Simulated floods, sediment entrainment, and debris-flow inundation in the Toutle and Cowlitz River valleys resulting from hypothetical dam breaches of Spirit Lake, Washington.

This data release contains postprocessed model output from a set of numerical simulations of hypothetical outburst floods of Spirit Lake, downstream sediment entrainment, and emergent debris flows, in the Toutle and Cowlitz River valleys in Washington State. The data release provides debris-flow inundation extent, travel times, maximum depths, and model input data (including hypothetical channel-cut geometry and Spirit Lake bathymetry as digital elevation models (DEMs)) for eight model scenarios. The simulations and encompassing study are described by George and Cannon (2025). Model Description Simulations were performed with the D-Claw model (George and Iverson, 2014; Iverson and George, 2014; George and others, 2025), a depth-averaged, two-phase model for conservation of mass and momentum of variably concentrated granular-fluid mixtures flowing over variable topography. D-Claw has been used previously for modeling landslides, debris flows, floods, and tsunamis, and in hazard assessments (for example, George and others, 2022). Model input data included a Base DEM assembled from multiple sources and merged with bathymetry, as well as hypothetical channel cuts into the North Fork Toutle River, included in this data release. Additionally, model inputs included a DEM of erodible sediment depths estimated from historical and current topography, not included in this data release (see, Cannon, 2023). See the accompanying readme.md file for more information about the datasets included in this data release. ## References - Cannon, C.M., 2023, [Digital terrain model of upper North Fork Toutle River valley](https://doi.org/10.5066/P9MT4FVL), U.S. Geological Survey Data Release, https://doi.org/10.5066/P9MT4FVL. - Gawel, J.E., et al., 2018, *The New Spirit Lake: Changes to Hydrology, Nutrient Cycling, and Biological Productivity*, in Crisafulli & Dale (eds), Springer, https://doi.org/10.1007/978-1-4939-7451-1_4 - George, D.L., Barnhart, K.R., and Iverson, R.M., 2025, D-Claw - A library for simulation of granular-fluid flows, version 1.0.0: U.S. Geological Survey software release, https://doi.org/10.5066/P13GUXUT. - George, D.L. and Cannon, C.M., 2025, *Modeling floods, sediment entrainment, and downstream debris flows from hypothetical dam breaches of Spirit Lake, Washington*, U.S. Geological Survey Open-file report. *(DOI not available as of this time)* - George, D.L. and Iverson, R.M., 2014, *A depth-averaged debris-flow model that includes the effects of evolving dilatancy II. Numerical predictions and experimental tests*, Proceedings of the Royal Society A, 470(2170), https://doi.org/10.1098/rspa.2013.0820 - George, D.L., Iverson, R.M., and Cannon, C.M., 2022, *Modeling the dynamics of lahars that originate as landslides on the west side of Mount Rainier, Washington*, USGS Open-File Report 2021-1118, https://doi.org/10.3133/ofr20211118 - Iverson, R.M., and George, D.L., 2014, *A depth-averaged debris-flow model that includes the effects of evolving dilatancy I. Physical basis*, Proceedings of the Royal Society A, 471(2170), https://doi.org/10.1098/rspa.2013.0819 - Mosbrucker, A.R., 2014, *High-resolution digital elevation model of Mount St. Helens crater and upper North Fork Toutle River basin, Washington*, U.S. Geological Survey Data Series 904, https://doi.org/10.3133/ds904 - Mosbrucker, A.R., 2015, *High-resolution digital elevation model of lower Cowlitz and Toutle Rivers, adjacent to Mount St. Helens, Washington, based on an airborne lidar survey of October 2007*, U.S. Geological Survey Data Series 936, https://doi.org/10.3133/ds936. - U.S. Army Corps of Engineers [USACE], 2010, Lower Columbia digital elevation model, 2010: Lower Columbia Estuary Partnership website, accessed June 26, 2025, at https://www.estuarypartnership.org/lower-columbia-digital-elevation-model-2010. - U.S. Geological Survey [USGS], [1990], National elevation dataset seamless 1/3 arc-second: U.S. Geological Survey data. [Data may now be available at https://www.usgs.gov/3d-elevation-program.] - Washington Department of Natural Resources, Division of Geology and Earth Resources, 202X, Washington lidar portal [Clark 2002, Lower Columbia 2005, St Helens 2002, St Helens Oct and Nov 2004, Toutle River 2012]: Washington Department of Natural Resources, Division of Geology and Earth Resources database, accessed June 26, 2025, at https://lidarportal.dnr.wa.gov/.

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