“…Deposition of sediment by repeated flows results in the construction of debris-flow fans that can potentially record information on past flow size, timing, composition, and depositional pattern (Schumm et al, 1987;Harvey, 2011). Such fans are therefore a potentially powerful archive of debris-flow processes (e.g., Whipple and Dunne, 1992;Dühnforth et al, 2007;d'Arcy et al, 2015;de Haas et al, 2015ade Haas et al, , 2015b, hazard (e.g., Hubert and Filipov, 1989;Helsen et al, 2002;Stoffel et al, 2008a;Arattano et al, 2010;de Scally et al, 2010), and sediment supply (e.g., McDonald et al, 2003;Dühnforth et al, 2008;Hornung et al, 2010;Savi et al, 2014). Reading that archive, however, and extracting quantitative information about past debris flows, requires that we understand the pattern and timing of debris flow deposition on fans so that the evolution of the fan can be reconstructed.…”