Retention is the process of permanently keeping storm water from leaving a property. It can be accomplished through infiltration, evaporation, transpiration (water uptake through plants) or water reuse. This process helps to remove volumes of storm water from your storm and sewer system.
Detention is the process of temporarily storing storm water to mitigate sewer over flows. This process helps reduce the flow rate (volume per unit time) of storm water through the sewer system and off of your site. This storm water is later released into the system after the rainfall event or storm melt subsides. This delay has major benefits to any sites storm water design.