Flash Floods and Lyons Colorado

 Lyons, Colorado – in Boulder County Colorado – was the site of horrific flooding over the past few days. The flooding was not just due to rising water levels in rivers and other bodies of water. The flooding was also due to flash flooding that resulted from the huge amount of rain that fell in a very short time.

Lyons, home to “2,000 really attractive and accomplished people,” according to their Visitors Guide. Also according to their Visitors Guide, Lyons is located in the foothills of the Rocky Mountains and surrounded by sandstone ridges that reach to 6,500 feet. This small town also happens to be at the intersection of two canyons. The photos in the Visitors Guide and on the town Web site show a place that is breathtaking – in stark contrast to the images we’re seeing in the news.

ClimateProgress included coverage of ‘Biblical’ Amounts of Rainfall on their site. “Boulder County Sheriff Joe Pelle, after facing 20-foot walls of water racing down canyons already stripped bare by wildfires and drought, said, “This is not an ordinary day. It is not an ordinary disaster.” “A dozen dams overflowed and six actually blew out…” Meanwhile, Lyons was one of three towns that were totally isolated by the water. “There’s no way out of town. There’s now way into town. So, basically, now we’re just on an island,” Lyons resident Jason Stillman told the Weather Channel after he had to evacuate his home at 3 am.m. due to a river flooding into the street.”

Since water is a fluid, and fluids flow in the direction of least resistance, we can take a look at the flood and apply what we know of the nature of fluids. First, the rain that fell in the areas that were bare of vegetation created a perfect sluice for the water. It was able to run rapidly, with minimal absorption, along the crevices and natural ridges and gullies that existed. This fast-flowing water then met with the rivers that were already swelling from the rain being dumped on them. As the ground around the river became soaked, it could not absorb any more water. That left the rain water runoff to flow into the rivers or on the roads or into low lying areas adjacent to the soaked ground. Paved driveways, rooftops, and roadways also resisted absorption of the falling rain – resulting in still more water that raced along the path of least resistance.

The net result? Flooding in areas that did not normally have flooding. Why? Because the problem was not simply that the rivers were rising due to rainfall in the mountains. The problem was that the rainfall in the mountains was creating rushing torrents of water of their own. These torrents were not necessarily following the path of the river. In many instances they were racing down the hillside and through the basement of homes and other buildings. In low lying areas, these torrents created rising water conditions that resulted in flash floods. Add in the water from burst dams and you have enough water to qualify as a 500-year event (something that would only happen once every 500 years) in some areas.

According to a report on Weather.com, this flood “was worse than previous flash floods because of the sustained rains and widespread damage to infrastructure across the Rocky Mountain Foothills. Major roads were washed away, small towns like Glen Haven reduced to debris and key infrastructure like gas lines and swear systems destroyed, meaning hundreds of homes in Estes Park [20 miles from Lyons] alone could be unreachable and uninhabitable for up to a a year.”

In Estes Park, about 20 miles from Lyons, a bluegrass musician has been visiting his home every day and taking photos. the house has a river running through it and he can’t get close, according to a report on Weather.com.

Update 9/19/13:  “It’s amazing how different Lyons looks in terms of what this looked like before,” Mayor Julie Van Domelen told CBS News. “Whole river patterns have changed.”

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