Riverdale landslide moves closer to homes
RIVERDALE, Utah – The latest measurement of a landslide in Riverdale revealed that three to four feet of additional land have recently fallen away — prompting new concerns that three homes situated above the slide are in danger of collapsing down the hillside.
The measurement, taken on Wednesday by geologists with Utah’s Geologic Hazards Program, showed that the new movement took place since April 3, according to Ben Erickson with the Utah Geological Survey.
Erickson said the top of the slide is now about 12 feet from one of the homes above. In all, three homes are under mandatory evacuations with the residents of a neighboring home evacuating voluntarily. If nothing changes, he said it is “inevitable” that the homes will be completely lost.
The Spring Creek Road Landside started on November 19, 2017, as a result of spring water flowing from the middle of the bluff that stands 200 feet tall. Mud and debris now cover farm buildings and pastures below.
“You could hear it flowing out of the hillside,” geologist Greg McDonald said of the water. “When this thing first triggered, it was pretty rapid—it’s what we call an earthflow.”
McDonald, who also works for the Utah Geological Survey, said they are monitoring several points along the face of the slide, as well as the amount of groundwater flowing from the bluff. If the water keeps carrying sediment away from the base, he says the top of the slide will continue to retreat toward the homes.
“It wants to lay back at a more natural slope,” he said of the hillside, “so we’re seeing big pieces of head scarp fall in onto the landslide.”
The timing of the landslide is unique because it happened in the fall, McDonald explained. Typically, spring runoff from mountain snowmelt causes landslides in Utah. His department hasn’t been able to collect enough data on the groundwater network in the area to understand what recently changed to trigger the slide.
Riverdale City warns on its website that the slide area is “active and extremely dangerous” and urges residents to stay out of the area for their own safety.