Introduction to Coastal Engineering

• Zone where land meets sea. It extends inland from the sea to the first major change in topography
• Composite of physical science and engineering disciplines applied to coastal areas
• These disciplines include Geology, Meteorology, Environmental Sciences, Hydrology, Physics, Mathematics, Statistics, Oceanography, Marine Science, Hydraulics, Structural Dynamics, and Naval Architecture.

Primary Areas

• Harbor Works

• Navigation Channel Improvements

• Shore Protection

• Flood Damage Reduction

• Environmental Preservation and Restoration

• The Coastal Engineer must consider environmental, hydrodynamic, seasonal meteorological, sediment, geological, long-term environmental, and social and political conditions

Coastal Science

• Interdisciplinary technologies applied to understanding processes, environments, and characteristics of the coastal zone

Coastal Resources

• Food, livelihood, economic development, clean water and fresh air

• Over half of Philippines municipalities are coastal, and almost all major cities are coastal

• 62% of the population lives in the coastal zone

• 27,000 km2 of coral reef exists, but less than 5% is in excellent condition

• 120,000 ha of mangrove remains, only about 25% of what existed in 1920

• Over half of animal protein intake in the Philippines comes from marine fisheries

Issues Affecting the Philippine Coastal and Marine Environment

• Resource use conflicts, high population growth rate and poverty, illegal activities, pollution, food security, biodiversity conservation, and policy and institutional gaps and conflicts

Experience and Lessons Learned

• Coastal management initiatives in the Philippines have changed in response to different situations over the last 20 years

Types of Waves

• Mechanical Waves: Disturbances in any medium or substance that transfers energy through a medium
• Electromagnetic Waves: Disturbance or oscillations in electrical and magnetic fields but can travel through air, solid materials and vacuum of space

Types of Mechanical Waves

• Internal waves form at water mass boundaries of differing densities and propatage at depth
• Tidal waves dues to the movement of tides and are generated by the earth's rotation and gravitational attraction from the moon and sun
• Their period is between 12 to 24 hours, and their wavelength is in the order of hundreds to thousand kilometers
• Tsunamis are giant waves caused by sudden displacement of ocean water
• The result from earthquakes or other seismic disturbances
• Storm surges are coastal floods or tsunami-like phenomena associated with low-pressure, and generate abnormal water level generated by a storm above the predicted astronomical tide
• Caused primarily by a storm's winds pushing water on shore
• Splash waves are created when something falls into the ocean
• Atmospheric Waves form in the sky at the boundary between air masses of different densities. These often create ripple effects
• Wind waves are waves created by local winds, swells are waves created by distant winds
• Wind waves are choppy and irregular, swells are smooth and regular
• When wind waves have moved away from the area they were formed, they change name and become swell waves

Basic Wave Components

• Still water level is where the water surface would be if there were no waves present
• Crest is the highest point of the wave, and trough is the lowest point of the wave
• Wave height is the distance between the crest and the trough
• Wavelength is the distance between two identical points on successive waves
• Wave steepness is the ratio of wave height to length; if the ratio exceeds 1/7 wave gets too steep and will break
• Period is the time it takes for two successive crest to past a given point.
• Frequency is the number of waves passing a point in a given amount of time, usually expressed as waves per second
• The inverse of the period
• Speed is how fast the wave travels, or the distance traveled per unit of time and is also called Celerity (c)
• c= wavelength x frequency

Sea Level Rise

• Increase in the height of the ocean's surface relative to land caused by melting ice sheets and glaciers, and by the expansion of ocean water as it warms
• Both are consequences of climate change, which is driven by human activities like burning fossil fuels

Short-Term Sea-Level Rise

• Sea level rise is noticeable through an increase in the frequency and severity of coastal flooding
• The accelerating rate of global sea level rise is around 3.6 millimeters per year, which is significantly higher than historical averages

Seasonal Sea Level Rise

• Natural fluctuation in ocean levels throughout the year due to changes in water temperature (thermal expansion) and local factors

Long Term Sea Level Rise

• Results from climate change and is expected to continue to accelerate

Causes and Effects of Sea Level Rise

• Causes are Melting glaciers and polar icecaps, Thermal expansion and salinity changes, and Changes in ocean circulation
• Effects are Flooding, Damage to coastal communities, and Displacement of people

Wind Wave Generation

• In coastal engineering, this refers to waves created on the water surface due to friction between wind and the water -Factors like wind speed, duration, and fetch play a crucial role in determining the size and characteristics of waves
• As wind blows over the water surface, it creates small ripples which gradually grow into larger waves through process of energy transfer Factors of Wave Generation = Wind speed, fetch, wind duration, and water depth
• Wave height is The vertical distance between the crest and trough of a wave
• Wave period is The time taken for one wavelength to pass a fixed point
• Wavelength is The horizontal distance between two successive wave crests

Importance in Coastal Engineering

• Coastal structure design relies on understanding wind wave generation
• Erosion studies consider wave forces generated by wind
• Offshore operations must consider wind wave conditions

Models for Wind Wave Generation

• Coastal engineers use sophisticated numerical models like SWAN (Simulating Waves Nearshore) to simulate wind wave characteristcs, and forecast accurately

• Wind is movement of gases in the air

• Uneven heating occurs because the sun heats different parts of the Earth's surface at different rates

• Rising warm air becomes less dense and rises creating a low-pressure area

• Sinking cool air creates a high-pressure area by moving to fill the space left by rising warm air

• The pressure gradient causes air to move creating wind

Factors Influencing Wind Patterns

• The Earth's rotation and topography as well as seasonal changes all influence wind patterns

Standing Waves

• These form when two waves of the same frequency, amplitude, and wavelength travel in opposite directions and interfere such as traveling wave and its reflection
• Points where destructive interference occurs are nodes, and points of maximum oscillation due to constructive interference are antinodes
• Unlike traveling waves that transfer energy, standing waves do not transport energy, but only form at a specific resonant frequency

Formation of Standing Waves

• Wave Reflection: When a traveling wave encounters a boundary, it reflects back
• Interference: The original (incident) wave and the reflected wave superpose
• Resonance Condition: Standing waves only form at specific resonant frequencies, where the wave fits perfectly into the medium

Wave Shoaling

• Change in shape and behavior waves propagating into water of decreasing depth that results in decreases in wave speed and wavelength while wave height increases
• Waves travel faster in deep water, but slow down because the wave "feels" the bottom in lower depths
• Wave Shortens due slowing of the distances between successive waves crests
• Occurs because energy in the wave remains nearly constant

Characteristics of Wave Shoaling

• Decrease in Wave Speed, Decrease in Wavelength, and Increase in Wave Height and Energy Redistribution
• Transition to Wave Breaking, and Coastal Impact

Effects of Wave Shoaling

• Wave Steepening: As height increases and wavelength shortens, the wave becomes steeper
• Wave Breaking: Occurs when the wave becomes too steep and then collapses into surf
• Coastal Erosion & Sediment Transport: Impacts shorelines and influences erosion, beach formation, and sand transport

Wave Refraction

• Process by which ocean waves bend as they approach a shoreline at an angle because different parts of the wave travel at different speeds due to variations in water depth

Wave Refraction Factors

• Depth Dependence of Wave Speed occurs because wave speed depends on water depth
• Uneven Shorelines: Waves in deep water move faster than those in shallow water, causing the wave front to bend

Characteristics of Wave Refraction

• Decreases in Wave Speed occurs because it is water depth dependent
• Bending of Wave Crests are such that the part of the wave in shallower water moves slower than the part in deeper water, making the wave be more parallel to shore

Characteristics of Wave Refraction

• Unequal Energy Distribution
• Concentration of Energy at Headlands
• Dispersion of Energy in Bays
• Changes in Wavelength and Wave Height
• Influence on Coastal Currents
• Formation of Coastal Features

Effects of Wave Refraction

• Erosion of Headlands, Deposition in Bays, and Longshore Drift and Coastal Sediment Transport as well as Impact on Surfing Conditions
• Challenges for Coastal Structures and Navigation, Influence on Tsunami Wave Behavior, and Formation of Tidal Inlets and Sandbars

Wave Diffraction

• This is the bending and spreading of waves as they pass around obstacles or through narrow openings

Wave Diffraction Occurs

• Passing Through an Opening where wave spreads out and If the gap is much larger than the wavelength, little diffraction occurs
• When Encountering an Obstacle, the sides of the wave bends around it, and Longer wavelengths diffract more than shorter ones

Characteristics of Wave Diffraction

• Depends on Wavelength where Longer wavelengths diffract more than shorter wavelengths
• Increases with Smaller Openings, Creates Circular or Bent Wavefronts, Partial or Total Obstacle Coverage, and Occurs with All Types of Waves

Wave Breaking

• Occurs when a wave reaches a critical steepness, making the crest unstable and causing it to collapse

Wave Breaking Happen

• Wave Growth and Steepening occures as waves grows in height from wind energy or the environment
• Friction with the Seafloor(Shallow Water Waves slowing the crest
• Instability and Collapse when the wave continues moving at its original speed, causing it to lean forward and eventually collapse

Characteristics of Wave Breaking

• As a wave approaches the shore and the crest becomes increasingly steep and eventually topple over is Steepness
• Prone to breaking in wave height becomes a sizable part of its wavelength
• Waves become likely to break when the angle of the crest becomes less than 120 degrees.
• Water depth contributes a lot to how high the waves are, and how they facilitate breaking
• Foam formation when the wave collapses and makes a crest with white foam

Types of Wave Breaking

• Spilling waves are gentle waves with crests that break softly towards the shore
• Plunging waves break when the ocean floor is steep or has sudden depth changes
• Surging waves are the result of long period swells
• Collapsing waves is a mix of spilling and plunging waves

Effects of Wave Breaking

• Coastal Erosion, Sand Transport and Beach Formation, Surfing and Recreation
• Rip Currents and Coastal Hazards, and Mixing of Ocean Water