埤塘與滯洪空間關聯性探討──以桃園為例

Detention Analysis of Farm Pond and Ditch Network in Taoyuan City

氣候變遷下經常衍生突然的暴雨，傳統智慧的埤塘藉由地形與溝圳流通，形成水域網絡，應可適度減緩水災所造成的衝擊。本研究以桃園市為場域，透過調查與分析埤塘位置，模擬不同雨量之淹水潛勢，搭配田野調查瞭解並對應歷史災害範圍，剔除已失去水圳連結的埤塘，探討埤塘於災害治理上利用水位連通及高低差調節，透過水域網絡系統達成滯洪、納洪、調洪之功能。桃園市目前淹水潛勢以中壢區、平鎮區、大園區、觀音區等區最高，其中大園區尤其嚴重。埤塘調適暴雨之可能性極高，尤其在面對日降雨量200mm時，埤塘滯洪成效最為明顯。如果善用埤塘和水圳網絡，將能有效降低水患風險，日降雨量150mm及200mm為55%左右。再以風險管理的角度觀察，日降雨量300mm時有818口埤塘可利用，對於紓解水患非常重要，其中的539口更是降低水災風險的關鍵。

Farm ponds constructed using conventional wisdom to form water networks to reduce and moderate impacts from flood and stormwater due to climate change. This study used Taoyuan City in northern Taiwan as its target area and performed a survey and analysis of farm pond location, floodprone GIS stimulations based on various rainfall types. The field research included its corresponding historical disaster area, excluding farm ponds that are no longer connected with ditches as well. The objective was to determine how farm ponds prevent floods and improve flood storage and flood adjustment through water network by water level connectivity and level of regulations towards disaster governance. Chungli, Pingzhen, Dayuan, and Guanyin Districts are the most vulnerable areas to flood in Taoyuan City, Dayuan District in particular. Farm ponds effectively moderate stormwater, especially when daily precipitation reaches 200mm. The flood detention effect of farm ponds is highest when daily precipitation reaches 200mm. Flood risk is substantially reduced when farm pond and ditch network are used pragmatically. It decreases 55% of flood on average at 150mm and 200mm daily precipitation. Regarding risk management, the 818 usable farm ponds are crucial for alleviating floods when daily precipitation reaches 300mm, 539 among them are substantial to reduce flood risk to entire Taoyuan City.