UDOT is just one of the agencies working to repair erosion that occurred during a flash flood in Huntington Canyon in the Manti-La Sal National Forest.
A rain storm that occurred on August 1 caused a flash flood that washed trees, soil and rocks from the canyon walls into cut-ditches and culverts and onto SR-31. The flooding event was made worse by the Seeley Fire that occurred in the area before the flood. Because much of the vegetation was burned away, the runoff washed debris down the canyon. “It was an incredible flood,” says Jim Chandler, UDOT Region Four Area Engineer.
UDOT crews made a herculean effort to clear and open the road during the week after the flood, according to Chandler. But without the natural vegetation on the slopes, rain or snow melt in the spring could cause more erosion in Huntington Canyon. “It damaged more than just a highway,” says Chandler.
The flood also took its toll on the natural environment explains Darren Olsen, U.S. Forest Service District Ranger. The flash flood “scoured out the natural drainage areas” including seasonal stream beds that carry spring runoff or flooding to Huntington Creek and out of the canyon. Ash from the fire washed into the streams and killed fish and downstream agricultural users are dealing with sediment that clogs irrigation systems.
The most significant fire damage and erosion occurred on north-facing slopes where conifers typically grow. Many of those trees had been killed by beetles, and that dry wood provided fuel for the fire.
Olsen is helping to plan some mitigation in targeted areas to prevent similar flash floods in the future. “Already Mother Nature is doing a good job at re-vegetating the south facing slopes” where new growth is coming in. The USFS is planning to place wood mulch on 540 acres of area on steep slopes. The mulch will slow down runoff until vegetation can be reestablished. Reseeding areas of the Seeley Fire will be flown in to help get plants established. This reseeding effort aims at encouraging “quick plant growth that will capture the rain.”
Olsen says that between Mother Nature and the USFS efforts, two to five years is the expected time for vegetation to fill in the burned areas. He says one concern is spring weather; a cold spell followed by warm weather could cause heavy runoff from snow melt.