Summer storms have ripped through Colorado over the past several weeks leaving the landscape decimated. The picture associated with this post was taken in Denver at a newly completed hospital with a retaining wall, catchment system for snow melt and storm waters, and landscaping which can help prevent soil erosion. Walking down the street reveals numerous areas where heavy rains have washed away soil and rock used to cover bare land.
In the case of the hospital parking lot, part of the fence sunk, the retaining wall washed away, and the plantings were uprooted. The parking lot covers what looks to be 2-3 acres. What happens to all of the rain that falls on that cement? A look at the picture reveals the answer. There is another option though. Pervious pavement, sometimes known as permeable pavement, allows for water to run through, not off, the pavement and return to the groundwater. This provides several benefits, especially during times of heavy rains. For a video demonstrate, see below.
A recent Science Friday topic titled “Creating Reservoirs Under Roads And Parking Lots” looked at the issue. Consider how much land is paved in this country. While roads only take up a small percentage of the total paved surfaces, I have heard estimates on the total covered surfaces (including sidewalks and buildings) range upwards of 25% in some places like New York City. All of the water diverted from underground aquifers is a problem. However, the bigger issue may be the raging rivers and instant floods created by impervious surfaces.
As floods increase in frequency and severity, there are a few choices that can help alleviate the strain on local water ways. Home catchment systems make sense for new construction, but not retrofitting, as cost of both is high, but the latter is exorbitant. As a guest post pointed out a last year, rain barrels can also be a hassle from a couple of perspectives. Costs associated with damage from floods, erosion, and storm damage will continue to mount over the coming years. One option, albeit an expensive upfront cost, is to replace roads as they age with permeable ones that reduce runoff and return water to underground sources.