Tag Archive for: debris flow

GEOLOGIC HAZARDS

Fire-related debris flows damage houses in Spring Lake and Santaquin, Utah County, September 2002




On the evening of September 12, 2002, intense thunderstorm rainfall on Dry Mountain, about 18 miles south of Provo, triggered fire-related debris flows that traveled down drainages and onto alluvial fans, damaging houses and property in Spring Lake and Santaquin east of Interstate 15. Fire-related debris flows are debris flows that start in areas burned by wildfires.

The debris flows started high in the drainages on the east side of Dry Mountain that burned in the 2001 Mollie wildfire, a human-caused fire that burned 8,000 acres between August 18 and September 1, 2001.

The most damaging debris flow traveled through a subdivision in Santaquin. This debris flow moved and partially buried several vehicles, broke through a house wall, and entered other houses through broken basement windows and doors. Debris-flow impacts also tore gas meters from their mounts, causing gas leaks and a small fire. Sediment flow and burial on lots also damaged landscaping and property outside the houses.

A debris flow in Spring Lake filled part of the High Line irrigation canal with sediment, causing flooding in addition to debris-flow damage.

For additional information read the Geologic Hazards Program Technical Report (pdf-4MB).


GEOLOGIC HAZARDS

April 6, 2004, Fire-related Flooding and Debris Flows in Farmington

By Richard E. Giraud and Greg N. McDonald




Intense thunderstorms on the evening of April 6, 2004, caused flooding and debris flows in areas along the east bench of Farmington between Farmington and Shepard Canyons. The sources of the floodwaters were mainly small, range-front drainages burned in the July 2003 Farmington fire.

Most damage occurred in subdivisions on small alluvial fans below two unnamed drainages south of Shepard Creek (see adjacent map).

Floodwaters and sediment deposition were mostly restricted to streets and yards, but damage also occurred to several vehicles, garages, and homes (see photos below).

At one locality, erosion by floodwaters threatened a section of a Weber Basin Water Conservancy District aqueduct running along the mountain front (see photo below).

The lower slopes of the Wasatch Range above Farmington were burned in the July 2003 Farmington fire. Following the fire, the Utah Geological Survey (UGS) assessed the heightened fire-related debris-flow hazard and produced a map showing debris basins and areas of possible flooding and debris flows. Letter Report to Wasatch-Cache National Forest (pdf).

A U.S. Forest Service (USFS) Burned Area Emergency Rehabilitation (BAER) team assessed the severity of the burn and resulting increased flood hazard.

Following the BAER team assessment, the USFS and U.S. Natural Resources Conservation Service undertook various watershed-protection measures to reduce flooding and debris-flow hazards. These were completed in late fall 2003.

Factors probably contributing to the flooding in addition to heavy rainfall and burned hillsides include steep slopes, ample supplies of sediment, and increased runoff caused by already wet soil conditions from recent snowmelt.

Davis County and Farmington have a long history of flooding and debris flows, and as a result many of the larger drainages such as Farmington and Rudd Canyons are protected by debris basins. However, most small drainages are not.

Although emergency watershed protection measures, such as were completed last fall following the fire, are designed to reduce flooding and debris-flow hazards, they do not eliminate hazards and are not permanent. Therefore, the heightened flooding and debris-flow hazard from the fire will exist for several more years while the watershed recovers to preburn conditions.

A field survey on April 7, 2004, by UGS geologists found that drainages in the flood area contain ample sediment for future debris flows.

GEOLOGIC HAZARDS

July 26th, 2004, fire-related debris flows near Spring Lake and Santaquin, Utah

By Christopher B. DuRoss
and Greg N. McDonald




Intense rainfall in the afternoon and evening of July 26th, 2004, triggered two fire-related debris flows south of Provo, near Spring Lake and Santaquin, Utah. Mud-, cobble-, and boulder-rich sediment discharged from two drainages on the northwest flank of Dry Mountain, and was deposited on alluvial fans north of the range-front. The debris originated from drainage areas burned by the human-caused 8,000-acre Mollie wildfire of 2001.

The fire-related debris flows were in the same general location as the two northernmost flows of September 12th, 2002; however, the July 2004 flows were smaller and did not travel as far north as the 2002 flows (see maps below). No damage to residential homes or property was reported. Conversely, the September 2002 flows resulted in significant damage to a subdivision due to a large volume of debris that originated from a drainage farther to the south. No debris flows were generated from that drainage in the July 2004 storm.

The larger debris flow is located southwest of Spring Lake and traveled to the northwest, filling part of the High Line irrigation canal with cobbles and silt. The debris was quickly excavated to prevent overflow and flooding of the canal.

The thickness of new material in the 2004 deposit could not be determined as an unknown amount of the September 2002 debris was incorporated into the flow.

About a mile east of Santaquin, a smaller debris flow traveled to the northwest into a storm-water catchment basin. The deposit is approximately 9 to 12 inches thick.

Some of our geologists are studying the hazards in this area. Take a look at this article at what they have to say about the rock-fall hazards and other geologic hazards present in Washington County.

kutv.com

Communities from La Verkin to Springdale have “significant geologic hazards” along State Route 9, according to a report released on Thursday by the Utah Geological Survey (UGS).

READ MORE

video courtesy of David Rankin

After 4 consecutive days of heavy rain, another day of large flash floods strikes southern Utah. Inches of rain have fallen with more in the forecast for the next few days. The 2013 southwest monsoon season has been insane.

 
 

washingtonpost.com

Once in a great while, I stumble upon extreme weather video unlike anything I’ve ever seen. Today’s example? A large, violent debris flash flood that gutted a creek basin in southern Utah Thursday afternoon (south of Bryce Canyon National Park, about eight miles north of Lake Powell).

 

READ MORE

 

Joseph M. Dougherty Deseret News

A new report by the Utah Geological Survey shows that Deuel Creek in Centerville Canyon, given the right conditions, could dump 196,000 cubic yards of mud on Centerville homes.

The last time Deuel Creek had a devastating debris flow event was, well, never.

But creeks in similar canyons to the north of Centerville Canyon have produced debris flows, which are characterized by large amounts of mud, rocks, trees and boulders. That’s different from a flood, says UGS geologist Rich Giraud, which is mostly water with some eroded material.

READ MORE

Tag Archive for: debris flow

GEOLOGIC HAZARDS

Fire-related debris flows damage houses in Spring Lake and Santaquin, Utah County, September 2002




On the evening of September 12, 2002, intense thunderstorm rainfall on Dry Mountain, about 18 miles south of Provo, triggered fire-related debris flows that traveled down drainages and onto alluvial fans, damaging houses and property in Spring Lake and Santaquin east of Interstate 15. Fire-related debris flows are debris flows that start in areas burned by wildfires.

The debris flows started high in the drainages on the east side of Dry Mountain that burned in the 2001 Mollie wildfire, a human-caused fire that burned 8,000 acres between August 18 and September 1, 2001.

The most damaging debris flow traveled through a subdivision in Santaquin. This debris flow moved and partially buried several vehicles, broke through a house wall, and entered other houses through broken basement windows and doors. Debris-flow impacts also tore gas meters from their mounts, causing gas leaks and a small fire. Sediment flow and burial on lots also damaged landscaping and property outside the houses.

A debris flow in Spring Lake filled part of the High Line irrigation canal with sediment, causing flooding in addition to debris-flow damage.

For additional information read the Geologic Hazards Program Technical Report (pdf-4MB).


GEOLOGIC HAZARDS

April 6, 2004, Fire-related Flooding and Debris Flows in Farmington

By Richard E. Giraud and Greg N. McDonald




Intense thunderstorms on the evening of April 6, 2004, caused flooding and debris flows in areas along the east bench of Farmington between Farmington and Shepard Canyons. The sources of the floodwaters were mainly small, range-front drainages burned in the July 2003 Farmington fire.

Most damage occurred in subdivisions on small alluvial fans below two unnamed drainages south of Shepard Creek (see adjacent map).

Floodwaters and sediment deposition were mostly restricted to streets and yards, but damage also occurred to several vehicles, garages, and homes (see photos below).

At one locality, erosion by floodwaters threatened a section of a Weber Basin Water Conservancy District aqueduct running along the mountain front (see photo below).

The lower slopes of the Wasatch Range above Farmington were burned in the July 2003 Farmington fire. Following the fire, the Utah Geological Survey (UGS) assessed the heightened fire-related debris-flow hazard and produced a map showing debris basins and areas of possible flooding and debris flows. Letter Report to Wasatch-Cache National Forest (pdf).

A U.S. Forest Service (USFS) Burned Area Emergency Rehabilitation (BAER) team assessed the severity of the burn and resulting increased flood hazard.

Following the BAER team assessment, the USFS and U.S. Natural Resources Conservation Service undertook various watershed-protection measures to reduce flooding and debris-flow hazards. These were completed in late fall 2003.

Factors probably contributing to the flooding in addition to heavy rainfall and burned hillsides include steep slopes, ample supplies of sediment, and increased runoff caused by already wet soil conditions from recent snowmelt.

Davis County and Farmington have a long history of flooding and debris flows, and as a result many of the larger drainages such as Farmington and Rudd Canyons are protected by debris basins. However, most small drainages are not.

Although emergency watershed protection measures, such as were completed last fall following the fire, are designed to reduce flooding and debris-flow hazards, they do not eliminate hazards and are not permanent. Therefore, the heightened flooding and debris-flow hazard from the fire will exist for several more years while the watershed recovers to preburn conditions.

A field survey on April 7, 2004, by UGS geologists found that drainages in the flood area contain ample sediment for future debris flows.

GEOLOGIC HAZARDS

July 26th, 2004, fire-related debris flows near Spring Lake and Santaquin, Utah

By Christopher B. DuRoss
and Greg N. McDonald




Intense rainfall in the afternoon and evening of July 26th, 2004, triggered two fire-related debris flows south of Provo, near Spring Lake and Santaquin, Utah. Mud-, cobble-, and boulder-rich sediment discharged from two drainages on the northwest flank of Dry Mountain, and was deposited on alluvial fans north of the range-front. The debris originated from drainage areas burned by the human-caused 8,000-acre Mollie wildfire of 2001.

The fire-related debris flows were in the same general location as the two northernmost flows of September 12th, 2002; however, the July 2004 flows were smaller and did not travel as far north as the 2002 flows (see maps below). No damage to residential homes or property was reported. Conversely, the September 2002 flows resulted in significant damage to a subdivision due to a large volume of debris that originated from a drainage farther to the south. No debris flows were generated from that drainage in the July 2004 storm.

The larger debris flow is located southwest of Spring Lake and traveled to the northwest, filling part of the High Line irrigation canal with cobbles and silt. The debris was quickly excavated to prevent overflow and flooding of the canal.

The thickness of new material in the 2004 deposit could not be determined as an unknown amount of the September 2002 debris was incorporated into the flow.

About a mile east of Santaquin, a smaller debris flow traveled to the northwest into a storm-water catchment basin. The deposit is approximately 9 to 12 inches thick.

Some of our geologists are studying the hazards in this area. Take a look at this article at what they have to say about the rock-fall hazards and other geologic hazards present in Washington County.

kutv.com

Communities from La Verkin to Springdale have “significant geologic hazards” along State Route 9, according to a report released on Thursday by the Utah Geological Survey (UGS).

READ MORE

video courtesy of David Rankin

After 4 consecutive days of heavy rain, another day of large flash floods strikes southern Utah. Inches of rain have fallen with more in the forecast for the next few days. The 2013 southwest monsoon season has been insane.

 
 

washingtonpost.com

Once in a great while, I stumble upon extreme weather video unlike anything I’ve ever seen. Today’s example? A large, violent debris flash flood that gutted a creek basin in southern Utah Thursday afternoon (south of Bryce Canyon National Park, about eight miles north of Lake Powell).

 

READ MORE

 

Joseph M. Dougherty Deseret News

A new report by the Utah Geological Survey shows that Deuel Creek in Centerville Canyon, given the right conditions, could dump 196,000 cubic yards of mud on Centerville homes.

The last time Deuel Creek had a devastating debris flow event was, well, never.

But creeks in similar canyons to the north of Centerville Canyon have produced debris flows, which are characterized by large amounts of mud, rocks, trees and boulders. That’s different from a flood, says UGS geologist Rich Giraud, which is mostly water with some eroded material.

READ MORE