圖書典藏及影音數位平台

本計畫集水區範圍包含嘉義縣竹崎鄉、番路鄕及嘉義市東區，集水區北側為牛稠溪，東邊有東灣橋排水集水區，南面及西南面分別與嘉義市鹿寮排水、北排排水集水區相鄰，西側則為西灣橋排水集水區。主流排水路上游源自嘉義縣番路鄕，向西北流經竹崎鄉，最後匯入牛稠溪左岸，排水長度約4.13公里，集水區面積約2.66平方公里。 一、結論 (一) 治理保護標準 排水屬區域排水，保護基準以「通過10年重現期洪峰流量、25年重現期洪峰流量不溢堤」為原則。 (二) 建議改善方案 現地調查及水理分析結果，災害主要原因為局部渠道通洪斷面不足、渠道淤積、局部地區地勢低窪排水不良等因素，故考量淹水位置、範圍及原因、地形條件、土地利用情況、改善經濟效益等，建議採方案B為後續工程設計之依據，工程內容包含跨渠構造物改善、渠道護岸加高工程及道路排水改善工程等，並以方案B之10年重現期洪峰流量為計畫流量。 灣橋排水系統改善方案表 方案A 方案B 灣橋排水 排水路整治+分洪 排水路整治 灣橋支排 排水路整治 排水路整治 採用方案 ◎ (三) 建議改善順序 先針對集水區內人口較密集溢淹區域進行改善，改善位置位於灣橋支排與159縣道交會處西側之社區道路側溝，而計畫排水路則先進行跨渠構造物改善為優先，再者斷面不足、護岸太低者，規劃護岸加高工程，而排水路寬度已足夠者，則維持原斷面加以例行維護管理為主，並盡量減少徵收私有土地為原則。 (四) 工程經費 考量計畫區內保全對象、減少災害損失等，本計畫不分期，工程項目著重於改善人口密集區或災害嚴重區段之淹水問題，有效減輕灣橋排水集水區內淹水情形。總工程經費估算約3,614萬元。 (五) 效益評估結果 灣橋排水治理工程主要著重於改善人口密集區及排水路旁農田淹水問題，其益本比(=0.87)雖小於1，但因治理工程可有效減輕計畫區域之淹水問題，保護民眾生命財產安全，對靠農作物收入作為經濟來源的居民而言，其農業損失得以降低，考量近來人民生活水準提高，對生命、財產、居住環境等基本保護之需求日殷，同時治理工程施做後除可提高土地利用價值外，亦可增進人民對政府之信心、增進地方繁榮及保障經濟交通安全等不可計之效益，如一併納入評估，效益將提高不少，故本計畫工程建議早日付諸實施。本治理工程竣工後，預計可增加保護面積11.71公頃，增加保護人口50人。 二、建議 (一) 本計畫排水路上游有廢棄物隨意棄置之現象，建議縣政府除了定期辦理渠道清淤、疏浚外，亦需解決上游集水區垃圾棄置的問題，以維持原排水路之通洪能力與生態環境。 (二) 對於局部地區淹水情形，本計畫建議先以道路側溝改善，配合移動式抽水機等方式減輕洪災損失。 (三) 在本計畫改善工程未完成前，建議備妥汛期防災應變措施，並加強緊急應變、機動抽水機之調度、運用，以減輕災害程度。 (四) 為符合目前民眾對提升生活周遭環境品質的期待，建議主管單位應積極逐年編列預算進行整治及環境營造。 (五) 本計畫區上游集水區之農業區或保護區，如欲開發應配合本治理計畫，並依照水土保持技術規範等相關法規，做好水土保持措施，以涵養水源、降低逕流及土壤沖刷、減少下游水道淤積。 (六) 公告集水區範圍內之土地開發利用、變更使用計畫或其他事由，致增加排水之逕流量者，應依排水管理辦法第11條規定送排水計畫書並獲管理機關審查同意後始得辦理。

Wan -Chiau drainage system is located in Chia-yi County, and the catchment area is about 2.66 km2. The catchment area includes Chia-yi County Ju-Chi town, Fan-lu is town and eastern Chai-yi city. The total drainage length is 5.24 km (main drainage is about 4.13 km and the tributaries are around 1.11 kilometers); its flows through Chiayi County Ju-Chi Town Wan-Chiau Village and Chia-yi County Fan-lu Villsge, and finally converges to Niu-chou River. Since every continuous heavy rain or typhoon, Wan -chiau drainage system will encounter flood disaster which make people suffer from flooding. This project, in order to reduce flooding damage, has cooperated with the “Regulation Project Flood-prone Areas” promoted by the Ministry of Economic Affairs in 2005.The planning uses the integrated water management approach, which should accommodate the 10-year return period peak flow, and the original and new embankment elevation setting should follow the peak flow height of the 25-year return period. In order to understand the inundation areas and the flooding reasons of this project, at the beginning, this project collects past data first. However, because of the lack of information, the flooding analysis is based on on-site field survey and investigation, and the survey results of interview with local residents. Recently flooding disasters occur during Na-li Typhoon in 2001 and Morakot Typhoon in 2009. There are 3 flooding regions- the first place is the main stream of the middle reaches of Wan-chiao, the second place is the middle reaches of Wan-chiao drainage canal, and the third place is located at the low-lying areas near 159 County Road. The preliminary conclusion shows the flooding reasons includes the inadequate drainage section, sediment deposition and waste in the channel and the local low-lying topography. The main flooding area is between Yuen-long Temple Drainage and 159 County Road, and the flooding duration is about 1~2 hr. Besides the actual field investigation, this project also determines the causes of flooding and provides the basic information for the follow-up work requirement by performing the hydrological and hydraulic analysis. The main process of the hydrological analysis as following： 1. The average precipitation is obtained by Thiessen polygons method. 2. The annual maximum precipitation within 24 successive hours. Through the frequency analysis of Chi-square test, Pearson Type III is the most appropriate distribution for following analysis. 3. The peak flow of each return period is estimated by the triangle unit hydrograph with the Horner precipitation pattern. Since Wan-chiao Drainage System belongs to regional drainages, it should accommodate the 10-year return period peak flow, and the original and new embankment elevation setting should follow the peak flow height of the 25-year return period. Again, according to the results of the hydrological and hydraulic analysis, combined with the field investigation, the reasons of the flooding in waterways are wastes and sediments deposition, insufficient cross sections in the original channels and under the water drainage structures. Other reason of flooding is due to local low-lying areas. According to the results of on-site investigation and hydrological and hydraulic analysis, in order to mitigate the flood disaster, the project draws up several engineering approaches such as maintaining the drainage on a regular basis, combined with the reconstruction of some ditch structures, revetment heightening in partial drainage area, and the road drainage improvement. The expense is approximately 3,614 ten thousand dollars, and the benefit/cost ratio is approximately 0.87.