Tidal bore
Topic: Movements of Ocean Water: Waves, Tides and Currents · NCERT: Beyond NCERT
Meaning
A tidal bore is a wall of water that rushes up a river against its flow. It forms when a strong incoming tide is forced into an estuary that gets narrower and shallower. The rising sea water cannot spread out, so it piles up into a steep wave front that moves upstream. Bores can be dangerous to boats and to people on the riverbanks.
Example
The Hooghly river in West Bengal has a tidal bore that moves up from the Bay of Bengal. Other well-known bores are on the Qiantang in China (the largest), the Severn in the UK, and the Amazon in Brazil, where it is called the pororoca.
Don't confuse with
- Tsunami: a series of huge sea waves caused by undersea earthquakes. A bore is caused by the tide.
- Tidal current: the general to-and-fro flow of the tide. A bore is a single steep wall of water moving up a river.