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Changes of rural to urban areas in hydrograph characteristics on watershed divisions |
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| Authors: | Jet-chau Wen Yen-jen Lee Shin-jen Cheng Ju-huang Lee |
| Institution: | 1. Department of Safety Health and Environmental Engineering, National Yunlin University of Science and Technology, Douliou, Yunlin, 640, Taiwan 2. Graduate School of Engineering Science and Technology, National Yunlin University of Science and Technology, Douliou, Yunlin, 640, Taiwan 3. Department of Leisure and Recreation Management, Taiwan Shoufu University, 168, Nan-shih Li, Madou, Tainan, 721, Taiwan 4. Water Resources Agency, Ministry of Economic Affairs, Taipei, 106, Taiwan |
| Abstract: | This study examined changes in hydrograph characteristics of rural statuses to urban statuses on watershed divisions in Taiwan. The main approach was to relate applicable model parameters with the corresponding imperviousness based on calibration and verification using a semidistributed model and 102 events. The model structure is conceptual linear reservoirs with parallel-type cascaded storages which is represented by overland and channel coefficients. The hourly mean rainfall of the watershed and its divisions were calculated using the Kriging method. The time-variant rainfall losses were calculated using the constant percentage method. The spatial and temporal model inputs, division effective rainfall, were obtained by subtracting mean rainfall of divisions from the rainfall losses. In calibration, the storage values of 50 events derived using appropriate parameter bounds were more reasonable than those using inappropriate bounds. Based on the optimal interval method, the overland storages displayed more marked change than did channel storage in response to imperviousness changes. By contrast, the channel storages were unaffected by the changes in urbanization. The overland storages were related with the imperviousness by using the regression equations for determining their relationships in continuous changes of urbanized divisions. The verification of the regression relationships was based on 52 events. The results indicated that power linkage was an available selection for linking division parameters with the corresponding imperviousness. Finally, the study concludes (1) appropriate bounds in parameter calibration are useful for obtaining significant storage values and (2) the study results using these suitable storages indicated large changes in imperviousness on the downstream divisions, marked urbanization resulted in reduced the time to peak at least 10 %, the peak discharge exceeded an increment of 20–30 %. |
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