EXAMPLE PROBLEM II-6-1

EM 1110-2-1100 (Part II)

30 Apr 02

Find:

If a channel has a depth below MSL of 3.7 m (12.1 ft) and a width of 180 m (590 ft), what are the

maximum flow velocity, maximum discharge bay tidal range, and the volume of water flowing into and

out of the bay on a tidal cycle (tidal prism) for a tide having the spring range?

Given:

A bay with a surface area of 1.9 107 m2 (2.0 108 ft2) and an average depth of 6.0 m (19.7 ft) is located

on the Atlantic coast. The tide is semidiurnal (T = 12.42 hr), with a spring range of 1.30 m (4.3 ft), as

given by the National Ocean Survey Tide Tables (U.S. Department of Commerce 1989). An inlet channel,

that will be the only entrance to the bay, is to be constructed across the barrier beach that separates the bay

from the ocean. The inlet is to provide a navigation passage for small vessels, dilution water to control

both salinity and pollution levels, and a channel for fish migration. The channel is to have a design length

of 1,100.0 m (3,609 ft) with a pair of vertical sheet-pile jetties that will extend the full length of the

channel.

Solution:

Using King's method, assume ken = 0.1, kex = 1.0, and f = 0.03: B = 180 m and d = 3.7 m.

Ac ' Bd ' 180 (3.7) ' 666 m2 (7166 ft 2)

Ac

666.

' 3.55 m (11.54 ft)

R'

'

(B % 2d)

(180 % 2 ( 3.7 ))

fL

0.03 (1100)

' 1.0 % 0.1 %

' 3.42

F ' ken % kex %

4R

4 (3.55)

ao Ab F

(1.30/2 (1.9) (107) 3.42

K1 '

' 28.8

'

2 L Ac

2 (1100) (666)

L Ab

1100 (1.9) 107

2π

K2 '

' 0.25

'

g Ac

9.8 (666)

T

12.4 (60 (60)

From Figures II-6-18, II-6-19, and II-6-20 with the above values of K1 and K2

ab

' 0.78

as

)

Vm ' 0.66

ε ' 53o

(Continued)

II-6-24

Hydrodynamics of Tidal Inlets