Monsoon arrives, bringing risk of flooding

Grab an umbrella and raincoat: The monsoon has arrived. And with the seasonal storms, an increased chance of flooding below the 416 Fire burn scar.

While new vegetation has greened up parts of the burn area, the risk of flooding and debris flows persists below the scorched landscape, including in Hermosa, said Butch Knowlton, director of La Plata County’s Office of Emergency Management.

“People need to be cautious and aware,” he said.

This year’s monsoon is expected to be fairly average, which means far more moisture than last year, when the rains barely showed up because of a high-pressure system that blocked storms from arriving, said Megan Stackhouse, a National Weather Service meteorologist. Durango typically receives 1.48 inches of rain in August, according to the NWS.

Monsoon precipitation typically arrives from the south starting mid-July and lasts until mid-September. Afternoon thunderstorms are typical across much of Colorado, said Tom Renwick, an NWS meteorologist.

In the next few days, Durango’s best chance for rain is Thursday evening and Friday morning, he said. But the storm is expected to bring only about 0.01 inch of rain, he said.

Daily highs in the area should be in the mid-80s this week, as cloud cover moves into the region, which is on par with the average for this time of year, he said.

“You’re going to stay right about where you should be,” he said.

During August, September and October, the area could see daily highs a few degrees higher than average, said Dan Collins, seasonal forecaster with the Climate Prediction Center.

From September through November, warm surface temperatures in the eastern Pacific could send more moisture into the atmosphere and bring above-average precipitation to the region, he said.

The flood-prone Hermosa area receives some of the highest levels of precipitation in La Plata County, and the area is susceptible to intense isolated storms, Knowlton said.

“We are going to be doing the best we can to watch that area and try to anticipate what the storms are going to deliver,” he said.

La Plata County Sheriff’s Office deputies and Road and Bridge crews have been sent to areas below the burn scar during storms to monitor for debris flows. That will continue during the monsoon, Knowlton said.

Some of the areas most likely to see runoff are north-facing slopes, previously home to conifers where the fire burned hotter than slopes with mixed vegetation, such as aspen and shrubs, Knowlton said.

Some of those slopes are in Tripp, Dyke and Buck canyons on the southern end of the burn scar. Vegetation on those slopes will take several years to recover, he said.

Last July and September, some residents below the burn scar experienced firsthand the damage flooding can cause. Many have taken action to protect their homes, Knowlton said.

Residents near the burn scar have cleaned out ditches and ravines to divert water and put in berms and other defensive structures since last year to help protect their property, he said.

The National Resources Conservation Service started a $7 million project this month to put in additional flood-mitigation measures to protect about 120 homes.

The monsoon may also bring down ash and debris into the Animas River, which can hurt the ecosystem by reducing the oxygen in the water and increasing the heavy metals in the water, said Marcie Bidwell, executive director of Mountain Studies Institute.

Damaging runoff from the scar could continue for years. Some portions of the Missionary Ridge Fire that burned in 2002 still see heavy debris flows, Knowlton said.

The public can receive warnings about flooding by signing up for CodeRed at www.co.laplata.co.us/emergency.

Residents can also watch storms approach through a temporary radar system on top of Missionary Ridge at www.arrc.ou.edu/px1000.

mshinn@durangoherald.com