Analysis and evaluation of a sewage network during heavy rains using the SSOAP toolbox

Abstract

Abstract One of the major problems facing urban areas is the recent increase in precipitation intensity over design standards due to global warming. This significantly increased precipitation depth directly influences sewage systems by causing increased flow and infiltration (RDII), which eventually leads to flooding of the systems. The aim of this study was to analyse and evaluate a sewage network during such severe rainfall, to determine the excess amount of rain entering the system. To achieve this, the Hay Al-Hurr region of Karbala was selected as a case study, and the Sanitary Sewer Overflow Analysis and Planning (SSOAP) toolbox was used to estimate the volumes of inflow and infiltration (RDII) entering the sewer network, while the stormwater management software (SWMM5) within the toolbox was used for hydraulic assessment of the sewage system. The sewage network of the main pipeline of the study area was analysed with regard to two rain events in 2016, one of which was a standard event of 25 mm, and the other a torrential event of 105 mm. The RDII was 2.29 mm for the first event and 2.58 mm for the second event; on calibrating these results with SWMM5, a display of flood areas for each event was created showing the percentage overflows for two events were 30% and 65%, respectively. These results were realistic and according to predictions, allowing the study to help improve engineering knowledge and decision-making capabilities with regard to designing sewage networks, as well as facilitating the development of appropriate solutions to rehabilitate those areas most vulnerable to standardised entry by developing specific strategies to reduce or eliminate the surplus runoff.