fundamentals of engineering supplied-reference handbook - Ventech!

ENVIRONMENTAL ENGINEERING
For information about environmental engineering refer
to the ENVIRONMENTAL ENGINEERING section.
HYDROLOGY
NRCS (SCS) Rainfall-Runoff
2 ( P − 0.
2S
)
Q =
,
P + 0.
8S
1,
000
S = −10,
CN
1,
000
CN = ,
S + 10
P = precipitation (inches),
S = maximum basin retention (inches),
Q = runoff (inches), and
CN = curve number.
Rational Formula
Q = CIA, where
A = watershed area (acres),
C = runoff coefficient,
I = rainfall intensity (in/hr), and
Q = peak discharge (cfs).
SEWAGE FLOW RATIO CURVES
Population in Thousands (P)
135
DARCY'S LAW
Q = –KA(dh/dx), where
Q = Discharge rate (ft 3 /s or m 3 /s),
K = Hydraulic conductivity (ft/s or m/s),
h = Hydraulic head (ft or m), and
CIVIL ENGINEERING (continued)
A = Cross-sectional area of flow (ft 2 or m 2 ).
q = –K(dh/dx)
q = specific discharge or Darcy velocity
v = q/n = –K/n(dh/dx)
v = average seepage velocity
n = effective porosity
Unit hydrograph: The direct runoff hydrograph that would
result from one unit of effective rainfall
occurring uniformly in space and time
over a unit period of time.
Transmissivity, T, is the product of hydraulic conductivity
and thickness, b, of the aquifer (L 2 T –1 ).
Storativity or storage
coefficient, S, of an aquifer is the volume of water
taken into or released from storage per
unit surface area per unit change in
potentiometric (piezometric) head.
CurveA
2 :
0.2
P
5
14
Curve B:
+ 1
4 + P
18 + P
CurveG:
4 + P