Calculation

External Area Approximate Plaze Area Total Drainage Area Length (m) General Fall (m)

m2 95956 543000 638956 1776 6

Runoff Coefficient (C) Concrete/Roof Asphalt Landscape Area

5 year 100 year 0.8 0.97 0.77 0.95 0.34 0.47

Existing Site: Area (ha) = 63.9 Since the percentage of the paved road is very small when compared to the landscape area, so the runoff coefficent for the existing area is assumed to be cultivated land

Tc = L/3600V L = 1776 m = 1776 * 3.28 = 5825.28 ft V = 2.75 ft/sec (Paved area) from fig. 8.8.2 water resource engineering by L. Mays Tc = 0.59 hr 35.3 mins Return period 5 years 100 years

Intensity (mm/hr) 46 75 from IDF curve

Q = CiA/360 Pre-Development Peak Flows Return Period Area Coefficient (C) 5 yrs 63.9 0.34 100 yrs 63.9 0.47

Peak Flows (m3/s) 2.7759 6.2564

Post-Development Peak Flows Return Period Area 5 yrs Landscape 33.22 Paved area 29.01 Concrete 1.66 total 63.9 100 yrs

Landscape 33.22 Paved area 29.01 Concrete 1.66 63.9

Coefficient (C) 0.34 0.77 0.8 0.5472 0.47 0.95 0.97 0.7009

Peak Flows (m3/s)

4.4675

9.3305

Storage = 0.5(Qpost*Tbase) - 0.5*(Qpre*Tbase) Tbase = 94.26 mins 5655.82 secs 5 years storage required (m3) = ### 100 yr storage required (m3) =8693.13

Detention Storage Quality Control Level 1 protection Total Active Storage Permanent Pool Active Storage Total Storage =

8693.13 m3

80% S.S Removal

for quantity 70% impervious 225

85% impervious 250

m3/ha

40 m3/ha (250-40)*63.8956 =13418.08 m3 40*63.8956 = 2555.82 m3 15973.9 m3

15973.9 5795.42

27.13

if total 1.75m depth 9127.94 m2 permanent depth 1.47 m active depth 0.28 m

water level

175 m

42.73

213.63

43 27

215

Quality +Quantity

24667.03

w l

40 200