Page 570 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

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14.10 Capacity Design in Storm Drainage 527

1.0
Horner:
impervious
0.9
areas
Hoad: c t impervious areas
0.8 t 8
1 3
Gregory: c 0.175t
0.7
Runoff coefficient, c 0.6 Hoad: c 0.5t improved pervious areas
0.5
0.4
0.3

0.2 t 15
0.3t
Hoad: c t 20 sandy pervious areas
0.1
Figure 14.17 Variation in Runoff
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 Coefficients with Duration of Rainfall and
Duration of rainfall, t, minutes Nature of Area Drained.

Table 14.5 Values of Runoff Coefficients

Description of Area Component Runoff Coefficient (%)
Pavement, asphalt and concrete 70–95
Pavement, brick 70–85
Roofs 75–95
Lawns:
Sandy, flat (2%) 5–10
Steep (7%) 15–20
Heavy, flat (2%) 13–17
Steep (7%) 25–35

Table 14.6 Values of Overall Runoff Coefficients for North
American Communities
Areas Coefficient (%)
Business:
Downtown 70–95
Neighborhood 50–70
Residential:
Single-family 30–50
Multifamily, detached 40–60
Multifamily, attached 60–75
Suburban 25–40
Apartments 50–70
Industrial:
Light 50–80
Heavy 60–90
Parks, cemeteries 10–25
Playgrounds 20–35
Unimproved land 10–30