Life Cycle Cost Analysis and Resilience Evaluation for LID Implementation in Urban Drainage Systems using SWMM

Urban flooding poses a growing challenge, intensified by rapid urbanization and climate change, which strains traditional drainage systems. This study investigates the application of Low Impact Development (LID) techniques as a sustainable solution to enhance urban drainage system resilience. Using Gurugram, India, as a case study, the research evaluates the functional and structural resilience improvements achieved through LID implementation, alongside a Life Cycle Cost (LCC) analysis to assess cost-effectiveness.

LID Performance Index (LPI) was employed to quantify the functional resilience – a  measure of system resilience under varying scenarios of urbanization and increased rainfall intensities. Structural resilience was analyzed by assessing reductions in vulnerable locations through one-at-a-time failure simulations. To effectively integrate the green roofs and rain gardens in the runoff management, the subcatchments with substantial impervious area and high runoff volume were designated as the potential subcatchments for LIDs’ application. The study examines four LID implementation scenarios, incorporating green roofs and rain gardens into 10% (S1), 25% (S2), 50% (S3), and 100% (S4) potential subcatchments.

The finding reveals that incorporating LIDs into 10% of potential subcatchments (Scenario S1) enhances functional resilience by 21% and reduces vulnerable nodes by 8.7%. The corresponding Benefit-Cost Ratio (BCR) for Scenario S1 is 2.05 under a 5-year return period design storm, indicating its cost-effectiveness. While increasing LID coverage improves resilience, the cost-effectiveness diminishes due to higher implementation costs.

The LCC analysis incorporates construction, maintenance, and salvage costs to evaluate the economic viability of LID practices. It highlights that LIDs are particularly effective for moderate storm events, with a noticeable decrease in effectiveness for extreme storms with higher return periods. The findings underscore the limitations of relying solely on LIDs for stormwater management, advocating for their integration with conventional drainage systems to address extreme scenarios effectively.

The insights provided in study are valuable for urban planners, engineers, and policymakers aiming to develop sustainable and resilient urban drainage systems capable of mitigating urban flooding impacts.