Summer thunderstorms pose a greater threat to burned areas of Yellowstone National Park and Shoshone National Forest than does spring runoff, according to two water specialists.
So far no significant erosion problems have been noticed in either reserve during the runoff season."Most of us felt all along that summer thundershowers were more of a threat" than spring runoff, said Greg Bevinger, a hydrologist at Shoshone National Forest.
In the forest, spring runoff on some 140,000 acres burned last year is almost over, said Bevinger. Recent heavy rains in the Cody area fell as well as new snow in the burned areas of the forest, but no erosion or flooding problems arose, he said.
"Most of the fire areas have melted out," he said. Grasses already are beginning to sprout in the areas, he added.
"We haven't seen a whole lot of surface soil erosion," the hydrologist said. However, some stream channels did widen because of the runoff, he said.
"It is making for fairly muddy water," said Bevinger.
Phil Farnes, a water supply specialist with the USDA's Soil Conservation Service office in Bozeman, Mont., also said no problems occurred with the runoff season.
"We don't see it much different than we would expect to see in a normal situation," said Farnes.
The specialist said there has been "a fair amount of sediment" in Yellowstone's rivers. However, he expects much of that can be attributed to an accumulation of soils in the absence of heavy runoff in recent years.
The sediment load has increased in both burned and unburned areas, said Farnes.
Both men say peak streamflows from the spring runoff are yet to come. Farnes predicts that peak flows on the Yellowstone River will be seen in mid-June. Already the river is carrying twice as much water as the highest flows of last year, he said.
While Farnes also expects to see increased sediment flows from some burned areas, exactly how much is swept into rivers depends on the amount of moisture produced by thunderstorms.
In an effort to minimize runoff problems, Shoshone forest crews used aerial seeding to spread 500,000 pounds of seed over some 23,000 acres hit by the Clover-Mist fire, he said. The seeding was concentrated on slopes of less than 40 percent next to stream channels.
Bevinger also said new stream gauges installed along the North Fork of the Shoshone River will provide a warning if thunderstorms create flood conditions.