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Pakistan
• Indus (1)
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India
• Hooghly (2)
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Bangladesh
• Ganges (3)
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Myanmar
• Pegu (4)
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China
• Qiantang (5)
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Malaysia
• Lupar (6) • Samarahan (7) |
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There appear to be two separate classes of bore that occur in Asia. Those that are determined by large spring tides, and those that are a by-product of cyclonic activity in monsoon season.
Tidal-bores reported in the Bay of Bengal fall under the later. In particular the Ganges (Bangladesh) and Hooghly (India) have a mean spring mesotidal range of only 2m. The tidal oscillation in this region is semi-diurnal so there is not a significant change between the two daily tides.
The bores in China and Malaysia fall into the former category, and these are the only bores in Asia we have managed to acquire pictorial evidence for.
Bores are also found in Pakistan on the Indus and in the Gulf Of Martaban (Burma). These are more likely to be caused by high spring tides essentially with monsoon activity causing an incremental surge.
Although bores have been reported in historical documents, in India, Pakistan and Bangladesh, it is likely that the numerous dams that have been built on their principle waterways will have affected bore activity due to reductions in fluvial flow.
These bores seem to only occur in the monsoon season from May to October when prevailing winds blow from the south-west. Combined with cyclonic activity in the Bay this creates huge tidal surges in excess of the average range and the bores result from these. Therefore, concomitant with cyclonic activity, these bores are not likely to be surfable!
(Note: The Hooghly does exhibit a funnel estuary and bores may occur on large spring tides alone).
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However, there are numerous occassions when news reports have included tidal bores as a damaging factor in the destruction of the Bangladesh coastline. But these appear to be concomitant with powerful cyclonic activity and therefore are likely to be produced by wind-created surges.
As such it is difficult to define these as regular occuring upriver bores, and more information is really required before we can confirm anything on this country.
Around the same period Branner (1884), in his work on the Amazon Pororoca, reported a bore on the Brahmaputra. The Brahmaputra converges with the Ganges in central Bangladesh to from the mighty Padma river. Such a report implies a bore occuring over 150km inland making it second only to the Amazon Basin for bore-penetration! But this is highly speculative and the report is a touch anachronistic!
Any tidal-bore activity that does occur is likely to be in the branches of the Ganges Delta a vast rugged swamp forest (over 42,000sqkm) called the Sunderbahns. The area is covered by a vast network of rivers flowing out of the Ganges and Padma. It is also home to the Royal Bengal Tiger so probably a fairly dangerous place to start searching!!
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The Ganges river holds a very significant role in Hindu mythology and religion appearing on numerous occassions in The Vedas. The Hindu people believe it is the holiest of water and has magical healing powers. The river spreads out as it travels towards the Bay of Bengal forming the vast Ganges Basin (or Mouth Of The Ganges).
There is only a single report of the bore on the Ganges written over a century ago (see Further Notes).
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With a mean tidal range of only 2m it is highly likely that this bore is only a by-product of cyclonic condtions in the monsoon season.
It is also likely that the performance of any bore activity will have been gravely affected by modern dam construction along the river.
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India has two areas of macrotidal waters where bores are reported to occur.
In the far east the Hooghly, the far western arm of the Ganges Basin, has a famous bore that regularly appears (by name only) in accounts of bores around the world.
The Gulf of Cambay which flows into the Arabian Sea on the eastern coast is macro-tidal and one of a few places where bores occur in a mixed semi-diurnal tide cycle. Bores are reported on the Narmada and Mahi, but these are observational only with no material evidence.
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The Hooghly is the far western channel of the Ganges river basin. It drains into the Bay of Bengal and many accounts of the tidal-bore at its mouth have been recorded.
The bore occurs in monsoon season, from May through to October, when the prevailing winds blow from the south-west pushing larger tides into the bay. The bore travels from Hooghly Point in the river mouth as far as Balagarh and has been observed at around two metres.
The Hooghly river flows through Calcutta and is a major shipping route.
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The mean spring tidal range at the mouth of the river is 2.7m which rises rapidly to 4.9m upriver due to the funnel shape of the estuary.
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Bores might be found in the vast Irawaddy Delta spreading through western Myanmar and draining into the Andaman Sea. Bores are actually reported on two of the rivers flowing into the Gulf Of Martaban.
The Pegu has been recorded at a height of three metres, placing it in the higher echelon of world bores. The Sittang flows directly into the northern end of the Gulf Of Martaban. A bore has been recorded on the river at about half a metre.
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The Pegu River flows into the eastern end of the Rangoon (Yangon) estuary having run its course from the north. The river's course takes it through the small Buddhist town of Pegu about 30km north. |
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There is only one documented bore in Pakistan that has been observed on the Indus, the only major waterway in the country. There is not much information to confirm the occurance of the bore though.
The river flows into the Arabian Sea, south-east of Karachi, where the mean tidal range is 2.6m (mesotidal). The bore is reported as effective on tides over 3.3m at the river mouth.
The area of the Indus Delta is vast flatlands shaped over many years and facing south-west it is very likely that the Delta and any tidal-bore would be greatly magnified by the prevailing monsoon winds blowing straight up the river channels.
Any bore that occurs on the Indus will have decreased over the last few decades as a high proportion of the Indus river has been diverted for irrigation considerably reducing the effective discharge (by more than four times in the last century!).
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The Indus river flows from high up in the Tibetan Plateau to the Arabian Sea about 100km south-west of Karachi. Here it branches off into a vast lowland delta. Information on the area is lacking, but any bore occurance will have been greatly reduced by extensive use of the freshwater for irrigation and inter-river link canals, and the construction of the Tarbela hydroelectric dam on the river.
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A bore has also been observed on the Zhujiang (Pearl River) in southern China just north of Hong Kong. The tidal source is the South China Sea, a region of mesotide range and mixed semi-diurnal oscillation - as is the case for the tidal source of the bores in Sarawak. The bore on the Zhu is reported to form near Hong Kong and travel as far as Zhao-ching with several other offshoot bores in the Zhu's tributaries. There is no satistical data that we have been able to acquire for this bore.
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The Qiantang is certainly the largest tidal-bore in the world reaching as high as 8.93m - that's nearly thirty feet! The wave is so vast that in one violent tide of history over 10,000 people were swept away! Only five years ago 87 people were killed for venturing too close. The bore is effective for about a third of the year, the tides are semi-diurnal and September and October are probably the best times.
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The bore forms near Jianshan and then travels through the city of Hangzhou and about another 40km upstream. The wave can apparantly be heard coming from over 22km away!
The bore can be viewed from Xiaoshan in Hangzhou but the most popular spot is Haining in Yanguan Town.
The Chinese call the wave the Black Dragon and have built temples and pagodas to ward off the Dragon along the river banks of Haining (the Sea-Pacifying Pagoda, Temple Of The Ocean God and Turtle Tower to name a few). August 18th of the Chinese Lunar Calender is the traditional tide watching day (or Birthday Of The God Of Waves) when thousands of Chinese flock from across the country to await the bore!
It is only in recent years that the local Chinese have been prepared to allow outsiders to ride the wave and with such an opportunity a group of English surfers decided to take on the Dragon. With the rest of the team in back-up boats Stuart Matthews from Gloucester surfed the head wave for 11 seconds. This is certainly not a wave to be taken lightly!
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Malaysia is made up of Sarawak and Sabah, on the north side of the island of Borneo, and the Malay Peninsula, the southern tip of the Asia mainland.
Located in the South China Sea tidal range is mesotidal (2-4 metres) and oscillation is mixed semi-diurnal. So one of the daily tides is much larger than the other.
The only location where tidal-bores have been reported is in south-west Sarawak in the area between Kuching and Betong where four major rivers drain into the South China Sea. The Lupar Batang which drains into the large estuary west of Lubuk Antu and the Samarahan, further north near Kabong, have both been observed at one metre high.
Bores are alco documented on the Sadong, west of the Lupar, near the town of Sebangan and the Saribas which froms near Supa. We have been unable to aquire any statistical data on these two rivers.
The coast of Sarawak faces the wrong way to be directly affected by the south west monsoon winds through the summer months as with much of southern Asia. However the north-east trade winds that blow from November to April could increment a surge.
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The Lupar Batang river is the largest of the four major rivers in the far south-west of Sarawak. The river flows west from the Batang Ai national park passing Tawai and Sri Aman on route to the South China Sea. The bore on the Lupar forms some way up river near the town of Lingga. |
We have very little information on the Samarahan and its precise location. Still researching!...