Lecture 19
Coastal Zone
The coastal zone is the area where land meets the sea, encompassing a dynamic interface between terrestrial and marine environments. It includes beaches, cliffs, estuaries, wetlands, and nearshore waters. This zone is characterized by unique ecosystems, high biodiversity, and significant human activity, making it vital for ecological, economic, and social reasons. It is also highly vulnerable to natural processes like erosion, storms, and sea-level rise, as well as human impacts such as pollution and development.
Coastal terminology
Fig: Coastal terminology
1.
Shore:
o The
zone between the water’s edge at low tide and the upper limit of effective wave
action (often the base of a cliff).
o Includes:
§ Foreshore:
Exposed at low tide and submerged at high tide.
§ Backshore:
Extends landward from the normal high tide limit, inundated only by
exceptionally high tides or storm waves.
2.
Shoreline:
o Strictly
the water’s edge, which migrates back and forth with the rise and fall of
tides.
o Can
be further defined as:
§ Low-tide
shoreline
§ Mid-tide
shoreline
§ High-tide
shoreline
3.
Nearshore Zone:
o The
zone comprising:
§ Surf
Zone: Where waves break.
§ Swash
Zone: Covered as waves run up the foreshore.
o Migrates
with the tides.
4.
Breaker Zone:
o The
area where waves are disrupted, bordered seaward by the offshore zone.
5.
Offshore Zone:
o Extends
from the breaker zone to an arbitrary limit in deep water.
6.
Beach:
o An
accumulation of loose sediment (e.g., sand, gravel, boulders).
o May
be confined to the backshore or extend across the foreshore and below low tide
level.
o Shingle:
Beach gravel with well-rounded stones.
7.
Coast:
o A
zone of varying width, including:
§ The
shore and nearshore zone (out to where waves break).
§ Extending
inland to the limit of marine influences (e.g., cliff crest, tidal estuary
head, or rising ground behind coastal lowlands, dunes, lagoons, or swamps).
o A
dynamic zone where land (lithosphere), sea (hydrosphere), and air (atmosphere)
interact.
o Shaped
by processes such as tectonic movements, sea level changes, tides, waves,
currents, and atmospheric variations.
8.
Coastline:
o The
land margin at normal high spring tide (behind the backshore zone).
o May
be the base of a cliff or the seaward margin of dunes or dry land.
o In
American literature, sometimes referred to as shoreline or seaboard.
9.
Erosion and Denudation:
o Erosion:
Removal of rock material.
o Denudation:
Removal of surface rock, exposing underlying formations to further erosion.
10. Directions
of Flow:
o Offshore:
Seaward direction.
o Onshore:
Landward direction.
o Longshore:
Parallel to the shore.
Key Distinctions:
- Shoreline:
The dynamic water’s edge that moves with tides.
- Coastline:
The land margin at normal high spring tide.
- Coast: The broader zone including the shore, nearshore, and inland areas influenced by marine processes.
Impact on Coastal Zones
Coastal zones are dynamic regions where land meets the
ocean, and they are highly vulnerable to natural and human-induced changes. The
impacts on coastal zones can be categorized into environmental, economic,
and social aspects:
1. Environmental Impacts:
- Coastal
Erosion: Wave action, wind, rising sea levels, and human activities
contribute to the gradual loss of coastal land.
- Sea-Level
Rise: Due to climate change, higher sea levels lead to flooding,
saltwater intrusion, and loss of habitats.
- Loss
of Biodiversity: Destruction of mangroves, coral reefs, and wetlands
threatens marine and terrestrial species.
- Water
Pollution: Industrial waste, plastic pollution, and oil spills degrade
coastal water quality, affecting ecosystems.
2. Economic Impacts:
- Damage
to Infrastructure: Coastal cities and ports face significant risks
from storms, flooding, and erosion.
- Decline
in Fisheries: Overfishing and habitat destruction reduce fish stocks,
affecting livelihoods.
- Tourism
Loss: Beach erosion and environmental degradation can reduce tourism
revenue.
3. Social Impacts:
- Displacement
of Communities: Rising sea levels and extreme weather events force
coastal populations to migrate.
- Health
Risks: Polluted water, habitat loss, and natural disasters increase
disease outbreaks.
- Cultural
Loss: Coastal communities with deep-rooted traditions face the risk of
losing their heritage due to environmental changes.