Flash Flood Watches, Warnings along foothills, Front Range are a particular threat around wildfire burn scars – Denver, Colorado

Denver, Colorado 2021-07-01 13:51:37 –

As the storm moves to Colorado on Thursday and Friday, there is growing concern about flash floods, especially in the massive burn scars of 2020. Forest fire..

According to the National Weather Service of Boulder, flash flood surveillance means flood-friendly conditions and is currently in effect, extending to the Wyoming border south of Colorado Springs, hills, front range, and South Park. is included. According to the NWS, the watch was published Thursday morning through midnight due to slow thunderstorms and heavy rains. May be upgraded to warning.

Flash flood warnings were issued from about 11:50 am to 1:45 pm in Larimer County, including the area burned by the Cameron Peak fire. Warnings were also issued to Idaho Springs, Central City and Blackhawk until 2:15 pm.

The NWS predicts that storms will begin to occur late in the morning, and by afternoon and evening, storms will slowly move into urban corridors, resulting in multiple thunderstorms. During this time, streams and small drainage channels can make roads impassable in some locations. The storm weakens from late evening (around 10 pm) to early Friday.

National Meteorological Service

At some point, 1-2 inches of rain can fall within an hour, according to NWS reports.

Flash floods can also occur on Thursdays and Fridays in urban areas and lowlands around Interstate 25.

The threat of flash floods and debris flows is especially high around the eastern slopes of the 2020 wildfire scars. Troublesome fire in the east, Cameron Peak Fire, Calwood Fire, Williams Folk Fire. According to the NWS, serious flash floods can occur in the area, and the threat remains high until Friday, before it declines slightly on Saturday and Sunday.

Burn the threat of flood scars_July 1, 2021_National Meteorological Service Boulder

National Meteorological Service

The highest risk of storms over burn scars is Thursday between 2 pm and 8 pm.

Thomas Veblen, a professor of geography at the University of Colorado at Boulder, spoke with Denver7 in February about the threat that a summer storm poses to the 2020 wildfire burns. He specializes in forest ecology and vegetation dynamics associated with natural and anthropogenic disturbances.

In short, he explained that the chemicals in the soil of the burn scars were rearranged by the effects of evaporation.

“So you get a layer that is the water repellent layer of the soil,” he said. “And because it’s water repellent, it’s like the same process as an avalanche. There’s saturated soil on top of that layer, and then it can just fall off.”

To prevent this, the crew would use a helicopter to drop the mulch into the soil to protect it from the intensity of the rainfall, he said.

“The main concern is the loss of forest cover that protects the surface from the extremely heavy precipitation during summer thunderstorms,” ​​Veblen said in February. “Yes, that’s probably a major management concern in all these burnt areas where thunderstorms will occur next year, next summer. Serious erosion is likely to occur.”

He said these concerns would not only last until 2021, but flooding with burn scars would continue to be an imminent concern for more than five years after the fire.

Tracie Harrison of FEMA Region 8 explained that these flood risks of burns remain fairly high until vegetation is restored and the basin stabilizes. She was one of three speakers featured in April at a webinar hosted by FEMA Region 8, the Colorado Department of Homeland Security and Emergency Management, and the Colorado Water Conservation Commission.

“Therefore, vegetation usually absorbs rainwater — reduces runoff, but wildfires burn the ground and cannot absorb this water from the fire,” she said. “It creates ideal conditions for flash floods. These flood events are generally more serious because much less rainfall is required to generate flash floods and lahars in these burn areas.”

Large wildfires, especially the East Troublesome Fire and Cameron Peak Fire, can dramatically change landscapes and create landscapes that significantly increase the risk of post-fire floods downstream of burn scars and downhill. She said. This can occur in areas that are traditionally less prone to flooding.

Floods of this type can be caused by small storms, loosening rocks, rolling downhills, tearing trees from the ground, and destroying buildings and bridges, Harrison said.

In the same webinar, the Colorado Water Conservation Commission and Colorado National Flood Insurance Program Coordinator Doug Mahan said that just one inch of water could cause $ 25,000 in flood damage to a home.He became a downhill resident of the burn scar Consider purchasing flood insurance..

Another webinar host, Peter Reinhardt of FEMA Region 8, said that the general rule of thumb is that if you can see the burn area from where you are standing looking up at the slope, you are at risk of flooding.

If you encounter flash floods, NWS tells you to follow three simple steps to stay safe.

  • Get on high ground and stay away from lowlands that can collect water and debris
  • Do not drive or walk in flooded areas. Only 6 inches of water can knock a person off his feet, and dangerous debris can be present beneath a muddy surface. The 12-inch water column can carry small cars away, and the 18-24-inch water column can carry most large SUVs, vans, and trucks.
  • Get information with emergency alerts from your county, social media, radio and other outlets.

Watch the Denver 7 live weather stream below. click here A 24-hour, 24/7 live update on current weather conditions around the state.

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Flash Flood Watches, Warnings along foothills, Front Range are a particular threat around wildfire burn scars Source link Flash Flood Watches, Warnings along foothills, Front Range are a particular threat around wildfire burn scars

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