Stormvand

Stormvand is the portion of precipitation that runs off surfaces rather than infiltrating the soil or evaporating. It includes water from roofs, streets, parking lots, and other impermeable surfaces and is collected by storm drainage systems. As it flows, stormvand can pick up sediments, nutrients, metals, hydrocarbons, litter and other pollutants, leading to water-quality concerns in rivers, lakes and coastal areas. In urban areas, stormvand is distinct from wastewater from toilets and sinks and is typically handled by separate storm sewers or combined sewer systems.

The main objectives of stormvand management are to prevent urban flooding, protect water quality, and maintain healthy aquatic ecosystems. Management strategies include structural controls such as detention and retention basins, stormwater outfalls and infiltration trenches, as well as non-structural approaches. In many regions, green infrastructure is used to imitate natural hydrology by promoting infiltration, evaporation or evapotranspiration. Examples include bioswales, rain gardens, green roofs, permeable pavements and constructed wetlands.

Effective stormvand management relies on planning, permitting, design standards and ongoing monitoring. It benefits from an integrated approach that combines source control (reducing pollutants at the source), treatment trains (series of treatment steps) and land-use planning to reduce imperviousness.

Challenges include increased rainfall intensity due to climate change, aging infrastructure, and urban development that reduces natural infiltration. Regulatory frameworks often require municipalities to monitor discharges, set performance targets, and implement best practices to protect water bodies.