Modeling climate change impacts on urban storm sewer network performance using SWMM

ABSTRACT This paper examines how climate change influences storm sewer network performance using the Storm Water Management Model (SWMM) with the Baro-Arabsa (a sub-city of Addis Ababa) case study. The assessment was done using node flooding, pipe surcharge, and system-limiting capacity performance parameters. The focus is on future rainfall scenarios predicted under Shared Socioeconomic Pathways (SSPs): SSP2-4.5 and SSP5-8.5. To this end, four CMIP6 models were selected: CESM2, GFDL-CM4, GFDL-ESM4, and NorESM2-MM. The daily climatic data were projected for the mid-century (2041–2060) and late-century (2081–2100). The projected daily rainfall data were then disaggregated into 15 min data using the HyetosMinute package of the R-programming to fit SWMM input. The simulation results reveal a notable increase in the instances of flooding and pipe surcharges, especially in the low-lying areas. Both the intensity and frequency of flooding and limited capacity became more pronounced and severe as we move from mid-century to late-century and from SSP2-4.5 to SSP5-8.5. This analysis highlights the significant influence of climate change on the storm sewer network performances and the existing infrastructure's susceptibility to the projected SSP scenarios, stressing the importance of implementing adaptive measures such as system enhancements and green infrastructure to improve resilience against climate-related stormwater challenges.