Fédération Internationale du Béton Proceedings of the 2 nd International Congress June 5-8, 2006 – Naples, Italy ID 19-5 Session 19 – Architectural and environmental design Concrete Structures for Mitigation of Debris-flow Hazard in the Montoro Inferiore Area, Southern Italy Cosenza, E. Department of Structural Analysis and Design, University of Naples Federico II, Via Claudio, 21 – 80125 Naples, Italy Cozzolino, L., Pianese, D. Department of Hydraulic and Environmental Engineering, University of Naples Federico II – 80125 Naples, Italy Fabbrocino, G. Department SAVA, Engineering & Environment Division, University of Molise, Via De Sanctis – 86100 Campobasso, Italy Acanfora, M. TRE Consortium - Technologies for the Building Recovery, Naples – 80125 Naples, Italy INTRODUCTION The paper deals with some aspects related to the design of structures able to mitigate the debris-flow hazard in the Montoro Inferiore area, Southern Italy. In particular, the attention has been focused on the integrated design process used to define structural performances of different concrete components and structures in the “Di Mezzo” and “Casapepe” hollows. Structural design represents one of the components of the process that has been characterised by a multidisciplinary approach to the problem of management and protection of large areas exposed to debris-flow hazard: geologists, hydraulic engineers and structural engineers worked together to give a rational answer to the problem of the definition and estimation of design actions on structures and consequently to assess relevant performances of components and systems from the structural viewpoint. Obviously, the extension of the area of intervention required accurate and planned geological surveys and tests; these investigations led to the estimation of volumes expected to be mobilised during extreme events, to the related distribution in plan and elevation and to the mechanical characterisation of the different soils concerned by the structures along the flow course. The study of the propagation of a debris-flows of given volume, accomplished by means of hydraulic numerical models, aiming at the determination of the loads acting on the mitigation structures, constituted the core of the debris- flow hazard mitigation project, bridging the gap between geology and structural design. In the following, attention will be focused mainly on one of the cited mitigation interventions, namely the protection system of the Di Mezzo Hollow, which will be extensively discussed. Keywords: environmental design, debris flow hazard; debris-flow protection systems DI MEZZO HOLLOW PROTECTION SYSTEM The Di Mezzo Hollow protection system, Fig. 1, consists of three components: a main closed check dam, which can be filled with about 2000 m 3 of debris material; an adequate number of secondary closed check dams, able to contain 100 m 3 of debris material; a valley stilling basin, with roof-shaped bottom, bounded by earthen levees, where 11 debris-breakers have been placed. Depending on the debris-flow volume mobilised from the basin slopes and from the hollow bed, the main upstream check dam behaves properly. If the debris-flow volume is less than 2000-2200 m 3 , the closed check dam firstly accomplishes a stopping function, and subsequently behaves as a sort of retaining wall, with loads that are greater than ordinary geotechnical ones. Whenever the debris-flow volume produced during an event (or during a rapid succession of events), exceeds the limit of 2200 m 3 , the following functions are accomplished: