What does the term 'first flush' refer to in stormwater management?

The term 'first flush' in stormwater management refers specifically to the initial runoff from impervious surfaces during a rain event. This initial runoff is significant because it often carries a higher concentration of pollutants and contaminants that have accumulated on these surfaces, such as oils, heavy metals, and nutrients, since the last significant rainfall. Addressing this aspect of stormwater management is crucial for reducing water pollution and protecting water quality.

Understanding the 'first flush' phenomenon helps in designing effective stormwater treatment systems and implementing best management practices. For instance, capturing and treating this initial volume of runoff can mitigate the negative impacts on receiving water bodies. Recognizing this concept is essential for landscape architects and planners focused on sustainable design and environmental compliance.