Guest post: Thank you, Andrew Johnson former employee of the UDOT Traffic Operation Center, for contributing this informative overview about how stormwater is managed. Great post! StormTrap provided the construction image below and information for this article.
How Stormwater Management Mitigates Flood Damage
With summer winding down, Utah’s flood control experts are indicating this year’s flood season may soon be coming to an end. That’s good news to hear, although officials will continue to monitor the snow pack on some of the highest elevations.
At ground level, we all know rain travels down the gutter to disappear underground. To many, stormwater management is a term that doesn’t mean much, unless they’re seeing the consequences of heavy rain or increased melting snow.
During a storm, a number of things take place. In warmer months, rain will collect on roads and sidewalks, and be directed into gutters. In parking lots, as well as residential and commercial developments, the water will follow the grade of the pavement or landscaping, and be funneled into an underground basin.
There are two types of vessels commonly used: retention and detention basins. A retention basin takes the collected water and provides an infiltration surface to recharge the water into the soil. This limits the contaminants entering the ground below. A detention basin is similar, but simply collects the runoff and releases it in a controlled rate.
Utah certainly saw the destructive nature of water in action this year, especially during the spring and summer months of 2011. But how did the beehive state fare compared with 2010? Roland Steadham is the chief meteorologist for KTVX-TV, a television station based in Salt Lake City, and tells me that we pulled out of this year’s flood season fairly well thanks to mitigation and stormwater management. “Some may say that the state hydrologists and the media were ‘crying wolf’. This is a case where the wolf was there, we just put up a fence to keep him out.” That proverbial “fence” came in the form of sandbags, according to Steadham, but also the effective mitigation efforts of Utah’s emergency management plan. For any possible natural disaster, there’s a response plan in place, and part of that plan includes efforts to collect, detain and disperse water in a controlled manner. That’s stormwater management in action.
According to the Federal Emergency Management Agency, FEMA, flooding is the most frequent severe weather threat across the country, and 90% of America’s natural disasters involve flooding. One component of the Agency is The Flood Insurance and Mitigation Administration, designed to handle flood insurance, flood hazard mapping and floodplain management. By recognizing which areas of the state are prone to flooding, and effectively managing the geographic floodplains, mitigation takes place. But identifying needs is only a fraction of the complete mitigation effort. When designing Utah’s transportation systems, for example, civil engineers plan for the elements by incorporating specific materials into the pavement or concrete surface of the road, adjusting the grade, and collecting the rain and melting snow in an underground detention basin.
The topography of the Wasatch Front poses a unique challenge for stormwater management. Since a majority of the population lives and works in the valley, collecting the water from melting snowpacks in the mountains, and releasing it in a controlled rate is key to preventing widespread flooding during the warmer months of the year. “…in one second, Little Cottonwood Creek at its peak transported approximately 60,000 pounds of water. Do the math; in one day one this creek transported over 5-Billion pounds of water. That’s a lot of wrecking balls,” Steadham points out.
Keeping the runoff away from the streets and highways is also important. That’s why many of Utah’s roads and freeways are equipped with cameras, which are monitored 24 hours a day, 7 days a week from the Traffic Operations Center. There’s also a staff of meteorologists at the TOC, who develop specialized forecasts for UDOT’s road maintenance crews and snowplow operators. If a band of heavy rain moves through a particular area, UDOT can pinpoint the location, monitor the road surfaces for standing water, and dispatch a crew to the site if needed.