Abstract:Traditional inter-event time definition (IETD) estimate methodologies generally take into account only rainfall characteristics and not drainage basin characteristics. Therefore, they may not succeed in providing an appropriate value of IETD for any sort of application to the design of urban drainage system devices. To overcome this limitation, this study presents a method of IETD determination that considers basin characteristics. The suggested definition of IETD is the time period from the end of a rainfall event to the end of a direct runoff. The suggested method can identify the independent events that are suitable for the statistical analysis of the recorded rainfall. Using the suggested IETD, the IETD of the Joong-Rang drainage system was determined and the area-IETD relation curve was drawn. The resulting regression curve can be used to determinate the IETD of ungauged urban drainage systems, with areas ranging between 40 and 4400 ha. Using the regression curve, the IETDs and time distribution of the design rainfall for four drainage systems in Korea were determined and rainfall-runoff simulations were performed with the Storm Water Management Model (SWMM). The results were compared with those from 46Huff's method which assumed a six-hour IETD. The peak flow rates obtained by the suggested method were 11%~15% greater than those obtained by Huff's method. The suggested IETD determination method can identify independent events that are suitable for the statistical analysis of the recorded rainfall aimed at the design of urban drainage system devices.

An optimal planning model for rehabilitation of water networks is presented. Capital costs (replacement, rehabilitation and repairing costs), benefits (by the reduction of pumping cost and leakage cost), and hydraulic reliability are used for making an optimal decision for the rehabilitation plan of a water pipe network. KYPIPE is used for checking the hydraulic reliability. A multi-objective optimization model is successfully developed in this study. And the task is tackled using a new meta-heuristic algorithm, Harmony Search, for solving a large optimization problem to which conventional optimization techniques are poorly suited. Five different models with different objective functions are developed and tested according to various conditions considered in this study. These models provide more options for the rehabilitation of pipe network systems compared to previously suggested models in the literature.

The permeable pavement is one of representative Low Impact Development (LID) facilities which were used to reduce flooding and recover the water cycle in urban environments. Since the unit cost of porous pavement is greater than that of non-porous pavement, the designs of permeable pavement need to consider reduction effect of rainwater runoff and cost of facilities. These are determined by the size and location of facilities. In this study, the optimal design of permeable pavement, considering the size and location of that, was simulated in a developed optimization model using the Harmony Search (HS)algorithm connected to the Storm Water Management Model (SWMM) to calculate urban Rainfall-Runoff.

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