Calculate tidal prism — the volume of water exchanged between a tidal basin and the sea each tidal cycle. Includes O'Brien inlet area estimate and optional average ebb/flood flow rate.
Open Channel Flow · CoastalNegative if below MSL datum
Tidal prism:
O'Brien inlet stability relationship:
Where:
O'Brien coefficient C by coast (SI units):
| Location | C | n |
|---|---|---|
| Pacific coast (Jarrett 1976) | 7.49×10⁻⁴ | 0.86 |
| Atlantic coast (Jarrett 1976) | 5.77×10⁻⁴ | 0.86 |
| Gulf of Mexico (Jarrett 1976) | 3.79×10⁻⁴ | 0.86 |
| Simplified (this calculator) | 6.25×10⁻⁴ | 1.0 |
The tidal prism governs inlet stability, flushing of estuaries, and sediment transport. Larger prisms maintain deeper, more stable inlets. The O'Brien relationship is empirical — actual inlet dimensions depend on sediment supply, wave energy, and coastal engineering structures.