| Summary: | 碩士 === 國立臺灣大學 === 農業工程學研究所 === 87 === The objective of this study is to establish and evaluate a distributed rainfall-runoff model based on triangulated irregular networks (TIN). Because of reflecting real terrain as a distributed runoff process, this model should be able to provide a better application for rainfall-runoff simulation of upland watersheds.
The triangulated irregular networks digital terrain model (TIN-DTM) is used to divide the project watershed and provides topographic data, which the model needs in the topographic analysis system. When developing a distributed rainfall-runoff model with the TIN-DTM, the most difficult problem is that there are too many overland flow paths to calculate. Therefore, this study suggests that the original overland flow paths should be reserved, and use FORTRAN programs to set up an available configuration of topographic data automatically. It provides a more accurate and efficient way to solve this problem.
To establish a distributed rainfall-runoff model with TIN-DTM, there are two major processes. First, ARC/INFO software of Geographic Information System is used to create three kinds of coverage: stream networks coverage, boundary coverage and very important point (VIP) coverage to represent the topographic variation of a basin. The TIN of the project area can be established by using these coverages. Each triangle in the TIN-DTM is depicted by three sets of data catalog, which are used to specify water flow direction and connect every triangle according to their topographic relations. Second, the kinematic wave model with finite-difference approximations is used to calculate the overland and channel flow of the basin.
The parameters of this model are determined by three parameter optimization methods. That includes the mean of every optimum parameter, the optimum parameters of total examining events and the fuzzy programming parameter optimization, respectively. The second and the third methods have a new concept of the parameter optimization: all examining issues are regarded as a unity. The feasibility of these three optimization methods is assessed in order to examine their applicability in this model.
The model as well as the parameter optimization methods established in this study is applied to Heng-Chi upstream watershed, a tributary of Tanshui River Basin, and the simulation results are very satisfactory. Therefore, the concept of parameter optimizations suggested in this study is adequate and practical. This model, moreover, provides a new approach to flood forecast and management of hillside watersheds in Taiwan.
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