Setdown At Breaker Point At Still-Water Shoreline Calculator

Formula Used:

\[ \eta_b = \eta_s - \frac{1}{1 + \frac{8}{3 \cdot \Upsilon_b'^2}} \cdot d_b \]

Set Down at the Breaker Point (ηb):

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1. What is Set Down at the Breaker Point?

Set Down at the Breaker Point is a wave-induced decrease of the mean water level before the waves break. It represents the lowering of the water surface elevation due to wave transformation processes as waves approach the shoreline.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ \eta_b = \eta_s - \frac{1}{1 + \frac{8}{3 \cdot \Upsilon_b'^2}} \cdot d_b \]

Where:

\( \eta_b \) — Set Down at the Breaker Point (m)
\( \eta_s \) — Setup at the Still-Water Shore Line (m)
\( \Upsilon_b' \) — Coastal Breaker Depth Index
\( d_b \) — Water Depth at Breaking (m)

Explanation: The formula calculates the wave setdown by considering the setup at the shoreline, the breaker depth index, and the water depth at the breaking point.

3. Importance of Set Down Calculation

Details: Accurate calculation of set down is crucial for coastal engineering, shoreline management, and understanding wave transformation processes near the coast. It helps predict changes in water levels that affect coastal structures and beach morphology.

4. Using the Calculator

Tips: Enter setup at still-water shore line in meters, coastal breaker depth index (dimensionless), and water depth at breaking in meters. All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the Coastal Breaker Depth Index?
A: The Coastal Breaker Depth Index is the ratio of the wave height at breaking to the water depth at the breakpoint.

Q2: How does set down differ from setup?
A: Set down is a decrease in mean water level before wave breaking, while setup is an increase in mean water level at the shoreline due to wave breaking.

Q3: When is set down most significant?
A: Set down is most significant for steep waves approaching the shore and is particularly important for predicting coastal flooding and erosion.

Q4: Are there limitations to this formula?
A: This formula provides an estimation and may need adjustment for specific coastal conditions, complex bathymetry, or unusual wave climates.

Q5: What units should be used for inputs?
A: All length measurements should be in meters, and the breaker depth index is dimensionless.