Stochastic lava flow forecasting code used during the 2014-2015 Pāhoa lava flow crisis, Kīlauea Volcano, Island of Hawai‘i

The 1983-2018 Puʻuʻōʻō eruption, on the East Rift Zone of Kīlauea volcano, consisted of many different episodes and several phases of lava flows threatening residential areas (Heliker and Mattox 2003; Orr and others 2015).  One of these crises occurred in 2014-2015, when lava erupting from Puʻuʻōʻō advanced north of the rift zone, towards the town of Pāhoa (Poland and others 2016; Brantley and others 2019).  This slow-moving crisis unfolded over approximately four months, as pāhoehoe lava gradually flowed towards the town.  In the end, the lava flow fortunately stalled at the edge of the residential area, destroying only one home.   
During the crisis, geologists at the U.S. Geological Survey (USGS) Hawaiian Volcano Observatory (HVO) quickly developed a stochastic algorithm to help forecast the potential descent paths of the lava flow (Brantley and others 2019).  This algorithm was based on DOWNFLOW (Favalli and others, 2005), though at the time of the crisis HVO scientists did not have access to the DOWNFLOW code. This version was developed to emulate the algorithm described in the manuscript by Favalli and others (2005).  Later comparisons of DOWNFLOW and the algorithm provided here showed close similarity in forecasted flow paths. This code was used in conjunction with analysis of steepest-descent lines (Kauahikaua and others 2017).   
We provide this code here to document what was used during the 2014-2015 Pāhoa lava flow crisis but emphasize that DOWNFLOW has gone through more rigorous peer review and evaluation, and is therefore a better choice to use during future lava flow crises.   
References
Brantley S, Kauahikaua J, Babb J, Orr T, Patrick M, Poland M, Trusdell F, Oliveira D. 2019. Communication strategy of the U.S. Geological Survey Hawaiian Volcano Observatory during the lava-flow crisis of 2014–2015, Kīlauea Volcano, Hawai‘i. in Field Volcanology: A Tribute to the Distinguished Career of Don Swanson, eds M. P. Poland, M. O. Garcia, V. E. Camp, and A. Grunder (Geological Society of America), 351–373 doi: 10.1130/2018.2538(16) 
Favalli M, Pareschi MT, Neri A, Isola I. 2005. Forecasting lava flow paths by a stochastic approach. Geophysical Research Letters 32, L03305, doi:10.1029/2004GL021718 
Heliker C, Mattox TN. 2003. The first two decades of the Pu‘u ‘Ō‘ō–Kupaianaha eruption—Chronology and selected bibliography, in Heliker C, Swanson DA, Takahashi TJ, eds., The Pu‘u ‘Ō‘ō–Kupaianaha eruption of Kīlauea Volcano, Hawai‘i—The first 20 years: U.S. Geological Survey Professional Paper 1676, p. 1–27. 
Kauahikaua JP, Orr T, Patrick MR, Trusdell FA. 2017. Steepest-Descent Lines for Kīlauea, Mauna Loa, Hualālai, and Mauna Kea Volcanoes, Hawaiʻi: U.S. Geological Survey data release, https://doi.org/10.5066/F7FJ2DX0. 
Orr TR, Poland MP, Patrick MR, Thelen WA, Sutton J, Elias T, Thornber CT, Parcheta C, Wooten KM. 2015. Kīlauea’s 5–9 March 2011 Kamoamoa fissure eruption and its relation to 30+ years of activity from Pu‘u ‘Ō‘ō, in Carey R, Poland M, Cayol V, Weis D, eds, Hawaiian Volcanism—From Source to Surface: American Geophysical Union Geophysical Monograph 208, 28 p. 
Poland MP, Orr TR, Kauahikaua JP, Brantley SR, Babb JL, Patrick MR, Neal CA, Anderson KR, Antolik L, Burgess M, Elias T, Fuke S, Fukunaga P, Johanson IA, Kagimoto M, Kamibayashi K, Lee L, Miklius A, Million W, Moniz C, Okubo PG, Sutton AJ, Takahashi TJ, Thelen WA, Tollett W, Trusdell FA. 2016. The 2014–2015 Pāhoa lava flow crisis at Kīlauea Volcano, Hawaiʻi—Disaster avoided and lessons learned: Geological Society of America Today, v. 26, p. 4–10.

Tags: biota, east-rift-zone, hazard-forecasting, island-of-hawaii, kilauea, lava-flow, pahoa, stochastic-modeling, usgs-65407ca8d34ee4b6e05bcc78
Organization: Department of the Interior