- Watershed and Environmental Issues
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Chianan irrigation project
The first proposals for the dam were made as early as the 1930s during the Japanese occupation of Taiwan. The Japanese had built the Chianan Irrigation system to increase Taiwan's agricultural output, which was supplied primarily by the Zengwen River. Because the Zengwen River does not cross the area of the Chianan Plain to be irrigated, a tunnel had to be punched through mountains to divert Zengwen water into the Guantian River. Between 1920 and 1930, the Wushantou Dam was built, forming an...
Due to Taiwan's highly seasonal rainfall, the Zengwen River contains little water except during the wet season from May to October, during which massive floods occur that exceed the capacity of the diversion tunnel. Out of the average 1.6 cubic kilometres (1,300,000 acre⋅ft) annual flow of the Zengwen River, only 25 percent of the water could be effectively used. Furthermore, the Zengwen river has a high silt content, which was causing the Wushantou reservoir to quickly lose its capacity. In...
Construction finally began at the Lioutengtan site on October 31, 1967. Two tunnels were excavated through the rock underneath the south abutment of the future dam site. The outer diversion tunnel was 1,240-metre (4,070 ft) long and the inner diversion tunnel was 1,038-metre (3,406 ft). A rolled-earth embankment cofferdamwas constructed to divert the Zengwen River and protect the dam site from flooding, up to an elevation of 165 metres (541 ft).
The Zengwen reservoir receives its water from an extremely steep and rugged catchment basin of 481-square-kilometre (186 sq mi) in the Alishan Range of south-central Taiwan. The elevation of the land ranges from 227 metres (745 ft) on the shore of the reservoir to over 2,500 metres (8,200 ft) in the Alishan National Scenic Area near the summit of the range. About 77 percent of the watershed is forest, 13 percent is agriculture, 9 percent other uses and less than 1 percent is urbanized. The reservoir has suffered severe siltation (sedimentation) from the watershed, which has caused a large reduction in its capacity. Siltation has reduced the volume of water available for irrigation and hydropower, as well as reducing the effectiveness of the Zengwen reservoir to control flooding. The siltation rate has greatly increased in recent years, in part due to a sharp increase in the intensity of typhoon rains, as well as a rising frequency of drought. In August 2009, Typhoon Morakot caused m...
The Zengwen dam and reservoir are part of the Zengwen Reservoir Scenic Area.The reservoir was first opened to the public in July 1974.
- Direct Effects
- Emergency Response
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The most damage done to Nantou County was in Xinyi, which had the greatest rainfall in the county. The currents of the Chenyoulan River caused the foundations of roads and buildings to be wiped away.A building in Longhua Elementary School tilted 30 degrees as a result of the foundations being washed away and was on the verge of falling into the river. Provincial Highway 16 collapsed between Jiji and Shuili, causing seven cars to be washed into the Zhuoshui River. So far, only four out of fift...
Typhoon Morakot caused Zengwen Reservoir, which was originally short on water, to suddenly exceed capacity. In response to the excess water, the reservoir released over 100,000,000 liters of water, which is about 80% of the dam's total capacity. The release of water caused severe flooding along the Zengwen River; in Xiaobei Village in Madou Township, the water level reached a story high.
Kaohsiung County saw over 2,500 millimeters of rainfall within three days (Kaohsiung typically receives the same amount of rain in a year). The rain brought severe floods on the plains and landslides in the mountains. On August 14, Xiaolin Village was completely covered due to a landslide, causing the deaths of 398 people. Due to the rain, many bridges were washed away, including those on Provincial Highways 20, 21, and 27 and the bridge to the Maolin National Scenic Area. 14 people went miss...
1. The Council of Agriculture estimates that a total of $19.217 billion NTD was lost due to the typhoon, making it the second-costliest typhoon behind Typhoon Herbin 1996. Out of this, farms lost $12.9 billion, fisheries lost $4.7 billion, and livestock lost $1.6 billion.
1. Twenty bridges were destroyed due to the typhoon, with eight being on a Provincial Highway. Seven of those on a highway were in Kaohsiung or Pingtung. Additionally, at least 16 landslide damswere formed during the typhoon.
1. Most of the damage done to railways are located in the south on the Pingtung, Taitung, and South Link lines. Also, the Alishan Forest Railwaysaw some serious damage.
The military was dispatched with responding to the disasters all around the country with transporting food and aid around. After the typhoon, soldiers were also used in cleanup and rebuilding.An estimated 15,815 soldiers were used in total. With the assistance of firefighters and policemen, an estimated 41,752 people were rescued. On August 11, a helicopter delivering aid crashed in the mountains of Pingtung County. All three of its crew were lost.
On August 15, the Executive Yuan formed the "Typhoon Morakot Rebuilding Committee". The 37 person committee was given a budget of $116.5 million NTD to rebuild infrastructure and economic losses. The committee has built 3,481 permanent housing units in 40 locations and repaired most damaged roads.However, there was controversy surrounding the relocation of people to these new housing units. After the flooding, many organizations began raising money for rebuilding in areas affected by the typh...
The Association for Relations Across the Taiwan Straits donated a total of $450 million Renminbi ($2 billion RMB) to rebuild. They specified that $150 million TWD be used on building 500 units of recovery housingand $1.7 billion TWD be used on rebuilding infrastructure. The Mainland Affairs Councilestimated that around $4 billion NTD was donated by China. Also, around $130 million NTD was donated by Taiwanese companies in China.