Analysis of river bed dynamic evolution following a landslide dam

Landslides and debris flows can strongly interact with the river network and its mass transport processes, determining modifications of the river pattern with consequent effects on the hydrodynamic phenomena, alterations of the existing morphologies and possible interferences with anthropic works. Modifications of the cross section geometry and channel slope may produce changes in the sediment budget, with consequent repercussions on the stream evolutionary dynamics and its equilibrium configuration, leading to a new river branch arrangement. In this paper, investigations were carried out on a gravel-bed reach in the middle valley of the Noce River in Basilicata (Italy), which in 2007 suffered a progressive morpho-hydrodynamic change caused by a landslide. Because of the phenomenon complexity, mainly due to the mutual interaction between the landslide and the river transport dynamics, an integrated approach that combines field observations and numerical modelling in a spatial scale and natural environment, rarely available in literature, is suggested. The results highlight a satisfying correspondence between the altimetric profiles obtained through the numerical models and those deriving from the field surveys.Peer ReviewedPostprint (published version

Modellazione fisica e numerica della variazione morfologica d'alveo indotta da restringimenti

Nella presente memoria vengono descritti i risultati ottenuti dall’applicazione di modelli numerici bidimensionali per la simulazione dell’evoluzione morfologica d’alveo in corrispondenza e nell’intorno di tronchi ristretti. In particolare, si è utilizzato il codice di calcolo CCHE2D sviluppato dall’Università del Mississippi nell’intento di riprodurre quanto osservato in laboratorio nel corso di alcune prove sperimentali condotte in condizioni di moto stazionario, assenza di trasporto solido da monte nonché caratterizzate da lunga durata, dell’ordine di uno o più giorni, ai fini del raggiungimento di condizioni di equilibrio dinamico. Si sono considerati restringimenti con diversi fattori di ingombro e lunghezza del tronco prismatico pari alla larghezza dell’alveo indisturbato. I risultati ottenuti dalle simulazioni si sono dimostrati in soddisfacente armonia con quanto osservato sperimentalmente. Ciò senza ricorrere a procedure di calibrazione del modello teorico e sebbene nella fase sperimentale si attuassero pressoché inevitabili interferenze fra fenomeni di trasporto solido localizzati e distribuiti

RISCHIO IDRAULICO IN AREE PIANEGGIANTI: ANALISI MEDIANTE MODELLI IDRODINAMICI BIDIMENSIONALI E DATI TOPOGRAFICI DA LASER SCANNER

Nella presente memoria si riportano alcune elaborazioni realizzate presso il Diparti-mento d’Ingegneria e Fisica dell’Ambiente (D.I.F.A.) dell’Università degli Studi della Basilicata nell’ambito di una convenzione con l’Autorità Interregionale di Bacino della Basilicata, finalizzata alla valutazione del pericolo di inondazione lungo la costa jonica lucana. La natura estremamente pianeggiante di tale area rende la stima dell’inondabilità particolarmente complessa: qui, infatti, l’assenza di limiti morfologici definiti, propri dei tratti medio-alti dei bacini idrografici, rende complessa l’individuazione del perime-tro dell’eventuale allagamento. Alla stima dell’estensione dell’allagamento e delle caratteristiche idrauliche della corrente sulla pianura di inondazione si è giunti attraverso l’utilizzo di modelli idrodi-namici bidimensionali di simulazione delle piene, implementati a partire da modelli di-gitali del terreno ottenuti da rilievo laser-scan. Dai risultati idraulici ottenuti si avanza una proposta di classificazione della pericolosità di inondazione funzione sia del tempo di ritorno che del tirante idrico massimo valutato sulla pianura di inondazione

GIS instruments and high resolution DTM to define risk flood areas

The Plan of Basin is the tool used by Italian Authority of Watershed to guarantee the hydraulic safety, the correct use of the water resource and the guardianship and management of Italian field. Particularly a detailed program for the flood defence contains the delineation of flooding risk areas and the actions to reduce the hazard to human life and the damages when a catastrophic flood event occurs. For these aim hydrodynamic studies has been carried out along the major rivers of Basilicata Region, in order to create flooded area maps. The present work shows GIS applications as instruments to support a more correct definition of flooding risk areas. The study area is Basento River in southern Italy and the software used for the hydrodynamic simulations are: Hec Ras (for mono dimensional studies) developed by the Hydrologic Engineering Centre; MIKE Flood developed from Danish Hydraulic Institute for bidimensional study in coastal plain. The river cross sections are obtained by grounded topographic relief in the first case, by laser scanned data in the second one. The GIS has been used either as input or as output of the hydraulic modelling. In the first case it has allowed to integrate the information about planimetric development of river and grounded cross sections through a detailed DTM (Digital Terrain Model). In the second one, the water surface elevation and top width achieved in riverbeds, for each hydrodynamic simulation, has been used with GIS software to draw the different flooded area maps. In particular differences between the results obtained using an automatic interpolation of cross sections with the HecRas tool and those obtained using river cross sections extracted by DEM are been evidenced. For the coastal plain, with the use of laser scanning techniques is possible apply bi-dimensional hydrodynamic model with accuracy data and more correct to describe the hydrodynamic motion on flat areas

Tecnologia laser-scan e modelli idraulici per la valutazione del rischio di inondazione nelle pianure costiere

Dottorato di Ricerca in Ingegneria Idraulica per l'Ambiente ed il Territorio, XX Ciclo,a.a. 2007Università della Calabri

FLORA-2D: A New Model to Simulate the Inundation in Areas Covered by Flexible and Rigid Vegetation

A two-dimensional (2D) hydraulic model for river flood inundation prediction is presented. This model named FLORA-2D (FLOod and Roughness Analysis) solves the shallow-water equations at each node of a regular mesh covering the channel and floodplain. Its special feature is the ability to consider the flow resistance due to vegetation as a function of both space and time. So, during a flood, in each grid node the resistance of vegetation is calculated considering the hydraulic characteristics of the flow which may vary over time as well as the characteristics of the plant. The model was tested in a study of a flood event which occurred on the River Bradano, Southern Italy, in March 2011. A first evaluation of the behavior of the model shows a good correspondence with the theories used in the code. Furthermore a satellite image acquired during the flood provided an observed flood extent against which to compare the predicted extent

Assessment of systemic vulnerability in flood prone areas

This paper deals with the conception, the development and the subsequent validation of an integrated numerical model for the assessment of systemic vulnerability in complex and urbanized areas subject to flood risk. The proposed model, which is based on the studies of Tamura et al. (Eu. J. Oper. Res., 2000) and Pascale et al. (Ad. Geo., 2007) considers vulnerability not as a characteristic of a particular element at risk, but as a peculiarity of a complex territorial system, in which different elements are reciprocally linked in a functional way. Therefore, it facilitates the identification, in selected areas, of the elements that are mainly responsible for functional loss and which thus make the whole system critical. This feature makes the proposed model effectively able to support correct territorial planning and suitable management of an emergency following natural disasters that trigger or remobilize mass movements