How a City Can Be More Like a Forest

from Greenbiz.com

One defining characteristic of a city is that it is full of hard surfaces. Streets, sidewalks, buildings and bridges shed water when it rains. All that water has to go somewhere, and it usually gets there fast. So for a city to function more like a forest or a field, step one is to slow down the water.

At THI our main business is slowing down the water with a process we call Experience EcoBlu. Healthy floodplains with lush, streamside vegetation provides ecological services like water filtration, absorption, and storage. When floodplains are destroyed, the inevitable result is lower water quality, more flooding, and more damage to life, limb and property. We answer many calls from landowners concerned about erosion and flooding.

The issue is becoming more urgent. According to the Natural Resources Defense Council (NRDC), a leading New York–based policy, science and advocacy organization, over the past 50 years the number of days with heavy precipitation events has increased more than 50 percent. If this trend continues, as climate models suggest it will, flash floods will pose an ever greater risk both to people and to the infrastructure built over decades — even centuries, in some places — to handle stormwater. On the flip side, droughts elsewhere will put drinking water supplies under greater stress and increase conflicts among agricultural, industrial and residential water users.

The role of water is so important to green infrastructure that some experts speak of blue-green or turquoise infrastructure. The reason is clear: in natural conditions, rocks, soil, plants and trees keep water where it falls, or slow water down on its way into wetlands, streams and rivers. As a result, only 10 percent of rain becomes runoff, half gets absorbed and the rest goes back into the air as water vapor. The páramo in Ecuador is a great example; a giant sponge that soaks up water where it falls. When the ground cannot absorb rain — whether because cattle have pounded it solid or because people have built office towers, apartment complexes, roads and parking lots on it — nearly all the rain washes away, carrying pollution with it, and with increasing frequency overrunning stormwater systems.