Beginning of sediment transport of incoherent grains in shallow shear flows

ln this paper the main results of an ex peri men tal investigation on the beginning of sediment transport of incoherent granular materials in shallow viscous llows are presented. The experiments, performed in a laboratory !lume in both laminar and smooth turbulent llow conditions, complement the data already available in literature, and confirm that the hyperbolic trend shown by the Shields curve when the grain Reynolds number X decreases to zero is not supported by experimental evidence. In addition, they confirm the Yalin and Karahan (1979) hypothesis on the existence of a distinct curve for the inception of sediment tran sport in viscous dominated llows. On the basis of the observed phenomenology, we propose to interpret the process as a function of the probability distribution of the repose angle of the grains of the erodible bed. Accordingly, a simple mechanical relati on is derived that explains the pattern exhibited by the experimental data

Sharing data and maps on flood and landslide hazards, vulnerability, and related risk reduction Public Works via a web platform at national scale: the case of #italiasicura

Italy has experienced many flood and landslide disasters, during and after which the local intrinsic risk management levels have been very different. This problem can be managed, in cooperation with other policies, through improvements in risk awareness and preparedness. With this aim in mind, #italiasicura web platform has been developed, based on a geographic “non-GIS” interface (although working with an underlying database system) to show hazard maps and risk reduction Public Works in the whole of Italy, up to local level. Such an instrument operates as an innovative “social tool”, developed to be used both by decision/makers and citizens, giving the possibility, at any stage of the user experience on the platform, of an easy information sharing via social media. Such a kind of tool represents an opportunity of increasing the knowledge linked to flood and landslide hazards and structural defence strategies. As a matter of fact, the #italiasicura web platform is based upon three pages: one, geographic, presenting hazard, risk and physical infrastructures; the second, also geographic, focused on national emergencies; the third, text and graphics, allowing a number of simple queries and rankings of the main parameters related to the topics of the platform. From a technical point of view, although there is a map on the screen and an underlying database system (permanently updated automatically), neither layers to be switched on and off are present nor any other typical GIS user interface function. All information is presented based upon the coordinates and the zoom level, to allow a better user experience, particularly with the responsive version toward mobiles. Both graphic pages open on the national map. A text box self customizes itself, aggregating data on the actual zoom level; the main navigation actions are performed moving the mouse and acting on the mouse wheel. A new URL is generated at any event generated by the user. Data shown and related web analytics are an interesting source of information for refining risk management strategies and studies; at the same time, they will allow a greater involvement of the scientific community and young researchers, enabling them to elaborate bottom-up suggestions to decision makers

A distributed package for sustainable water management: A case study in the Arno basin

MOBIDIC (MOdello di Bilancio Idrologico DIstribuito e Continuo) is a distributed hydrological modelling package for various applications. The main innovations concern: (a) the coupling of the water balance in the soil and vegetation with the surface energy balance, to the benefit of evapotranspiration computation and the use of remotely-sensed maps for calibration and validation; (b) the interaction between groundwater and surface water bodies, (c) the capability of easily managing data on withdrawals of water, reservoir operation and environmental flow. MOBIDIC-WRM can be used as an effective tool for the evaluation of basin scenarios (e.g. effects of changes in land cover/deforestation and irrigation strategies, exploitation policies for groundwater). It provides a reliable hydrological base for the assessment of crisis indicators such as vegetation stress and lack of environmental flow. In this work we present an application in the Arno basin, central Italy. The outcome of applying the package in order to determine the water budget management strategies is discussed. Copyright © 2009 IAHS Press

Effetti del cambiamento climatico e indicatori di stress per le specie ittiche

La definizione di strategie di adattamento ai cambiamenti climatici si articola su un ampio spettro di scale spaziali e temporali, e richiede un concerto di azioni diverse, integrate e sussidiarie a seconda del contesto considerato. L’Autorità di bacino del fiume Arno ha sviluppato da tempo una linea di ricerca tesa a valutare le peculiarità del cambiamento globale in atto nel territorio del bacino, attraverso l’attività di uno specifico laboratorio territoriale permanente. I risultati mostrano la validità dell’approccio e l’evidente deriva che caratterizza la non stazionarietà del regime delle portate alle scale d’interesse per la pianificazione territoriale. Ai fini del presente lavoro si pone particolare attenzione alla deriva del regime di portata che, a partire dagli anni ’70, mostra una sensibile riduzione della disponibilità idrica e una progressiva asimmetria rispetto agli usuali contributi stagionali. Tale effetto al suolo rispecchia gli aspetti del cambiamento climatico in termini di distribuzione spaziale e temporale delle precipitazioni e dell’andamento delle temperature. Tra gli indicatori di vulnerabilità l’evoluzione dell’Area Disponibile Ponderata (ADP, Bovee et al. 1998), in funzione dei diversi regimi, si è mostrata un indicatore efficace al quale è possibile affiancare specifici segnali di stress. Per questo si è effettuato un rilievo di dettaglio del fondo dell’alveo in un tronco posto nella sezione di chiusura del bacino laboratorio e, fissata la specie bersaglio nel barbo in fase riproduttiva, si è calcolata l’ADP utilizzando un modello idrodinamico bidimensionale a elementi finiti. Si è poi effettuata l’analisi della serie storica (quasi secolare) delle portate osservate scegliendo, come riferimento, la permanenza della portata media giornaliera al disotto del 50% e del 70% dell’ADP per due giorni consecutivi ed oltre. I risultati mostrano una forte dinamica del dato che, sopratutto negli ultimi dieci anni, indica un incremento notevole del numero di eventi e dei giorni di permanenza. Mostrano inoltre la validità dell’approccio seguito che tende a fornire una indispensabile dimensione temporale all’analisi alla scala del meso- e del microhabitat

Application Of Safety And Security Principles To Flood Event Management In Highly Populated Urban Areas

This paper refers to non-structural actions which are to be carried out on the Arno river basin (Italy). In particular the town of Florence is considered where 56 catastrophic flood events have been recorded in the last 1000 years, the latter in 1966 with damages estimated at 10,000 billion euros. A huge system of structural works is presently being carried out planned to the 200-year return period event in the next ten years. To manage the present and future residual risk, specific safety plans have been provided at the scale of single buildings in order to give residents an effective instrument to prevent and protect them from the major flooding risk. This paper illustrates how safety and security principles can be applied to the management of a flood event at the scale of several thousands of square kilometres. A specific Security Plan and, if needed, a Recovery Plan is linked to each building which is potentially subject to flooding. Based on analytical hazard assessment and mapping, techniques to improve or increase the safety-level as well as appropriated information are described. These local scale plans are interfaced with civil protection and disaster management plans at the regional scale by suitable procedures. Keywords: risk assessment, flood event, security plan, recovery plan, signs, procedures, building. 1 Introduction A study for a plan in order to provide the residents of the area of the Arno River basin (and in future perspective all the residents) with one useful instrument t

Assessing and Improving Flood and Landslide Community Social Awareness and Engagement via a Web Platform: The Case of Italy

Italy is significantly affected by ever-present flood and landslide risks and has experienced many disasters. Local social awareness and engagement, however, differ and need to be increased by decision makers and citizens through improvements in risk preparedness. With this aim, the #italiasicura web platform was developed by Fondazione Politecnico di Milano and released in 2015 to show country to local level hazard maps and risk reduction projects in Italy. Any stage of the user experience with the platform can be shared via social media. Using this tool, an awareness-oriented web analytics process was structured to develop a set of indicators for the increase of knowledge linked to flood and landslide hazards. In so doing, it is possible to measure community disaster awareness actions and competence in the area of hazard knowledge. This article presents the results obtained by using data from the platform