Hydraulic modeling of the main sewer conveyance pipeline in Central Karbala during mass religious pilgrimages and rainfall events

Sewage networks are one of the most critical elements of the urban infrastructure that is fundamental for the protection of public health and environment. This requires not only constant monitoring but also evaluation to ensure that the systems are functioning. Karbala hosts millions of yearly pilgrims which places an enormous hydraulic load on the sewerage system. This is even more severe during the pilgrimage season due to rainfall-derived infiltration and inflow where parts of the network may be overloaded or failed. The objective of this study is to investigate how the large main sewage pipeline located in the center of Karbala City behaves when subjected to the pressure applied during visitors' movement and rainfall events, using Personal Computer Storm Water Management Model software and Geographic Information Systems (GIS). The available data were then collated, processed, and pooled together with hydraulic modeling representing different human and climatic loading scenarios. The results demonstrated that this pipe was adequate to accommodate peak visitor numbers in dry conditions, and each visitor produces discharge into the network of approximately 29 l/d. In rainy conditions, rainfall intensity within the range of 17–21 mm/h was identified as the hydraulic failure threshold for the pipeline.