What is the purpose of a separate drainage system for stormwater?

The purpose of a separate drainage system for stormwater is primarily to prevent contaminants from entering storm sewers and to ensure proper drainage. Stormwater can pick up pollutants such as oil, heavy metals, sediments, and nutrients from surfaces like roads and parking lots during rain events. If these contaminants were allowed to flow freely into the stormwater drainage system without separation, it could lead to water pollution in nearby water bodies, cause harm to aquatic ecosystems, and pose health risks to communities.

By utilising a separate drainage system, these potentially harmful contaminants can be managed more effectively. This system is designed to direct stormwater runoff away from areas where it could mix with sewage or other waste, thereby protecting water quality and ensuring that rainwater is properly channeled away, reducing flooding and erosion.

The other options do not align with the fundamental goals of stormwater management. Consolidating all drainage would not protect water quality nor ensure the proper flow of rainwater. While collecting rainwater for irrigation purposes is beneficial, it is not the primary objective of a stormwater drainage system. Similarly, storing excess water during heavy rainfall is not a purpose but rather a potential function of certain systems, which still requires proper drainage to prevent overflow and flooding.