Traditionally engineered stormwater management is known as grey infrastructure. The goal of grey infrastructure is to move stormwater off site as quickly as possible, conveying it into the nearest water body.
Grey infrastructure includes pipes, curbs and sometimes water treatment plants. It is typically centralized and expensive to build and maintain. It can be very effective in transporting flood water away from buildings.
Unfortunately, this also pushes pollutants like trash, bacteria, and heavy metals directly into those same water bodies, leading to pollution, water quality impairment, and negative impacts on fish and other marine life.
Green infrastructure (GI) aims to mimic nature by slowing down stormwater and increasing permeable land area so that water can percolate into the ground. It is typically a decentralized approach that is less expensive to build and maintain. GI utilizes techniques such as rain gardens, pervious pavement and vegetated swales.