Drainage Design Manual, Hydrology - Flood Control District of ...

Drainage Design Manual for Maricopa County
Hydrology: Application
Subbasin ID VC %
S8 44
S9 30
S10 49
S11 30
7. Compute the average value of DTHETA using Table 9.9 for each subbasin based on the percent
developed and percent natural areas, from item #2 on pgs. 9-30.
Subbasin S2:
A T
=
2,
816.9 acres
Natural Area
=
1
------------------
, 627.1
= 58 %
2,
816.9
Developed Area
=
1
------------------
, 189.8
= 42 %
2,
816.9
DTHETA AVG
= (( 58)DTHETA Dry
+ ( 42)DTHETA Normal
) ⁄ 100
= (( 58) ( 0.35) + ( 42) ( 0.25)
) ⁄ 100
= 0.31
Using the above procedures, the average values of DTHETA each subbasin are as follows:
Subbasin ID DTHETA
S1 0.35
S2 0.31
S3 0.25
S4 0.25
S5 0.27
S6 0.26
S7 0.28
S8 0.29
S9 0.21
S10 0.21
S11 0.33
August 15, 2013 9-33