1. Large Tidal Range: A significant difference between high and low tide levels is necessary to generate a powerful incoming tide. Areas with a large tidal range, such as the Bay of Fundy in Canada, are more likely to experience tidal bores.
2. Funnel-shaped Estuary: The estuary or river into which the tide flows should have a funnel-shaped or converging geometry. This shape amplifies the incoming tidal wave and increases its speed as it moves upstream.
3. Shallow Waters: The water depth in the estuary or river should be relatively shallow, typically less than 10 meters (33 feet). Shallow water causes the incoming tide to slow down and pile up, building its energy and height.
4. Steep Riverbanks: The riverbanks along the estuary or river should be steep and reflective. This prevents the water from spreading out and dissipating its energy, allowing the tidal bore to maintain its momentum and propagate upstream.
When these conditions are met, the incoming tide forms a high-energy surge of water that travels upstream as a breaking wave. The leading edge of the bore is often steep and turbulent, while the water behind it is calmer. Tidal bores can range in size from small waves a few feet high to powerful surges several meters tall, depending on the specific geographic conditions.
