Recognition of debris flow, debris flood and flood hazard through watershed morphometrics

Abstract

Debris flows, debris floods and floods in mountainous areas are responsible for loss of life and damage to infrastructure, making it important to recognize these hazards in the early stage of planning land developments. Detailed terrain information is seldom available and basic watershed morphometrics must be used for hazard identification. An existing model uses watershed area and relief (the Melton ratio) to differentiate watersheds prone to flooding from those subject to debris flows and debris floods. However, the hazards related to debris flows and debris floods are not the same, requiring further differentiation. Here, we demonstrate that a model using watershed length combined with the Melton ratio can be used to differentiate debris-flow and debris-flood prone watersheds. This model was tested on 65 alluvial and colluvial fans in west central British Columbia, Canada, that were examined in the field. The model correctly identified 92% of the debris-flow, 83% of the debris-flood, and 88% of the flood watersheds. With adaptation for different regional conditions, the use of basic watershed morphometrics could assist land managers, scientists, and engineers with the identification of hydrogeomorphic hazards on fans elsewhere.

A dependence modelling study of extreme rainfall in Madeira Island

“…Although rare, such events can have significant impacts on the local natural environment and disastrous consequences for the affected communities and populations (Woo and Jones, 2002). Rainfall-induced debris flows are one of the most dangerous natural hazards in mountain regions (Hu et al, 2009), because their occurrence is unpredictable and this type of waterrelated natural disaster can be catastrophic, affecting significantly not only the landscape, but also causing damage to houses and infrastructures (Kanji et al, 2008), loss of lives (Wilford et al, 2004), and other negative economic and social impacts due to the increasing anthropisation of such areas (Hürlimann et al, 2006). Floods and associated landslides and debris-flows triggered by extreme rainfall events have been in reality the most devastating of natural disasters, both in Madeira Island (Baioni, 2011;Quintal, 1999) as in the rest of the world (Hong et al, 2007).…”

Multiscale map analysis in alluvial fan flood-prone areas

“…Df-dominated alluvial fans are susceptible to the occurrence of flows with high viscosity (high percentage of debris load) and hence this group of fans can be considered as having the highest danger levels (Aulitzky, 1980;Welsh & Davies, 2011). Many studies have proved that a detailed morphometric analysis of the basin/fan system, coupled with geomorphological, stratigraphic, sedimentological and historical analyses, may be useful to distinguish between Df and Wf fans (Bertrand, Liébault, & Piégay, 2013;Crosta & Frattini, 2004;De Scally & Owens, 2004;De Scally, Owens, & Louis, 2010;Hashimoto et al, 2008;Melton, 1965;Santangelo et al, 2012;Sorriso-Valvo, Antronico, & La Pera, 1998;Wilford, Sakals, Innes, Sidle, & Bergerud, 2004).…”

Recent debris flows in the Portainé catchment (Eastern Pyrenees, Spain): analysis of monitoring and field data focussing on the 2015 event

“…The Melton ratio is 0.62 and the relief ratio 0.3. The analysis of the morphometric parameters of the catchment indicates that the Portainé basin is susceptible of generating hyperconcentrated flows (Wilford et al 2004). …”