By: Stanford Gibson, Ph.D.
Wildfires are growing more frequent and more intense. Wildfires make watersheds more flood prone and can trigger destructive mud and debris flows, increasing the probability and consequence of flood hazards downstream. For example, in January 2018, a relatively modest rainfall on a recently burned watershed triggered debris flows in Santa Barbara, CA that killed 23 people and caused over $100 million of damage. Wildfires change the flood risk downstream. State and federal agencies are scrambling to develop emergency management strategies to predict the new flood-and-mud risk to downstream communities after a wildfire. But the standard, clear-water, approach to flood-plain mapping does not represent these processes well.
HEC, in collaboration with ERDC-CHL, added non-Newtonian flow physics to HEC-RAS 6.0 (Figure). These capabilities can automatically bulk flows with mud and debris and change the fluid physics to behave more like the high-concentration debris flows that threaten communities after wildfires.
In addition to Santa Barbara (SPL), USACE districts have applied these tools to post-wildfire and other non-Newtonian applications in Ouray, CO (SPK), Eagle Creek, OR (NWP), the Hermit's Peak fire, NM (SPA/SPK) and Brumadinho, Brazil (SAM). Now that non-Newtonian physics are included in the leading flood risk model, modelers have also applied them to other geophysical flow risks including mine tailing dam breaches, ice floes, alluvial fan avulsion risks, and paleo-flood analyses, and HEC even included an alpha version of a heat balance and a temperature-dependent viscosity term to support emergency management lava flow simulations for the Fagradalsfjall eruption in Iceland.
To support this new capability HEC rolled out an extensive multi-media technology transfer plan, including four classes or short courses this FY, detailed documentation, multiple videos, a podcast, and two peer-reviewed journal papers.
The Corps of Engineers recognized this work – along with the post-wildfire capabilities in HEC-HMS – with a USACE Innovation of the Year award.
Last Modified: 2023-06-09 09:43:32.903
