Due to the typhoon, Morakot hit Taiwan strongly and cause very serious damage, many experts, scholars and engineers contributed their time and energy for assisting the adversity region. They teamed up to follow the appeal from the geotechnical society and foundation of geotechnical construction. Meanwhile, one database information system of the natural disaster was introduced in order to record natural disaster information. There are more than 300 records gathered by the professional teams from August to now. The disaster photos, investigation tables, relevant geographic information, and so on are collected for the reconstruct purpose.
Lawnon River, the major branch of Kaoping River, was damaged by Typhoon Morakot which inducing the accumulation precipitation more than 3000mm and up to 100 mm/hr in intensity. A reconnaissance was conducted shown the severe slope failure and debris flows of Lawnon basin were related to the huge rain accumulation and long duration of intense precipitation by the typhoon. Besides, the topography and geology are enhanced the hazard of disaster, such as slope aspect in windward sides, dip slope topography, residents lived in deposition fan, lacked of buffer zone, river swing caused by dammed, and severe debris flow, inducing a face-off of basin environment.
Typhoon Morakat hit Taiwan in August, 2009 and resulted in flooding and a severe damage in mountain region. The damage and loss of properties caused by this typhoon is considered the worst one in 50 years in Taiwan. Damage of mountainous roadways and slope failures in Southern Taiwan were in a large scale and have a considerable impact on the land use and management in Taiwan in the future. This paper aims to present a summary of investigation of slope failures in Chishan river basin. Failures of roadways, levee, river bank, slopes, debris flow, and stream terrace are presented and discussed. In addition, the failure mechanism and environment-related issues are investigated for different types of slope failures.
Typhoon Morakot had caused serious damages to southern Taiwan. Almost all major mountain highways located in the affected region suffered severe damages from landslides, rockfalls, and debris flows. Among all these highways, Ali Mountain Highway was one of the most rigorous examples. Ali Mountain highway, i.e. T18 route was constructed in the early 80s. For the past 30 years of operation, it suffered from different natural hazards frequently. In an effort to document the damages and to provide mitigation strategies, the authors conducted extensive field surveys and aerial or satellite images analysis to preliminarily access the failure mechanisms of selected typical slope failures along T18 highway. For five selected sites in this study, engineering and hydraulic geological features were found to be most influential factors to the failures. The weak zones and impermeability of the discontinuities of geological structures, including faults, dominated the global stability of the slopes. In summary, geotechnical engineers should consider carefully the geological structure discontinuities and their properties for slope mitigation. Moreover, considerations of the extreme hazards such as Typhoon Morakot should be also included in future design.
During the five years period between 1996 and 2001, three major disasters, which were induced by Typhoon Herb in 1996, Chi-Chi Earthquake in 1999, and Typhoon Toraji in 2001, occurred in the watershed of Chenyoulan River. These disasters shadow people's mind until today. On August 7, 2009, Typhoon Morakot swept through Taiwan with heavy rains which induced severe damages in central, southern, and eastern Taiwan. It also caused several landslides, debris flows, and heavy floods in the watershed of Chenyoulan River. This paper investigates the impacts of geological and geographical conditions, Chi-Chi Earthquake, human activities, and severe rainfalls on slope failures of the Shinsan Village, Shenmu Village, and New Central Cross-Island Highway, especially from the view point of geotechnical engineering. The influences of debris flow, high concentrated flow, and geological structure on the extent of damage were also discussed.
The accumulated rainfall of typhoon Morakot is greater than 1500mm and the rainfall intensity is over 200yrs return period in Taitung county located in the southeast of Taiwan. Hence, the extreme rainfall triggered widespread and large magnitude geohazards in the south part of Taitung county. The serious geohazards along Jhihben river, Jinlun river, Taimali river, Darzu river and Darniau river are presented in this article. Field survey was conducted and the result shows that the type of geohazards include landslide, debris flow, river bed silt, nature dam, and flooding. All of them were triggered by extremely heavy rainfall and the characterization of those geohazards are accumulative, complex, and chain reactive. Therefore, those geohazards have relation between each other, so they could be represented as compound geohazards. In order to make strategies for rehabilitation, monitoring and quantitative analysis of hazard potential are indeed needed in the near future.
Typhoon Morakot made new landslide areas about 34,878 hectares, because the affected area is so wide, it is very difficult to obtain the disaster information of Typhoon. The aerial photographs and the Formosat-2 Satellite Image are two kinds of Methods to obtain the short term data of large area, but they also have their limitations, they are not easy to get complete short term data. The Central Geological Survey, where the "Geological Investigation and Database Construction for The Upstream Watershed of Flood-Prone Area" to provide, including watershed geological maps, landslide debris flows of information, serious collapse zone data, the Formosat-2 Satellite Image of sub-consciousness …etc, such as the latest achievements of information to promote post-disaster reconstruction work.
August 8, 2009, Typhoon Morokot with torrential rains brought a significant loss of lives and properties to the southern Taiwan, especially in the original residential land of tribes. These tribes are mostly on the Central Range area, and some tribes will migrate to the safety areas after the Morokot. This paper introduces the geologic characteristics of the southern Central Range and the migration history of the Dashe, Dewen and Dalai tribes It is hoped to find the relationship between the geologic characteristics of the Central Range and the migration of the original residential land of these tribes.
As other compound disasters due to climate change, the occurrence probabilities of the landslide dam and its secondary disasters have been increasing gradually. The landslide dam is formed mostly by rock fall, landslide and debris flow blocking river. The safety of the natural dam is far below the artificial dam built by engineers, and the dam is apt to failure. The lives of most landslide dams are extremely short, due to overflow and headcutting mainly. The life-span and failure pattern of the landslide dam are affected by size of dam, soil material, inflow and capacity of the barrier lake etc. Typhoon Morakot attacked Taiwan in 7-9 Aug. 2009 and brought heavy rainfall causing serious floods and 17 landslide dams in the east and central-south Taiwan, and caused a serious damage more than Chichi earthquake did. Most landslide dams overwhelmed within a short time, meanwhile caused flushing, and serious change on the river morphology, and even human injury and property loss in downstream communities, such as Shiaolin village. Therefore, disaster mitigation and risk management of landslide dam need a great attention in the future.
The 2009 Typhoon Morakot brought a huge amount of rainfall in southern Taiwan and caused a catastrophic landslide which buried houses and about 5 hundred people in the Siaolin Village, Jiasian Township, Kaohsiung County. The landslide initiated from a slope about 500m to 900m above the riverbed on about 6 o’clock in the morning, 9th August. Huge amount of slid materials moved quickly downward and became a debris flow. A part of debris topped over the 590 highland, spread on the hillslope, and finally reached and destroyed the Siaolin Village. Most debris kept downward movement along the gully and reached the Chishan Creek, and blocked the main stream forming a dam-up-lake. About 1 hour later, the lake started breaking, the flood flushed out the buried village remaining the present view.
The cruxes of the problem for the catastrophic landslide may include the following 3 points. (1) Geologically, there are unfavorable wedge combinations formed by bedding planes at north side and joints or small fault at south side, and also the wedges were overhanging. (2) The source area of slide locates at a stream head and was covered by very thick colluvium of different ages. These loose materials provided good chance for water infiltration and caused the unstable wedge easily saturated. (3) The source area of slide is too high above the village; the potential energy transferred into dynamic energy and enlarged the impact of the landslide.
Typhoon Morakot, a moderate typhoon, is the 8th typhoon hit Taiwan in 2009. It took Typhoon Morakot 61 hours to pass through Taiwan from August 7, 5:00A.M to August 9, 6:00P.M. A typhoon either has a short-duration rainfall with high rainfall intensity or a long-duration rainfall with heavy rainfall can easily become the disaster-causing factor of debris flow and floods to Taiwan. The high rainfall intensity and long-duration rainfall brought by Typhoon Morakot throughout the KaoPing River Basin has broken all rainfall records in Taiwan and caused severe and large-scale damages. This article is to survey the damages of southern Taiwan hydraulic facilities caused by Typhoon Morakot. Besides, this article makes suggestions for follow-up management and maintenance of the hydraulic facilities and for the design reference of new facilities in the future.
Morakot typhoon with the unprecedented large rainfall, resulted in central and southern Taiwan regions suffered from landslides, debris flow and floods inundation. Transport system plays a crucial role in the relief work of disaster. However, the breakage and damage of bridges and roads paralyzed the transportation system in some region hit by this natural adversity. It seriously delayed the operation of relief work. This article presents the damage states of bridges and slopes of highway system in Kao-Ping River Basin that has admitted the most damage from this disaster. Factors of causing the damage of bridges and slopes were explored as the references of future rehabilitation and reconstruction works.
On June August 2006, Typhoon Morakot invaded Taiwan island wide. Besides the record-breaking rainfall, Typhoon Morakot caused the most serious highway bridge damages ever, especially in central and southern Taiwan. With the steep rise and sink in geography, Taiwan is often seriously affected when huge amount of rainfall comes with typhoons that erode cliffy, unsteady hillsides to bring collapse resulting in volumes of mudflows and drift wood accompanied with bridge-scouring floods. It brings about acute harm to bridges and roads to induce traffic interruption, and further it impedes repair work. For this reason, this study applies the statistics of bridge damages and case analysis in Typhoon Morakot and synthesizes the various bridge damage models and their potentiality of flood scouring hazard. This research expects to provide references for future academic researches, bridge engineering design and post-disaster reconstruction in order to enhance bridge endurance of mudflows and flood scouring.
Typhoon Morakot struck southern Taiwan on August, 8, 2009 with high rainfall intensity and accumulated rainfall as high as 2860 mm for 72 hours. Severe landslide and debris flow hazards were induced. The debris flow cases resulted in severe impact to local community were selected for case study, for which field investigation and analysis were conducted. Results of this study provide information and suggestions for mitigation of secondary hazards, hazard reduction and drafting of mitigation strategy. The debris flow cases selected in this research are Nanshalu, Maya, and Dakanuwa villages of Namasha township, Shinkai and Shinfa areas of Liugui township, Kaohsiung county, and Chianghuangkern of Nanhua township, Tainan county.
This paper present the field exploration of the hazards of rainfall induced landslides by the Typhoon Morakot in Kao-Pin area, and the hydro-geological numerical simulation analysis for an integrity monitoring case study on the infiltration, seepage, groundwater variation, pore water pressure change and displacement of the slope land. The exploration routes are along the Chishan river and Laonong river watershed in Kaohsiung County. The main routes included are Route 20, Route 27, Route 27 A and county road No. 128 and No. 130. Type of disasters include: the landslides along road and river banks, and several large-scale rock falls and debris flows. The case study presented refers to the project on the landslide site of Baolong near to the local road No. 128, which was conducted by Sinotech Engineering Consultants Inc. and commissioned by Central Geological Survey, MOEA. For the numerical analysis, the program GeoStudioTM was used, and SEEP / W, SLOPE / W and SIGMA / W modules are applied. An integrated field investigation and test results, as well as on-site monitoring value are used and comparisons are made. The results show that the model of analysis fits the lifting state of water level in the period of typhoon Morakot. Furthermore, it may also appraise the performance of slope stability and deformation.
In this study, we used 3D distinct element method (PFC3D) with granular particle assemblage to simulate kinematic process and mechanics of two catastrophic landslides in Taiwan; one was the Tsaoling landslide induced by 1999 Chi-Chi Earthquake and the other was recent Hsiaoling landslide induced by 2009 Morakot Typhoon. When the residual friction coefficient of Tsaoling landslide is equal or less than 0.05 after a critical displacement due to the Chi-Chi earthquake, the landslide block can move across the Chinshui River and deposit on Diagiaoshan. The predicted maximum velocity is greater than 70 m/sec and the longest runout distance of the particle is about 3,500 m. According to the 3D numerical simulation, Hsiaoling village might be buried in 60 seconds after the Shamdushan landslide. The predicted maximum velocity is about 50 m/sec and the debris could reach to the other side of the Chishan River. Consequently a dammed lake was formed in the Chishan River. From the viewpoint of the assessment of catastrophic landslides, and the 3-D discrete element together cooperate with the analysis of sensibility of landslide potential is a potential tool to elucidate the mechanics and kinematics of landslide process and impact area induced by gigantic landslide events.