臺灣地形狹長，坡陡流急，降雨時間分布不均勻，導致臺灣降雨型態較為極端。近年來隨著都市地區高度的發展，因此許多都人口往都市地區遷移。隨著都市地區人口密度的增加，居住需求增加，因此產業、經濟活動等均會高度發展，導致都市洪災保全對象眾多，為渲洩洪水，都市地區密佈排水系統如：雨水下水道、區域排水、側邊溝等，其中雨水下水道因設置在路面下，可以減少占用地面面積的使用，在人口密集的都市區域顯得格外重要。近年來在氣候變遷的影響下，極端降雨事件頻傳，而都市地區排水系統，如：雨水下水道的保護標準約重現期2年至10年，一場極端降雨事件就有可能造成雨水下水道的超載，然而下水道之設計多半以渠流形式為主，當遇到超載現象時是否需要考慮管流現象還需進一步探討。
　　本研究欲探討雨水下水道系統在洪水期間之通洪能力，並考慮未超載(渠流)及超載(管流)之情況下，建立雨水下水道系統水工模型。以定量流進行試驗，並與管流理論進行比較，最終利用流量與壓力水頭，回歸出互相對應之關係式。以便未來快速推測雨水下水道系統在超載情況下之人孔溢流情形，進一步可應用於雨水下水道超載後判斷交通用路安全。

In recent years, due to an increase in the urban population, the corresponding housing demand has led to an increase in building construction. These countless building construction projects have increased the amount of impervious surface areas, which in turn has led to an increase in surface runoff. In order to ensure public safety and protect urban areas, the sewers in urban areas are particularly important. Generally speaking, the design standard for sewers in urban areas is approximately a return period of 2 to 10 years. Therefore, flooding in sewer leads to a risk of surcharge. However, current simulations of sewer systems, such as SWMM, MOUSE, and ISS, only consider open channel conditions.
As a result, this study is intended to explore storm sewer flooding capacity. A storm sewer model is developed that considers both open channel and pipe flow conditions based on the assumption of steady flow. An experiment is conducted, and the pipe flow theory is discussed in an effort to determine the relationship between pressure head and discharge, and then to predict the pressure head when storm sewers approaches surcharge situations.
The results show that a conflict between the experimental results and the pipe flow theory. In addition, the relationship between the pressure head and the discharge exhibits a power function.

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