Optimal implementation of lid facilities in the mid-upper youngsan river basin for runoff reduction performance and economic efficiency

This study aims to determine the optimal Low Impact Development (LID) implementation strategies considering runoff reduction performance and economic efficiency in the mid-upper region of the Youngsan River basin. The Storm Water Management Model (SWMM) was used to simulate rainfall-runoff processes and LID implementation strategies. The study focused on areas with an impervious surface ratio exceeding 50%, comparing the optimal design parameters and runoff reduction performance of Permeable Pavement (PP), Infiltration Trench (IT), Bio-Retention Cell (BRC), and Rain Garden (RG). To optimize the design parameters of these LID facilities two approaches were applied: (Case 1) determining a single design parameter minimizing total runoff across the entire study area and (Case 2) determining individual design parameters that minimize runoff for each sub-watershed. The comparison of runoff reduction performance between the two cases showed that Case 2 showed superior runoff reduction performance compared to Case 1. In Case 1, IT was identified as the optimal facility in all sub-watersheds, whereas Case 2 resulted in different optimal LID facility types depending on the runoff characteristics of each sub-watershed. In Case 2, BRC was determined as the most frequently selected facility. When considering the economic efficiency of construction and maintenance costs, RG demonstrated the highest cost-effectiveness in runoff mitigation for both cases. Consequently, applying the optimal LID facility allocation strategy that accounts for both runoff reduction performance and economic efficiency resulted in a total runoff reduction of 6.36% in Case 1 and 7.16% in Case 2.