The primary concern regarding urban runoff during heavy rains is the flooding and pollution of waterways. Runoff carries contaminants such as pesticides, heavy metals, and sediment into rivers and streams, harming aquatic ecosystems and degrading water quality. Additionally, increased runoff can overwhelm drainage systems, leading to flooding in urban areas and causing property damage. Implementing sustainable urban planning, such as green roofs and permeable pavements, can mitigate runoff and promote better water management, protecting both urban infrastructure and natural ecosystems from detrimental effects.