• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.485-489
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• 2008

To achieve the optimal sewer layout design, most developed models are designed to determine pipe diameter, slope and overall layout in order to minimize the least cost for the design rainfall. However, these models are not capable of considering the superposition effect of runoff hydrographs entering each junction. The suggested Optimal Sewer Layout Model (OSLM) is designed to control flows and distribute the node inflows while taking into consideration the superposition effect for reducing the inundation risk from the sewer pipes. The suggested model used the genetic algorithm to determine the optimal layout, which was connected to the SWMM (Storm Water Management Model) for the calculation of the hydraulic analysis. The suggested model was applied to an urban watershed of 35 ha, which is located in Seoul, Korea. By using the suggested model, several rainfall events, including the design rainfall and excessive rainfalls, were used to generate runoff hydrographs from a modified sewer layout. By the results, the peak outflows at the outlet were decreased and the overflows were also reduced.

• Journal of Korea Water Resources Association
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• v.44 no.10
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• pp.777-786
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• 2011

In the previous researches for storm sewer design, the flow path, pipe diameter and pipe slope were determined to minimize the construction cost. But in the sewer networks, the flows can be changed according to flow path. The current optimal sewer layout models have been focussed on satisfying the design inflow for sewer designs, whereas the models did not consider the occurrences of urban inundation from excessive rainfall events. However, in this research, the sewer networks are determined considering the superposition effect to reduce the inundation risk by controlling and distributing the inflows in sewer pipes. Then, urban inundation can be reduced for excessive rainfall events. An Optimal Sewer Layout Model (OSLM) was developed to control and distribute the inflows in sewer networks and reduce urban inundation. The OSLM uses GA (Genetic Algorithm) to solve the optimal problem for sewer network design and SWMM (Storm Water Management Model) to hydraulic analysis. This model was applied to Hagye basin with 44 ha. As the applied results, in the optimal sewer network, the peak outflow at outlet was reduced to 7.1% for the design rainfall event with 30 minutes rainfall duration versus that of current sewer network, and the inundation occurrence was reduced to 24.2% for the rainfall event with 20 years frequency and 1 hour duration.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1976-1981
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• 2011

In this study, the optimal sewer layout model(Lee, J.H., 2010)[1] was applied to verify the reduction effect of urban inundation in the optimal sewer networks, which designed by this optimal model, for various artificial rainfall events in urban areas. Then the optimal model was developed by Lee, J.H. to minimize the peak outflow at outlet in sewer network. The applied rainfall events are two types. One is the rainfall event which the double peak occurs between specific time distance continuously. The other is the continuous rainfall event with specific rainfall intensity. As the result, in two applied rainfall types, the peak outflows at outlet were reduced in the optimal sewer networks which designed the optimal sewer layout model of Lee, J.H.. Therefore, the peak outflow is reduced because the inflows at each manhole are distributed in the whole sewer networks, it's not delay of inflows by this optimal model.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.1
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• pp.1-7
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• 2009

Most developed models are designed to determine pipe diameter, slope and overall layout in order to minimize the cost for the design rainfall for the optimal sewer layout. However, these models are not capable of considering the superposition effect of runoff hydrographs in the sewer pipes. The flow characteristics in the sewer pipes, such as the sewer layout, pipe diameter and slope, vary according to the design of the sewer system. In particular, when the sewer network is modified, the shapes of the runoff hydrographs in the sewer pipes also change because of the superposition effect. In this study, the sewer layout is designed to control and distribute the flows in the sewer pipes, while considering the runoff superposition effect, in order to reduce the inundation risk at each junction. This is accomplished by separating the inflows that enter into each junction by changing the way in which pipes are connected between junctions. And this model combines SWMM (Storm Water Management Model) to perform the hydraulic analysis for the flows in the sewer network. The current sewer layout was modified to minimize the peak outflow at outlet in Garak basin, Seoul, South Korea. As the results, the peak outflows at the outlet were decreased by approximately 20% for the design rainfall during 30 minutes and the total overflows were also decreased for the excessive rainfalls.

• Journal of Korea Water Resources Association
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• v.38 no.12 s.161
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• pp.1029-1037
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• 2005

Urban Storm Sewer Optimal Design Model(USSOD) was developed to compute pipe capacity, pipe slope, crown elevation, excavation depth, risk and return cost in the condition of design discharge. Rational formula is adopted for design discharge and Manning's formula is used for pipe capacity. Discrete differential dynamic programming(DDDP) technique which is a kind of dynamic programming (DP) is used for optimization and first order second moment approximation method and uncertainty analysis is also for developing model. USSOD is applied to hypothetical drainage basin to test and verify. After testing the model, it is also applied to Ulsan drainage basin which was developed by Korea Land Cooperation(KOLAND). Comparing the design results of USSOD with those of KOLAND, discharge capacity 0.35 $m^3/sec$, the crown elevation is 0.77m higher and return cost is $9\%$ less than design results of KOLAND, which verify the improvement of USSOD. Layout design model using GIS and optimization including detention or retention effect are needed in the future study.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.2
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• pp.157-161
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• 2011

Although many researches have been carried out concerning the watershed division in natural areas, it has not been researched for the urban watershed division. If the boundary between two urban areas is indistinct because no natural distinction or no administrative division is between the areas, the boundary between the urban areas that have the different outlets (multi-outlet urban watershed) is determined by only designer of sewer system. The suggested urban watershed division model (UWDM) determines the watershed boundary to reduce simultaneously the peak outflows at the outlets of each watershed. Then, the UWDM determines the sewer network to reduce the peak outflow at outlet by determining the pipe connecting directions between the manholes that have the multi-possible pipe connecting directions. In the UWDM, because the modification of the sewer network changes the superposition effect of the runoff hydrographs in sewer pipes, the optimal sewer layout can reduce the peak outflow at outlet, as much as the superposition effects of the hydrographs are reduced. Therefore, the UWDM can optimize the watershed distinction in multi-outlet urban watershed by determining the connecting directions of the boundary-manholes using the genetic algorithm. The suggested model was applied to a multi-outlet urban watershed of 50.3ha, Seoul, Korea, and the watershed division of this model, the peak outflows at two outlets were decreased by approximately 15% for the design rainfall.