An Inter-agency collaboration for developing decision tools: How the U.S. Geological Survey works with the National Weather Service to issue warnings for post-fire flash floods and debris flows Sue Cannon, USGS

Wildfire:

Wildfire: potentially disastrous consequences It’s not over once the smoke clears……….. Missionary Ridge Fire, Durango CO Cedar Fire, San Diego, CA

Wildfire effects on watersheds : Consumption of rainfall-intercepting canopy and of soil-mantling litter and duffConsumption of rainfall-intercepting canopy and of soil-mantling litter and duff Intensive drying of the soilIntensive drying of the soil Generation of wood ash and water-repellent soilsGeneration of wood ash and water-repellent soils Removal of obstructions to flowRemoval of obstructions to flow Results in dramatic changes in erodibility, infiltration, and runoff

Debris flows!!

Southern California Wildfires: Oct 21, 2003 NASA Image >700,000 acres Grand Prix, Old Simi, Piru, Verdale Paradise, Cedar

Debris flows: Old Fire Greenwood Cyn, Southern CA 12/25/03

Debris Flow: Hazards to Life and Property Old Fire Waterman Cyn Southern CA 12/25/03 Cable Canyon, Dec 25, 2003 Camp St Sophia, Dec 25, 2003

Report of the Joint NOAA-USGS Debris Flow Warning System Task Force

Task Force Assignment:  Establish a prototype flash flood and debris flow warning system for burned areas in Southern California San Bernardino Mountains, Dec  Identify  scientific opportunities,  necessary advancements, and  costs Landslide overview map, conterminous U.S.  Expand system to  other burned areas,  unburned areas, and  to a national scope

Save lives and protect propertySave lives and protect property Provide timely information to emergency response personnel and the publicProvide timely information to emergency response personnel and the public Demonstrate merging of NOAA and USGS state- of-the-art forecast and prediction toolsDemonstrate merging of NOAA and USGS state- of-the-art forecast and prediction tools Wind profiling radar Prototype Warning System: Missionary Ridge Fire, Durango CO

Prototype Warning System: Links NWS and USGS expertise and NWS 24x7 operational capabilities Southern California radar coverage (blue regions), and real-time rain gage locations (red dots). Threshold rainfall conditions for flash flood and debris flow from recently burned basins in the San Bernardino Mountains safety danger

Peninsular Ranges San Gabriel, San Bernardino and San Jacinto Mtns Santa Lucia Range, Sierra Madre, and Santa Ynez, Topatopa, Santa Susana and Santa Monica Mtns Rainfall thresholds

Fresh Fires 1-2 years of recovery Rainfall thresholds

Continuous monitoring of rainfall rates and accumulations in comparison to threshold conditions for individual stream basins Continuous monitoring of rainfall rates and accumulations in comparison to threshold conditions for individual stream basins Automatically alerts forecasters when a dangerous flash flood or debris flow situation may be developing Automatically alerts forecasters when a dangerous flash flood or debris flow situation may be developing Flash Flood Monitoring and Prediction (FFMP) Map of Storm Precipitation Basin conditions relative to rainfall thresholds

Wildfire in southern CA steeplands Prototype System Operation: NWS compares forecasts and precip measurements with rainfall thresholds, and makes decision for Watch or Warning NWS precipitation observations and forecasts USGS rainfall thresholds for burned areas in So Cal Here comes a storm USGS develops Outlook that specifies areas that could be impacted Immediately post-fire Outlooks, Watches and Warnings issued through NWS channels to County OES, Public Works Depts and Flood Control Districts, and to the Public, and posted on the USGS NHSS web site

Outlooks: Natural Hazards Support System web site: Tovey Yorba Linda Soboba Pioneer Paradise Southern CA Fire Perimeters: August 25, 2005 The watersheds burned this summer by the Tovey Fire in Los Angeles County near the town of Palmdale are particularly susceptible to flash floods and debris flows during rainstorms….. Tovey Fire Palmdale

Watches: – Risk of hazardous weather or hydrologic event has increased significantly, but its occurrence, location, and/or timing are still uncertain – 3 days to a few hours lead time

Warnings: –Issued when hazardous weather or hydrologic event is occurring, is imminent, or has a very high probability of occurring - 1 day to 30 minute lead times

A test of the System: October 19, 2005 Floods and debris flows down County Club Drive and in Wildwood Canyon at 2:00 and 3:00 pm Burbank Harvard Fire: 2:00 pm event: 0.28 inches of rain in 29 minutes 3:00 pm event: 0.19 inches of rain in 7 minutes

Immediate System Expansion Peninsular Ranges San Gabriel, San Bernardino and San Jacinto Mtns Santa Lucia Range, Sierra Madre, and Santa Ynez, Topatopa, Santa Susana and Santa Monica Mtns  Refine existing rainfall thresholds and develop new ones

Potential System Expansion  Provide spatially specific information as storms develop Probability of debris flow from drainages burned by the Missionary Ridge Fire near Durango, Colorado Burned area 0.6 inches of rainfall in 30 minutes Burned area 1.2 inches of rainfall in 60 minutes Burned area 1.5 inches of rainfall in 1.5 hour 0-25% 26-50% 51-75% %

Model A: Probability of debris flow occurrence = exex 1 + e x A b = % of basin burned at high and moderate severities R = Basin ruggedness (Melton’s number = ΔH/A -0.5 ) C = % clay in soil O = % organic matter (by wt) in soil I = Average storm rainfall intensity x = (A b ) - 1.1(R) + 0.1(C) – 1.4(O) + 1.1(I)Example:

1. Delineate basins of interest Model Implementation

Burn Severity- High and moderate 2. Extract data necessary for model input for each basin Model Implementation

Burn Severity Ruggedness Model Implementation 2. Extract data necessary for model input for each basin

%Organics and Clay Burn Severity Ruggedness 2. Extract data necessary for model input for each basin Model Implementation

Burn Severity Ruggedness Soil O and C Storm Rainfall Model Implementation 2. Extract data necessary for model input for each basin 3. Calculate Probability for each basin, and parse into classes

Probability of debris-flow occurrence – Missionary Ridge Fire, Colorado Probability of Debris- Flow Occurrence 1-25% 25-50% 50-75% % In response to 0.5 inches of rainfall 30 minutes Burn Perimeter

Potential System Expansion

SMART-R radar Real-time stream gage network with video cameras Intensive Research Area: Harvard Fire Repeat Ground-Based LiDAR surveys

Potential Future Development  Expansion to unburned areas throughout the US Seattle, WA

Questions???