Why the hill slid on Carson City's Galaxy Fandango theater parking lot; will it happen again?
Submitted by Kelsey Penrose on Thu, 06/15/2023 - 9:37am
This past weekend, Carson City was inundated with a hail and rain storm that caused flooding in several neighborhoods around town. Calls of flooded streets, storm drains backing up, and even three-foot-high geysers shooting out of manholes were coming in one right after another. Units from Douglas County were called to assist after Carson City units quickly became inundated with calls.
However, what was the most alarming for southwest residents, businesses and movie-goers, was the report of a significant mudslide at the Fandango Galaxy movie theater.
The movie theater has since reopened. While the mudslide covered the parking lot in feet of mud and debris, mudslides during storm events are unfortunately not unheard of.
According to Deputy Public Works Director Rick Cooley, the mudslide that occurred in the area of the Fandango, as well as a slide that occurred at the same time on Goni Road, are typical of thunderstorms with heavy rains in the foothill areas of town.
“The issue is where a cell drops an intense amount of water,” Cooley said. “If it occurs in the bottom of the valley, we will experience drainages being overwhelmed which will cause localized street flooding and some flows onto properties and sometimes into businesses or residences. However when these cells drop intense rain in the foothills we will see what occurred (like) on Saturday.”
As rain is dropped on the hillsides, it collects into the canyons that brings loose soil and rocks along with it, Cooley said. As the rain water erodes the hillsides and canyons, it collects at the bottom and creates not only a powerful water flow, but a debris flow as well, which accelerates more erosion and intensifies that force of the flow, until it eventually spreads out over a flat area such as a road, parking lot, field, or becomes impounded in a basin or flows into the river.
“Voltaire Street, South Carson Street, and the theater parking lot are examples of where these flows began to lose energy and deposited a majority of the debris from the hills above,” Cooley said."
While residents and business owners may be asking how they can protect against these events, Cooley says it is difficult to protect against unpredictable storms.
“Unfortunately, there is no way to predict where and when storm cells will drop rain nor its intensity,” Cooley said. “Due to the unpredictability of thunderstorms and economics involved, it is not practical to protect properties against every event. A typical design criteria is for the 100-year event, however if a 500-year event occurs those protections may not be adequate."
There are some ways people can work to protect their properties from mudslides, however. According to Ready.gov, there is no way to stop or change the path of a debris flow; however, property owners may be able to protect their property from floodwaters or mudslides through the use of sandbags, retaining walls, or what are known as k-rails or Jersey barriers.
Property owners can consider building channels or deflection walls to try to direct the flow around buildings.
Learn to recognize warning signs, such as the sound of rushing water or unusual sounds such as trees cracking or boulders knocking together, or a faint rumbling that increases in volume. If you are near a stream or channel, look for changes to flows that increase, decrease, or change from clear to muddy.
If a mudslide or landslide is occurring, never cross a road with water or mud flowing. If you get stuck in the path of a landslide, move uphill as quickly as possible.
It is likely that, given our region being fire prone and low in vegetation, other mudslides will occur in the future. Becoming educated and aware are the best ways to protect your property — and your person — from mudslide threats.
