Beach and Coastal Terminology

• The beach encompasses the active coastal area affected by waves, from the low tide breaker line to the berm's edge

Coastal Region Definitions

• Shore: The zone between the low tide line and the highest land area affected by storm waves.
• Coast: The area extending inland as far as ocean-related features are found.
• Coastline: The boundary between the shore and coast,marking the limit of the highest storm wave impact.
• Backshore: The part of the shore above the high tide shoreline, covered during storms.
• Foreshore: The intertidal zone exposed at low tide and submerged at high tide.
• Shoreline: The migrating water's edge.
• Nearshore: Extends from the low tide shoreline to the low tide breaker line, always submerged, and impacted by waves.
• Offshore: The zone seaward of the low tide breakers.

Beach Features

• Berm: A dry, gently sloping, elevated beach margin at the foot of coastal cliffs or dunes.
• Beach face: A wet, sloping surface from the berm to the shoreline, also known as the low tide terrace.
• Wave-cut bench: A flat, wave-eroded surface along which beach sediment moves.
• Longshore bars: Sand bars parallel to the coast that may cause waves to break.
• Longshore trough: Separates the longshore bar from the beach face.

Beach Composition

• Beaches have material from locally available sources and is always in transit along the shoreline.
• Sediment composition ranges from coarse boulders to fine mud.
• Boulders from cliffs, sand and mud from rivers, or biologic matter on tropical beaches.

Sand Movement

• Swash moves water up the beach, depositing sand, while backwash drains water back, eroding sand.
• Longshore currents transport sand along the beach, parallel to the shoreline.

Beach Types

• Summertime Beach: Wide, sandy berm, steep beach face, with swash dominating and no longshore bars.
• Wintertime Beach: Narrower beach, flattened beach face, sediment moves offshore, backwash dominates, and longshore bars are present.

Longshore Currents and Drift

• Longshore currents move in a zigzag pattern at speeds up to 4 km/hour.
• Longshore drift transports sediment in the surf zone, with millions of tons moved yearly.

Shore Types

• Erosional Shores: Have well-developed cliffs and uplifted coasts, like the U.S. Pacific coast.
• Depositional Shores: Gradually subsiding and feature barrier islands and sand deposits, common in the Gulf Coast and U.S. Southeast Atlantic coast.

Features of Erosional Shores

• Headlands absorb wave energy, carving out wave-cut cliffs and sea caves.
• Sea arches form when sea caves erode through headlands.
• Sea stacks are the remnants of eroded sea arches.
• Marine terraces are generated by the uplift of wave-cut benches.
• Erosion rates increase with wave exposure, smaller tidal ranges, and weaker bedrock.

Features of Depositional Shores

• Wave action distributes sediment along the continental margin.
• Spit: A linear ridge of sediment connecting to the mainland and hooking into a bay.
• Bay barrier: Seals off a lagoon from the ocean, originating as a spit across a bay mouth.
• Tombolo: Connects an island or sea stack to the mainland, forming in the wave energy shadow.

Barrier Islands

• Long offshore deposits of sand parallel to the coast, protecting the mainland from high wave activity.
• Over 2000 worldwide, with almost 300 along the Atlantic and Gulf coasts of the U.S.
• They're separated from the mainland by a lagoon.
• Islands feature an ocean beach, dunes, a barrier flat, and salt marshes.
• They migrate landward over time due to rising sea levels.

Deltas

• Triangular sediment deposits at river mouths, fertile but prone to flooding.
• Distributaries are branching channels that carry sediment, creating a "bird's foot" pattern.
• Delta shorelines smooth when erosion exceeds deposition, as seen in the Nile River Delta after the Aswan Dam's construction.

Beach Compartments

• Include rivers which supply sediment, the beach itself, and offshore submarine canyons.
• Beach compartments experience beach starvation when human activities block the sand supply. For example, Southern California has 4: Santa Barbara, Santa Monica, San Pedro, and Oceanside.

Shoreline Changes

• Emerging Shorelines: Rising above sea level, with marine terraces and stranded beach deposits, seen on the U.S. Pacific Coast.
• Submerging Shorelines: Sinking below sea level, with drowned beaches, submerged dunes, and drowned river valleys (estuaries), common on the U.S. Atlantic Coast.

Sea Level Changes

• Local geologic processes: raise or lower Earth’s crust.
• Isostatic adjustments: rebound of crust after ice removal.
• Worldwide changes in sea level: alter seawater volume or ocean basin size.
• Eustatic changes result from forming/melting glaciers or thermal expansion/contraction of seawater.
• During ice ages, sea level was at least 120 meters lower.
• Complete melting of remaining ice would raise sea level by 70 meters.

Hard Stabilization

• Structures built to control coastal erosion often have unwanted outcomes.
• Groins: Perpendicular to the beach, trapping sand upcoast and causing erosion downcoast.
• Jetties: Built in pairs to protect harbor entrances.
• Breakwaters: Parallel to shore, protecting harbors but can cause erosion.
• Seawalls: Armor the coastline but can reflect wave energy and erode beaches.

Alternatives to Hard Stabilization

• Construction restrictions: Limit building near shorelines.
• Relocation: move structures from eroding areas.
• Beach replenishment: Add sand to beaches, an expensive and continuous process.

Coastal Water Characteristics

• Salinity: freshwater runoff doesn't mix well.
• Halocline: Represents salinity variations with depth.
• Temperature: Restricted mixing.
• Isothermal: Uniform temperature.
• Thermocline: Represents temperature variations with depth.

Coastal Geostrophic Currents

• Generated by wind and runoff and deflected by the Coriolis effect (to the right in the Northern Hemisphere).
• N. Hemisphere: curve northward on western coasts and southward on eastern coasts.

Estuaries

• Partially enclosed coastal water bodies where freshwater mixes with salty ocean water. Like River mouths, Bays, Inlets, Gulfs, and Sounds.
• They formed from sea level rise after glacier retreat.

Estuary Types

• Coastal plain estuary: Forms as sea level rises and floods existing river valleys (Chesapeake Bay).
• Fjord estuary: Forms as sea level rises and floods existing glaciated valleys (Alaska, Canada, New Zealand, Chile, and Norway).

Estuary Types Cont.

• Bar-built estuary: Shallow, separated from ocean by sand bars (U.S. Gulf and East coasts).
• Tectonic estuary: Forms due to faulting, San Francisco Bay

Water Mixing in Estuaries

• Vertically mixed: Shallow, salinity uniform from top to bottom.
• Slightly stratified: Salinity increases from head to mouth, with two water layers.
• Highly stratified: Deep, with a strong salinity gradient.
• Salt wedge: Salty water wedges under river water.

Estuaries and Human Impact

• Threatened by human populations.
• Estuaries serve as breeding grounds and nurseries.
• Activities like the Columbia River logging industry and Chesapeake Bay nutrient pollution damage the water.

Lagoons

• Shallow water bodies landward of islands with restricted circulation; form in bar-built estuaries.
• The 3 distinct zones include freshwater, transitional, and saltwater.
• E.g. Laguna Madre, along the Texas coast.

Marginal Seas

• Large, semi-isolated water bodies that result from tectonic events.(Mediterranean, Caribbean)

Mediterranean Sea

• Remnant of the ancient Tethys Sea. Narrow strait of Gibraltar connects it to the Atlantic.
• Underwater sill separates major basins, restricting flow.
• The circulation is opposite most estuaries, driven by Middle East heat and evaporation.

Coastal Wetlands

• Ecosystems with a high water table.
• Occur along coastal waters, including estuaries, lagoons, and marginal seas.
• Include swamps, tidal flats, coastal marshes, and bayous, highly biologically productive, with low oxygen in sediments.

Types of Coastal Wetlands

• Salt marshes: Between 30 and 65 degrees latitude, support salt-tolerant grasses.
• Mangroves: Tropics below 30 degrees latitude, salt-tolerant trees with oxygen-depleted sediments.

Wetland Characteristics

• Home to diverse plants and animals, serving as nurseries for fish.
• Soak up nutrients, remove pollutants, protect shorelines, dissipate wave energy, and absorb floodwater.

Wetland Loss

• More than half of U.S. wetlands have vanished due to development.
• Establishment of the EPA's Office of Wetlands Protection in 1986 has slowed losses.
• Future sea level rise is predicted to exacerbate losses.