Le occlusioni d'alveo per frana (LANdslide DAMs): caratterizzazione, previsione e gestione dell'emergenza (RETURN - Multi-Risk sciEnce for resilienT commUnities undeR a changiNg climate, Spoke 2)

Bando a cascata, ai sensi dell’Avviso MUR n. 341 del 15/03/2022, per il finanziamento di proposte di intervento per attività di ricerca svolte da Organismi di Ricerca in collaborazione con le imprese – con riferimento al Progetto Codice PE_00000005 dal titolo Partenariato Esteso RETURN - Multi-Risk sciEnce for resilienT commUnities undeR a changiNg climate, Spoke 2, CUP B53C22004020002 nell’ambito del Piano Nazionale di Ripresa e Resilienza, Missione 4 “Istruzione e ricerca” – Componente 2“Dalla ricerca all’impresa” – Investimento 1.3, finanziato dall’Unione europea – NextGenerationEU

Descrizione Progetto: 

The LanDam project is included as a project proposal for the Cascade Call Spoke 2 - RETURN (PNRR). The operating units coordinated by the University of Perugia consist of the Universities of Chieti-Pescara, Pavia, Sannio, Urbino, and the external unit MapSAT.

The interference between fluvial and gravitational slope dynamics processes is a complex issue. The two components, relating to rivers and landslides, respectively, have always been considered separately in the assessment of hazard and consequent risk. The scenarios that can result from these relationships are, in general, complicated and not always easily predicted and defined (Cencetti et al, 2001): they range from debris production from the slope, resulting in increased solid transport in streams, to partial or total occlusion of the riverbed, resulting in diversion of the river course within the floodplain, if present, up to complete damming of the valley, i.e., landslide dams s.s. (LSDs) and involving, generally, the formation of a lake reservoir (dam lake). The consequence of an LSD is a noticeable increase in the extent of the area exposed to the hazard resulting from the complex phenomenon of interference between the two processes, in terms of: i) submergence of the areas located upstream of the landslide barrage due to the formation of a natural reservoir; ii) possibility of overflow and rapid erosion of the landslide body, or even collapse of the barrage itself, with formation of an abnormal flood wave downstream due to the rapid emptying of the reservoir. The project involves a series of interrelated activities, divided into phases, each with a precise work program (WP).

WP1) Characterization of the phenomenon. Consists of the census and analysis of significant LSDs case histories from the collection of data in the literature, both Italian and foreign, including older cases and more recent ones, implemented with data from the experiences gained by members of the research group .

WP2) Prevision of the phenomenon. This phase consists of: 1) identifying active slope landslides, which make their interaction with river dynamics likely; 2) comparing the two systems (landslide-river) from the “energy” point of view: for the landslide, it is a matter of defining, in addition to the geotechnical characteristics of the affected material, its kinetic energy; on the other hand, a landslide that mobilizes a few thousand cubic meters of material, and therefore of modest volume, but fast (debris flow) could cause the occlusion of even important watercourses with considerable flows, if the morphology of the valley allows it; 3) in identifying the sectors of the watercourses that can most likely be reached by materials that have been mobilized by slope instability phenomena.

This second phase of the project, to be applied to a test basin, will lead to the development of a forecasting model that succeeds in relating the variables of the two systems (geometric and morphometric on the one hand, energetic on the other), so as to predict whether or not a landslide riverbed occlusion is likely to occur.

WP3) Emergency Management represents the third phase of the project. After the prediction of the phenomenon and its characterization in geometric terms for the purpose of defining its intrinsic hazard to be eroded, overflowed or prone to collapse, a classification will be drawn up that can be useful as a “guide” for the interventions to be adopted. One purpose of the project, in this sense, is precisely the drafting of intervention guidelines according to the type of landslide dam considered. The “guidelines” are intended for civil defence structures to define the methodologies to be adopted in the study of LSD phenomena and in the management of the resulting emergency. They will be accompanied by interpretive and guidance sheets and procedures for defining the state of the sites. They will enable operators to use a uniform approach that, starting with the identification of the most susceptible sites and pre-existing landslide dams, will lead to the determination of a “class” of attention according to the possible risks. In fact, this analysis will make it possible to arrive at a preliminary assessment of hazard and associated risk with the aim of directing toward the definition of the most suitable interventions aimed at avoiding the possibility of occlusion or, in the case of occlusion in progress, at avoiding the overflow of the dam, for the mitigation of the resulting hydraulic risk.

 

Capofila: Università La Sapienza è partner di progetto e Leader dello Spoke 2; Università di Perugia è Coordinatore del bando a cascata; Università “G. d’Annunzio” di Chieti-Pescara è Componente 2“Dalla ricerca all’impresa” 

Investimento 1.3, finanziato dall’Unione europea – NextGenerationEU