Lu-Hsien Chen

A Forecasting Approach Combining Self-Organizing Map with Support Vector Regression for Reservoir Inflow during Typhoon Periods

This study describes the development of a reservoir inflow forecasting model for typhoon events to improve short lead-time flood forecasting performance. To strengthen the forecasting ability of the original support vector machines (SVMs) model, the self-organizing map (SOM) is adopted to group inputs into different clusters in advance of the proposed SOM-SVM model. Two different input methods are proposed for the SVM-based forecasting method, namely, SOM-SVM1 and SOM-SVM2. The methods are applied to an actual reservoir watershed to determine the 1 to 3 h ahead inflow forecasts. For 1, 2, and 3 h ahead forecasts, improvements in mean coefficient of efficiency (MCE) due to the clusters obtained from SOM-SVM1 are 21.5%, 18.5%, and 23.0%, respectively. Furthermore, improvement in MCE for SOM-SVM2 is 20.9%, 21.2%, and 35.4%, respectively. Another SOM-SVM2 model increases the SOM-SVM1 model for 1, 2, and 3 h ahead forecasts obtained improvement increases of 0.33%, 2.25%, and 10.08%, respectively. These results show that the performance of the proposed model can provide improved forecasts of hourly inflow, especially in the proposed SOM-SVM2 model. In conclusion, the proposed model, which considers limit and higher related inputs instead of all inputs, can generate better forecasts in different clusters than are generated from the SOM process. The SOM-SVM2 model is recommended as an alternative to the original SVR (Support Vector Regression) model because of its accuracy and robustness.

Reliability-Based Delineation of Debris-Flow Deposition Areas

In this paper, a methodology is proposedfor the delineation of debris-flow deposition areas.First, based on the theory of reliability,the delineated hazardous area is defined. Then,uncertainty analyses of all the uncertainparameters affecting the probable maximum length,width and thickness are performed. Finally,the proposed methodology is applied to an actualsite susceptible to debris flow. It is foundthat the maximum deposition length is much moreuncertain than the maximum deposition width.The delineated hazardous areas for variousreliability are obtained using the inversefirst-order second moment method. The proposedmethodology is recommended for the delineation ofdebris-flow hazardous areas, because theinfluence of all the uncertainparameters is considered.