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:

·         Developing a dynamic GIS-based burned-index map of burned areas correlated with transportation infrastructure that would be impacted by debris flow.

·         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.

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

      a.     Current available technologies that can be used to create a 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.  Some of the potential approaches to be researched are Structure from Motion (SfM) photogrammetry, Three-Dimensional Mapping using Time-of-Flight (3D ToF) Camera, and Interferometric Synthetic Aperture Radar (InSAR).

      b.     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). 

      c.     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. 

      d.     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.).

     e.     Collect available information on depths of hydrophobic layers, soil structure (e.g., bulk density, porosity, erodibility etc.) from various previously burned sites. This should cover the member states of this Pooled Fund project.

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

     g.     Research and compile remote sensing and support platform capabilities with payload between 30 lbs and 50 lbs.

       h.     Research and compile best practices for determining hydrophobicity using in-field testing, aerial survey with sUAS or manned equipment, and other techniques.

2.     Task 2 – GIS-based burned-index map

From the knowledge gained in Task 1.a., provide a comparison, including associated cost, of the technologies found to create the 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. 

3.     Task 3 – Dashboard and Action Decision Flowchart 

     a.     From the knowledge gained in Task 1.b., 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 and NOAA, as well as the most up-to-date situations for Western States.

     b.     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.

4.     Task 4 – Remediation and Risk Mitigation

     a.     Based on the knowledge gained from Task 1.c. to 1.f., 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.

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

5.     Task 5 – Sensor Deployment Platforms

     a.     From Task 1.g. and 1.h., develop remote sensing and support platforms or alternative means to deliver and deploy moisture and hydrophobicity sensors to burned areas.  The same platform shall also have the capability to capture and report data from these sensors. 

     b.     Outline the required actions and identify all necessary communication/coordination with appropriate authorities to launch the remote sensing platform and collect data as soon as allowable after the fire is contained.

     c.     Develop a maintenance and technical support program for the developed platform.

     d.     Develop an analytical program to quickly analyze the data obtained and generate predictions and probabilities of debris flow so that states have sufficient time to respond to the situations.

     e.     Develop a machine-learning/deep-learning (ML/DL) application using the historical data collected in the previous tasks to predict the evolution of the hydrophobic soil layer and thereby predict the recovery rate of the soil’s hydrologic properties.

6.     Task 6 - Training 

Develop a training program on the use of systems developed in Tasks 3 to 5. 

7.     Task 7 - Reporting?

Consolidate all background and outcomes from Task 1 to Task 5 and provided a detailed final report. 

Currently, it is estimated that 4 states will join this TPF project.  At a total of $700K for a duration of 5 years, it is anticipated that each state will need to contribute $35K per year for 5 years.