Strategic coastal dike shape for enhanced tsunami overflow reduction.

Area of Science:

• Coastal engineering
• Tsunami mitigation
• Hydraulic engineering

Background:

• Coastal dikes are crucial infrastructure for mitigating tsunami damage.
• Current guidelines lack specific recommendations for effective dike shapes to reduce tsunami overflow.
• Tsunami events pose significant risks to human life and social infrastructure.

Purpose of the Study:

• To investigate the effectiveness of different coastal dike shapes in reducing tsunami overflow.
• To establish rational design guidelines for coastal dikes based on tsunami overflow reduction.
• To analyze the impact of dike geometry on tsunami wave interaction.

Main Methods:

• Numerical simulations were performed using tsunami waveforms from the Great East Japan Earthquake.
• The amount of tsunami overflow for various dike shapes was calculated.
• The relationship between dike shape parameters and overflow reduction was analyzed.

Main Results:

• The seaward slope of a dike significantly influences tsunami overflow more than the landward slope.
• Dikes with a vertical seaward wall or a wave return structure reduced overflow by 5%-30% compared to a 1:2 slope.
• Optimal landward slope design depends on tsunami scale and dike stability considerations.

Conclusions:

• Vertical seaward walls and wave return structures are effective in reducing tsunami overflow without increasing dike height.
• The study provides valuable insights for developing rational design guidelines for coastal dikes.
• Optimizing dike shape is vital for enhancing coastal protection against tsunamis.