom Width = W1 - 2 × Z × y1/2 + y2) WB = 3.20 m
= 10.00 - 2 × 2 × (1.00/2 + 1.20) = 3.20 m
3
Bottom Length = L1 - 2 × Z × y1/2 + y2) LB = 49.20 m
= 56.00 - 2 × 2 × (1.00/2 + 1.20) = 49.20 m
Depth: y1 = 1.00 m
Settling Zone, y1 = 1.0 m
Sediment Storage Zone, y2 = 1.20 m y2 = 1.20 m
Side Slope:
Z = 2(H): 1(V) Z=2(H):1(V)
4. Sizing of Basin Outlet
The Spillway is designed for 10 year ARI flood.
Qrequired = Q10 - Qriser
a) Design rainfall intensity equation
Eq. 2.2 i = λTK/(d + θ)ƞ
where:
i = average rainfall intensity (mm/hr) for selected ARI (T) and storm
duration (d)
T = average recurrence interval, ARI (years)
d = storm duration (hours); 0.20 ≤ d ≤ 72
λ , K, θ and ƞ = fitting constants dependent on the rain gauge location
Location ARI, T Storm Derrived Parameters
(years) duratio λ K θ ƞ
n,
d(min)
Johor - Stor JPS 10 15.00 59.972 0.163 0.121 0.793
Johor Bahru
i = 59.972 × 100.163/(15.00/60 + 0.121)0.793 i=191.617mm/
= 191.617 mm/hr hr
b) Determine runoff coefficient, C
Table 2.6 C (Impervious) = 0.80 (Landuse = Flat and Apartment)
C (Pervious) = 0.80 (Landuse = Flat and Apartment)
Eq. 2.3 Q10 = CIA/360 Q10=0.809 m3/s
= [(1.70 × 0.80) + (0.20 × 0.80)] × 191.617/360
= 0.809 m3/s
4
c) Determination of Outlet Pipe Sizing and Qriser
Outlet Riser: 900 mm diameter perforated pipe.
Average Surface Area,
Aav = [(12.00 × 58.00) + (49.20 × 3.20)]/2 = 426.72 m2
Orifice Area,
Atotal = (2Aav/tCd√2g) × √y
= (2 × 426.72)/(24 × 60 × 60) × 0.6 × √(2 × 9.81)) × √(1.00 + 1.20)
= 0.00551 m3
Using an orifice of 50 mm, area of each orifice is
Ao = (π × D2)/4 = (3.142 × 0.0502)/4 = 0.00196 m2
Total number of orifice required = 0.00551/0.001963
=3
Eq. 2.6 Qriser = CoAo(2gHo)0.5 Qriser=0.845
= 0.6 × (3.142 × 0.902)/4 × (2 × 9.81 × 0.250)0.5 = 0.845 m3/s m3/s
d) Spillway Sizing
Qrequired = Q10 - Qriser = 0.809 - 0.845 = -0.036 m3/s Qrequired=-0.036
m3/s
Eq. 2.10 Qspillway = CspBH1.5
Table 2.7 B = 2.00 m, H = 0.25 and Csp = 1.49 from Table 2.7
Qspillway = 1.49 × 2.00 × 0.251.5 Qspillway=0.371
= 0.371 m3/s m3/s>-0.036 m3
OK
Total Basin Depth including spillway
= 1.00 + 1.20 + 0.30 + 0.25
= 2.75 m
