圖書典藏及影音數位平台

曾文溪為中央管河川之一，堤防或護岸部分興建已完成，惟近年全球暖化，氣候變化急遽，颱風豪雨等雨量集中且短延時現象明顯，及大小地震影響，對於現況水利建造物的安全性影響極大，故針對部分水利建造物加強檢測。 目前各水利建造物仍隨時受到颱風豪雨或地震等不可預期等災害威脅，為能永續使用，擬藉由風險評估及水利建造物安全性檢測(含現場目視檢查及非破壞性檢測方法)，針對部分有疑慮水利建造物加以檢測構造物，以利尋求有效維修與補強方案，及後續維護管理。

As for the handling process, collect, assess and analyze the basic data of basin first, and then carry out the safety inspection of hydraulic structures and the comprehensive risk assessment of river system. Furthermore, review the safety assessment regulation, set up the complete risk assessment, safety inspection and safe assessment system in accordance with the assessment results. The project will be carried out in two years. In the first year (2017), carry out the basic data collection and establishment of basin and the inspection of hydraulic structures at the downstream of Siekang Bridge of Tsengwen River. In the second year (2018), carry out the inspection of hydraulic structures at the upstream of Siekang Bridge and tributary of Tsengwen River and the risk assessment work of river system. As for the inspection results in 2017, 39 places should be projected for improvement and 5 places should be noticed for improvement at the downstream of Siekang Bridge of Tsengwen River. As for the inspection results in 2018, 38 places should be projected for improvement and 1 place should be noticed for improvement at the upstream of Siekang Bridge of Tsengwen River, and 1 place should be improved immediately, 11 places should be noticed for improvement and 3 places should be projected for improvement at the tributary. As for the follow-up tracking results, 8 damaged places have already been improved. At present, 73 places should be projected for improvement and 2 places should be noticed for improvement at the main stream of Tsengwen River; 1 place should be improved immediately, 11 places should be noticed for improvement and 3 places should be projected for improvement at the tributary of Tsengwen River. The contracted length of the ground penetrating radar in this project is 43,000m. The test length is 13,556m in 2017, and the test length is 31,291m in 2018. The test length is 44,847m in total. It was found that 2,382m of levee had slightly cavity signal, accounted for 5.31% of total test length; 600m had intermediate cavity signal, accounted for 1.34% of total test length; 172m had serious cavity signal, accounted for 0.38% of total test length. Taking a broad view for the results of this project, there was no cavity signal above intermediate state at Maopu Revetment, Danei Levee and Balin Levee, and the whole state is still good; There was intermediate to serious cavity signal at other levees, where Shensan Levee and Dongchang Levee had over 1% of serious signal, which had poorer state in the tested levees. In this project, the risk assessment and field survey results are used as the priority basis for the improvement of the damaged structures. As for the downstream levee of Tsengwen River, the major damages were cavities and cracks. The Jongye Levee had higher risk levee per the risk assessment of this project, because there was the flushing situation at the exit of water gate. It is recommended to set up rock cage and backfill earth to slow down the flushing water and stabilize the structure; As for the Shensan Levee, the continuous intermediate to serious were distributed on some parts of its slope, so the stability of whole slope was relatively poor. It is recommended to use the repair and improvement way. The total repair cost of main stream will be about NT$ 55,452,277. As for the tributary, some levees had hollow foundation or flood prevention function loss, It is recommended to use the repair or newly revetment setup way. The total repair cost of tributary will be about NT$ 4,671,755. Referring to the relevant researches, under future climate change, the rainfall might increase by 6% to 25% in the Tsengwen River basin. According to the results of every planning report in the Tsengwen River basin and the influence of climate change, this project sets up 10% to 20% of hydrological increment, reviews the flood control situation of every levee in the Tsengwen River basin and carries out the analysis. According to the risk assessment technology of United Nations International Strategy for Disaster Reduction, this project derives the following equation to describe the relationship of predicted risk with respect to the hazard and vulnerability, which can be used as the concept of the risk assessment of this project. Risk = Hazard × Vulnerability In order to find out the factors which might threaten the safety, this project collects the safety factors influencing all kinds of rivers according to the “River System Risk Assessment” meeting of Water Resources Agency held on June 20, 2018, and considers the historical cause of calamity, basin and structure characteristics of Tsengwen River, data availability and difference on nature of main river and tributary, to select the suitable safety factors influencing the Tsengwen River basin. As for the risk assessment way, refer to the calamity risk assessment scheme provided by the International Risk Governance Council (IRGC). Four steps are used to carry out the risk assessment operation of Tsengwen River, including the risk identification, risk analysis, risk evaluation and risk management. This project adopts the Risk Assessment Matrix to show the results of risk evaluation, which possess the characteristics of arranging the risk level, and can understand the risk level of whole levee quickly. According to the results of risk evaluation, the Hailiao, Madoe to Liaolang Levee, Liaolang to Anding Levee are the areas with higher risk at the downstream of Tsengwen River. The main reasons are high hazard caused by the characteristics of river course and the comprehensive evaluation result of high vulnerability at the back side. As for the tributary part, the general risk level is relatively low. Because many mountains or high tablelands are located at both sides of river bank, which have lower vulnerability. The main risk is located in population village adjacent to the river bank or the place of major traffic facilities. The last step of risk assessment is the risk management. The risk management is to provide several alternatives which can reduce the risk in accordance with the results of risk evaluation, and assess the implement effect of these alternatives. The administrator must assess the risk reduction alternatives in accordance with the risk reduction level, required cost and the creatable benefit and chance. This project lists the risk management strategy, such as avoid risk, reduce risk, transfer risk and inhibit risk, and offer the corresponding structural and nonstructural measures. This project uses safely assessment technical specification as the basis, and involves the risk assessment concept. The risk level of basin and the corresponding management measures are adopted to offer the recommendation with “certain scale” and safety assessment reference. Due to different function and scheme of hydraulic structures, the items and contents of safely assessment should be handled in accordance with their characteristics.