圖書典藏及影音數位平台

為有效監測地層下陷行為，及時掌握地層下陷之發生趨勢，依據地下水保育管理暨地層下陷防治第2期計畫（104～109年度）持續規劃辦理臺北、桃園、嘉義、臺南及屏東地區地層下陷監測，並維護宜蘭、桃園、嘉義、臺南、高雄及屏東等地區19口地層下陷監測井，同時整合相關監測資料進行分析探討，釐清下陷發生機制，據以研擬因應對策，有效達成地層下陷之防治目標。

The objectives of project are to monitor the land subsidence and to explore the subsidence mechanisms in Taipei, Taoyuan, Chiayi, Tainan and Pingtung, Taiwan. Consequently, these results will provide precaution for the potential areas of land subsidence and develop the conceptual strategy for the mitigation of serious land subsidence. This project contains five tasks including: 1260km length leveling survey, constructed 1 land subsidence monitoring wells and maintained the existed land subsidence monitoring wells, constructed 1 continuous GPS stations and maintained the existed stations, constructed 1 deep benchmark and maintained the existed deep benchmark, and maintained the ground water monitoring station in the area. The integrated analysis of monitored data obtained from the land subsidence area and there main results are summarized as follows : I. The results of leveling survey The areas of leveling survey include Taipei(120km), Taoyuan (250km), Chiayi(360km), Tainan(240km) and Pingtung(290km), total length of surveyed routes is about 1260 km. The results of the leveling survey are as follows: (I) In Taipei County, 2017, the maximum subsidence rate is about 0.9 cm/yr and the obviously subsiding area is about 0.0 km2. (II) In Taoyuan County from 2010 to 2017, the maximum subsidence rate is about 0.3 cm/yr and the obviously subsiding area is about 0.0 km2 (III) In Chiayi County, 2017, the maximum subsidence rate is about 3.2 cm/yr (Lioujiao and Singang Township) and the obviously subsiding area is about 7.0 km2. In 2016, the maximum subsidence rate is about 2.6 cm/yr (Budai Township) and Dongshih Township with subsidence rate 2.3 cm/yr. The subsidence rate and area increased from 2016 to 2017. (IV) In Tainan County from 2014 to 2017, the maximum subsidence rate is about 2.1 cm/yr and the obviously subsiding area is about 0.0 km2. Beimen District, Syuejia District and Annan District are the areas with subsidence rate over 1.0 cm/yr. Beimen District was the main subsidence area in Tainan County hence the leveling survey conducted independently from 2016 to 2017 and indicated the subsidence rate about 3.0 cm/yr. (V) In Pingtung County, 2017, the maximum subsidence rate is about 3.8 cm/yr and the obviously subsiding area is about 4.9 km2. The subsidence rate and area increased from 2016 to 2017 in Linbian Township and Jiadong Township. II. Maintenance and measurement of the existed land subsidence monitoring wells, continuous GPS stations and deep benchmark and (I) The land subsidence monitoring wells The maintenance of land subsidence monitoring wells in Yilan(1), Taoyuan(1), Chiayi(7), Tainan(4), Kaohsiung(1) and Pingtung(6, include 1 new built well). A total of 20 land subsidence monitoring wells are in the areas. All of the monitoring wells and instruments are with good status of all systems facilities. (II) The continuous GPS stations 1. The maintenance of continuous GPS stations in Budai elementary school in Chiayi, Linbian junior high school in Pingtung, and Dingliao station in Pingtung. All of the continuous GPS stations worked stable in project duration. Data acquisition are more than 20000 per day, with cycle slip index between 0~5 and MP1 and MP2 value between 0.1~0.5. 2. Moreover, the GPS data from total 190 stations from Water Resources Agency (WRA), National Land Surveying and Mapping Center (NLSC), Department of Land Administration, Central Weather Bureau (CWB), Academia Sinica, International GNSS Service (IGS), Central Geological Survey (CGS) and Industrial Technology Research Institute (ITRI) also joined into the computation. III. Construction a new continuous GPS station and a 100m deep benchmark (I) The results of land subsidence monitoring wells indicated that the dry season compression occurred in depth 49 to 126m in Singang, Chiayi, that may cause the safety concerns of HSR. Hence, the new continuous GPS station and deep benchmark constructed in Wannei elementary school, Chiayi, September 2017. (II) The continuous GPS station and deep benchmark in Wannei elementary school worked stable in project duration. Data acquisition are more than 43000 per day, with cycle slip index between 0~2 and MP1 and MP2 value between 0.1~0.3. IV. Construction a new land subsidence monitoring well (I) The results of land subsidence monitoring from 2001 to 2016 indicated that the accumulated subsidence length in Pingtung was over 45cm and the ground water monitoring stations indicated the ground water level became decreasing in the observation period. Hence, the new land subsidence monitoring well constructed in Dingliao station, Pingtung, September 2017. (II) The accuracy of the uncertainty analysis of Dingliao land subsidence monitoring well shows about ±0.064cm in 15 days measurement periods from September to November, 2017.? V. Analysis of the integrated monitoring data in land subsidence area (I) Yilan area The accumulated subsidence length in Jhuangwei Township from 2009 to 2017 was 4.4cm. The subsidence rate was less than 1cm/yr. (II) Taipei area 1. The results of leveling survey in 2017 indicated the subsidence rate in Taipei area was less than 1cm/yr. 2. The ground water level data indicated the tendency of ground water level was increasing and with the highest level occurred in 2017. (III) Taoyuan area 1. The leveling survey results indicated the highest subsidence rate was 0.4cm/yr from 2010 to 2017 in Taoyuan area. 2. The results of land subsidence monitoring well in Shulin elementary school indicated the land compression phenomenon and ground water level was irrelevant in Taoyuan area. (IV) Chiayi area The land subsidence in Chiayi was obviously, especially in coast areas with compression rate larger than 1.5cm/yr 1. Dongshih Township The results of benchmark G056 indicated the 9.0 cm/yr subsidence rate occurred in 2004 which was the largest value in observation period. The subsidence rate decreased to 1.0 cm/yr from 2013 to 2014, but increased to 4.0 cm/yr in 2015. The subsidence rate decreased again to 2.3 cm/yr in 2016. Now the subsidence rate is 0.9 cm/yr in 2017. ? 2. Budai Township The results of benchmark 45 indicated the 6.6 cm/yr subsidence rate occurred in 2004 which was the largest value in observation period. The subsidence rate decreased from 2010 to 2014, but increased to 4.4 cm/yr in 2015. The subsidence rate decreased again to 0.9 cm/yr in 2016, but increased to 1.2 cm/yr in 2017. 3. Yijhu Township The results of benchmark 09 indicated the 5.5 cm/yr subsidence rate occurred in 2004 which was the largest value in observation period. The subsidence rate decreased from 2010 to 2014, but increased to 3.0 cm/yr in 2015. The subsidence rate decreased again to 1.1 cm/yr in 2016, but increased to 1.9 cm/yr in 2017. 4. Puzih City The results of benchmark I042 indicated the subsidence rate decreased from 2010 to 2014, but increased to 3.7 cm/yr in 2015. The subsidence rate decreased again to 1.5 cm/yr in 2016 and 1.2 cm/yr in 2017. 5. Singang Township and Lioujiao Township (1) The results of benchmark BM28 indicated the 4.3 cm/yr subsidence rate occurred in 2004 which was the largest value in observation period. The subsidence rate decreased from 2010 to 2014, but increased to 3.8 cm/yr in 2015. The subsidence rate decreased again to 0.4 cm/yr in 2016, but increased to 3.0 cm/yr in 2017. (2) The results of land subsidence monitoring wells in Singang Anhe elementary school indicated that the main compression occurred in depth 49 to 126 m and the result of ground water monitoring station also indicated the same phenomenon, that may cause the safety concerns of HSR. (V) Tainan area The rainfall in 2017 was obviously less than 2016, that may cause the land compression in Tainan area. The results of land subsidence monitoring well in Xiaying elementary school and Syuejia junior high school indicated the comprssion rate was larger than 1 cm/yr. 1. Beimen District (1) The main subsidence area in Tainan located in north Beimen which will measure every year with leveling survey in Chiayi together. Others area will measure every 3 years. (2) The results of benchmarks G068, JBM-1 and 83 indicated the subsidence rate 3.0, 2.4 and 2.3 cm/yr, respectively. The subsidence rate increased from 2007 to 2010, but decreased after 2011 with subsidence rate less than 1 cm/yr. 2. Syuejia District The results of benchmark 12 indicated the subsidence rate increased from 2007 to 2010, but decreased after 2011 with subsidence rate less than 1 cm/yr. 3. Annan District The results of benchmark 8686 indicated the subsidence rate increased to 2.0 cm/yr from 2014 to 2017. After the field survey, the subsidence phenomenon maybe caused by reclamation land and construction in near area. ? (VI) Kaohsiung area The accumulated subsidence length in Yantian area from 2003 to 2017 was 4.4 cm. The subsidence phenomenon was implicit. (VII) Pingtung area The rainfall in 2017 was obviously less than 2016 and the ground water level decreased obviously than 2016. The results of land subsidence monitoring wells in Linbian and Jiadong Township indicated the comprssion rate was larger than 1 cm/yr. 1. Linbian Township (1) The results of benchmark G127 indicated the 5.3 cm/yr subsidence rate occurred in 2011 which was the largest value in observation period. The subsidence rate increased from 2012 to 2015, but decreased to 2.2 cm/yr in 2016. The subsidence rate increased again to 2.7 cm/yr in 2017. (2) The results of land subsidence monitoring wells in Linbian junior high school indicated that the main compression occurred in depth 0 to 254 m and the result of ground water monitoring station also indicated the same phenomenon. The ground water level have the lowest value in 2016 and 2017. 2. Jiadong Township (1) The results of benchmark G129 indicated the 4.6 cm/yr subsidence rate occurred in 2011 which was the largest value in observation period. The subsidence rate increased from 2012 to 2015, but decreased to 1.8 cm/yr in 2016. The subsidence rate increased again to 2.6 cm/yr in 2017. (2) The results of land subsidence monitoring wells in Jiadong elementary school indicated that the main compression occurred in depth 0 to 102 m and the result of ground water monitoring station also indicated the same phenomenon.