Street Tree Species
| |
---|---|
Small – Medium Trees (overhead utility wires above)
| |
Carpinus (Hornbeam)
| |
Cercis canadensis (Redbud)
| |
Crataegus (various Hawthorn species)
| |
Malus (various Crabapples)
| |
Prunus "Okame" (Okame Cherry)
| |
Syringa Reticulata "Ivory Silk" Japanese Tree Lilac
| |
Stewartia Pseudocamellia Japanese or Korean Stewartia
| |
Large Trees
| |
Acer rubrum (Red Maple)
| |
Acer saccharum (Sugar Maple)
| |
Cladrastis kentukea (American Yellowwood)
| |
Gleditsia (various seedless Locust species)
| |
Liquidambar styraciflua (Sweetgum)
| |
Nyssa Sylvatica (Tupelo)
| |
Quercus (Oak)
| |
Tilia (Linden)
| |
Ulmus (Elm)
| |
Zelkova serrata (Zelkova)
|
FORMULA
|
Q=ciA
|
Where:
| |||
Q
|
=
|
runoff, cubic feet per second
| |
i
|
=
|
intensity of rainfall, inches per hour for duration equal to
time of concentration
| |
c
|
=
|
runoff coefficient expressing the ratio of rate of runoff to
rate of rainfall
| |
A
|
=
|
area of watershed in acres
| |
The average rainfall intensity in inches per hour shall be obtained
from Plate 2.[10]
|
The runoff coefficients shall reflect developed conditions.
The following composite values may be used:
|
Residential Areas
(lot size in square feet)
|
Roof and Pavements
%
|
Coefficient of Runoff
|
---|---|---|
12,000
|
30
|
0.44
|
20,000
|
26
|
0.42
|
40,000
|
22
|
0.40
|
80,000
|
16
|
0.35
|
Business areas
|
70
|
0.80
|
Industrial areas
|
50
|
0.58
|
Schools
|
10
|
0.32
|
Multiple-family
|
60
|
0.70
|
The time of concentration (t) shall be the total of overland
flow, channel flow and pipe flow. The Kutter and Manning formula shall
be standard for channel flow and pipe flow and the overland flow time
shall be determined from standard MDOT or Elwyn Seelye's nomograph
considering the factors of length of slope, including slope and type
of service. Minimum time of concentration will be 10 minutes.
|