The Earth sometimes amazed us with its geological marvel which is accompanied by the natural phenomenon. Tidal bore is one of them. Before moving on to the discussion firstly knows that-What is Tide?
Tides are natural phenomenon the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun, and the rotation of the Earth.
What is Tidal Bore?
A tidal bore is a large wave or bore caused by the constriction of the spring tide as it enters a long, narrow, shallow inlet. In other words, it is a tidal phenomenon in which the leading edge of the incoming tide forms a wave of water or group of waves of water that travels up a river or narrow bay against the direction of the river or bay's current.
What happens during a tidal bore?
A tidal bore occurs in two ways- firstly, it appears as a single breaking wave; secondly, it appears as a whelp which means smooth wave front came with smaller and lower velocity secondary waves. But no matter on the typology, both forms are the process of intense, turbulent driven and came with rumbling noises. Simple, we can say that these waves are resultant of the forces and turbulence in the whelps which causes rumble roar. This roar is characterised by the lower frequencies because air bubbles are trapped in the circular movement of water. But the bubbles are amplified and active which travel longer distances with produced rumble.
Regional distribution tidal bore
Tidal bore can be found almost every part of the world. It can occur in rivers and lakes. The lakes, rivers and bays that have been known to exhibit bores are given below:
1. Asia: Ganges, Brahmaputra, Indus River, Sittaung River, Burma, Qiantang River, Batang Lupar or Lupar River, Batang Sadong or Sadong River, Bono, Kampar River.
2. Australia: Styx River and Daly River
3. Europe: River Shannon, River Trent, River Dee, River Mersey, River Severn, River Parrett, River Welland, River Kent, River Great Ouse, River Ouse, River Eden, River Esk, River Nith, River Lune, Lancashire, River Ribble, River Yealm, Devon, River Leven, River Ribble, Durme, river training, Bay of Mont-Saint-Michel, Arguenon, Baie de la Frênaye, Vire, Sienne, Vilaine (locally named le mascarin), Dordogne and Garonne.
4. Papua New Guinea: Fly River and Turama River
5. North America: Petitcodiac River, Turnagain arm of Cook Inlet (Alaska), Colorado River, Savannah River, Mississippi Gulf Coast, Bay of Fundy (between Nova Scotia and New Brunswick), Petitcodiac River, Shubenacadie River, River Hebert and Maccan River, the St. Croix and Kennetcook rivers, the Salmon River, Colorado River
6. South America: Amazon River, Orinoco River, Mearim River and Araguari River
Effects of Tidal Bores
As we know that tidal bore is a combination of forces and activities including turbulence in the whelps, as well as impacts on other obstacles on the riverfront. Therefore, it is considered as dangerous because these waves are turbulence and rumble is driven, which interfere the navigation routes and shipping activities. It also provides ample space for rich breeding and spawning ground for fishes and to support the shrimp species through inducing aeration.