圖書典藏及影音數位平台

花蓮溪原名紅巖溪，流域位於台灣東部花蓮縣內，北接吉安溪，南界秀姑巒溪流域。本溪幹流全長57.28公里，流域面積1,507.09平方公里，主要支流有五條均在西側，由南往北依序為光復溪、馬鞍溪、萬里溪、壽豐溪及木瓜溪。 本溪支流坡陡流急，崩山處處，每遇颱洪挾帶巨量砂石而下，數小時內即由橫谷進入縱谷平原。河床比降在谷口由急陡驟變為百分之一左右坡度，使砂礫淤積於下淤平原段，威脅溪旁兩岸人民生命財產安全，故防洪構造物之安全性影響甚大。 花蓮溪堤防多屬老舊堤防，為能尋求有效維修與補強方案，擬藉由安全性評估計畫來全面檢視花蓮溪堤防之安全，以利後續維護管理。 本計畫主要目的為暸解花蓮溪堤防內容結構現況，採用非破壞檢測方式，檢查堤防構造物之使用狀況與內部損壞狀態，包含結構體內部裂縫及含水狀況等情形，以便未來做為堤防管理、維護之參考依據，以及尋求有效維修與補強方案，擬委外辦理安全性評估分析及研擬改善方案。

Hualien River mostly old dike along the river. The existing structures of flood wall of the River system were found partially collapsed, hollowed out, and material deterioration due to long years of weathering effect and struck by typhoon and heavy rains. In order to look for effective maintenance and reinforcement programs to ensure the safety of lives and property of the people on both sides, there is a need to perform the safety assessment program, whereby the stream carried Hualien River System comprehensive review of the safety of the dike, in order to reach the subsequent maintenance and management. I. Project Scope and Main Work Items The scope of this project includes the dike of Wanli River, Ma-an River and Hualien River. The total length is 36,508m. The main work items of project are divided into: (1) The site inspection of dike structure and facilities, including one time of regular inspection and two times of casual inspection; (2) The strength investigation of dike structure, adopting at least 18 sets of drilling core sample to conduct the strength test and rebound hammer test for verification and comparison; (3) Nondestructive test, carrying out 31,600m of ground penetrating radar test and 500m of shock wave test; (4) Data collection and analysis and safety assessment of dike, drafting the recommended maintenance proposal and subsequent maintenance and management direction. II. Basic Data Investigation for Scope of Project （1）Capability for Water Conveyance The elevation for the dike of Wanli River, Ma-an River and Hualien River can resist the flooding level of 200-year recurrence interval. （2）Investigation of River Flow Route Change The flow route of Hualien River (cross-section 44 to cross-section 48-1) leaned towards the left bank. It leaned towards the right bank from 2005. The flow route of Wanli River to cross-section 6 (between Fonglin No. 2 Dike and Chungsinpu Dike) usually leaned towards the right bank but leaned towards the left bank in recent years. The flow route of Ma-an River leaned towards the left bank in recent years, and its downstream section is still unstable. （3）Investigation of River Silting Change The Hualien River (cross-section 44 to cross-section 48-1) revealed the scouring trend in 2005~2008, but it revealed the silting trend since 2008 to 2016. From 2005 to 2016, the whole section of Wanli River revealed the scouring trend, and the river bed is still scoured continuously at present. From 2005 to 2016, the Ma-an River revealed the silting trend at the downstream of cross-section 09, and it revealed the scouring trend at the upstream of cross-section 09. （4）Investigation for Depth of Dike Structure Foundation According to 2016 “Project on Big Cross-Section Measurement and Hydrography and Silting Change of Hualien River Water System”, compared the elevation, flood-preventing record table and main trough position, it was known that the foundation of Fonglin No. 2 Dike (cross-section 00), Sibao Shore Protection (cross-section 20), upstream dike of railway bridge (cross-section 13-1) and Dongfu Dike (cross-section 46-1) might be scoured in the future. III. Site Inspection Result of Dike Structure In the scope of project, there were 92 damaged places assessed by visual inspection, in which 91 places should be planned for improvement, 1 place should be noticed for improvement, and no place should be improved immediately. The major damage type includes 66 crack damages and 17 peeling damages. The place of noticed for improvement was located at Wanjon Dike 6K+715 of Hualien River, where a 7m x 6m x 0.5m (L x W x D) sinking hole was generated at the top of dike. IV. Inspection Result of Non-destructive inspection The non-destructive inspection includes the ground penetrating radar test, shock wave test, rebound hammer test and drilling core test etc. After cross verification and comparison, mostly identical reality of result can be achieved. It can fully grasp the present situation within the structure of river embankment. The results are described as follows: (1). Result of Ground Penetrating Radar Test The finished length was 32,068m. After analyzing, it was found that 372.0m (1.16% of total length) of dike was slightly cleaned out mainly, 2.5m of dike was intermediately cleaned out, and 4.0m of dike was seriously cleaned out. (2). Result of Shock Wave Test The sections conducted by shock wave test included Chungsinpu Dike, Sibao Shore Protection, upstream dike of railway bridge and Kwangfu Dike. The total length was 500m. Every dike section had slightly low wave speed region, it might be related to local loosens of material under the dike. (3). Investigation for Strength of Dike Structure The drilling core test and rebound hammer test were adopted for the investigation. It was shown that the tensile strength of samples from 18 places was 193.3 kgf/cm2~408 kgf/cm2. V. Safety Assessment Result of Dike According to 2015 “Project on Safety Assessment and Analysis for Upstream Dike of Hualien River Basin”, the site inspection result (including non-destructive test result), river embankment historical data, dike security target, dike body structure assessment, environmental factor assessment and hydrography analysis were used as six assessment indicators. Every 500m was used as an assessment section. It was divided into 77 sections. The assessment result revealed that 58 sections were classified as the normal sections, 19 sections were classified as the planned improvement sections, and there was no noticed improvement dike section and immediate improvement dike section. VI. Subsequent Treatment Way for Damaged Dike Section in Scope of Project There were 92 damaged places in scope of project. It was judged only 25 places should be repaired. The repair fee is about NT$ 1,001,000. The other 67 damaged places should only be traced and observed continuously.