# (The Coastal Zone and Waves)

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(The Coastal Zone and Waves)
Monday March 26, 2012 (The Coastal Zone and Waves)

What happens to the water pressure, temperature, and light levels as you dive deeper and deeper under the sea, and why? Water pressure increases because more and more water is above you and is pressing down with its weight. Temperature and light levels decrease because there is less and less solar radiation as you go deeper.

WS – Ocean Water Movements F 3/19 3/21 WS – Ocean Surface Circulation
Assignment Currently Open Summative or Formative Date Issued Date Due Date Into Grade Speed Last Day Quiz 23 S4 3/9 3/30 WS – Ocean Water Movements F 3/19 3/21 WS – Ocean Surface Circulation 3/20 3/22 Quiz 24 S5 3/23

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The Coastal Zone and Waves
Begin Worksheet The Coastal Zone and Waves

The Coastal Zone A shoreline; it is the contact between land and sea.
The shore is the area between the lowest tidal level and highest areas affected by storm waves. The coastline is the seaward edge of the coast. A beach is an accumulation of sediment along the landward margin of the ocean.

The Coastal Zone Figure 15.10

Waves Waves are created by energy traveling along the interface between ocean and atmosphere (the surface.) Waves derive their energy and motion from wind. The major parts of a wave are: the crest the trough

Wave height is the distance between a trough and a crest.
Wave Measurements Wave period is the time interval for one full wave to pass a fixed position. Wavelength is the horizontal distance between successive crests (or troughs.)

Characteristics and Movement of a Wave
Figure 15.12

Waves Wave height, length, and period depend upon: the wind speed
the length of time the wind blows. Fetch is the distance that the wind travels. As the wave travels, the water passes energy along by moving in a circle The waveform (energy) moves forward. At a depth of about one-half the wavelength, the movement of water particles becomes negligible (called the wave base.)

Changes That Occur When a Wave Moves Onto Shore
Figure 15.14

Wave Erosion Wave erosion is caused by wave impact and pressure.
Wave erosion breaks down rock material and supplies sand to beaches. The sawing and grinding action of water armed with rock fragments is called abrasion.

Sand Movement on the Beach
Beaches are composed of whatever material is available.

Sand Movement on the Beach
Some beaches have a significant biological component.

Sand Movement on the Beach
Beach material does not stay in one place. Wave energy moves large quantities of sand parallel and perpendicular to the shoreline.

Beach and Shoreline Processes
Wave refraction is the bending of a wave so that the wave arrives parallel to the shore The result of wave refraction is that wave energy is concentrated against the sides and ends of headland. Wave erosion straightens an irregular shoreline

Beach and Shoreline Processes
Longshore transport consists of the movement of sediments (generally sand, but may also consist of coarser sediments such as gravels) along a coast at an angle to the shoreline, which is dependent on prevailing wind direction.

Beach and Shoreline Processes
Beach drift is one of the most important transport mechanisms results from wave refraction. Since waves rarely break onto a shore at right angles, the upward movement of water onto the beach (swash) occurs at an oblique angle. However, the return of water (backwash) is at right angles to the beach, resulting in the net movement of beach material laterally. This movement is known as beach drift. The endless cycle of swash and backwash and resulting beach drift can be observed on all beaches. – sediment moves in a zigzag pattern along the beach face.

Beach and Shoreline Processes
Longshore current is current that flows in the surf zone. Longshore current flows parallel to the shore, and moves substantially more sediment than beach drift.

Beach Drift and Longshore Currents
Figure 15.18

Shoreline features created by erosional effects include:
Wave-cut cliffs Wave-cut platforms Marine terraces Sea arches Sea stacks

Figure A

A Sea Stack and a Sea Arch
Figure 15.21

Depositional Features
Shoreline Features Depositional Features A spit is a ridge of sand extending from the land into the mouth of an adjacent bay with an end that often hooks landward.

Figure C

A baymouth bar is a sand bar that completely crosses a bay.
Shoreline Features Depositional Features A baymouth bar is a sand bar that completely crosses a bay.

Aerial View of a Spit and Baymouth Bar Along the Massachusetts Coastline
Figure A

A tombolo is a ridge of sand that connects an island to the mainland.
Shoreline Features Depositional Features A tombolo is a ridge of sand that connects an island to the mainland.

Figure B

Shoreline Features Depositional Features Barrier islands occur mainly along the Atlantic and Gulf Coastal Plains. They run parallel the coast and can originate in several ways.

Stabilizing the Shore Shoreline erosion is influenced by several local factors the proximity to sediment-laden rivers the degree of tectonic activity the topography and composition of the land the prevailing wind and weather patterns the configuration of the coastline

Stabilizing the Shore Responses to Erosion Problems
“Hard stabilization” refers to building structures to lessen the effects of shoreline erosion. Types of structures Groins are barriers built at a right angles to the beach that are designed to trap sand. Breakwaters are barriers built offshore and parallel to the coast to protect boats from breaking waves. Seawalls armors the coast against the force of breaking waves. Often these structures are not effective.

Responses to Erosion Problems
Stabilizing the Shore Responses to Erosion Problems Alternatives to hard stabilization: In beach nourishment, sand is added to the beach system. Relocating buildings away from a beach

Miami Beach Before and After Beach Nourishment
Figure A

Responses to Erosion Problems
Stabilizing the Shore Responses to Erosion Problems Shoreline erosion problems are different along the different U.S. coasts. Along the Atlantic and Gulf Coasts, development occurs mainly on barrier islands that face the open ocean. These islands receive the full force of storms. Development has taken place more rapidly than our understanding of barrier island dynamics.

Stabilizing the Shore Responses to Erosion Problems Shoreline erosion problems are different along the different U.S. coasts. The Pacific Coast is characterized by relatively narrow beaches backed by steep cliffs and mountain ranges. The major problem here is the narrowing of the beaches. Sediment for beaches is interrupted by dams and reservoirs; therefore, rapid erosion occurs along the beaches.

Coastal Classification
Shoreline classification is difficult, and is based mainly on changes with respect to sea level. An emergent coast is caused by an uplift of the land, or a drop in sea level.

Coastal Classification
Features of an emergent coast include: wave-cut cliffs marine terraces

Coastal Classification
Submergent coasts are caused when the land adjacent to the sea subsides, or sea level rises. Features of a submergent coast include: a highly irregular shoreline estuaries – drowned river mouths

Major Estuaries Along the East Coast of the United States

The Coastal Zone and Waves
Complete Worksheet The Coastal Zone and Waves