1,721,003 research outputs found
Flood hazard maps in the European context
No full textThe implementation of the EU Floods Directive by water authorities across Europe has generated a lack of consistency in the present situation, especially regarding the scales adopted, the hydrological scenarios and the elements represented on flood hazard and risk maps. From the EU-funded project HYTECH, this article presents a general overview of Floods Directive implementation in eight European countries, highlighting the differences between them, with particular attention to flood hazard maps. For the implementation cycle that started at the beginning of 2016, a minimization of such differences is necessary in order to manage flood risk in a better and more integrated way
Implementation of the floods directive in selected EU member states
No full textTo reduce the flood risk at European scale, the Floods Directive (FD) became into force in 2007. Each member state had transposed the directive in national laws and guidelines, generating a quite spotted situation. This work is intended to compare and briefly assess the implementation process on rivers in selected European countries by means of the available literature and a specific questionnaire. Different structures, methodologies and data conditions used for preliminary flood risk assessment, flood hazard maps, flood risk maps and flood risk management plans are here presented and analysed. To minimise the flood risk, the technical differences between the EU countries need to be reduced in the next implementation cycles of the FD
Is public participation an added value for river basin management?
No full textABSTRACT: The Water Framework Directive (WFD) represents one of the most advanced pieces of water policy developed during the last decades. Since its introduction in 2000, several technical and political issues arose regarding this Directive and its implementation, and have to be managed by European Member States at the national level, but in strict collaboration with local authorities and stakeholders. Whilst several studies have analysed the WFD from a technical point of view, a few are available that assess and compare the quality of public participation processes in river basin management at the European level. The present paper shows the outcomes of an own-developed questionnaire sent to European water and environmental authorities during 2015, which highlights the variable situation in terms of stakeholders’ involvement and methods adopted to interact with them, and also points out the scarce results that the consultation has obtained in terms of innovative measures to fulfil the requirements of the WFD. In light of the present situation, a better consideration of public consultation and associated methodologies is necessary for future management cycles, as well as a better coordination between Member States sharing river basins
Aspects of riverine hydro-morpho-biodynamics at watershed scale
Full text linkThe integration of various scientific disciplines is becoming more and more important to define the complete evolution of an entire river system, both in time and in space.
The aim of this thesis is to analyze the evolution of a river subjected to hydrological, morphological and biological interactions. This analysis is done at watershed scale, by using a numerical 1-D model plus a quasi 2-D sub-model. These models are able to integrate the available data, often scarce both qualitatively and quantitatively, especially in large unsurveyed rivers, typical of less developed countries.
The models analysis allows to study the evolution of a river system at large space-scale and long-time scale, because the computational effort required by simplified models are quite low. The results of these models are indicative of a trend of the evolution of the river, in space and time, which can be useful in different studies, for example as input for other detailed models.
In the first Chapter we analyze the principal mechanisms of formation and transport of sediments, making an overview of the various models that can be adopted to describe the morphological evolution of a river system. In addition to this description, in this chapter we study the different conformations of riverbeds, classified on the basis of their geometry and morphology.
The lack of detailed data, from the point of view both of geometry and biology, implies the application of a non-detailed model, able to describe the hydrodynamic, morphodynamic and biological main processes of the river along its course. This model, essentially 1-D, is based on simplifications related to the hypothesis of the Local Uniform Flow. The 1-D model is associated to a quasi 2-D sub-model, able to provide a synthetic description of the river cross-section. This sub-model is useful for the analysis of large river systems, for which often we do not have bathymetric surveys. In the second Chapter and in the third Chapter is made a detailed analysis of these models, highlighting the advantages and disadvantages of the various simplifications.
The growth of the riparian vegetation is strongly influenced by the forcing terms present in a river, related to hydrology and morphology. In Literature there are only a few site-specific studies or purely qualitative analysis, which study the interaction between the forcing terms and the riparian vegetation. The aim of this thesis is trying to model the influence of hydrology and morphology on the growth of the riparian vegetation, by a simplification of all the possible mechanisms involved. In this Chapter we have reported a detailed analysis of our studies, highlighting the limitations related to the lack of experimental data needed for a good calibration of our quasi 2-D sub-model.
In the next two Chapters two different applications of the complete model are given: the first one about the Paranà River, and the second one about the Zambezi River.
The application to the Paranà River has been made to highlight the goodness of the model for describing the evolution of the river, even compared to a commercial 1-D model as the Hec-Ras code. That application was also made to verify the general approach and the formulation used in the description of the synthetic river cross-section and the interaction between the river forcing terms and the growth of the riparian vegetation.
The study of the Zambezi River is useful to see how the alteration of flow due to hydropower dams along the river strongly influences both morphology and biology of the river, with medium and long term effects.
This analysis evaluates the planimetric and bathymetric changes subsequent to an alteration of the natural flow regime of a river due to the construction of hydroelectric reservoirs.
In the last Chapter we have discussed the general results and the future developments, underlining, however, that the simplified models used in this work require further verifications, also against the analysis of more experimental data.L’integrazione di varie discipline scientifiche sta diventando sempre più importante nel definire in maniera compiuta l’evoluzione di un intero sistema fluviale, sia dal punto di vista spaziale che temporale.
Questo lavoro di tesi si prefigge lo scopo di analizzare l’evolversi di un fiume sottoposto ad interazioni idrologiche, morfologiche e biologiche.
Tale analisi viene fatta a scala di bacino, adottando un modello numerico 1-D integrato con un sottomodello quasi 2-D. Entrambi i modelli sono capaci di utilizzare ed integrare i dati reperibili lungo un corso d’acqua, che spesso risultano carenti sia qualitativamente che quantitativamente, soprattutto nel caso di grandi fiumi non strumentati, tipici dei paesi in via di sviluppo.
Tale approccio permette quindi di studiare l’evolversi di un complesso sistema fluviale a grande scala e a lungo termine, in quanto i tempi computazionali richiesti dal codice semplificato risultano piuttosto contenuti. I risultati ottenuti sono indicativi di una tendenza evolutiva del fiume a media risoluzione, che può essere utile in differenti studi, anche come dato di input per successive modellizzazioni di maggior dettaglio.
Nel primo capitolo si evidenziano tutti i meccanismi di formazione e trasporto dei sedimenti, in modo tale da fornire una panoramica sui vari modelli che si possono adottare per descrivere l’evoluzione morfologica di un sistema fluviale. Oltre a tale descrizione, in questo capitolo vengono messe in evidenza anche le differenti conformazioni fluviali presenti in natura, suddivise sulla base della loro morfologia dominante.
La mancanza di dati specifici, sia dal punto di vista dell’idrologia che della morfologia e della biologia, comporta l’applicazione di un modello, sia pure non di dettaglio, capace di descrivere i principali processi dell’idrodinamica, della morfodinamica e della crescita della vegetazione riparia lungo il corso del fiume.
Questo modello, sostanzialmente 1-D, si basa sulle semplificazioni connesse all’imposizione del moto localmente uniforme. Al modello 1-D viene associato un sottomodello quasi 2-D, capace di fornire una descrizione sintetica della sezione trasversale del fiume. Tale sottomodello si rende necessario per l’analisi di grandi sistemi fluviali, dei quali spesso non si dispone di un rilievo batimetrico di dettaglio. Nel secondo e nel terzo capitolo viene quindi fatta un’analisi di tali modelli, evidenziando i pregi ed i difetti delle varie semplificazioni effettuate.
Lo sviluppo della vegetazione riparia è fortemente influenzato dalle forzanti agenti su di essa, sia quelle idrologiche che quelle morfologiche. Allo stadio attuale, esistono solo alcuni studi sito-specifici o di carattere puramente qualitativo che analizzano compiutamente l’interazione tra le forzanti fluviali e la vegetazione riparia. In questa tesi si è quindi voluto provare a descrivere l’influenza dell’idrologia e della morfologia sullo sviluppo della vegetazione, semplificando il più possibile i meccanismi coinvolti. Viene quindi proposta tale analisi, evidenziandone i limiti legati all’assenza di dati sperimentali tali da permettere una buona taratura del modello.
Nei successivi due capitoli vengono riportate due differenti applicazioni del modello completo: la prima al fiume Paranà e la seconda al fiume Zambezi.
L’applicazione al fiume Paranà viene fatta per mettere in evidenza la bontà del modello nel descrivere l’evoluzione fluviale, anche mediante un raffronto con un modello commerciale unidimensionale quale Hec-Ras. Tale applicazione è stata fatta anche per verificare l’impostazione generale e le formulazioni adottate nella descrizione della sezione sintetica e dell’interazione tra le forzanti fluviali e lo sviluppo della vegetazione riparia.
Lo studio del fiume Zambezi vuole invece verificare come l’alterazione delle portate a causa degli sbarramenti idroelettrici presenti lungo il corso d’acqua influenzi fortemente sia la morfologia che la biologia dell’ambiente fluviale, con effetti sia a medio che a lungo termine. Questa analisi è stata fatta con l’intento di analizzare le variazioni planimetriche e batimetriche susseguenti all’alterazione del regime idrologico naturale di un corso d’acqua causata dalla costruzione di sbarramenti idroelettrici.
Nell’ultimo capitolo vengono discussi i risultati generali ed introdotti i possibili sviluppi futuri, sottolineando come tutti i modelli semplificati analizzati in questo lavoro di tesi necessitino di ulteriori verifiche e validazioni, anche attraverso l’analisi di ulteriori dati sperimentali
Morphodynamics of the Parana River in the light of climate change
No full textThe work highlights the sediment dynamics that takes place at different scales along the Middle and Lower Parana River (Argentina), by means of different numerical models. The principal aim of this study is to provide a multi-disciplinary and multi-scale approach to predict the future river’s morphodynamics in the light of climate change. This approach may be applied to evaluate the long-term impact of the river’s morphodynamics on anthropogenic structures and activities over or nearby the watercourse (i.e., bridges, levees, navigation way). The study was realized by using three different levels of detail of mathematical modelling. Climate models give the input ensemble, i.e., future precipitation and temperature over the La Plata Basin. The VIC hydrological model simulated the flow discharge time-series, which were then used as input for an own-developed 1-D hydro-morphodynamic model. This 1-D code was able to simulate future rate of sediment transport and corresponding bed-level changes at watershed scale and provided the initial and the boundary conditions for a more detailed 2-D model. Therefore, future evolutions of a specific part of the main and the secondary channels were simulated with the MIKE21C code, developed by the Danish Hydraulic Institute.
The performed analysis indicated a rather low sensitivity of the Middle and Lower Parana River bed profile to the relevant increase forecasted in flow discharge, whereas the channels appreciably divagates. In particular, variability increase rather than averaged value of predicted discharges appeared effective in driving current bifurcated morphology into a meandering-multithread pattern
Modeling of river width variations based on hydrological, morphological, and biological dynamics
No full textOne-dimensional (1D) models can be applied, for engineering purposes, to long-term and large-scale morphodynamic simulations of entire river systems only if appropriate simplifications are introduced. This paper proposes an improvement of an existing simplified 1D model based on the local uniform flow hypothesis, coupled with a synthetic description of the transverse profile, which provides the active river width by analyzing the total and the vegetated widths of a watercourse, with assumed variables of the water flow. The overall density of the riparian vegetation, expressed in terms of biological carrying capacity, is predicted as a function of the local climate and some stresses due to interaction between hydrology, morphology, and biology. The constitutive equations have been deduced and the relevant parameters have been calibrated and validated against various hydrological and geometrical data, taken by satellite imagery covering two large watercourses located in tropical and subtropical areas (Parana and Zambezi rivers) and small streams located in temperate zones. The work confirms the opportunity to deal with hydro-morpho-biodynamic river modeling at large spatial and temporal scale through a mixed 1D + quasi-2D approach. The 1D submodel permits long-term computations at watershed scale of the river longitudinal evolution, while the quasi-2D submodel provides the transversal description of the watercourse in terms of vegetated and nonvegetated widths and vegetation density, which in its turn reflects on the 1D computations
Cascading Events, Technology and the Floods Directive: future challenges
No full textCascading events can be referred to multidimensional disasters, where a primary trigger generates a nonlinear series of secondary emergencies that escalate in time, becoming eventually the priority to tackle. In this process, critical infrastructure can be handled as roots of vulnerabilities, because they accumulate both physical attributes and functional nodes. When compromised, they produce widespread breakdowns of society, but also orient emergency responses and long-term recovery. Although floods have been widely associated to the failure of vulnerable equipments or to the disruption of strategic sectors such as energy, communication and transportation, their integration with the emerging concept of cascading has been limited. This open topic presents many challenges for scholars, researchers and practitioners, in particular when the implementation of the EU Floods Directive is considered. The paper presents an overview of the Floods Directive and its relation with the cascading events, using case studies and examples from the existing literature to point out missing links and gaps in the legislation. Conclusions argue that the Directive considers only local geographical scales and limited temporal horizons, which can be result inadequate to limit the escalation of events
Modelling the impact of large impoundments on the Lower Zambezi River
No full textThe Lower Zambezi River is influenced by the presence of two very large hydropower impoundments which have modified the natural seasonal flows, the sediment balance, the morphology of the river and the pattern of the riparian vegetation. Downstream of these large impoundments, appreciable local effects are reported to take place, such as scour, bank collapse and shoreline degradation. In order to quantify the sediment transport along the Lower Zambezi River and to predict the effects of the dams on morphology we have developed a simplified 1-D hydro-morphodynamic model capable to deal with the scarcity of available data. Besides the systematic flow records at the dam gauging station and few occasional measurements of turbidity and grain size of the river bed, only the Digital Elevation Model (DEM) and some recent satellite images of the river have been used as the input data of the model. The results confirm the expected qualitative response of the river to the constructions of dams: the reduction of water flow has an immediate effect downstream of the reservoirs by initially fostering the sediment deposition; afterwards, the total interception of sediment by the dams slowly takes over and inverts this tendency; a smaller aggradation rate with respect to the natural conditions without dams, seems to represent the dominant effect of damming in the long-term evolution of the river. The morphological effects of damming over the transversal cross-section of the river have been studied by a simplified transversal quasi 2-D sub-model, coupled to a 1-D longitudinal model. Besides the evolution of the bottom longitudinal profile and grain size composition, the model simulates also the evolution of the cross-section shape and the growth of the riparian vegetation. A first application confirms the qualitative observations reported in the literature on the recent planimetric evolution of the Lower Zambezi. © 2013 Copyright International Association for Hydro-Environment Engineering and Research
Implications of cascading effects for the EU Floods Directive
Full text linkThe adoption of the European Floods Directive (2007/60/EC) represented a crucial improvement in the management of watercourses and coastlines. However, the beginning of a new phase of implementation requires the assessment of which emerging topics may be included in the review process. The aim of our research is to understand the existence of any legislative gaps that could limit the preparedness to cascading events and critical infrastructures breakdowns. First, we provide a review of the Floods Directive, the cascading phenomena and the vulnerability of critical infrastructures in the European legislation. Secondly, we analyse some case-studies to test the present approach and to improve the work of decision makers. Our results suggest that the Floods Directive tends to focus on localized flood impacts at smaller time scale and it could be ineffective to address the cross-scale impact of cascading events. Although some of the corrective actions may not be of competence of the Directive, we argue that their inclusion could limit uncertainties in the attribution of responsibilities and the coordination among different institutional levels
Vulnerability, impacts and assessment of climate change on Jakarta and Venice
No full textIn the next future, cities located in coastal areas are likely to suffer for climatic changes more than all other human systems. The demographic growth, combined with sea-level rise and global warming related to natural causes and anthropogenic activities, endanger those systems. Thence, to effectually cope with new climate forcing, coastal cities need improvements to be sustainable, resilient and liveable, applying flexible design approaches rather than a traditional one. The paper highlights such concepts presenting two case studies of important coastal cities: Venice, in Northern Italy, and Jakarta, the capital city of Indonesia. Although characterized by completely different climatic conditions and living habits, these two metropolises are highly impacted by humans and threatened by similar factors like subsidence and sea-level rise, which increase their exposure to future calamities principally driven by climate change but strictly related to anthropic pressures. The present situation shows that, for the future, the resilience of coastal megalopolis can be increased only using a mix of approaches at various levels, spanning from technical measures to adaptable planning instruments that consider future uncertainties
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