A natural phenomenon - a tidal bore, locally known as "Benak", usually occurs at the Batang Lupar during the third and 18th day of the Chinese Lunar calendar month. It can also occur when the high tide is rushing up the Batang Lupar.

The tidal bore is created when the force of the tide water rushing up the river causes the river to reverse its flow. The height of the tidal bore depends on the time of the year, weather and phase of the moon. The tidal action is significant for the speed in which a large volume of water fills the river channel.

The tidal bore in the Batang Lupar reaches its height at the river in front of the Sri Aman Town, which is about 28 kilometres from its mouth. The tidal bore travels further up river for another 30 kilometres to reach Engkilili, a total of 68 kilometres from the sea.

Although a regular occurrence, it is much awaited by the riverine folk and residents of the riverside town of Sri Aman who gather at the jetty to witness the bore.

The Sungai Skrang, a tributary of the Upper Lupar, is a very scenic river and equally popular among tourists. The longhouses of the native Ibans along the Skrang River are always open to visitors and if one is lucky, one might chance upon an Iban ceremony or celebration in progress.