New Tools Available for Infrastructure Design

This year’s low snowpack in the northwestern region is—not surprisingly—raising concerns among farmers, water system operators, and forest managers. Not only are they worried about the dry conditions that lead to wildfires, but if precipitation occurs in a burned area, there may be an increased risk of post-fire flooding and debris flows.

After several years of record fire seasons, new tools are now available to help design culverts, bridges, diversions, and other infrastructure at risk from flooding after wildfires.

Rural areas and communities in Montana, Wyoming, Oregon, and Washington are experiencing an influx of population, which puts the wildland-urban interface at risk. Due to this risk, public safety officials are increasingly concerned about post-fire flood risks, such as the damage and tragedy caused by the Montecito debris flows of 2018. The debris flows started in the nearby Thomas Fire, which ignited in December 2017. While the fire was still burning, heavy rain fell on the burned hill slopes above Montecito, resulting in debris flows that caused catastrophic damage along the nearby creeks.

Modeling to Avoid for Potential Hazards

After this flood, I was part of a team that analyzed hydrologic conditions in the burned watersheds of both creeks. Our team modeled the inundation patterns of potential future debris flows and calibrated our models to data collected in the field by USGS. These models allowed us to develop conceptual designs for measures to mitigate risk to the public. Our modeling work relied on new approaches and capabilities developed by the talented staff of the US Army Corps of Engineers’ Hydrologic Engineering Center (HEC) and Engineer Research and Development Center (ERDC). These new capabilities are now standard in HEC’s Hydrologic Modeling System (HEC-HMS) and River Analysis System (HEC-RAS).

The Montecito debris flow project I worked on with HEC’s team and others was a validation case of the new modeling capabilities. The article we published in Geosciences in 2023 describes the validation case. The article also explores how the new tools can more accurately capture the flooding and debris runout following a tailings dam failure, such as the Brumadinho tailings dam failure in Brazil in 2019.