Cantilever beams were developed in order to cross increasingly wide streams or rivers, where simple wooden beams had a limited range of about 10 meters. Two arms with timber superimposed are built on either side of the river, above the highest flood-level point, while being weighted to allow an increasingly large cantilevering, and solid wooden beams are then fixed on each end of the arms with wooden pegs. Bridges of this type were very common in mountainous region of India, Nepal and Tibet with an average span of 20 metres (66ft), but those from bhutan have the particularity of being more elaborate with stone masonry bridge towers, roofed with wooden shingles above the abutments or bridge head structures.[1][2] The main purpose of these towers was to act as a counterweight to stiffen the structure.[3]
A traditional suspension bridge in the foreground and a modern one in the background
The use of more layers of wooden beams with more pronounced inclinations permit to achieve greater spans, one of the most significant example is the Wangdue Zam with a span reported from 112 to 180 feet (34.1 to 54.9m) according to different sources.[4][5][6] The renovation of the Punakha Bridge in the city of the same name in 2008 by a swiss company[7] made it possible with this technique to reach a span of 55 metres (180ft), the largest for this type of bridge in Bhutan.
All these bridges are called Bazam, a word composed of Ba which means Cattle and Zam who is the traduction of Bridge in Dzongkha, the national language of Bhutan. This comes from the resemblance of the cantilever beams that sit opposite each other with two noses of cattle.[8]
A major innovation was created by Thang Tong Gyalpo regarding the crossing of large spans, he developed iron chains working techniques and adapted them to the construction of bridges. By adding arsenic to the iron (a bit more than 2.8%),[9] it was easier to work with and had good resistance against rust, some of these chains are still functional today. This made it possible to reach spans to over a hundred meters which had not yet been reached in Europe at this time, the Chushul Chakzam in Tibet is reported to be 150 yards (140m) long.[4]
After making more than a hundred such bridges in Tibet, Thang Tong Gyalpo came to Bhutan in 1433 where he found big iron ore deposits and locals blacksmiths, many chains forged here were shipped from Bhutan to Tibet.[10] He build 8 bridges in the country, oftentime near ore deposits, and some of them were still in use in the 20ht century, the last existing bridges are Tamchog Chakzam, Doksum Chakzam, Dangme Chakzam, and Khoma Chakzam[11] (Chakzam literally means "iron bridge" in standard Tibetan).
↑ The Tamchog Chakzam was washed away in a flood in 1969, he still had his iron chains on that date. For the reconstruction in 2005, four chains were recovered from the river and four others were brought from the dismantled Doksum Chakzam in East Bhutan.[10]
↑ The rupture and fall of a glacier into a lake in 1958 created a devastating wave that swept the Mo-Chhu River for miles, taking with it the tree trunks that destroyed the cantilever bridge. The west tower, on the side of the dzong, spared was preserved during the restoration of 2006-2008, the other tower was shifted by 20 metres (66ft) (the old bridge had a span of 35 metres (115ft).[13]
↑ Also called Paro Dzong Covered Bridge or Nyamai Zam Footbridge.
↑ Also called Wangdü, Wangdi or Wandipore Bridge, the date of construction is between 1684 and the mid-18th century,[3][6] its span has been reported from 112 to 180 feet (34.1 to 54.9m).[5][6]
↑ The bridge was mentioned by John Claude White during his expedition in Bhutan between 1887 and 1908.[17]
Bhutan's early history is steeped in mythology and remains obscure. Some of the structures provide evidence that the region has been settled as early as 2000 BC. According to a legend it was ruled by a Cooch-Behar king, Sangaldip, around the 7th century BC, but not much is known prior to the introduction of Tibetan Buddhism in the 9th century, when turmoil in Tibet forced many monks to flee to Bhutan. In the 12th century, the Drukpa Kagyupa school was established and remains the dominant form of Buddhism in Bhutan today. The country's political history is intimately tied to its religious history and relations among the various monastic schools and monasteries.
A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders. The first modern examples of this type of bridge were built in the early 1800s. Simple suspension bridges, which lack vertical suspenders, have a long history in many mountainous parts of the world.
Dzong architecture is used for dzongs, a distinctive type of fortified monastery architecture found mainly in Bhutan and Tibet. The architecture is massive in style with towering exterior walls surrounding a complex of courtyards, temples, administrative offices, and monks' accommodation.
Jigme Wangchuck was the 2nd Druk Gyalpo or king of Bhutan from 26 August 1926, until his death. He pursued legal and infrastructural reform during his reign. Bhutan continued to maintain almost complete isolation from the outside world during this period; its only foreign relations were with the British Raj in India. He was succeeded by his son, Jigme Dorji Wangchuck.
Gasa District or Gasa Dzongkhag is one of the 20 dzongkhags (districts) comprising Bhutan. The capital of Gasa District is Gasa Dzong near Gasa. It is located in the far north of the county and spans the Middle and High regions of the Tibetan Himalayas. The dominant language of the district is Dzongkha, which is the national language. Related languages, Layakha and Lunanakha, are spoken by semi-nomadic communities in the north of the district. The People's Republic of China claims the northern part of Gasa District.
Punakha is the administrative centre of Punakha dzongkhag, one of the 20 districts of Bhutan. Punakha was the capital of Bhutan and the seat of government until 1955, when the capital was moved to Thimphu. It is about 72 km away from Thimphu, and it takes about 3 hours by car from the capital. Unlike Thimphu, it is quite warm in winter and hot in summer. It is located at an elevation of 1,200 metres above sea level, and rice is grown as the main crop along the river valleys of two main rivers of Bhutan, the Pho Chu and Mo Chu. Dzongkha is widely spoken in this district.
Penlop is a Dzongkha term roughly translated as provincial governor. Bhutanese penlops, prior to unification, controlled certain districts of the country, but now hold no administrative office. Rather, penlops are now entirely subservient to the House of Wangchuck.
Wangdue Phodrang is a town and capital of Wangdue Phodrang District in central Bhutan. It is located in Thedtsho Gewog.
Ngamring County is a county of Xigazê in the Tibet Autonomous Region, China. "Ngamring County, sometimes referred to as the gateway to Mount Kailash and Far West Tibet, is the barren area which divides the Raga Tsangpo and the Brahmaputra."
The following outline is provided as an overview of and topical guide to Bhutan:
Thangtong Gyalpo, also known as Chakzampa, the "Iron Bridge Maker", Tsöndrü Zangpo "Excellent Persistence", and the King of the Empty Plain. He was also known by a variation of this name, Madman of the Empty Valley. He was a great Buddhist adept, a Chöd master, yogi, physician, blacksmith, architect, and a pioneering civil engineer. He is considered a mind emanation of Padmasambhava and a reincarnation of Dolpopa Sherab Gyaltsen. He founded the Iron Chain lineage of the Shangpa Kagyu school of Tibetan Buddhism, and he recognized the first Samding Dorje Phagmo, Chökyi Drönma (1422–1455), the female incarnation lineage of Vajravārāhī.
Duksum, also known in the past as Doksum, Dogsum or Dosum is a village in north-eastern Bhutan. It is located in Khamdang Gewog in Trashiyangtse District. By road it is 21 km. from Trashigang town and only 2 km. from the well known religious site of Gomphu Kora. Duksum was famous for its ancient Chazam, which was, however, dismantled in 2004 for restoration. Originally built by lama Thang Tong Gyalpo, it was rebuilt after 2004 at Tamchog Lhakhang near Paro. The township of Duksum was mainly a trading post for nearby, off-the-road settlements. Its importance declined with the extension of rural roads and especially because of a heavy rockfall of 2004 which destroyed many shops, restaurants and houses.
The Penlop of Trongsa, also called Chhoetse Penlop, is a Dzongkha title meaning "Governor of the Province of Trongsa (Chhoetse)". It is now generally given to the heir apparent of the Kingdom of Bhutan, but historically was an important title, for the governor of Trongsa and the surrounding area, and was the route by which the House of Wangchuck came to the throne.
The Punakha Dzong, also known as Pungthang Dewa chhenbi Phodrang, is the administrative centre of Punakha District in Punakha, Bhutan. Constructed by Ngawang Namgyal, 1st Zhabdrung Rinpoche, in 1637–38, it is the second oldest and second-largest dzong in Bhutan and one of its most majestic structures. The dzong houses the sacred relics of the southern Drukpa Lineage of the Kagyu school of Tibetan Buddhism, including the Rangjung Kharsapani and the sacred remains of Ngawang Namgyal and the tertön Pema Lingpa.
The Chushul Chakzam, or simply Chakzam which literally means "iron bridge" in Standard Tibetan, was a suspension bridge that spanned the Yarlung Tsangpo river in modern-day Qüxü County near Lhasa, Tibet. It was built in 1430 by Thang Tong Gyalpo. The southern bridgehead was built on the mountain Chowuri, which is sacred in Tibetan Buddhism. This mountain was a site where Guru Rinpoche and Trisong Detsen had meditated during the 8th Century. When it was built, its main section was the longest unsupported span in the world, with a central span estimated at around 150 yards.
Public holidays in Bhutan consist of both national holidays and local festivals or tshechus. While national holidays are observed throughout Bhutan, tsechus are only observed in their areas. Bhutan uses its own calendar, a variant of the lunisolar Tibetan calendar. Because it is a lunisolar calendar, dates of some national holidays and most tshechus change from year to year. For example, the new year, Losar, generally falls between February and March.
Bumthang Province was one of the nine historical Provinces of Bhutan.
The valleys of Bhutan are carved into the Himalaya by Bhutan's rivers, fed by glacial melt and monsoon rains. As Bhutan is landlocked in the mountainous eastern Himalaya, much of its population is concentrated in valleys and lowlands, separated by rugged southward spurs of the Inner Himalaya. Despite modernization and development of transport in Bhutan, including a national highway system, travel from one valley to the next remains difficult. Western valleys are bound to the east by the Black Mountains in central Bhutan, which form a watershed between two major river systems, the Mo Chhu and the Drangme Chhu. Central valleys are separated from the east by the Donga Range. The more isolated mountain valleys protect several tiny, distinct cultural and linguistic groups. Reflecting this isolation, most valleys have their own local protector deities.
The lakes of Bhutan comprise its glacial lakes and its natural mountain lakes. Bhutanese territory contains some 2,674 high altitude glacial lakes and subsidiary lakes, out of which 25 pose a risk of GLOFs. There are also more than 59 natural non-glacial lakes in Bhutan, covering about 4,250 hectares (16.4 sq mi). Most are located above an altitude of 3,500 metres (11,500 ft), and most have no permanent human settlements nearby, though many are used for grazing yaks and may have scattered temporary settlements.
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