Mud & Debris Flows

Mud & Debris Flows First Responder Awareness & Safety Considerations Are We Ready ? PLAN - PREVENT - RESPOND - RECOVER Historical Perspective . “A Predictable Disaster” SanSan GabrielGabriel MountainsMountains “The San Gabriels are young mountains and are still rising as rapidly as any mountain range in the world.” “Riddled with faults, the San Gabriels have long fractured easily and crumbled in the face of Pacific Ocean storms.” “The San Gabriels are disintegrating at one of the fastest rates in the world, but they are building up faster than they disintegrate.” Exerpts from “Infamous New Year’s Day Flood, Los Angeles Basin, 1934”* Biot Report #365: May 28, 2006 (httpwww.semp.uspublicationsbiot_reader.phpBiot) SanSan GabrielGabriel MountainsMountains “For the past million years, nearly every storm blowing in from the Pacific Ocean has stalled at the San Gabriels, releasing heavy rain and deep snow.” “Some of the most concentrated rainfall ever recorded in the US has occurred in the San Gabriel Mountains. When slope saturation points have been reached, massive debris flows have started off the mountains, scouring deep canyons, and shooting out into the populated areas.” Exerpts from “Infamous New Year’s Day Flood, Los Angeles Basin, 1934”* Biot Report #365: May 28, 2006 (httpwww.semp.uspublicationsbiot_reader.phpBiot) How Orographic Lifting Increases Rainfall on the Slopes of the San Gabriels and Other Mountains Predicted rainfall in the basins and valleys is often DOUBLED in the mountains due to orographic lifting and other factors. WhatWhat isis MudMud && DebrisDebris FlowFlow ?? MudMud && DebrisDebris FlowFlow PLAY Mud and Debris Flows are rivers of rock, earth, and other debris saturated with water. They develop when water rapidly accumulates in the ground during heavy rainfall changing the earth into a flowing river of mud or “slurry.” MudMud && DebrisDebris FlowFlow • Can move at avalanche speeds. • Occur where there is a combination of heavy rain, steep slopes, and loose soil. • Can travel several miles from their source, growing in size as they pick up trees, boulders, cars, and other materials. Slopes most susceptible to Debris Flows are 30 degrees or greater! MudMud && DebrisDebris FlowFlow • Debris flows can travel a few feet to tens of miles. It will vary depending on slope and mixture. • A series of debris flows in Wrightwood traveled 15 miles into the desert in 1941. • It covered parts of Wrightwood beneath 148 feet of debris. The scarp where the flow originated is still visible above the town. Notice that trees still have not grown back. MudMud && DebrisDebris FlowFlow • Objects carried in a Mud & Debris Flow are considered to weigh only 22% of their actual weight. • Boulders will actually “float” within the flow. • Other large objects will also “float” with the flow . – Houses, Structures – Automobiles – Dozers – Fire Apparatus We Have a Long History of Post-Fire Mud & Debris Flow Disasters PLAN – PREVENT – RESPOND - RECOVER Historical Perspective . “A Predictable Disaster” • 1934 La Crescenta “Pickens Fire” • 1969 Glendora “Canyon Fire” • 1978 Mill Creek “Mill Creek Fire” • 1993 Alta Dena “Kinneloa Fire” • 1994 Bailey Cyn “Kinneloa Fire” • 1995 Topanga Cyn “Old Topanga Fire” • 2003 Devore “Old Fire” • 2003 Waterman Cyn “Old Fire” • 2003 Cable Cyn “Grand Prix Fire” LaLa CrescentaCrescenta,, 19341934 100100 fatalitiesfatalities LaLa CrescentaCrescenta,, 19341934 The fire/mud & debris flow cycle was the main cause of the disaster. •7,000 acres burned off the slopes above La Crescenta in October of 1933 “Pickens Fire” LaLa CrescentaCrescenta,, 19341934 On December 31, 1933 a steady drenching rain (7 inches in 24hrs) fell all day and continued into the night. LaLa CrescentaCrescenta,, 19341934 The accumulated rain, perhaps intensified by a thunder cell, triggered a series of mud & debris flows that swept into the populated areas. LaLa CrescentaCrescenta,, 19341934 The “The New Year’s Day Flood” was a series of mud & debris flows that struck two minutes after midnight, killing nearly 100 and injuring dozens more. The Last Thing Many People Heard Was A “Freight Train Roar” as 20-Foot Walls of Mud & Debris Blasted Into Town. LaLa CrescentaCrescenta,, 19341934 Waves of Mud & Debris Flow Roared Out of Several Canyons Simultaneously, Damaging or Destroying Hundreds of Homes and Hundreds of Cars LaLa CrescentaCrescenta,, 19341934 Los Angeles County Fire Department Photo Archives These Rocks Came From Those Mountains LaLa CrescentaCrescenta,, 19341934 Entire Neighborhoods In Our Jurisdiction Were Wiped Out! LaLa CrescentaCrescenta,, 19341934 Hundreds of Homes Were Impacted Without Any Evacuation. LaLa CrescentaCrescenta,, 19341934 More Than 700,000 Cubic Yards of Mud and Debris Flow Swept Into Populated Areas. LaLa CrescentaCrescenta,, 19341934 Rosemont Avenue & Fairway Avenue 12 People Were Killed When Mud and Debris Blasted Through the American Legion Hall LaLa CrescentaCrescenta,, 19341934 Entire Homes Were Washed Away And Became Part of The Debris Flow LaLa CrescentaCrescenta,, 19341934 45 People Missing Many Victims Were Never Found LaLa CrescentaCrescenta,, 19341934 This Boulder Ended Up On Foothill Boulevard Some Boulders Were Too Large to Move, So they Were Buried And Built Upon LaLa CrescentaCrescenta,, 19341934 200 Homes Damaged 800 Automobiles Buried Nearly 100 Fatalities with Dozens Injured 200 - 400 Homes Buried or Destroyed Glendora,Glendora, 19691969 7373 fatalitiesfatalities Glendora,Glendora, 19691969 7373 fatalitiesfatalities Glendora,Glendora, 19691969 Los Angeles County Fire Department Photo Archives 7373 fatalitiesfatalities Glendora,Glendora, 19691969 Los Angeles County Fire Department Photo Archives No Evacuation: These Homes Were Occupied! Some Survivors Floated To the Ceilings In Their Beds, And Were Trapped Until Firefighters Rescued Them Through the Roof. MillMill Creek,Creek, 19781978 Within the “Station Fire” Burn Area 1313 fatalitiesfatalities Altadena,Altadena, 19931993 October 1993’s “Kinneloa Fire” (Altadena) Also Led to Deadly Mud & Debris Flow in the San Gabriels BaileyBailey Canyon,Canyon, 19941994 A 20-Foot High Mud & Debris Flow Near Sierra Madre 22 fatalitiesfatalities TopangaTopanga Canyon,Canyon, 19951995 October 1993 “Old Topanga Fire” Leads to Several Years of Mud & Debris Flow Disasters in Malibu Many Rescue Situations and Scenes Like This Played Out in Malibu in the Winters Following the Old Topanga Fire Experts Advise to Anticipate Up to 5 Years of Mud & Debris Flow After Large Wildland Fires. Devore,Devore, ChristmasChristmas DayDay 20032003 PLAY Devore,Devore, ChristmasChristmas DayDay 20032003 Down the street, a curve in the road caused this . CableCable Canyon,Canyon, ChristmasChristmas DayDay 20032003 22 fatalitiesfatalities FFrreeeewwaayy WatermanWaterman Canyon,Canyon, ChristmasChristmas DayDay 20032003 1212 fatalitiesfatalities WatermanWaterman Canyon,Canyon, ChristmasChristmas DayDay 20032003 Survivor found downstream of camp - he and his daughter were separated by the flow and she died. LaLa CrescentaCrescenta,, 20092009 Are We Ready ? Could This Happen Again? What is the Same? What Has Changed? Foothill Blvd & Briggs 1934 Foothill Blvd & Briggs 2009 Verdugo Rd & Ocean View Blvd 1934 Verdugo Rd & Ocean View Blvd 2009 The L.A. County Department of Public Works, the L.A. County Flood Control District, and Allied Agencies Have Developed One of the Most Elaborate Flood Control Systems In the World We Have One of the Most Sophisticated Mud & Debris Control Systems in the World Many debris basins have been designed to protect downstream neighborhoods 1934 The Original Cause & Effect Remains the Same Major Fires Followed by Mud & Debris Flow Events 2009 20092009 StationStation FireFire The Critical Difference - The 1933 Pickens Fire Was “Only” 7,000 Acres. The 2009 Station Fire burned within the same area of the San Gabriel Mountains, but this time the area of burned terrain is much larger. 20092009 StationStation FireFire Station Fire, 2009 • 160,000 + Acres In Some of the Highest Producing Mud & Debris Flow Terrain in N. America < Pickens Canyon Fire, 1933 •7,000 Acres LaLa Canada,Canada, 20092009 November 12, 2009 Surprise “Un-Tracked” Storm Causes Mud & Debris Flows in La Canada LaLa Canada,Canada, 20092009 LaLa Canada,Canada, 20092009 X Debris Flow Site The Impact Area Was Already Identified As A Likely Mud & Debris Flow Site LaLa Canada,Canada, 20092009 Debris Flows X LaLa Canada,Canada, 20092009 There Was A Forecast Only for Light Rain In Some Areas… The Forecast Met None of the Criteria For A Storm Deployment of Resources… And Yet, In One Small Area of the Station Fire Burn Area, A Storm Cell Developed and Dumped Nearly 2 Inches of Rain in 1 Hour LaLa Canada,Canada, 20092009 X Debris Flow Site L.A. County DPW Phase Map The Cell Hit One of the Most Vulnerable Neighborhoods, Which Has Been Identified As A Possible Site for Future Disastrous Floods LaLa Canada,Canada, 20092009 It did not rain on Foothill Blvd or at any of the local fire stations LaLa Canada,Canada, 20092009 The Debris Basin was full within 15 Minutes. LaLa Canada,Canada, 20092009 5 feet of mud in some areas . No time to evacuate residents! LaLa Canada,Canada, 20092009 These residents heard the “roar” of Mud & Debris, felt the ground rattling, saw the “black mass of mud coming down, and barely escaped in a car. A Related Danger Another Hazard Where Mud & Debris Flow Conditions Are Found LANDSLIDES Conditions That Cause Mud & Debris Flows Are Also Implicated in Land Slides! LaLa ConchitaConchita,, 20052005 1010 fatalitiesfatalities LaLa ConchitaConchita,, 20052005 The Event Took Only 8 Seconds, Killed 10, and Injured Dozens Japan,Japan, 20042004 PLAY Mud & Debris Flows First Responder Awareness & Safety Considerations Are We Ready ? PLAN - PREVENT - RESPOND - RECOVER.

Load more