圖書典藏及影音數位平台

許多易淹水地區位於沿海低地平原，各排水系統之排水能力及淹水減免能力之影響因素包括：(1)集水區中豪雨逕流；(2)相鄰海域及潟湖之暴潮進出；(3)因相鄰集水區間分水嶺高度不足導致之越域水流。故自流域綜合治水之需求而言，應發展可涵蓋沿海低地及其相鄰山區丘陵與海域之淹水─排水演算模式，以比較檢討區域排水系統之排水改善功能及尚需改善地區，並推廣應用。

Taiwan terrain is very steep and locates on the route of typhoons in the east Pacific Ocean. These typhoons on average strike Taiwan 3.5 times annually, which usually induce storms to bring heavy rain and thus lead flood-prone areas to result in extensive inundation, especially in coastal low-altitude plains. Because climate has changed rapidly in recent years, extreme hydrological event occurs very often and sea water level is also raised. This has made the flood problem in coastal low-altitude plains become a central issue. The objective of this project is to develop a physiographic inundation-drainage computation model for the areas covering coastal low-altitude plains and nearby mountain and ocean regions. An auxiliary system of inundation warning was also developed based on the forecast rainfall and tidal level, together with the timely monitor and historic rainfall and inundation information before and during the period of typhoons. By incorporating the timely inundation warning model and the inundation probability forecast model, the timely inundation depth and area can be provided, the information of which can thus serve as the guideline for the disaster-prevent and disaster-rescue organizations for disaster-prevent, disaster-alleviate, and disaster-response tasks. The study area in this year covers the hill and coastal low-altitude plain ones from the south of the Erren creek to the north of the Gaoping creek. Our physiographic inundation-drainage model was applied to simulate the phenomenon of inundation and drainage during the period of Typhoon Kalmaegi (2008), Typhoon Morakot (2009), Typhoon Fanapi (2010), and Typhoon Nanmadol (2011), the result of which was compared to that obtained from field investigation on inundation. It is revealed that the simulated inundation range is consistent with the investigated inundation range, which indicates that our physiographic inundation-drainage model is able to reasonably simulate the inundation location of the study area in this year During the period of Typhoon Nanmadol, three areas were used as illustrative examples for timely inundation simulation to predict the inundation potential within next three hours, which include the area from the south of the south embankment of the Bazhang creek to the north of the north embankment of the Tsenwen creek, the one from the south of the north embankment of the Tsenwen creek to the north of the south embankment of the Yanshuei creek, and the one from the south of the south embankment of the Yanshuei creek to the north of the south embankment of the Erren creek. This simulation took five minutes for each area, which implies that our physiographic inundation warning model is able to provide inundation forecast efficiently. After Typhoon Nanmadol, we collected the observed rainfall data and then compared that to the rainfall data forecasted during the period of Typhoon Nanmadol. By doing so, we can enhance the reliability of our model simulation. This project also specifies the target computation cells in the crucial inundation area. Next, we established the relation among accumulated rainfall, inundation warning depth, and inundation inception depth. As 70% occurrence probability is considered to be a criterion, accumulated rainfall and inundation monitor depth (or simulated inundation depth) was used to assess whether the water depth in each target computation cell achieves inundation warning depth or inundation inception depth, the information of which can thus be provided as the reference for the decision system of flood warning.