这是从Wiki上截下来的解释。
Bioswales are landscape structures designed to remove silt and pollution from runoff water. They consist of a swaled drainage ditch with gently sloped sides (less than six percent) and filled with vegetation, compost and riprap. The water's flow path, along with the wide and shallow ditch, are designed to maximize the time water spends in the swale, which aids the trapping of pollutants and silt. Biological factors also contribute to the breakdown of certain pollutants.
大体意思是说Biowales是一种由植被，腐殖质，和乱石组成的设施，用于去除淤泥和污染物。具体的你自己看吧。
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