Natural disasters in Taiwan.Taiwan is an island that lies on the western edge of the Pacific-rim earthquake belt, which is an extremely active tectonic tectonic /tec·ton·ic/ (tek-ton´ik) pertaining to construction. region with seismic activities among the highest in the world. The boundary of the Eurasian and Philippine Sea Plates is near the island of Taiwan. Earthquake occurs frequently, and a recent catastrophic event, the Chi-Chi earthquake Ji-Ji earthquake (Traditional Chinese: 集集大地震; Pinyin: jíjí dàdìzhèn , is known to the world. Taiwan also is located in the subtropical sub·trop·i·cal
Of, relating to, or being the geographic areas adjacent to the Tropics.
of the region lying between the tropics and temperate lands
climate region with high average temperature and precipitation. May and August are periods influenced by continuous seasonal rains that occasionally come with an extraordinary intensity. From summer to fall, Taiwan is affected by typhoons. Some extreme events would accumulate significant rainfalls within a relatively short period of time and result in disastrous consequences such as floods. Given the topography of Taiwan, which is covered by slopelands and high mountains over two third of the island, landslides and debris flows Debris flows are often referred to as mudslides, mudflows, jökulhlaups, or debris avalanches. There is also a debris flow type that has rocky front called 'the head' and a 'tail' like wet concrete. This debris flow has been well reported in the scientific literature. often were triggered after heavy rainfalls. The remaining quarter of the land is plains, but they have been densely inhabited and developed. Due to excess extraction of groundwater for fish farming Fish farming is the principal form of aquaculture, while other methods may fall under mariculture. It involves raising fish commercially in tanks or enclosures, usually for food. , significant portion of the plains have suffered severe ground subsidence subsidence, lowering of a portion of the earth's crust. The subsidence of land areas over time has resulted in submergence by shallow seas (see oceans). Land subsidence can occur naturally or through human activity. over the past decades. As a result, Taiwan has to cope with various hazardous situations caused by the Mother Nature. Most significant natural disasters in this island include earthquakes, floods, landslides, debris flows, and land subsidence. The government and people in Taiwan have long being aware of the disastrous consequence of these natural hazards, and continuous efforts have been placed on prevention and mitigation of these natural disasters. This paper discusses these natural disasters that confront the people in Taiwan. Studies and investigations carried out to understand the characteristics of these natural hazards are discussed, and development of programs and approaches in preventing and mitigating natural disasters in Taiwan are also addressed.
Since the end of the 20th century, natural disasters started to take heavier tolls than ever on human lives and properties around the world owing to owing to
Because of; on account of: I couldn't attend, owing to illness.
owing to prep → debido a, por causa de the unprecedented global climate variation and accelerating urbanization in mankind history. Among all kinds of natural disasters in the world, the earthquakes, followed by floods and fierce winds (typhoons, hurricanes, tornados, etc.), are the most catastrophic and have taken the most monetary loss in urban areas. The damages caused by earthquakes, floods, and fierce winds have totaled almost 90% of the monetary loss from all the natural disasters worldwide in the past decade (Guy Carpenter Guy Carpenter was fictional character in the Australian soap opera Neighbours played by Andrew Williams from 1991 to 1992. Family Tree
Taiwan is located along the west rim of Pacific Ocean with Tropic of Cancer Tropic of Cancer, parallel of latitude at 23°30' north of the equator; it is the northern boundary of the tropics. This parallel marks the farthest point north at which the sun can be seen directly overhead at noon; north of the parallel the sun appears less than across the middle. It is at all times under the threats of earthquakes, typhoons, and torrential rains. In 1999, the Chi-Chi earthquake declared a death toll of 2,434, 12,029 wounded, and a total loss of about 11.4 billion US dollars. In 2001, the Toraji typhoon typhoon: see hurricane. claimed 214 lives including the missing. Later in September of the same year, the flood caused by the extremely heavy precipitation (425mm/day, record high in Taipei City) brought by the Nari typhoon cast a severe hit on northern Taiwan with a monetary loss estimated to 5.7 billion US dollars (Chang, 2002). The monetary loss in the event of Chi-Chi earthquake alone was approximately 3% of the Taiwan GDP GDP (guanosine diphosphate): see guanine. in 1999 and human life loss was approximately one-ten thousandth of the total Taiwan population.
Along with the earthquakes and typhoons, landslides and debris flows in Taiwan seem to have higher occurrence rates after the Chi-Chi earthquake (Chin et al., 2005). The loss of lives and properties from debris flows was the highest in 2001 with a death toll of 129. Damages from landslides and debris flows on landscapes, water resource systems, transportation and lifeline systems are much more often reported during heavy precipitation.
In light of the significant increase in damages caused by natural disasters island-wide and around the world, many studies initiated by government and private sectors have been carried out in various aspects for the prevention and mitigation of natural disasters in Taiwan. Some resolutions have been implemented. As the effort for prevention and mitigation of natural disasters continues, it is of supreme importance to understand the characteristics of these natural hazards and their interaction with local environment. The dynamic interaction between unpredictable natural events of earthquakes, typhoons, precipitation and changing local environment by continuous urbanization as well as civilization has significant impact on the outcomes of natural hazards.
NATURAL ENVIRONMENT OF TAIWAN
Tectonic formations, geology, and topography
The island of Taiwan is located approximately 150 km off the southeast coast of China mainland on the convergent boundary In plate tectonics, a convergent boundary – also known as a convergent plate boundary or a destructive plate boundary – is an actively deforming region where two (or more) tectonic plates or fragments of lithosphere move toward one another. of the Eurasian and the Philippine Sea tectonic Plates This is a list of tectonic plates on Earth. Tectonic plates are pieces of the Earth's crust and uppermost mantle, together referred to as the lithosphere. The plates are around 100 km (60 miles) thick and consist of two principal types of material: oceanic crust (also called . It is spindle-shaped, with the longitudinal axis extending roughly north-south for a length of 385 km and an east-west width of 143 km (Moh and Ou, 1979). The island is composed of geosynclinal ge·o·syn·cline
An extensive, usually linear depression in the earth's crust.
geo·syn·cli deposition of Tertiary sediments of the most recent era (the Cenozoic) to a thickness of more than 10,000 meters on a metamorphic met·a·mor·phic
1. also met·a·mor·phous Of, relating to, or characterized by metamorphosis.
2. Geology Changed in structure or composition as a result of metamorphism. Used of rock. base formation (Figure 1). As the result of northwestward north·west·ward
adv. & adj.
Toward, to, or in the northwest.
A northwestward direction, point, or region.
north·west movement of the Philippine Sea Plate, the tectonic interactions between the Philippine Sea Plate and the Eurasian Plate The Eurasian Plate is a tectonic plate covering Eurasia (a landmass consisting of the traditional continents of Europe and Asia) except that it does not cover the Indian subcontinent, the Arabian subcontinent, and the area east of the Verkhoyansk Range in East Siberia. are extremely complex in the vicinity of Taiwan. There has been apparent northward north·ward
adv. & adj.
Toward, to, or in the north.
A northern direction, point, or region.
north subduction sub·duc·tion
A geologic process in which one edge of one crustal plate is forced below the edge of another.
[French, from Latin subductus, past participle of of the Philippine Sea Plate beneath the Eurasian Plate and an eastward subduction of the Eurasian Plate underneath the Philippine Sea Plate (Figure 2). This active tectonic interaction and collision have produced the Central Mountain Range in Taiwan (Penglai Orogeny orogeny
Mountain-building event, generally one that occurs in a geosyncline. Orogeny tends to occur during a relatively short geologic time frame. It is usually accompanied by folding and faulting of strata and by the deposition of sediments in areas adjacent to the orogenic ) and the prevailing structural pattern of rock formations on the island aligning in long narrow belts of elongated e·lon·gate
tr. & intr.v. e·lon·gat·ed, e·lon·gat·ing, e·lon·gates
To make or grow longer.
adj. or elongated
1. Made longer; extended.
2. Having more length than width; slender. arcs with their convexities facing the west. All the major geological structures, including the faults and fold axes, align fairly well with this structure throughout the whole island and roughly parallel to the longitudinal axis of the the diameter of the sphere which is perpendicular to the plane of the circle.
See also: Axis island. The Penglai Orogeny has been continuously elevating the surface of Taiwan. In term of geological time, Taiwan is still a young and developing land (Lin and Chou, 1978).
[FIGURES 1-2 OMITTED]
The topography and geological condition of Taiwan are closely related to the above tectonic activity. The rock formations are often fractured. In the island of approximately 35,960 sq. km, there are more than 200 peaks of over 3000 m and occupy approximately 1.3% of the island surface (Table 1). The plains with elevations below 100 m take about 31.3% of the island surface and lie mostly on the western side of island, which leaves approximately two-third of the island covered by slopeland merging from mountains to plains (Figure 3). Considering the dimensions of Taiwan, the heights of mountains, and the area of slopeland, the slopes in slopeland area are relatively steep and pose high threats to development in these areas.
[FIGURE 3 OMITTED]
Central Mountain Range generally serves as the water divide of river system on the island of Taiwan. Conforming to the topography, the rivers are generally short with steep slopes and possess high scouring scouring
characterized by scour.
a colloquial name for secondary nutritional copper deficiency. capacity in the upstream due to high gradients (Figure 4). Moreover, the flow rates are highly seasonal and fluctuated with the precipitation.
As the result of tectonic interaction and collision of the Eurasian and Philippine Sea Plates, the seismicity seis·mic·i·ty
The frequency or magnitude of earthquake activity in a given area.
The frequency or magnitude of earthquake activity in a given area. in Taiwan is among the highest in world (Figure 5). More than 200 earthquakes with tremors sensible to human (usually with Level 2 intensity and above) each year in Taiwan were recorded in the past century. In the last 15 years, more than 30 earthquakes of Ritcher's scale of 5.0 and above were recorded (Figure 6).
[FIGURES 5-6 OMITTED]
Located in western Pacific Ocean with Tropic of Cancer across the middle, Taiwan is warm and humid. The average annual precipitation in Taiwan over the past 30 years is around 2,400mm, which is almost 3 times of the world average annual precipitation, 800 mm. Approximately 80% of the precipitation is cumulated from May to October (Figure 7). With the topographical and geological conditions of Taiwan, approximately 71% of the precipitation becomes surface runoff Surface runoff is a term used to describe the flow of water, from rain, snowmelt, or other sources, over the land surface, and is a major component of the water cycle. , 24% evaporation evaporation, change of a liquid into vapor at any temperature below its boiling point. For example, water, when placed in a shallow open container exposed to air, gradually disappears, evaporating at a rate that depends on the amount of surface exposed, the humidity , and 5% infiltration. Only about 15% of the precipitation can be retained in surface water bodies. The amount of fresh water stored in the island is around 20% of annual precipitation including 5% of infiltration into groundwater.
[FIGURE 7 OMITTED]
In the past, Taiwan was subjected to the attack of typhoons mostly from May to October at an average rate of 3.7 times a year with dominant routes in northwestward direction (Figure 8). Heavy precipitation is usually associated with typhoons visiting Taiwan and constitutes one of many major parts of precipitation in addition to monsoon monsoon (mŏnsn) [Arab., mausium=season], wind that changes direction with change of season, notably in India and SE Asia. in May and June.
As a result of global climate variation, Taiwan has also been experiencing a gradual climate change. The number of rainy days Rainy Days itself isn't an official XYZ release, it's a collection of demo tapes from 1985 which has been released by guitarist Bobby Pieper, who recorded the said demos with the band. is decreasing with higher rainfall intensity (Figure 9) even though the annual precipitation remains fairly constant in the past few years.
[FIGURE 9 OMITTED]
NATURAL DISASTERS IN TAIWAN
The tectonic setting and dynamics of the Eurasian and Philippine Sea Plates are the major triggering mechanism of seismic activities in vicinity of Taiwan. Although occurring often, most of the seismic activities caused very minimal damage on the island. However, the catastrophic ones from time to time rock the island and induce significant loss of lives and properties.
In the Chi-Chi earthquake, the total loss in Taiwan was roughly 11.4 billion US dollars including an asset loss of more than 8 billion dollars and indirect loss of approximately 3 billion dollars. Three areas, respectively the vicinity of Chelungpu fault, the densely populated pop·u·late
tr.v. pop·u·lat·ed, pop·u·lat·ing, pop·u·lates
1. To supply with inhabitants, as by colonization; people.
2. Taipei City and County area, and Yuanlin area, were identified later in study with major building and infrastructure damages (Figure 10) in the earthquake. In the area within a 6 km distance from Chelungpu and Shuangtung Faults, the damages were caused primarily by high seismic forces (a recorded horizontal peak acceleration of 989 gals in east-west direction Noun 1. east-west direction - in a direction parallel with lines of latitude
direction, way - a line leading to a place or point; "he looked the other direction"; "didn't know the way home" at Station TCU (Transmission Control Unit) A communications control unit controlled by the computer that does not execute internally stored programs. Contrast with front end processor, which executes its own instructions. 084, and a vertical peak acceleration of 716 gals at Station CHY CHY Commission for Hydrology (WMO)
CHY Cherry-Burrel Corporation 080) and large relative displacement at surface (average fault dislocations of 1.5 m horizontally and 3 m vertically). Most of the structures near the fault were severely damaged even for buildings designed in compliance with modern design codes. The bridges in central Taiwan suffered severe damages from collapsed spans, cracked piers, and distressed components (Figure 11). The damages on dams, lifelines and critical facilities, and power systems were also reported. In Hsinchu Industrial Park along, an estimated loss of 400 million US dollars was reported and most of which was incurred in semiconductor and silicon wafer production facilities.
[FIGURES 10-11 OMITTED]
In Yuanlin Town and Changhwa County, soil liquefaction Soil liquefaction describes the behavior of loose saturated cohesionless soils, i.e. loose sands, which go from a solid state to have the consistency of a heavy liquid, or reach a liquefied state as a consequence of increasing porewater pressures, and thus decreasing effective seriously affected an area of approximately 60 sq. km in the Chi Chi earthquake (Moh et al., 2002). Sand boils Sand Boils occur when water under pressure wells up through a bed of sand. It looks like it is "boiling" up from the bed of sand hence the name. It also appears from a web search that this phenomena can be either man-made or natural. were found at locations at which the clay covers are either too thin or totally missing. At some locations where the clay covers are thick, the settlements of buildings up to 1 m or so as a result of ground subsidence were observed. The buildings in these areas suffered severe damages from soil liquefaction. Soil liquefaction also caused damages on levees and resulted in lateral spreading A technique used to place the mean point of impact of two or more units 100 meters apart on a line perpendicular to the gun-target line. at several locations along Koniaokeng Creek near Chelungpu Fault. Moreover, over the reclaimed land of Taichung Port liquefaction liquefaction, change of a substance from the solid or the gaseous state to the liquid state. Since the different states of matter correspond to different amounts of energy of the molecules making up the substance, energy in the form of heat must either be supplied to , damaged 4 of its 45 docking wharves Structures erected on the margin of Navigable Waters where vessels can stop to load and unload cargo.
Cities located on lakes, rivers, and oceans usually have at least one wharf, where ships can deliver and pick up passengers and load and unload various types of goods. (Figure 12).
[FIGURE 12 OMITTED]
Located approximately 150 km north of the epicenter, Taipei area suffered damages more than anticipated in the Chi Chi earthquake. The result of study indicates that the geological condition with thick soft and poorly cemented young sediment deposits could have adverse site response effect in bowl shape base formation of Taipei basin Taipei Basin (Traditional Chinese:台北盆地) is a geographic region in northern Taiwan. It is the second largest basin in Taiwan. The basin is bounded by Yangmingshan to the north, Linkou mesa to the west, and the Ridge of Syue Mountains (Traditional and be rationally argued to contribute to this consequence (Tsai, 1987). The adverse site response effects in Taipei basin include amplification of earthquake magnitudes and extended period of maximum design spectral response The variable output of a light-sensitive device that is based on the color of the light it perceives. acceleration (Chen and Chen, 1995). In 1986, two earthquakes with magnitudes of 6.2 and 6.8 and epicenters approximately 15 and 10 km east of Taiwan respectively have caused damages on buildings in Taipei predominantly of 10 to 16 stories (estimated predominant structural periods between 1.0 and 1.6 sec). In light of the above findings, the seismic design code revised in 1989 included the site response effect and extended the predominant period with revised design response spectra for Taipei area. In July 2005 the design response spectrum was further modified with higher design seismic force (Figure 13).
[FIGURE 13 OMITTED]
Landslides were also reported during the Chi Chi earthquake. Almost all of the slope failures occurred east of Chelungpu Fault on the hanging wall with shallow slips in residual soils of depths between 1 m to 5 m. At Tsao Lin, the debris from a massive landslide landslide, rapid slipping of a mass of earth or rock from a higher elevation to a lower level under the influence of gravity and water lubrication. More specifically, rockslides are the rapid downhill movement of large masses of rock with little or no hydraulic flow, slammed into the valley of Ching For the Chinese surname Ching 程, see .
For the Chinese dynasty, see .
The ching (Thai: ฉิ่ง; sometimes romanized as chhing) are small bowl-shaped finger cymbals of thick and heavy bronze, with a broad rim commonly used in Cambodia and Shui River, blocked the river, and formed a reservoir behind (Moh et al., 2002).
Landslides and debris flows
Landslides and debris flows are two major natural disasters that threaten the people and environment in Taiwan, and the later has caused greater disasters in this island over the past few years. The geological settings, topographical features, and climatic conditions of Taiwan provide the inherent factors for potential cause of these disasters. In addition, the population congregation, excessive land development, and rapid economy growth over past decades contributed more potential adverse effects to the environmental condition. The precipitation statistics of Taiwan indicate the tendency of decreasing total raining days per year but increasing precipitation intensity per rainy day. The change in raining pattern suggests that the intensity of a raining event is becoming higher, which can be easily related to the increased possibility of landslide and debris flow hazards.
In 1999, the Chi-Chi earthquake triggered over 20,000 landslides island-wide (Chin et. al., 2005). The deposited landslide masses of critically stable conditions became the source materials Noun 1. source materials - publications from which information is obtained
source - a document (or organization) from which information is obtained; "the reporter had two sources for the story" for debris flows during or after intensive precipitation. As a result, approximately 250 hazardous debris flow events have been reported during or after the earthquake. This hazardous threat of landslide and debris flow is aggravated ag·gra·vate
tr.v. ag·gra·vat·ed, ag·gra·vat·ing, ag·gra·vates
1. To make worse or more troublesome.
2. To rouse to exasperation or anger; provoke. See Synonyms at annoy. with a higher occurrence rate and greater intensity after the Chi-Chi earthquake, and debris flows were easily triggered than ever during an event of heavy rain or typhoon (Table 2).
Typhoons and floods
Taiwan is located in the area with primary passages of typhoons originated in northwest Pacific Ocean. The average number of visitation VISITATION. The act of examining into the affairs of a corporation.
2. The power of visitation is applicable only to ecclesiastical and eleemosynary corporations. 1 Bl. Com. 480; 2 Kid on Corp. 174. of typhoons to the island is approximately 3.7 per year, which is roughly 15% of the typhoons originated in the region of northwest Pacific Ocean and South China Sea. When visiting Taiwan (Figure 8), the typhoons with tracks through either northern or southern Taiwan (Tracks 1, 2, 4 and 9) tend to pose higher threats to the island.
The damages by typhoons in Taiwan are primarily incurred by the strong winds, storm surges in the coastal area, and heavy precipitation. In addition to strong winds, the foehn foehn (fān, Ger. fön), warm, dry wind that occurs on the leeward slopes of a ridge of mountains. The term was originally applied to a wind of the Alps but is now used as a generic term for all winds of this type. and salty winds associated with typhoons have caused significant damages on agricultural produces and plants. The ground subsidence induced by excessive groundwater extraction has worsened the harm of storm surges to coastal areas, and the drainage of areas with seawater seawater
Water that makes up the oceans and seas. Seawater is a complex mixture of 96.5% water, 2.5% salts, and small amounts of other substances. Much of the world's magnesium is recovered from seawater, as are large quantities of bromine. encroachment An illegal intrusion in a highway or navigable river, with or without obstruction. An encroachment upon a street or highway is a fixture, such as a wall or fence, which illegally intrudes into or invades the highway or encloses a portion of it, diminishing its width or area, but takes longer to complete. The precipitation further can easily trigger the landslides and debris flows. Moreover, the concentrated precipitation can cause extremely high flow rates in water channels and serious scouring problems on riverbeds and bridge foundations.
Nevertheless, the floods generated by heavy precipitation associated with typhoons have been the predominant cause of damage in Taiwan. In 2000 and 2001, the Xangsane, Troaji, and Nari typhoons caused severe damages on agriculture and transportation systems, and triggered landslides and debris flows island-wide. The flood in Verb 1. flood in - arrive in great numbers
arrive, come, get - reach a destination; arrive by movement or progress; "She arrived home at 7 o'clock"; "She didn't get to Chicago until after midnight" Taipei caused by the Nari typhoon severely damaged the MRT MRT,
n manual resistance technique, a treatment method used during the acute and recovery phases to relieve pain and rehabilitate the body's tissues and muscles. system at Taipei Station and it took several months for restoration to complete.
Ground subsidence can be triggered by many factors such as seismic activities, volcano eruptions, dissolution of limestone, etc. and exploitation of underground resources (groundwater, oil, coal, etc.) as well as underground space excavation. In Taiwan, the primary reason for regional ground subsidence is excessive exploitation of groundwater. Until now, more than 11% of the land in Taiwan has subsided, which was increased from 7.4% in 2001 and mostly along west coast of the island (Figure 14).
[FIGURE 14 OMITTED]
In 1960s, the ground subsidence in Taipei City was recognized as a result of excessive usage of groundwater for industry and domestic consumption. A surface settlement of more than 2 m was recorded near the center of city (Figure 15). Regulatory restriction on groundwater pumping activity was later reinforced within the city limit and had successfully stopped the subsidence in 1980s. With the gradually elevated groundwater levels, rebound of ground surface was observed from the elastic portion of soils due to decreased effective overburden o·ver·bur·den
tr.v. o·ver·bur·dened, o·ver·bur·den·ing, o·ver·bur·dens
1. To burden with too much weight; overload.
2. To subject to an excessive burden or strain; overtax.
1. stresses (Figure 15).
[FIGURE 15 OMITTED]
However, continuous subsidence with extending territory still occurs along the southwest coast of Taiwan, where the land has long been used for agricultural purposes and fishery farms. Due to limited precipitation, relatively level topography, predominately granular alluvial al·lu·vi·al
Of, relating to, or found in alluvium: alluvial soil; alluvial gold.
of or relating to alluvium
Noun formation, and unstable flow rates of rivers in the western plains of Taiwan, the surface water resources are rare and insufficient to provide steady supply of fresh water for consumption. Groundwater became the only economical and steady water supply in this area. Extensive pumping of groundwater for usage in fishery farm and agricultural purposes further aggravates ground subsidence and causes the intrusion of salt water into the groundwater systems.
Ground subsidence over the western plains of the island leads to irreversible consequences of infrastructure settlements and regional drainage difficulties in addition to the loss of land. Floods in these areas have occurred more often and the retention times become longer than ever.
The average annual precipitation of Taiwan is roughly 2,400 mm/year, approximately three times of the world average. However, with concentrated precipitation over the period from May to October and with regional discrepancy, topography of steep slopes, and rivers of limited lengths, only one-sixth of the precipitation was able to be retained as surface water for consumption in addition to 5% of infiltration into groundwater. The surface water features and geological as well as topographical conditions in the island provide very limited locations for construction of water storage facilities. Retention of fresh water has long been a challenging task in Taiwan. In the densely populated western plains of Taiwan, sufficient and steady supply of fresh water for agricultural, industrial, and domestic consumptions has been sustained by continuous exploitation of groundwater, which is the main cause of ground subsidence in this area.
After the Chi-Chi earthquake, significantly increased events of landslides and debris flows, mostly in areas of watersheds, have stripped, to certain degrees, the slopeland and damaged hydraulic facilities. Surface erosion during heavy precipitation is aggravated on non-vegetated and steep slopes, which leads to large quantities of sediments in reservoirs, and generates high turbidity turbidity /tur·bid·i·ty/ (ter-bid´i-te) cloudiness; disturbance of solids (sediment) in a solution, so that it is not clear.tur´bid
The cloudiness or lack of transparency of a solution. in surface water and causes much difficulty in water treatment processes.
In the past, the precipitation incurred from visitation of typhoons has been a major replenishing source of water storage in the island. However, in recent years, the Years, The
the seven decades of Eleanor Pargiter’s life. [Br. Lit.: Benét, 1109]
See : Time high turbidity of surface water after typhoons significantly reduced the treatment capacity of water treatment plants and created water supply shortage in certain areas.
NATURAL DISASTERS MITIGATION
Disaster warning and monitoring systems
The issues regarding natural hazards started to receive more attention in Taiwan since the disastrous events of the Chi Chi earthquake in 1999 and the floods in 2000 and 2001. The issues regarding natural hazard forecast, prevention, and mitigation have been intensively discussed and studied by government agencies and private sectors. The government has taken initiatives to integrate loosely kept information in various different government agencies and to enhance capabilities in tasks of hazard warning and monitoring.
The Central Weather Bureau (CWB CWB Canadian Wheat Board
CWB Central Weather Bureau
CWB Canadian Welding Bureau
CWB Causeway Bay (Hong Kong)
CWB Corpus Workbench
CWB Certified Wildlife Biologist
CWB Child Welfare Board ), Ministry of Transportation and Communications, is the primary government agency responsible for collecting and interpretation of climatic and seismic information in Taiwan. As part of the island-wide climatic monitoring system, it implements a total of 362 automated rain gauges island-wide (Figure 16) to collect real-time precipitation data, which is now incorporated with geographical information system Geographical Information System - Geographic Information System (GIS) to provide early warnings on floods and debris flows. The CWB also operates one of the most advanced systems in the world on seismic monitoring in Taiwan area. The system includes 75 short period seismometers, 680 strong motion seismometers, 12 broadband seismometer seis·mom·e·ter
A detecting device that receives seismic impulses.
seismo·met stations, and 68 strong motion seismometers in major cities on buildings and bridges (Figure 17). With this system, the CWB made crucial information of the Chi Chi earthquake available within 102 seconds from the moment when earthquake occurred. The information included location of hypocenter hy·po·cen·ter
The surface position directly beneath the center of a nuclear explosion.
hypo·cen , magnitude, and island-wide intensities.
[FIGURES 16-17 OMITTED]
Also in the Chi Chi earthquake period, the groundwater monitoring system (Figure 18) implemented and maintained by the Water Resources Agency (WRA WRA Wisconsin Realtors Association (Madison, WI)
WRA War Relocation Authority (US WWII)
WRA Western Reserve Academy (Hudson, Ohio) ), Ministry of Economic Affairs The following nations have a Ministry of Economic Affairs:
[FIGURE 18 OMITTED]
Risk management and mitigation strategy formulation
To enhance the disaster response capability as part of the disaster mitigation resolution, the government enacted a Disaster Prevention and Response Act (DPRA DPRA Don Pedro Recreation Agency (California) ) in 2000 (Bylaws The rules and regulations enacted by an association or a corporation to provide a framework for its operation and management.
Bylaws may specify the qualifications, rights, and liabilities of membership, and the powers, duties, and grounds for the dissolution of an in 2001) soon after the Chi Chi earthquake. The National Disasters Prevention and Protection Commission of the Executive Yuan The Executive Yuan (Traditional Chinese: 行政院; Pinyin: Xíngzhèng Yuàn; literally "Executive court") is the executive branch of the government of the Republic of China. was also established to cope with the natural disaster related issues in the central government. DPRA is basically structured on four stages of disaster management, i.e., mitigation, preparedness, response, and recovery. With respect to different types of natural disasters, different government agencies are in charge of the matters regarding various stages of disaster management according to according to
1. As stated or indicated by; on the authority of: according to historians.
2. In keeping with: according to instructions.
3. DPRA (Table 3).
The Taipei City is the most populated area in Taiwan and had suffered serious damages in various events of natural disasters. In response to the urgent need for disaster mitigation in the city, the Taipei Disaster Prevention and Rescue Committee was established under the city government to develop and promote hazard mitigation work on earthquakes, typhoons and inundations, and landslides as well as debris flows (Figure 19).
[FIGURE 19 OMITTED]
The earthquake risk assessment model using HAZ-Taiwan and TELES (Taiwan Earthquake Loss Estimation System) based upon the framework of HAZUS (developed by the Federal Emergency Management Agency The Federal Emergency Management Agency (FEMA) is the federal agency responsible for coordinating emergency planning, preparedness, risk reduction, response, and recovery. The agency works closely with state and local governments by funding emergency programs and providing technical , FEMA FEMA,
n.pr See Federal Emergency Management Agency. , U.S.A.) is adopted by the Taipei City government to provide necessary information in forming the earthquake mitigation plans. Integrated with geological GIS information, demographic data, structure and building information, lifelines and critical facilities in the city, the assessment model can provide estimation on direct physical damages due to earthquakes and associated social losses (Figure 20). The city emergency preparedness and response plans are then developed in combination with transportation networks. With the city geotechnical boring data and geological GIS information, liquefaction potential maps can also be developed for reference of earthquake hazard and land use as part of mitigation plans in the city.
[FIGURE 20 OMITTED]
The Taipei City is located in the center of Taipei basin and surrounded by Tanshuei River, Keelung River Keelung River (基隆河) is a river in northern Taiwan.
The Keelung River originates in the mountains WNW of the town of Jingtong in Taipei County, flows down to a rift valley and then flows ENE to Sandiaoling. and Hsintein Creek. The city is protected by levees and pumping facilities along these rivers against floods during heavy precipitations. The flood mitigation plan of Taipei City is primarily constituted on the basis of the inundation INUNDATION. The overflow of waters by coming out of their bed.
2. Inundations may arise from three causes; from public necessity, as in defence of a place it may be necessary to dam the current of a stream, which will cause an inundation to the upper lands; potential maps. These maps are constructed in consideration of precipitation with various intensity and elapsed times, land development conditions, topography, drainage capacity from the sewer system Noun 1. sewer system - facility consisting of a system of sewers for carrying off liquid and solid sewage
sewage system, sewage works
facility, installation - a building or place that provides a particular service or is used for a particular industry; "the and pumping facilities. Different inundation hazard scenarios are formulated with different return periods of rainfall intensity and elapsed times and presumed drainage capacity with fully operational or partly failed pumping facilities. The inundation potential maps with inundated in·un·date
tr.v. in·un·dat·ed, in·un·dat·ing, in·un·dates
1. To cover with water, especially floodwaters.
2. areas and depths of flood can be generated for mitigation plans and decision making process of evacuation (Figure 21). With the transportation GIS information, the routes of evacuation and shelter information can also be supplemented.
[FIGURE 21 OMITTED]
To form the landslide/debris flow mitigation plan, the Taipei City government built a comprehensive geological and natural environment database for the slopes in the area. The database includes 49 areas of potential debris flow rivers, situations of the existing slope management by the administration, documentation of historical landslides, the relationship between precipitation and landslide potential, and geological, hydrological hy·drol·o·gy
The scientific study of the properties, distribution, and effects of water on the earth's surface, in the soil and underlying rocks, and in the atmosphere. , as well as geomorphic ge·o·mor·phic
Of or resembling the earth or its shape or surface configuration. information of potential landslide areas. In addition to the rain gauges installed by the CWB, many other rain gauges were established by the Taipei City government to collect real-time precipitation data as a crucial index for issuing early warning of debris flows. In addition to the warning issued during precipitation in areas with high risk of landslides and debris flows, long-term resolutions of slope management and relocation of villages along the potential paths of debris flows were implemented as part of the city mitigation plans.
Latest technical development
The CWB is conducting the Climate Variation and Severe Weather Monitoring and Forecasting Development Project, which is a multi-year project to establish monitoring and warning capabilities for climatic disaster prevention, to develop techniques of short-term climate analysis and prediction, and to strengthen the capabilities of very short-term severe weather analysis and forecasting. The capability of the CWB in typhoon monitoring and prediction, precipitation monitoring and forecasting, and marine climate forecast can be significantly improved. With the Third-Phase Strong-Motion Observing Project to develop an earthquake real-time warning system, the CWB will be able to reduce the earthquake rapid reporting time from the currently 60 seconds to 30 seconds by 2009 and even provide an early warning of major earthquakes in matter of seconds to organizations and facilities in pre-established system.
[FIGURE 22 OMITTED]
After the Chi Chi earthquake, the building seismic design codes in Taiwan were revised immediately in 2000 according to recorded seismometer data and field observations. Two seismic zones were adopted for seismic design of buildings and infrastructure in Taiwan (Figure 23). However, based upon further analysis of seismic data and new findings in earthquake, the latest revision of building seismic design codes was issued in July 2005. The major changes include larger seismic design loads in most areas, additional requirement on structure ductility ductility, ability of a metal to plastically deform without breaking or fracturing, with the cohesion between the molecules remaining sufficient to hold them together (see adhesion and cohesion). Ductility is important in wire drawing and sheet stamping. under maximum considered earthquake with return period of 2,500 years, supplement of near fault effects and special consideration on site response characteristics of soft deposits, addition of provisions on seismic retrofit ret·ro·fit
v. ret·ro·fit·ted or ret·ro·fit, ret·ro·fit·ting, ret·ro·fits
1. To provide (a jet, automobile, computer, or factory, for example) with parts, devices, or equipment not in , isolation, and damper damp·er
1. One that deadens, restrains, or depresses: Rain put a damper on our picnic plans.
2. An adjustable plate, as in the flue of a furnace or stove, for controlling the draft. design guidance.
[FIGURE 23 OMITTED]
Modeling techniques of debris flows is also advanced in predicting the flow paths. A numerical solution using rheological rhe·ol·o·gy
The study of the deformation and flow of matter.
rheo·log model with two-layer system consisting of a plug region and the bottom boundary layer boundary layer
In fluid mechanics, a thin layer of flowing gas or liquid in contact with a surface (e.g., of an airplane wing or the inside of a pipe). The fluid in the boundary layer is subjected to shear forces. has provided better simulation on debris flow propagation (Liu and Huang, 2005). This advancement enables a physics based model to estimate the extent of influence of a given debris flow event. The result can be implemented to provide useful information for slopeland management and necessary information for urgent evacuation in debris flow areas.
[FIGURE 24 OMITTED]
Typhoons, earthquakes, and precipitations are natural events occurring in Taiwan all the time. It is, however, the interaction between those natural events and the natural as well as man-made environments that determines the outcomes and consequences of these events. Even though the occurrences of these natural events are inevitable, the extent of preparedness beforehand and action taken afterwards certainly decide the cost incurred at each event. Taiwan has encountered many different types of natural hazards. The unique natural environment brings out the complexity of natural hazards. Systematic resolutions in many aspects to mitigate the disasters caused by natural events are needed. Even though the natural hazards may evolve with changing environments, knowledge of fundamental issues can always be exercised to provide valuable insights to the trends and resolutions to these disastrous events.
The writers wish to acknowledge the assistance and advices provided by their colleagues in the MAA MAA
macroaggregated albumin Group, particularly Dr. Chung-Tien Chin, Dr. Richard N. Huang, Dr. Jie-Ru Chen, Mr. Chi-Hung Chao, and Mr. Cheng-Chen Wu.
Guy Carpenter & Company (2000). "Natural Hazard Review of the Year 1999", Marsh and McLennan Companies, New York New York, state, United States
New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of , New York, U.S.A.
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The study of the flows of air and water, of the species carried by them, and of their interactions with geological, biological, social, and engineering systems in the vicinity of a planet's surface. , Guwahati, Assam, India. (in printing)
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Study of soils and their utilization, especially in planning foundations for structures and highways. How the soil of a given site will support the weight of structures or respond to movement in the course of construction depends on a number of properties (e.g. and Foundation Engineering, Singapore, 205-209.
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Ou, C.D. (2004). "Sustainable development Sustainable development is a socio-ecological process characterized by the fulfilment of human needs while maintaining the quality of the natural environment indefinitely. The linkage between environment and development was globally recognized in 1980, when the International Union and natural Hazard mitigation in Taipei City", Proc. The 3rd Civil Engineering Conference in Asian Region, Special Forum 2, Seoul, Korea, 51-60.
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MAA Group Consulting Engineers,11th Floor, No. 3, Tunhwa South Road, Section 1 Taipei 105, Taiwan
DANIEL T. C. YAO
MAA Group Consulting Engineers,11th Floor, No. 3, Tunhwa South Road, Section 1 Taipei 105, Taiwan
Table 1. Topographical distribution of Taiwan (from Lin and Chou, 1978). Elevations (m) 0/100 100/500 500/1000 1000/2000 2000/3000 3000+ (From/To) Area (%) 31.3 23.5 13.7 19.7 10.5 1.3 Figure 4. Rivers of Taiwan. Elevation River Average River Name (m) Length Slope (origin-end) (km) (%) Danshuei River 3529-0 158.7 0.82 Fongshan River 1320-0 45.5 0.44 Toucian River 1913-0 63.0 0.53 Jhonggang River 2616-0 54.0 0.67 Houlong River 2616-0 58.3 0.63 Da-an River 3488-0 95.8 1.33 Dajia River 3740-0 124.2 1.67 Wu River 2596-0 119.1 1.09 Jhuoshuei River 3220-0 186.6 0.53 Beigang River 516-0 82.0 1.69 Puzih River 1421-0 75.9 1.89 Bajhang River 1940-0 80.9 2.38 Jishuei River 550-0 65.0 0.85 Zengwun River 2609-0 138.5 0.50 Yanshuei River 350-0 41.3 0.34 Eren River 460-0 61.2 0.13 Agongdian River 300-0 38.0 0.14 Gaoping River 3330-0 171.0 0.67 Donggang River 1166-0 44.0 0.20 Sihchong River 1062-0 31.9 1.69 Lanyang River 3536-0 73.0 1.82 Heping River 3536-0 48.2 2.70 Hualien River 1200-0 57.3 0.35 Siouguluan River 2360-0 81.2 2.94 Beinan River 3293-0 84.4 0.61 Figure 8. Major tracks and statistics of typhoons visiting Taiwan. Track Visits % 1 50 13.4 2 45 12.3 3 40 10.7 4 35 9.3 5 76 20.3 6 53 14.2 7 30 8 8 16 4.3 9 28 7.5 Total 374 100 From 1897 to 1996 Table 2. Losses from recent debris flow disasters in Taiwan (from Chin et al., 2005) People Typhoon Location Missing Time Event (Township/County) and Dead Property Loss 6/23/1990 OFELIA Sioulin / Hualien 35 35 houses damaged 7/31/1996 HERB Sinyi / Nantou 2 21 houses and roadways damaged 7/31/1996 HERB Shueili / Nantou 8 17 houses damaged 10/29/2000 XANGSANE Rueifang / Taipei 8 20+ houses, roadways, and bridges damaged 7/28/2001 TORAJI Fonglin / Hualien 6 3 houses and a wastewater treatment plant damaged 7/28/2001 TORAJI Guangfu / Hualien 43 150+ houses damaged 7/28/2001 TORAJI Sinyi / Nantou 16 67 houses, roadways, and bridges damaged 7/28/2001 TORAJI Shueili / Nantou 1 21 houses and roadways damaged 7/28/2001 TORAJI Shueili / Nantou 17 55 houses damaged and all public infrastructures fully destroyed 7/28/2001 TORAJI Sinyi / Nantou 46 20+ houses, roadways, and bridges damaged 6/30/2004 MINDULLE Heping / Taichung 3 30 houses and roadways damaged 6/30/2004 MINDULLE Heping / Taichung 1 40 houses Dongshih / damaged 6/30/2004 MINDULLE 1 Roadways Taichung damaged 6/30/2004 MINDULLE Puli / Nantou 2 17 houses damaged 6/30/2004 MINDULLE Hezuo / Nantou 1 6 houses damaged 8/23/2004 AERE Wufong / Hsinchu 28 20+ houses damaged 9/11/2004 AERE Jianshih / Hsinchu 4 1 house damaged Table 3. Administrative agencies for natural disasters in Taiwan (DPRA). Agency Types of Natural Disasters Ministry of the Interior earthquakes and strong winds Ministry of Economic Affairs floods and droughts Council of Agriculture, landslides and debris flows Executive Yuan