The objective of this research was to identify the appropriate factors for green infrastructure design by analyzing the correlation between water quantity and stream ecology. This study quantifies the hydrological and ecological impact of post-development based on pre-development. A continuous simulation using hourly rainfall for 41 years from 1980 to 2020 was applied to the Gunja drainage basin. Design rainfall was produced by Huff’s 3rd quantile method. Scenarios for design rainfall with a duration of 24 hours, 2-, 10-, and 100-year frequency were set for the Gunja drainage basin in Seoul, South Korea. This analysis is performed using EPA SWMM5, an urban runoff model. Pre-development, post-development, and post-development with detention basin scenarios were modeled to estimate flow rate and stream ecology impact reduction. To quantify the evaluation efficiency of the model, R2, NSE and RSR were applied. Stream ecologic impact reduction was simulated using the hydrological index (T_0.5yr), which is known to have a high correlation with the Benthic index of biological integrity (B-IBI), a stream ecology ecosystem index. Finally, this study suggests that the factors of flow rate and stream ecology are deeply related and produces a robust management of hydrologic and ecologic impacts with a green infrastructure. Acknowledgments This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (NRF-2019R1A2C1007447) and by Korea Environment Industry & Technology Institute(KEITI) through Aquatic Ecosystem Conservation Research Program(or Project), funded by Korea Ministry of Environment(MOE) (2022003050007).
