In city centers, the damage caused by inundation is aggravated by rising populations and urbanization, which extend impermeable areas. Research is needed to identify the inundation risks caused by climate change and quantitatively assess the consequences. In this study, we proposed an improved reliability study which considers resilience in the original evaluation method for the reliability of a storm sewer network. Rainfall-runoff analysises were performed on a part of Bangbae 2 drainage basin in Seoul by applying Storm Water Management Model 5 Ver. Based on the results of the application of excessive rainfall events, the original reliability evaluation method was compared with the improved reliability evaluation method. Consequently, the effect of the improvement of the cluster about 30% was confirmed when selection the central value rather than the existing representative value. The improved reliability evaluation method proposed in this study can be used as a design objective function and as an index for evaluating the inundation risk in adjacent drainage basins.

The installation of rainwater storage facilities is mandatory for public buildings over a certain size. However, the standards for determining the capacity of rainwater storage facilities vary by ministries and agencies. Even within the same institution, various unifying standards are often applied. In addition, rainwater storage facilities generally have a low B/C (Benefit-Cost ratio), which is negatively evaluated in terms of economy. Therefore, this study sought to improve the existing non-standard capacity reference problem for rainwater storage facilities and to suggest more efficient capacity determination measures. To this end, the study proposed a plan for calculating the benefits and determining the capacity of the reservoir through the analysis of the water balance in order to take into account the utility of the rainwater reservoir in terms of actual use. The empirical analysis was conducted on rainwater storage facilities in the Korea Land and Housing Institute, and the water balance analysis was conducted based on the actual rainfall data of 2019 by Daejeon Metropolitan City. Among the factors to evaluate the benefit and cost of rainwater storage facilities were the reduction of rainwater runoff, reduction of heat waves, reduction of fine dust, and use of landscaping water. In addition, the benefit analysis was conducted by the reservoir capacity and collection area, and the guide for determining the optimum capacity of the rainwater reservoir was presented accordingly.