Hybrid system analysis for surface rainwater drainage in urban highway underpasses: The case of Diyarbakir city

Drowning deaths in traffic accidents in the world and in our country generally occur in the sloped or collapsed sections of the highway. While there is growing concern about how to quickly and safely remove rainwater from highway low points in an urban area, solutions to this problem are also sought. In this study, the Maternity Hospital Bridge Interchange, one of the interchanges on the Diyarbakır-Sanlıurfa city highway, was chosen as the application area, and a new hybrid system is presented to improve the highway underpass drainage design for both safety and hydraulic efficiency. It is recommended that the underpass drainage facility consists of two systems: a sized underground sewer line to collect the small currents by gravity, and a pump system to remove excess water during a major current. The pump system can be a fixed station or a mobile unit on urgent needs. To design such a drainage system for multiple currents, two hydrological methods are used, including the Rational Method used to size the sewer pipes and sump pumps, respectively, and the EPA SWMM computer model adopted to validate the performance of the proposed system under two current. Hydraulic analyzes at the underpass points selected for the system will be analyzed with the Stormwater Management Model (SWMM), a computer program recommended by the United States Environmental Protection Agency (EPA).