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37-801: In the Taivoan language, the Kong-kài is generally called Kuba or any similar spelling among different communities. For example, in Siaolin , the older generation still refers to the highest ancestral spirits in the Kong-kài as Kuba-tsóo , literally "the ancestors of the Kuba ". Some spellings from different Taivoan communities include: The Kong-kài of the Taivoan people generally faces west and east. The pre- Kuomintang government Kong-kài in Siaolin came with different parts and materials such as: The Taivoan Kong-kài may differ in

74-408: A debris-flow surge often contains an abundance of coarse material such as boulders and logs that impart a great deal of friction . Trailing behind the high-friction flow head is a lower-friction, mostly liquefied flow body that contains a higher percentage of sand , silt and clay. These fine sediments help retain high pore-fluid pressures that enhance debris-flow mobility. In some cases the flow body

111-418: A last resort because they are expensive to construct and require commitment to annual maintenance. Also, debris basins may only retain debris flows from a fraction of streams that drain mountainous terrain. Before a storm that can potentially nucleate debris flows, forecasting frameworks can often quantify the likelihood that a debris flow might occur in a watershed; however, it remains challenging to predict

148-706: A result of their high sediment concentrations and mobility, debris flows can be very destructive. Notable debris-flow disasters of the twentieth century involved more than 20,000 fatalities in Armero, Colombia , in 1985 and tens of thousands in Vargas State , Venezuela , in 1999. Debris flows have volumetric sediment concentrations exceeding about 40 to 50%, and the remainder of a flow's volume consists of water. By definition, “debris” includes sediment grains with diverse shapes and sizes, commonly ranging from microscopic clay particles to great boulders . Media reports often use

185-647: A significant hazard in many steep, mountainous areas, and have received particular attention in Japan, China, Taiwan, USA, Canada, New Zealand, the Philippines, the European Alps, Russia, and Kazakhstan. In Japan a large debris flow or landslide is called yamatsunami ( 山津波 ), literally mountain tsunami . Debris flows are accelerated downhill by gravity and tend to follow steep mountain channels that debouche onto alluvial fans or floodplains . The front, or 'head' of

222-399: A strong coupling between the solid and the fluid momentum transfer , where the solid's normal stress is reduced by buoyancy , which in turn diminishes the frictional resistance, enhances the pressure gradient , and reduces the drag on the solid component. Buoyancy is an important aspect of two-phase debris flow, because it enhances flow mobility (longer travel distances) by reducing

259-545: Is a village in Jiasian District , Kaohsiung , Taiwan . It is mostly agricultural and home to one of the largest communities of the Taivoan people . In 2009, Typhoon Morakot brought unprecedented rainfall to southern Taiwan, including Siaolin. A landslide dam upstream of Siaolin failed catastrophically, resulting in a devastating mudflow to completely cover the northern half of the village. 471 people lost their lives in

296-434: Is a debris flow related in some way to volcanic activity , either directly as a result of an eruption, or indirectly by the collapse of loose material on the flanks of a volcano. A variety of phenomena may trigger a lahar, including melting of glacial ice, sector collapse , intense rainfall on loose pyroclastic material, or the outburst of a lake that was previously dammed by pyroclastic or glacial sediments. The word lahar

333-477: Is followed by a more watery tail that transitions into a hyperconcentrated stream flow. Debris flows tend to move in a series of pulses, or discrete surges, wherein each pulse or surge has a distinctive head, body and tail. Debris-flow deposits are readily recognizable in the field. They make up significant percentages of many alluvial fans and debris cones along steep mountain fronts. Fully exposed deposits commonly have lobate forms with boulder-rich snouts, and

370-528: Is of Indonesian origin, but is now routinely used by geologists worldwide to describe volcanogenic debris flows. Nearly all of Earth's largest, most destructive debris flows are lahars that originate on volcanoes. An example is the lahar that inundated the city of Armero , Colombia. A jökulhlaup is a glacial outburst flood. Jökulhlaup is an Icelandic word, and in Iceland many glacial outburst floods are triggered by sub-glacial volcanic eruptions. (Iceland sits atop

407-527: The Mid-Atlantic Ridge, which is formed by a chain of mostly submarine volcanoes). Elsewhere, a more common cause of jökulhlaups is the breaching of ice-dammed or moraine -dammed lakes. Such breaching events are often caused by the sudden calving of glacier ice into a lake, which then causes a displacement wave to breach a moraine or ice dam. Downvalley of the breach point, a jökulhlaup may increase greatly in size through entrainment of loose sediment from

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444-669: The Mountain Indigenous people so as to control the camphor forest in Jiasian and Namasia , Japanese government collectively moved more Taivoan people to the river terrace, which later became Siaolin Village in 1904, said to be named after the family name of the local Japanese police officer Kobayashi ( Hiragana : こばやし; Chinese : 小林 ; Tongyong Pinyin : Siǎolín ). Siaolin is the largest village within Jiasian District, covering

481-422: The amount of sediment mobilized and therefore, the total size of debris flows that may nucleate for a given storm, and whether or not debris basins will have the capacity to protect downstream communities. These challenges make debris flows particularly dangerous to mountain front communities. In 1989, as part of his large-scale piece David Gordon's United States , and later, in 1999, as part of Autobiography of

518-937: The architectural layout by different communities. For example, in Laonong and Lakku, there is no central pillar in the shrine, and the Sacred bamboo basket is placed in the corner as in Laonong or under the offering table as in Lakku. The Makatao Kong-kàis are currently mainly distributed along the mountainous areas of Pingtung . There have been activities to revitalize the traditional culture in recent years. The main Makatao Kong-kàis are as follows: Siaolin Village Siaolin Village ( Chinese : 小林里 ; Hanyu Pinyin : Xiǎolín ; Tongyong Pinyin : Siǎolín ; Wade–Giles : Hsiao-Lin ), also spelled Xiaolin Village ,

555-473: The buildings, only 2 were left standing. Soon after, more helicopters were sent out, rescuing 61 people from Siaolin and 14 from other villages. Survivors were directed to evacuation centers in Wulipu, Qishan , and Meinong . Officials from the district fire department also entered the settlement via foot, reporting that around 500-600 people may have lost their lives. On August 11, rescuers were finally able to reach

592-444: The chief conditions required for debris flow initiation include the presence of slopes steeper than about 25 degrees , the availability of abundant loose sediment, soil, or weathered rock, and sufficient water to bring this loose material to a state of almost complete saturation (with all the pore space filled). Debris flows can be more frequent following forest and brush fires, as experience in southern California demonstrates. They pose

629-413: The country. The heavy rainfall caused landslides in mountainous regions in southern Taiwan, especially Jiasian , Liouguei , Taoyuan , and Namasia districts. According to National Taiwan University professor Chen Hong-yu, in the 5 day period before the landslide, Qishan River and the nearby Laonong River carried an abnormal amount of sediment. The sediment carried during the typhoon exceeded 80% of

666-444: The debris flow. The slide immediately covered the northern half of Siaolin and formed a landslide dam , blocking the river's flow. Within 50 minutes, the landslide dam failed catastrophically, causing another debris flow with a 38% solid composition to erupt downstream, covering the rest of Siaolin. The average depth of the flow was 44.6 m. In the incident, the entirety of Siaolin, including around 169 residences, were covered by

703-512: The effective frictional shear stress for the solid phase is that of pure granular flow. In this case the force due to the pressure gradient is altered, the drag is high and the effect of the virtual mass disappears in the solid momentum. All this leads to slowing down the motion . To prevent debris flows reaching property and people, a debris basin may be constructed. Debris basins are designed to protect soil and water resources or to prevent downstream damage. Such constructions are considered to be

740-494: The flooding. Wulipu, which had a higher elevation, was not damaged. The incident resulted in the deaths of 471 people. A bus driven by 60 year-old Bang Rong-gui was just leaving Siaolin when Bang saw the landslide. Dropping off his passengers in Wulipu, he turned around and went back to transport more survivors. He managed to pick up 30 more people, but was unfortunately covered by a separate landslide. All lives aboard were lost. Initially, rescuers and soldiers were dispatched by

777-513: The fluid and the solid phases. The effect is substantial when the density ratio ( γ {\displaystyle \gamma } ) is large (e.g., in the natural debris flow). If the flow is neutrally buoyant, i.e., γ = 1 {\displaystyle \gamma =1} , (see, e.g., Bagnold, 1954) the debris mass is fluidized and moves longer travel distances. This can happen in highly viscous natural debris flows. For neutrally buoyant flows, Coulomb friction disappears,

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814-424: The frictional resistance in the mixture . Buoyancy is present as long as there is fluid in the mixture. It reduces the solid normal stress, solid lateral normal stresses, and the basal shear stress (thus, frictional resistance) by a factor ( 1 − γ {\displaystyle 1-\gamma } ), where γ {\displaystyle \gamma } is the density ratio between

851-475: The government to look for survivors, but no progress was made due to poor weather conditions. Helicopters from Shanlin District were grounded, while collapsed road surfaces along Highway 29 also prevented rescuers from reaching the settlement. The following day, twenty one rescuers, eight from the district fire department and thirteen from the military, arrived in Siaolin via helicopter. They reported that out of all

888-601: The incident. Due to the influx of Siraya people in early 18th century to Yujin Basin , Taivoan people started to migrate from Tainan to Kaohsiung between 1722 and 1744. Nearly 150 years later, some Taivoan people from Aliguan in Kaohsiung further migrated to a river terrace 10 km (6.2 mi) to the north of Aliguan for hunting. During the Japanese Occupation Period , in order to have Taivoan people counter

925-491: The landslide. Some blame this construction for weakening the soil and causing the landslide; however, the government held that the heavy rainfall was the real cause. After the incident, construction of the pipeline continued for a year, but was halted due to backlash from residents. After the landslide, researchers found a new fault line at the site of the landslide. Minor planet 185636 , discovered by Lulin Observatory ,

962-432: The lateral margins of debris-flow deposits and paths are commonly marked by the presence of boulder-rich lateral levees . These natural levees form when relatively mobile, liquefied, fine-grained debris in the body of debris flows shoulders aside coarse, high-friction debris that collects in debris-flow heads as a consequence of grain-size segregation (a familiar phenomenon in granular mechanics ). Lateral levees can confine

999-483: The lateral solid pressure gradient vanishes, the drag coefficient is zero, and the basal slope effect on the solid phase also vanishes. In this limiting case , the only remaining solid force is due to gravity , and thus the force associated with buoyancy. Under these conditions of hydrodynamic support of the particles by the fluid, the debris mass is fully fluidized (or lubricated ) and moves very economically, promoting long travel distances. Compared to buoyant flow,

1036-401: The neutrally buoyant flow shows completely different behaviour. For the latter case, the solid and fluid phases move together, the debris bulk mass is fluidized, the front moves substantially farther, the tail lags behind, and the overall flow height is also reduced. When γ = 0 {\displaystyle \gamma =0} , the flow does not experience any buoyancy effect. Then

1073-643: The northern half of the district. It sits in a valley along the Qishan River , surrounded by the Alishan Range to the west and the Yushan Range to the east. There are two major settlements within Siaolin Village: Siaolin to the north, and Wulipu to the south. Between August 6, 2009, and August 10, 2009, Taiwan was hit by Typhoon Morakot , which brought about unprecedented rainfall and flooding across

1110-795: The paths of ensuing debris flows, and the presence of older levees provides some idea of the magnitudes of previous debris flows in a particular area. Through dating of trees growing on such deposits, the approximate frequency of destructive debris flows can be estimated. This is important information for land development in areas where debris flows are common. Ancient debris-flow deposits that are exposed only in outcrops are more difficult to recognize, but are commonly typified by juxtaposition of grains with greatly differing shapes and sizes. This poor sorting of sediment grains distinguishes debris-flow deposits from most water-laid sediments. Other geological flows that can be described as debris flows are typically given more specific names. These include: A lahar

1147-560: The sediment that the Gaoping River , which both rivers empty into, carries in an entire year. At 6:16 AM, August 9, a debris flow occurred from a height of 1445 m on Xiandu Mountain, located upstream on the Qishan River from Siaolin. Saturated with water, 23,000,000 cubic meters of soil rushed downhill at a speed of 50 m/s into the Qishan River. Witnesses reported that two large bangs were heard on Xiandu Mountain immediately prior to

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1184-437: The settlement by car. Excavators were brought to find dead bodies, but none were found. Emergency housing was set up in Wulipu for Siaolin survivors. Due to safety concerns, residents and family members were not allowed to enter the settlement. However, people still snuck in by foot. Evidence of incense being burned were found on the bridge number 8, connecting Siaolin with Wulipu. On August 13, residents were allowed to enter

1221-867: The term mudflow to describe debris flows, but true mudflows are composed mostly of grains smaller than sand . On Earth's land surface, mudflows are far less common than debris flows. However, underwater mudflows are prevalent on submarine continental margins , where they may spawn turbidity currents . Debris flows in forested regions can contain large quantities of woody debris such as logs and tree stumps. Sediment-rich water floods with solid concentrations ranging from about 10 to 40% behave somewhat differently from debris flows and are known as hyperconcentrated floods. Normal stream flows contain even lower concentrations of sediment. Debris flows can be triggered by intense rainfall or snowmelt, by dam-break or glacial outburst floods, or by landsliding that may or may not be associated with intense rain or earthquakes. In all cases

1258-624: The valley through which it travels. Ample entrainment can enable the flood to transform to a debris flow. Travel distances may exceed 100 km. Numerous different approaches have been used to model debris-flow properties, kinematics , and dynamics . Some are listed here. Calibrating and validating such sophisticated models require well-documented data from field surveys or minute laboratory experiments. The mixture theory , originally proposed by Iverson and later adopted and modified by others, treats debris flows as two-phase solid-fluid mixtures. In real two-phase (debris) mass flows there exists

1295-635: The village guided by the military. Three permanent settlements for residents were built, with one in Wulipu, one on Taiwan Sugar 's land in Shanlin, and third on Tsu Chi's land in Shanlin. The first two villages are organized by the Red Cross Society of the Republic of China , while the third is by Tsu Chi. Xiaolin Elementary School was rebuilt in Wulipu in 2012. A memorial park at the site of Xiaolin

1332-638: Was constructed with 100 trees, symbolizing the families that lost their lives in the landslide. Some pointed to a construction by the Water Resources Agency as the cause of the landslide. Since 2003, a pipeline was under construction to redirect water from the Laonong River into the Caolan River, which would feed into the Zengwen Reservoir . The pipeline passes north of Siaolin, near the site of

1369-996: Was named "Siao Lin" in memorial of Siaolin Village. Debris flow Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock flow down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. They generally have bulk densities comparable to those of rock avalanches and other types of landslides (roughly 2000 kilograms per cubic meter), but owing to widespread sediment liquefaction caused by high pore-fluid pressures , they can flow almost as fluidly as water. Debris flows descending steep channels commonly attain speeds that surpass 10 m/s (36 km/h), although some large flows can reach speeds that are much greater. Debris flows with volumes ranging up to about 100,000 cubic meters occur frequently in mountainous regions worldwide. The largest prehistoric flows have had volumes exceeding 1 billion cubic meters (i.e., 1 cubic kilometer). As

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