lII. Sediment Transport
2.2.2
Shape of Coastal Profile
127
In addition to the studies aimed at finding a criterion for defining the type of
coastal profile (bar/step, eroding/accreting), various attempts have been made to
describe the shape of the equilibrium profile. On the basis of an analysis of beach
profiles along the Danish North Sea Coast and Mission Bay, California, Bruun
(1954) found that the equilibrium profile can be approximated by a simple power
fimction, viz.
d = A y2/3
(65)
The above concept has been applied in an extensive analysis of beach response to
storm surge (Dean, 1983a). The conclusion was that eq. (16) is consistent with a
spilling breaker model and uniform wave energy dissipation per unit volume of
water which means that m = 0.67.
where :
d
Y
= water depth,
= distance from the shoreline and,
A = factor
£
<
Z
I.O
OJC
O~
OD~
From Individual ~;eld P,o~iles ~em ~ l
/'~
R--" ~""
=a~qe o,S(~ncl S,~es w~, G,ven
I
.....
l .......
' i
/"- FrOI ~ Swor~ Lohoro~oty
1 Re' ~u.l ~
I
Oa
LO
I00
I00.0
SEOi t VI ENT S|ZE, D(mrn}
Fig. 26 : Value of A in d = Ay m versus sediment size
Using physical considerations of the various forces acting in the surf zone Dean
(1977) arrived at the following description of the nearshore profile:
d=Ay m
(66)