Coastal Surge Risk Assessment for Steep Waves

Steep Waves: Understanding the Risks of Coastal Surge

As coastal communities around the world prepare for the annual threat of storm surges, it's essential to understand the risks associated with steep waves. A wave is considered steep if its run-up slope exceeds 1:3 to 1:5, which translates to a wave height that can cause significant flooding and damage inland.

In this blog post, we'll explore the concept of wave selection and why it's crucial to identify the right waves before they become a problem. We'll also discuss how to read and analyze curl, face steepness, and safety considerations related to steep waves.

Scenario: A Coastal Town Faces Its First Storm

It's November 15th in coastal town, Bayshore, Florida, where residents have been preparing for Hurricane Joaquin. The storm is expected to make landfall within the next 48 hours, bringing with it a powerful storm surge that could inundate low-lying areas.

As the townspeople gather at the local community center, they anxiously await the storm's arrival. Suddenly, their resident meteorologist, Dr. Maria Rodriguez, takes the stage to give an update on the latest forecast models.

"Friends, I've been analyzing the latest data, and it looks like we're looking at a classic scenario: a moderate-to-strengthen hurricane bearing down on us. The storm surge is expected to be around 6-8 feet high, which will put areas like Bayshore and nearby cities under significant flooding risks."

Dr. Rodriguez then proceeds to explain the concept of wave selection.

Wave Selection: A Critical Factor in Coastal Resilience

Wave selection refers to identifying the types of waves that are most likely to cause damage or flooding when they make landfall. There are several factors to consider when evaluating wave selectivity:

1. Wave period: Shorter waves tend to be more destructive, especially during storms with strong winds.
2. Wind speed: Higher wind speeds can generate more power in the storm, leading to larger and more damaging waves.
3. Wave height: As mentioned earlier, steep waves are more likely to cause flooding.
4. Coastal geometry: The shape of the coastline can affect wave selection; for example, a narrow beach may favor shorter, less destructive waves.

In Dr. Rodriguez's analysis, she concludes that Bayshore is at risk for several types of waves:

1. Short-period swells: These are often associated with tropical cyclones and can be particularly hazardous due to their short period.
2. Wind-driven waves: These are generated by strong winds blowing over the water and can produce larger waves.
3. Coastal oblique waves: These occur when wind blows across the beach, creating a wave that's not directly in front of or behind the shore.

Reading Wave Signatures: An Essential Skill for Coastal Residents

Now that we've explored wave selection, it's essential to understand how to read and analyze wave signatures. A wave signature is the unique pattern of energy that defines a particular wave type:

1. Run-up slope: This measures the steepness of the wave as it approaches the shore.
2. Face steepness: This refers to the angle at which the wind is blowing, relative to the direction of the incoming wave.
3. Curl: The curl is the rate at which the ocean surface is distorted by the wave's energy.

To read a wave signature, you need to understand the relationships between these parameters:

• A steeper run-up slope indicates a more energetic wave that's likely to produce higher waves.
• A greater face steepness implies stronger wind blowing over the water.
• The curl of the wave should be positive (i.e., increasing) as the wave approaches the shore, indicating that the wind is pushing against the incoming wave.

Face Steepness and Curl: Key Factors in Wave Selection

When analyzing a wave signature, it's essential to consider face steepness and curl. A greater face steepness indicates:

1. Stronger wind: Strong winds can generate more power in the storm, leading to larger waves.
2. Higher wave energy: Steeper faces tend to produce higher waves, which can increase flooding risks.

Similarly, a positive curl (increasing rate of wave distortion) implies that:

1. Wind is pushing against the incoming wave: This can lead to a steeper run-up slope and increased wave size.
2. More destructive wave energy: A stronger curl indicates a more energetic wave that's likely to cause damage.

Safety Considerations: Preparing for Steep Waves

Steep waves pose significant risks to coastal residents, infrastructure, and the environment. To stay safe, follow these guidelines:

1. Monitor weather forecasts and warnings: Stay informed about storm predictions and watch for updates on wave height and selectivity.
2. Know your flood zones: Familiarize yourself with local flood maps and evacuation routes in case of extreme flooding.
3. Secure outdoor furniture and debris: Protect your home, garden, and vehicles from potential damage caused by strong winds or flooding.
4. Have a emergency kit ready: Stock up on essentials like food, water, first aid supplies, and communication devices in case you're unable to access shelter.

By understanding wave selection and analyzing wave signatures, coastal residents can better prepare for steep waves and minimize their risk of injury or property damage. Remember to stay informed, secure your belongings, and follow safety guidelines to ensure a safe and resilient coastline. Here's the information you requested in a table view:

Factor	Description
Wave Period	Shorter waves tend to be more destructive.
Wind Speed	Higher wind speeds can generate more power in the storm, leading to larger and more damaging waves.
Wave Height	Steep waves are more likely to cause flooding.
Coastal Geometry	The shape of the coastline can affect wave selection. (e.g., a narrow beach may favor shorter, less destructive waves)
Wave Selection	A wave is considered steep if its run-up slope exceeds 1:3 to 1:5. This translates to a wave height that can cause significant flooding and damage inland.

Wave Signatures

Parameter	Description
Run-up Slope (RUS)	Measures the steepness of the wave as it approaches the shore.
Face Steepness (FS)	Refers to the angle at which the wind is blowing, relative to the direction of the incoming wave.
Curl (C)	The rate at which the ocean surface is distorted by the wave's energy. A positive curl indicates an increasing wave size and potential flooding risks.

Factors Influencing Wave Selection

Factor	Description
Wind Speed	Stronger winds can generate more power in the storm, leading to larger waves.
Face Steepness (FS)	Greater face steepness indicates stronger wind, higher wave energy, and potentially greater flooding risks.
Curl (C)	A positive curl implies a stronger wind pushing against the incoming wave, increasing its size and potential destruction.

Safety Considerations

Recommendation	Description
Monitor weather forecasts and warnings to stay informed about storm predictions and wave height.
Know your flood zones and have evacuation routes in place if necessary.
Secure outdoor furniture, debris, and valuables from potential damage or flooding.
Have an emergency kit ready with essentials like food, water, first aid supplies, and communication devices in case of a disaster.