Wildfires have been posing significant problems for many states in the US in recent years. In addition to the immediate damage and destruction to the natural environment, insurable properties, and public infrastructure, other longer-term risks persist in the post-wildfire condition.  The natural diversity of the watersheds and channels can be compromised due to loss of woody material and vegetation, and soil nutrients and cohesion are diminished in areas of particularly high burn intensity, sometimes resulting in hydrophobic soils.  The post-wildfire condition susceptibility to debris flows and increased erosional patterns can pose significant risks to transportation infrastructure and lead to increased disruption and cost due to road closures and repair/replacement of pavement, subgrade, culverts, and embankment fill.

Although much research has been conducted, and continues to be conducted, on estimating the risks and degree of damage posed by post-wildfire debris flows, the applicability of results is often limited geographically. Results must often be extrapolated to other areas which may not have sufficiently similar characteristics.  For example, data collected and calibrated to the foothills of a temperate grasslands environment may be extrapolated to a canyon environment with a flashy, desert hydrologic pattern, resulting in a poor prediction.  With the increased frequency of these fires, as well as increased risk to life and property in the paths of these types of events, additional effort is warranted to remediate areas prone to post-wildfire debris flows and to reduce damage from future wildfires.

The primary objective of this proposed pooled-fund project is to address post-wildfire debris-flow issues. Outcomes will be:

• Tailoring and building upon the existing dynamic GIS-based burned-index map of burned areas correlated with transportation infrastructure that would be impacted by debris flow to meet the needs of pooled-fund member states.
• Surveying past observed post-wildfire debris activity which affected transportation infrastructure in diverse parts of the Western United States.  These surveys will take particular note of the type(s) of precipitation patterns that triggered the debris flows – variables such as rainfall intensity and duration, monsoonal vs. steady seasonal rain; and the topography of the watershed (described with standard variables such as valley slope, channel slope, area, min/max elevations, etc.).
• Developing a compendium of the tools that are used to predict the potential of debris flow.
• Developing a compendium of remediation approaches that can be applied to burned areas, depending on the situation.
• Providing guidelines on the use of the tools and approaches compiled in the above-mentioned compendiums.
• Addressing some of the existing data gaps in current research on this issue.
  
  

Task 1 - Literature Search and Current Information Search.  Conduct thorough searches and produce DOT-implementable recommendations toward:

1.  Current available technologies that can be used to enhance the existing USGS dynamic GIS-based burned-index map of burned areas correlated with transportation infrastructure that would be impacted by debris flow.  A minimum of three Commercial Off-the-Shelf (COTS) technologies are required.  Current in-progress research approaches are also encouraged.  Some of the potential approaches to be researched are Structure from Motion (SfM) photogrammetry, Three-Dimensional Mapping using Time-of-Flight (3D ToF) Camera, Interferometric Synthetic Aperture Radar (InSAR), and Software-Defined Radar (SDRadar).

2.  Applicable resources, including the Federal Emergency Management Agency (FEMA) National Risk Index (https://hazards.fema.gov/nri/map), National Oceanic and Atmospheric Administration (NOAA) National Weather Service information such as River Observations and the NOAA drought monitoring program (https://water.weather.gov/ahps/ and https://www.cpc.ncep.noaa.gov/products/Drought/), and hazard mapping websites created or used by other states (for example the Floodplain Mapping product of the CO Hazard Mapping Program – https://coloradohazardmapping.com/hazardMapping/floodplainMapping), the United States Forest Services (USFS) Burned Area Emergency Response Treatments (BAER) – https://burnseverity.cr.usgs.gov/baer/, the United States Geological Survey (USGS) Emergency Assessment of Post-Fire Debris-Flow Hazards – https://landslides.usgs.gov/hazards/postfire_debrisflow/

3.  Methodologies currently in use by DOTs, FHWA, Canadian provinces, and other related public transportation management organizations to estimate risk along corridors and at discrete locations due to precipitation and seasonal weather patterns.  This may include records of typical precipitation durations and intensities which have produced past post-wildfire debris events; times of year that debris flows are most often recorded for a given cluster of watersheds or fire perimeter; and collection of streamflow and/or precipitation records and comparison to baseline non-wildfire data of the same nature.

4.  Surveying past observed post-wildfire debris activity which affected transportation infrastructure in diverse parts of the Western United States.  These surveys will take particular note of the type(s) of precipitation patterns which triggered the debris flows – variables such as rainfall intensity and duration, monsoonal vs. steady seasonal patterns; and the topography of the watershed (described with standard variables such as valley slope, channel slope, area, min/max elevations, etc.).

5.  From the USGS and other official states‘ websites, compile available information on depths of hydrophobic layers, soil structure (e.g., bulk density, porosity, erodibility etc.) from various previously burned sites. The compilation of this data should cover only the member states of this Pooled Fund project.

6.  Research and compile existing remediation methods for burned areas, such as the Burned Area Emergency Response Treatments Catalog (USFS BAERCAT).

7.  Be familiar with the USGS Landslide Hazards Program that is currently being developed.

Task 2 – Dashboard and Action Decision Flowchart

1.  From the knowledge gained in Task 1, create a dashboard that provides all necessary resources to help end-users formulate sufficient and reasonable boundary conditions to predict the likelihood and extent of debris flow.  The dashboard shall include quick access to external sites such as FEMA, NOAA, USFS, and USGS as well as the most up-to-date situations for Western States.

2.  Create an action flowchart for the period between the time a fire is contained and the burn area can be accessed, and the time (or season) when there is a significant risk of debris flow.  This should provide guidance to decision-makers, engineers, scientists, and maintenance personnel as they determine the risk envelope and mitigations for a given post-wildfire site.

3. Create a compendium of existing tools and resources that allows end-users to use the most appropriate ones for a given situation.

4.  Based on the knowledge gained from Task 1, propose new method(s) to remediate burned areas, that are in addition to existing remediation methods. These may be variations on existing methods, for example those found in the BAERCAT and other resources but are optimized for transportation risk mitigation.

Task 3 –Deployment Platforms and Data Collections

1.  Provide a comparison, including associated cost, of technologies (based on Task 1a) to enhance the existing GIS-based burned-index map.  Rather than determining the “best” technology, outline which technologies are best suited for different situations commonly experienced by a transportation agency in post-wildfire conditions.

2.  Installing additional rainfall gauges and collecting data from these gauges.  The data collection needs to have the capability to be done remotely, for example via UAS or satellites, so that member states can continue to collection data after the completion of this pooled-fund project.

3.  The inventories available to constrain the likelihood and volume models only contain data from debris flows triggered by distributed runoff and erosion (runoff-generated debris flows). The USGS Landslide Hazards Program does not yet have data from post-fire shallow landslides, which are more commonly observed in partially recovered burn areas (typically years 3 and older) or burn areas in wetter climates like west of the Cascades. The rainfall triggering conditions are different for shallow landslides vs runoff-generated debris flows.  Collect and compile data for member states for future use of the above-mentioned program.

4.  Compile past debris-flow volumes and provide techniques to determine the debris flow volumes in future events.  This will include a recommended approach for estimating volumetric bulking of post-wildfire flow.

5.  Conduct hazard assessments of past incidents to address issues related to debris-flow inundation and updates on durations of post-fire recoveries.

Task 4 - Reporting

1.  Reporting shall be made at the end of each task allowing member states the ability to implement the outcomes of tasks outlined above.

2.  Consolidate all background and outcomes from Task 1 to Task 3 and provide a consolidated, detailed final report, presentation, and a research brief (template to be provided).

• The duration of this study is 3 years.  However, if more funding is available, this study can be extended with additional scope of work.
• The annual commitment is $25,000/year/participating agency, which includes travel costs for one representative/year/participating agency.
• The matching funds waiver for 100% SP&R funding is in progress.  If it is not approved, the standard 80/20 participation ratio will be required.