By Katrina Mendrey
Before we began using pipes, drains, pumps, and other “grey infrastructure” to manage stormwater, nature provided the “green infrastructure” to slow, filter, and move water to where it belonged. In forests and wetlands, water is still managed naturally. The foundation of this network is the soil. It is the drain, the pipe, the pump, and the water treatment plant all in one.
As we’ve continued to pave over our soils, however, demands on both natural and manmade stormwater management systems have increased. In cities the use of green infrastructure to alleviate strain on these systems has become a popular alternative to costly grey infrastructure expansion. These green infrastructure techniques rely heavily on the inherent and unique qualities of soil.
Certain soil properties determine how quickly and how much water can be infiltrate, or permeate, the ground—preventing flooding, and the overloading of streams and water treatment plants, as well as recharging groundwater supplies. The soil is also responsible for much of the filtering of contaminants in urban stormwater, which can otherwise lead to serious water quality issues.
Moreover, soil provides the nutrients and water holding capacity needed to support plants, which help prevent erosion, reduce runoff by using and storing water, clean and cool the air, and provide an aesthetic quality to urban spaces. Hence the soil is responsible both for reducing water quantity and improving water quality—the primary goals of stormwater management.