Characterization of a landslide-triggered debris flow at a rainforest-covered mountain region in Brazil

Abstract

Debris flows represent great hazard to humans due to their high destructive power. Understanding their hydrogeomorphic dynamics is fundamental in hazard assessment studies, especially in subtropical and tropical regions where debris flows have scarcely been studied when compared to other mass-wasting processes. Thus, this study aims at systematically analyzing the meteorological and geomorphological factors that characterize a landslide-triggered debris flow at the Pedra Branca catchment (Serra do Mar, Brazil), to quantify the debris flow’s magnitude, peak discharge and velocity. A magnitude comparison with empirical equations (Italian Alps, Taiwan, Serra do Mar) is also conducted. The meteorological analysis is based on satellite data and rain gauge measurements, while the geomorphological characterization is based on terrestrial and aerial investigations, with high spatial resolution. The results indicate that it was a large-sized stony debris flow, with a total magnitude of 120,195 m3, a peak discharge of 2146.7 m3 s−1 and a peak velocity of 26.5 m s−1. The debris flow was triggered by a 188-mm rainfall in 3 h (maximum intensity of 128 mm h−1), with an estimated return period of 15 to 20 years, which, combined with the intense accumulation of on-channel debris (ca. 37,000 m3), indicates that new high-magnitude debris flows in the catchment and the region are likely to occur within the next two decades. The knowledge of the potential frequency and magnitude (F–M) can support the creation of F–M relationships for Serra do Mar, a prerequisite for reliable hazard management and monitoring programs.

The consequences of debris flows in Brazil: a historical analysis based on recorded events in the last 100 years

“…Landslides in the headwaters’ region triggered a high-magnitude debris flow (120,000 m 3 ). Picture from Cabral et al ( 2021 ). h Vale do Itajaí (Ibirama city) 2020.…”

Hazard assessment of debris-flow-prone watersheds in Cubatão, São Paulo State, Brazil

“…Hazard assessments are a great instrument to identify and delineate the most impacted areas by debris flows (Corominas et al 2014;Costa 1984;Egashira, et al 1997;Fiebinger, 1997;Jakob, 2005;Jakob & Hungr, 2005;Takahashi, 1981;Takahashi 2009). Among the most commonly used methodologies are those based on morphometric parameters (Corrêa et al 2021;Chen & Yu 2011;De Scally Slaymaker & Owens 2001;Nery 2017;Wilford et al 2004) and on empirical equations (Cabral et al 2021;Chang et al 2011;Fiebieger, 1997;Hungr, et al 1984;Kanji 1997;Martinez and Garcia, 1999;Massad, 2002;Petracheck & Kenholz, 2003;Rickenmann, 1999;Takahashi, 1991). In Japan, mapping of risk and hazard of debris-flow prone areas are based on combination of parameters, such as morphometry, back-analysis of historical events and on empirical equations (Japan Ministery of Land, Infrastructure and Transport, 1988).…”

Bacias hidrográficas em relevos escarpados: implicações para a análise da suscetibilidade a corridas de detritos

“…Dessa forma, justifica-se o grande número de trabalhos ao redor do mundo que, nas últimas décadas, utilizaram os parâmetros morfométricos na determinação de áreas suscetíveis à ocorrência de corridas de detritos (JAKOB, 1996; VAN DINE, 1996;VIEIRA et. al., 1997;KANJI;GRAMANI, 2001;WILFORD et al, 2004;TAKAHASHI, 2007;CHEN;YU, 2011;DIAS et al, 2016;GOMES et al, 2018;CABRAL et al, 2021).…”