DEFINITION OF THE COAST

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Introduction to Waves and BeachesOCS
2010OBJECTIVES

• What are the main physical processes operative on
  the inner shelf-nearshore and beach environments?
• What is the connection between hydrodynamic
  processes, seafloor morphologies and change?
• Evolution of coasts over thousands of years

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SHELF SEDIMENTS AND GEOMETRY
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Introduction to Waves and BeachesOCS
2010Highlights

• Tropical and Extratropical storms
• Deltaic environments
• Coastal erosion and sea level rise
• Ocean observing systems
• Contemporary issues in coastal science

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One Meter Sea Level Rise
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DEFINITION OF THE COAST
COASTAL ZONE The space in which terrestrial
environments influence marine (or lacustrine)
environments and vice versa.

• Variable in width and composition
• May be highly dynamic over time
• Zonal boundaries often difficult to define
  (highly ephemeral)
• Coastal zone may be strongly characterized by
• Physical
• Biological
• Cultural Criteria

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FOREDUNE-BEACH-NEARSHORE PROFILE
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FOREDUNE-BEACH-NEARSHORE DEFINITIONS
BEACH Zone of unconsolidated material that
extends landward from the low water line to a
marked change of material or morphology or to the
line of permanent vegetation (usually the
effective limit of storm waves). Unless
otherwise stated the seaward limit of the beach
is the mean low water line.
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FOREDUNE-BEACH-NEARSHORE DEFINITIONS
BACKSHORE Zone of the beach lying between the
bluff/foredune and the foreshore. Comprises the
berm/s and is reworked only by storm wave activity
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FOREDUNE-BEACH-NEARSHORE PROFILE
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FOREDUNE-BEACH-NEARSHORE DEFINITIONS
BERM Nearly horizontal section of beach formed by
wave deposits.
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FOREDUNE-BEACH-NEARSHORE DEFINITIONS
BEACH SCARP Almost vertical slope along beach
caused by wave erosion. Highly variable in height
(cm-m) due to wave energy and beach composition
variability.
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FOREDUNE-BEACH-NEARSHORE DEFINITIONS
BREAKER Point of instability

• Breaker Types
• Spilling
• Plunging
• Collapsing
• Surging

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FOREDUNE-BEACH-NEARSHORE DEFINITIONS
FORESHORE Zone between the crest of the seaward
berm (or upper limit of uprush at high tide) and
low water that is normally traversed during
uprush and backwash of waves during a tidal cycle.
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FOREDUNE-BEACH-NEARSHORE DEFINITIONS
NEARSHORE Zone extending seaward of the shoreline
well beyond the breaker zone. Zone in which
nearshore currents occur.
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FOREDUNE-BEACH-NEARSHORE DEFINITIONS
INSHORE/SHOREFACE Zone of variable width
extending from the low water line through the
breaker zone.
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FOREDUNE-BEACH-NEARSHORE DEFINITIONS
OFFSHORE Comparatively flat zone of variable
width extending from the breaker zone to the
seaward edge of the continental shelf.
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FOREDUNE-BEACH-NEARSHORE DEFINITIONS
LONGSHORE BAR Mound of unconsolidated material
located parallel to the beach. Seasonally
controlled by wave energy conditions.
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TECTONIC CLASSIFICATION
Inman Nordstrom (1971) Lithosphere comprised
of a series of plates moving over athenosphere
(denser) plate boundaries either collide or
spread.
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TECTONIC CLASSIFICATION
SPREADING PLATES
Create new ocean basins,

e.g.. Atlantic and Pacific widening
at 0.04-0.06 m/yr.

• COLLISION COASTS (active coasts)
• e.g.. Pacific coasts of North and South America
  (thick and thin plates collide)
• ISLAND ARC COLLISION COASTS
• e.g.. Philippines, Indonesian and Aleutian
  Island arcs (thin plates collide)

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The Tectonic Classification of the Worlds
Coastlines, Based on the Work of Inman and
Nordstrom (1971)
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TECTONIC CLASSIFICATION
TRAILING EDGE COASTS

• NEO-TRAILING EDGE COAST
  New trailing edge coasts formed near
  beginning separation centers and rifts
  
  e.g.. Red Sea and Gulf of California
• AFRO-TRAILING EDGE COAST
  Opposite coast of the continent is also
  trailing thus potential for terrestrial erosion
  and deposition is low e.g.. Atlantic and Indian
  Ocean coasts of Africa
• AMERO-TRAILING EDGE COAST
  Trailing edge of a continent with a
  collision coast modified by depositional
  material and erosive effects from high interior
  mountains
  e.g.. East coasts of North and South
  America

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TECTONIC CLASSIFICATION
MARGINAL SEA COASTS Coasts fronting on
marginal seas and protected by island arcs
from the open sea e.g. Vietnam, South China,
Korea, Gulf of Mexico, Northeast Australia
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FIRST ORDER COASTS

• Mountain Coast
• Narrow Shelf
• Headlands and Bays
• Coastal Plain
• Wide Shelf
• Headlands and Bays
• Coastal Plain
• Deltaic Coast
• Reef Coast
• Glaciated Coast

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The Tectonic Classification of the Worlds
Coastlines, Based on the Work of Inman and
Nordstrom (1971)
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SYSTEMS APPROACH TO COASTAL OCEANOGRAPHY
Definition A group of objects within a boundary
between which energy or material flows or has
flowed.
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FEEDBACK MECHANISMS
FEEDBACK When a change in one element produces a
sequence of other changes in other elements which
ultimately leads back to the element whose
initial change set off the original
sequence. POSITIVE/NEGATIVE FEEDBACK
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NEGATIVE FEEDBACK In opposition to any initial
changes within the system. (SELF REGULATION)
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