Coasts

Coasts can beCoasts can be

• فعالفعال• غیرفعالغیرفعال

• erosional or erosional or depositionaldepositional

Parts of a beach

Wave refraction along a straight coast

Ele

vati

on

(ft

)

Distance (ft)

The gentler the beach slope, the finer the beach sediments tend to be, as can be seen from these profiles of the Half Moon Bay, California.

2 4 6 8 10 12 140

20

40

60

80

100

Seawater temperature (°C)D

epth

fro

m s

ea-s

urf

ace

(m)

SeptemberSeptember

No

vemb

er

Janu

ary

Mar

ch

May

Jun

e

August

Thermocline at the Carmel

Beach is seasonal ...

August

6

3

0

0 30 60 90 120 150

Distance from the sea cliff (m)

Hei

gh

t ab

ove

mea

n l

ow

wat

er (

m)

February

AprilSeptem

ber

December

July

August

JuneMay

… … and so isand so is the beach the beach

profile.profile.

Seawater Temperature

De

pth

Win

ter

Summer

De

pth

Seasurface

Beach profile

Winter

Summer

Longshore current and littoral drift

1940 1963

XX

N

These two pictures of Sandy Beach (shown by cross here), New Jersey, were taken in 1940(left) and 1963 (right). Can we infer from these that

These two pictures are of the same beach at Barnes Bay, Anguilla. The one on the left was taken in 1994 ….

… and the one on the right was taken sometime in 1995.

How baymouth bars and spits form

Formation of a tambolo

Coastal straightening by wave-erosion

The development of a wave-cut platform

Deltas can be 1.

tide-dominated, river dominated,

andwave-dominated

Continental shelf, slope, and submarine canyon

A submarine canyon is a collapsed river channel

How construction modifies the

shoreline:

• The constructing

a groin or a pier, i.e., a

structure perpendicular

to the shoreline

How construction modifies the shoreline:

• Constructing a breakwater wall means sand pile-up right behind the breakwater wall and erosion downstream

Santa Barbara Harbor