魚塭區域之排洪特性與防止溢堤方案

臺灣西南沿海魚塭養殖業發達，但魚塭區域多為低窪地區，在暴雨時常因重力排水不良加上魚塭抽排水造成排水幹線溢堤而淹水。為掌握魚塭區域排洪特性及提出淹水改善方案，本文以嘉義縣義竹鄉後鎮大排為研究區域，應用暴雨水流經理模式（SWMM, Storm Water Management Model）進行該區域水理演算，並以莫拉克颱風（2009/8）實測水位進行模式校驗。研究中以重現期25年設計降雨（350 mm/day）進行水理模擬，且給定魚塭抽排規則。淹水改善方案則考慮：1)堤防加高；2)設置抽水機組及3)魚塭預先抽排等三種。模擬結果顯示魚塭預先抽排可有效防止排水幹線溢淹情況發生。魚塭若能於降雨前進行抽排降低水位，且配合低潮位時利用重力方式控制排水幹線內為低水位，之後關閉出口閘門以隔絕潮位對排水幹線水位之影響。如此將製造整體滯洪儲水空間以有效容納降雨並減少魚塭抽排至排水幹線之水量，進而防止進入排水幹線之水量超過其負荷而溢淹。研究區域僅需整體降低魚塭內7cm水深及控制後鎮大排初始水位於0m則可於重現期25年設計降雨時不發生溢淹。魚塭預先抽排改善方案為預防型作為，因此在實際操作時可參考降雨預報資料做為模擬輸入條件，以決定魚塭抽排深度，而河川管理單位則可依此逕行公布並協助預先抽排以降低災損。

關鍵字

養殖魚塭；排洪特性；暴雨水流經理模式

並列摘要

Most of fish farms in Taiwan are located near the southwest coast where the ground level is low, even lower than the sea level. Inundations often happen in typhoon event due to flow over embankment top. The two main causes are poor gravitational drainage system and extra inflow drained from fish farms. To master the drainage characteristics in fish farm area and suggest measures of inundation prevention, the Houzhen catchment system in the Chiayi County was selected as study area. The numerical model, Storm Water Management Model (SWMM), was applied to water level simulations in the Houzhen drainage system and the measured water level data in the Morakot Typhoon were used for model calibration and validation. In this study, the 25 year return period design rainfall (350 mm) and drainage regulation in fish farm were given for all scenarios. Three measures for inundation prevention were considered: 1) raising embankment top; 2) installing pumps and 3) fish farm pre-drainage. Based on simulation results, the fish farm pre-drainage effectively prevented inundation. Lowing water level in the fish farms and keeping the low water level in the main drainage channel by gravitational drainage in low tide were performed before rainfall. The channel gate was finally closed to isolate the tide influence. Fish farm pre-drainage created enough storage space for rainfall and extra inflow from fish farms. In this area and based on the given situations, lowering water level of 7 cm in fish farms and giving initial water level of 0 m in the main drainage channel would prevent inundation as 25 year return period design rainfall occurred. Fish farm pre-drainage was a preventive way for inundation. Therefore, rainfall forecasting could be used as input data of simulations to determine the pre-drained water depth. Furthermore, river management agency would announce and assist fish farm owners to operate the pre-drainage.

並列關鍵字

Fish farm ； Inundation ； Pre-drainage ； Storm water management model

國際替代計量

魚塭區域之排洪特性與防止溢堤方案

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