How can urban development change rainwater runoff and increase flood risks?

Urban development significantly alters the natural water cycle by replacing vegetation and permeable soils with vast areas of impermeable surfaces, such as roofs, roads, and parking lots. In the context of civil engineering, these surfaces prevent rainwater and snowmelt from being absorbed into the ground.1

Instead of infiltrating the soil, water runs off these surfaces rapidly, often pooling in low-lying areas and increasing the risk of local flooding. Furthermore, the development of water catchment areas can fundamentally change the nature of runoff, while the channeling of streams to improve drainage for infrastructure can disrupt natural flow patterns. These changes, combined with the speed at which water moves across impervious surfaces, can lead to more frequent and severe flood events. Additionally, this runoff often carries pollutants from pavement into aquatic ecosystems, further degrading water quality.123