Modeling urban drainage in intermediate cities under extreme climate change scenarios: a case study in Southeastern Tunja, Colombia

One of the major current environmental challenges in cities is urban drainage, which traditionally combines sewerage infrastructure with stormwater drainage. Construction and pavement reduce natural water infiltration into the ground, causing collapses in the drainage network and, consequently, flooding in low-lying urban areas. This study aimed to model urban drainage in a sector of Tunja, an intermediate Colombian city with a high risk of flooding. The Storm Water Management Model (SWMM) was used, incorporating climate change scenarios and the implementation of Sustainable Urban Drainage Systems (SUDS). Three precipitation scenarios were analyzed: a 6-h event with a runoff volume of approximately 1,990 m3, a 3-h event generating around 8,721 m3 of overflow, and a 1-h event producing up to 19,000 m3 of surface runoff. The results show that installing SUDS can significantly reduce flood risk by accumulating part of the runoff flow and decreasing the collapse of pipe systems. Thus, the modeling outcomes provide essential input for decision-making by urban planning authorities to improve flood resilience and infrastructure sustainability.