Coastal Erosion and Shoreline Hazards Lecture Notes

Comprehensive vocabulary flashcards covering coastal dynamics, wave processes, tidal phenomena, and shoreline protection structures based on the lecture material.

U.S. Coastal Shoreline Counties Population

Account for almost $40\%$ of the population and $10\%$ of the land mass (excluding Alaska).

U.S. Coastal Economy

Provides $10 trillion$ in goods and services annually, $54.6 million$ employees, and $4 trillion$ in wages annually.

Types of Coast

Includes Depositional and Erosional types such as Estuary (Coastal Marsh and Mangrove), Deltas, Sandy Coast, Rocky Coast, Barrier Island, and Cliffs.

Sand Shortage Causes

World population growth from $1.6 billion$ to $7.6 billion$ ($1900$ to $2018$) led to a $23-fold$ increase in usage for glass and concrete; additionally, dams prevent sand from reaching beaches.

Summer Wave Variation

Characterized by weaker weather systems, calmer winds, and waves with shorter wavelengths and lower heights that deposit sand onto the coast.

Winter Wave Variation

Characterized by stronger weather systems and winds, and waves with longer wavelengths and greater heights that erode sand from the coast.

Rip Currents

Powerful flows of water away from the shoreline that account for $80\%$ of lifeguard rescues; they form channels to flow offshore when water builds up near the shoreline.

Safety measures for Rip Currents

Swim parallel to the beach, do not fight the current, and think before helping others.

Great Lakes Rip Current Conditions

Commonly form when waves are > 3\,ft high, wave periods are > 6\,seconds, and offshore winds are blowing onshore.

Wave Refraction

The bending of waves caused by ocean depth and friction; waves slow down and bunch up in shallow water, while waves in deeper water move faster and spread out.

Longshore Drift

The process where beach sediment is carried along the shoreline because waves strike the beach at an angle.

Longshore Current

A current in the breaker zone that flows down the beach caused by waves hitting the shoreline at an angle.

Tides

The rise and fall of the ocean surface caused by gravitational forces and the rotation of the Earth.

King Tides

The highest tides of the year, occurring when Earth aligns with the Moon at perigee (closest) and the Sun at perihelion (closest).

Perigee

The point in the orbit of the Moon at which it is closest to the Earth.

Perihelion

The point in the orbit of the Earth at which it is closest to the Sun.

Tidal Bore

A tidal wave that occurs when topography funnels incoming tidal water into a narrow river, lake, or bay, creating turbulent waters and a specific sound.

Examples of Tidal Bores

The Amazon River, Qiantang River in China, and the Bay of Fundy.

Seawalls

Coastal structures designed to protect from wave erosion and reduce flooding, though they can eventually lead to the removal of the beach.

Jetties

Structures built perpendicular to the shore, usually to protect the entrance to a harbor by extending beyond the surf zone.

Groins

Low, narrow barriers built perpendicular to the shore to slow the longshore transport of sand, trapping sand on the up-drift side.

Breakwaters

Offshore structures built parallel to the coastline to provide shelter from wave attack and allow for sand deposition behind them.

Mangrove Forests

Dense stands of coastal trees that provide natural protection by absorbing wave energy from tropical cyclones and tsunamis and trapping mud to extend the shoreline.

Coral-Algal Reefs

Natural breakwaters created by corals and calcifying algae that can grow $10 - 15\,mm$ per year ($1 - 1.5\,m$ per century).