Design of active debris flow mitigation measures: a comprehensive analysis of existing impact models

Abstract

Debris flows occur in mountainous areas characterized by steep slope and occasional severe rainstorms. The massive urbanization in these areas raised the importance of studying and mitigating these phenomena. Concerning the strategy of protection, it is fundamental to evaluate both the effect of the magnitude (that concerns the definition of the hazard), in terms of mobilized volume and travel distance, and the best technical protection structures (that concerns the mitigation measures) to reduce the existing risk to an acceptable residual one. In particular, the mitigation measure design requires the evaluation of the effects of debris flow impact forces against them. In other words, once it is established that mitigation structures are required, the impacting pressure shall be evaluated and it should be verified that it does not exceed barrier resistance. In this paper the author wants to focus on the definition and the evaluation of the impacting load of debris flows on protection structures: a critical review of main existing models and equations treated in scientific literature is here presented. Although most of these equations are based on solid physical basis, they are always affected by an empirical nature due to the presence of coefficients for fitting the numerical results with laboratory and, less frequently, field data. The predicting capability of these equations, namely the capability of fitting experimental/field data, is analysed and evaluated using ten different datasets available in scientific literature. The purpose of this paper is to provide a comprehensive analysis of the existing debris flow impact models, highlighting their strong points and limits. Moreover, this paper could have a practical aspect by helping engineers in the choice of the best technical solution and the safe design of debris flow protection structures. Existing design guidelines for debris flow protection barrier have been analysed. Finally, starting from the analysis of the hydro-static model response to fit field data and introducing some practical assumptions, an empirical formula is proposed for taking into account the dynamic effects of the phenomenon.

Characteristics of a Debris Flow Disaster and Its Mitigation Countermeasures in Zechawa Gully, Jiuzhaigou Valley, China

“…In addition, studying the damage mechanism of mitigation structures is significant for effective debris flow mitigation. According to previous studies, the huge impact force of a debris flow can contribute significantly to the destruction of mitigation structures [34,77], and numerous impact models have been established [77][78][79][80]. Through comprehensive analysis of the existing debris flow impact models, a modified hydro-static model with a good prediction capability was proposed by Vagnon [77].…”

“…Therefore, the impact force of debris flow on the retaining wall was evaluated to study the damage mechanism by Ref. [77]:…”

Detection and forecasting of shallow landslides: lessons from a natural laboratory

“…Where debris-flows source across large areas with uncertain runout, a combination of active mitigation (physically controlling site aspects using engineering infrastructure) and passive mitigation (reducing impacts via land-use planning, closures and warning systems) methods can be used (Huebl and Fiebiger, 2005;Vagnon, 2020).…”

The Use of Unmanned Aerial Vehicles (UAVs) for Estimating Soil Volumes Retained by Check Dams after Wildfires in Mediterranean Forests

“…The check dams impact not only on torrent geomorphology (e.g., storing bed material, reducing sediment transport downstream, consolidating hillslopes, controlling the debris flows) but also favouring the establishment and growth of the riparian vegetation as well as enhancing its biodiversity [24][25][26][27][28]. An ample body of literature reports several successful examples of check dams for controlling geomorphology and hydrology in torrents as well as restoring vegetation in channels (e.g., [23,24,[29][30][31][32][33][34][35][36][37][38][39].…”