Analyzing the Effectiveness of Constructed Wetlands on Flood Reduction in Coastal areas of Yunlin County
Date Issued
2008
Date
2008
Author(s)
Hsu, Chin-An
Abstract
The coastal area of Yunlin County is listed as one of the focused areas in the National Land Recovery Program because of its severe land subsidence problem. As the drainage of this area continues to worsen due to land subsidence, flooding occurs regularly whenever a typhoon or a storm passes. Dikes and pump stations along rivers have not worked well in reducing the floods. This research investigates the idea of converting seriously subsided areas into wetlands as a solution to the flooding problem, and this research refers to Automated Assessment Method for Northeastern Wetlands(AMNEW). First, we evaluated potential areas for conversion to wetland. Second, we ran SOBEK, a software developed by the WL｜Delft Inc., the Netherlands, with a designed 10years-return-period storm and digital elevation models (DEMs) of four different resolutions (80m, 40m, 20m, and 10m) for the purpose of selecting a resolution that could provide adequate flooding information within an acceptable timeframe for warning assessment. For our study area, a SOBEK run ranged from 1.5 hours with the 80m DEM to 7.5 days with the 10m DEM.The optimal modeling input appeared to be the 20m DEM with 27-hours running time is selected to be the optimal modeling input. Finally, we evaluated three potential sites for wetland conversion and used the overland flow model in SOBEK to simulate the flooding conditions. This last experiment allowed us to compare the before and after conditions and measure the effectiveness of wetland on reducing the flooding problem. After comparison, we found that the flooding problem within 1000 m of the wetland reduced the most. The detention pond had the best effect in reducing the villages’ flooding problems. Five villages had their floods reduced by about 0.1m(10cm).
Subjects
Constructed wetland
Yunlin, flooding
land subsidence
SDGs
Type
thesis
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