HYDROLOGY BASIN CALCULATIONS

100-year storm

BASIN 1 (Proposed Condition)

In the proposed condition, the drainage runoff from the backyards will be directed towards catch basins/storm drain

pipes which will direct the flow towards the concentration point. The drainage runoff from the frontyards will be directed

towards the gutters on the Private Driveway, Vista De Lamar, and direct the runoff to the concentration point. The

concentration point is the same point as in the existing condition for both runoffs (see the attached Drainage Map 2).

FLOW RATE: Q100 = C * I * A (Rational Method)

AREA:

A = 1.36 Acres (see Drainage Map 2, attached)

C-VALUE:

C = 0.57 (see Table 3-1, Section 4)

TIME OF CONCENTRATION:

TC = Ti

+ Tt

Where:

Initial Time, Ti

Land Use = MDR

Slope = 1 % (See Drainage Map 2, attached)

Ti = 8.4 min (see Table 3-2, Section 4)

And:

Travel Time, Tt

Tt:

Tt is the time it takes the runoff to travel along the landscaped and developed areas

after the initial travel period. Said flow will be assumed to be developed sheet flow. The time it takes the runoff to

travel from the end of the initial travel time to the concentration point is calculated using the velocity and the

distance traveled. The velocity is assumed for each specific condition and the travel distance is obtained from the

Drainage Map 2. See below for calculations:

Assumed Q100 = 3.8 cfs

At:

Q100(Avg) = 3.8 / 2 = 1.9 cfs

Assumed Velocity (V100(Avg)) = 8.3 fps (see Hydraulic Calculations, Section 4)

Then:

Tt = Travel Distance / Velocity = D / V100

Where:

Distance Traveled (D) = 460 ft (see Drainage Map 2, attached)

Then:

Tt = 460 / 8.3 = 55.42 sec = 0.9 minutes

Therefore:

TC = 8.4 + 0.9 = 9.3 minutes

HYDROLOGY BASIN CALCULATIONS

(100-year storm)

BASIN 1 (Proposed Condition) Contâ€¦.

INTENSITY CALCULATIONS:

I = 7.44 P6 TC

-0.645 (see Figure 3-1, Section 4)

Where

P6 = 2.8 in (see 100-year Rainfall Isopluvial, Section 4)

Then:

I = 7.44 (2.8) (9.3)-0.645 (see Figure 3-1, Section 4)

Therefore:

I = 4.9 in/hr per Equation

FLOW RATE:

Q100 = C * I * A = 0.57 * 4.9 * 1.36

Q100 = 3.8 CFS

Don't use plagiarized sources. Get Your Custom Essay on

100-year storm BASIN 1 (Proposed Condition)

Just from $13/Page