Modeling the effects of land-use and climate change on the performance of stormwater sewer system using SWMM simulation: case study

Flooding of stormwater drainage systems represents a major problem in developing urban areas that could be influenced by land-use and climate change. Flooding problems can be assessed using simulation models such as the stormwater management model (SWMM). In this study, the generation of intensity duration frequency curves (IDF) that integrates climate change effect was conducted for Al-Najaf Governorate in Iraq for the first time. In addition, the effects of land-use and climate change on the stormwater sewer system of Al-Ameer District was simulated using SWMM. The results indicated that by increasing the sub-catchment area from 50 to 100%, an increment in total surface runoff from 20,380 to 37,350 m3, and total flooding from 10,513 to 26,032 m3 have occurred, respectively. As a response to climate change, changing the return period from 2 to 5 years has increased the total surface runoff from 14,120 to 27,110 m3 (representing 48% of raise), and total flooding increased from 5,914 to 17,591 m3 (accounting 72% of increment). To conclude, flooding locations and magnitude were identified, whilst the system failed to discharge surface runoff at critical conditions, whereas the effect of climate change on the stormwater drainage system was more adverse than the effect of land-use.