ALBERT

Description: Methodologies to estimate economic flood damages are increasingly important for flood risk assessment and management. In this work, we present a new synthetic flood damage model based on a component-by-component analysis of physical damage to buildings. The damage functions are designed using an expert-based approach with the support of existing scientific and technical literature, loss adjustment studies, and damage surveys carried out for past flood events in Italy. The model structure is designed to be transparent and flexible, and therefore it can be applied in different geographical contexts and adapted to the actual knowledge of hazard and vulnerability variables. The model has been tested in a recent flood event in northern Italy. Validation results provided good estimates of post-event damages, with similar or superior performances when compared with other damage models available in the literature. In addition, a local sensitivity analysis was performed in order to identify the hazard variables that have more influence on damage assessment results.

Description: On 6 February 2013 an Mw = 8.0 subduction earthquake occurred close to Santa Cruz Islands at the transition between the Solomon and the New Hebrides Trench. The ensuing tsunami caused significant inundation on the closest Nendo Island. The seismic source was studied with teleseismic broadband P-wave inversion optimized with tsunami forward modelling at DART buoys (Lay et al., 2013) and with inversion of teleseismic body and surface waves (Hayes et al., 2014a). The two studies also use different hypocentres and different planar fault models and found quite different slip models. In particular, Hayes et al. (2014a) argued for an aseismic slip patch SE from the hypocentre. We here develop a 3-D model of the fault surface from seismicity analysis and retrieve the tsunami source by inverting DART and tide-gauge data. Our tsunami source model features a main slip patch (peak value of ~ 11 m) SE of the hypocentre and reaching the trench. The rake direction is consistent with the progressively more oblique plate convergence towards the Solomon trench. The tsunami source partially overlaps the hypothesized aseismic slip area, which then might have slipped coseismically.

Description: In recent years, awareness of a need for more effective disaster data collection, storage, and sharing of analyses has developed in many parts of the world. In line with this advance, Italian local authorities have expressed the need for enhanced methods and procedures for post-event damage assessment in order to obtain data that can serve numerous purposes: to create a reliable and consistent database on the basis of which damage models can be defined or validated; and to supply a comprehensive scenario of flooding impacts according to which priorities can be identified during the emergency and recovery phase, and the compensation due to citizens from insurers or local authorities can be established. This paper studies this context, and describes ongoing activities in the Umbria and Sicily regions of Italy intended to identifying new tools and procedures for flood damage data surveys and storage in the aftermath of floods. In the first part of the paper, the current procedures for data gathering in Italy are analysed. The analysis shows that the available knowledge does not enable the definition or validation of damage curves, as information is poor, fragmented, and inconsistent. A new procedure for data collection and storage is therefore proposed. The entire analysis was carried out at a local level for the residential and commercial sectors only. The objective of the next steps for the research in the short term will be (i) to extend the procedure to other types of damage, and (ii) to make the procedure operational with the Italian Civil Protection system. The long-term aim is to develop specific depth–damage curves for Italian contexts.

Description: The European "Floods Directive" 2007/60/EU has produced an important shift from a traditional approach to flood risk management centred only on hazard analysis and forecast to a newer one which encompasses other aspects relevant to decision-making and which reflect recent research advances in both hydraulic engineering and social studies on disaster risk. This paper accordingly proposes a way of modelling the benefits of flood emergency management interventions calculating the possible damages by taking into account exposure, vulnerability, and expected damage reduction. The results of this model can be used to inform decisions and choices for the implementation of flood emergency management measures. A central role is played by expected damages, which are the direct and indirect consequence of the occurrence of floods in exposed and vulnerable urban systems. How damages should be defined and measured is a key question that this paper tries to address. The Floods Directive suggests that mitigation measures taken to reduce flood impact need to be evaluated also by means of a cost–benefit analysis. The paper presents a methodology for assessing the effectiveness of early warning for flash floods, considering its potential impact in reducing direct physical damage, and it assesses the general benefit in regard to other types of damages and losses compared with the emergency management costs. The methodology is applied to the case study area of the city of Sondrio in the northern Alpine region of Italy. A critical discussion follows the application. Its purpose is to highlight the strengths and weaknesses of available models for quantifying direct physical damage and of the general model proposed, given the current state of the art in damage and loss assessment.

Description: On 6 February 2013 an Mw 8.0 subduction earthquake occurred close to Santa Cruz Islands at the transition between the Solomon and the New Hebrides Trench. The ensuing tsunami caused significant inundation on the closest Nendo Island. The seismic source was studied with teleseismic broadband P waves inversion optimized with tsunami forward modeling at DART buoys (Lay et al., 2013), and with inversion of teleseismic body and surface waves (Hayes et al., 2014). The two studies also use different hypocenters and different planar fault models, and found quite different slip models. In particular, Hayes et al. (2014) argued for an aseismic slip patch SE from the hypocenter. We here develop a 3-D model of the fault surface from seismicity analysis and retrieve the tsunami source by inverting DART and tide-gauge data. Our tsunami source model features a main slip patch (peak value of ~11 m) SE of the hypocentre, and reaching to the trench. The rake direction is consistent with the progressively more oblique plate convergence towards the Solomon trench. The tsunami source partially overlaps the hypothesized aseismic slip area, which then might have slipped coseismically.

Description: Effective flood risk mitigation requires the impacts of flood events to be much better and more reliably known than is currently the case. Available post-flood damage assessments usually supply only a partial vision of the consequences of the floods as they typically respond to the specific needs of a particular stakeholder. Consequently, they generally focus (i) on particular items at risk, (ii) on a certain time window after the occurrence of the flood, (iii) on a specific scale of analysis or (iv) on the analysis of damage only, without an investigation of damage mechanisms and root causes. This paper responds to the necessity of a more integrated interpretation of flood events as the base to address the variety of needs arising after a disaster. In particular, a model is supplied to develop multipurpose complete event scenarios. The model organizes available information after the event according to five logical axes. This way post-flood damage assessments can be developed that (i) are multisectoral, (ii) consider physical as well as functional and systemic damage, (iii) address the spatial scales that are relevant for the event at stake depending on the type of damage that has to be analyzed, i.e., direct, functional and systemic, (iv) consider the temporal evolution of damage and finally (v) allow damage mechanisms and root causes to be understood. All the above features are key for the multi-usability of resulting flood scenarios. The model allows, on the one hand, the rationalization of efforts currently implemented in ex post damage assessments, also with the objective of better programming financial resources that will be needed for these types of events in the future. On the other hand, integrated interpretations of flood events are fundamental to adapting and optimizing flood mitigation strategies on the basis of thorough forensic investigation of each event, as corroborated by the implementation of the model in a case study.

Description: We present a database of pre-calculated tsunami waveforms for the entire Mediterranean Sea, obtained by numerical propagation of uniformly spaced Gaussian-shaped elementary sources for the sea level elevation. Based on any initial sea surface displacement, the database allows the fast calculation of full waveforms at the 50 m isobath offshore of coastal sites of interest by linear superposition. A computationally inexpensive procedure is set to estimate the coefficients for the linear superposition based on the potential energy of the initial elevation field. The elementary sources size and spacing is fine enough to satisfactorily reproduce the effects of M〉 = 6.0 earthquakes. Tsunami propagation is modelled by using the Tsunami-HySEA code, a GPU finite volume solver for the non-linear shallow water equations. Like other existing methods based on the initial sea level elevation, the database is independent on the faulting geometry and mechanism, which makes it applicable in any tectonic environment. We model a large set of synthetic tsunami test scenarios, selected to explore the uncertainty introduced when approximating tsunami waveforms and their maxima by fast and simplified linear combination. This is the first time to our knowledge that the uncertainty associated to such a procedure is systematically analysed and that relatively small earthquakes are considered, which may be relevant in the near-field of the source in a complex tectonic setting. We find that non-linearity of tsunami evolution affects the reconstruction of the waveforms and of their maxima by introducing an almost unbiased (centred at zero) error distribution of relatively modest extent. The uncertainty introduced by our approximation can be in principle propagated to forecast results. The resulting product then is suitable for different applications such as probabilistic tsunami hazard analysis, tsunami source inversions and tsunami warning systems.

Description: This paper presents AGRIDE-c, a conceptual model for the assessment of flood damage to crops, in favour of more comprehensive flood damage assessments. Available knowledge on damage mechanisms triggered by inundation phenomena is systematised in a usable and consistent tool, with the main strength represented by the integration of physical damage assessment into the evaluation of its economic consequences on the income of the farmers. This allows AGRIDE-c to be used to guide the flood damage assessment process in different geographical and economic contexts, as demonstrated by the example provided in this study for the Po Plain (north of Italy). The development and implementation of the model highlighted that a thorough understanding and modelling of mechanisms causing damage to crops is a powerful tool to support more effective damage mitigation strategies, both at public and at private (i.e. farmers) levels.

Description: The present level of pollution, increasingly involving ground waters, constitutes a serious risk for the environment and also for human health. Therefore the remediation of saturated and unsaturated soils to remove the pollutant materials is required more and more frequently. In the present paper, the possibility of removing the specific pollutant typology constituted of heavy metals by permeable reactive barrier (PRB) from the groundwater, carried out with natural fibers, specifically with broom fibers, is investigated. Once shown the economic benefits deriving from the use of this plant, a hydraulic characterization of the broom fiber mass was performed, determining the permeability and the porosity in correspondence to different levels of compactness of the fibers. Having verified the effectiveness of these fibers for some heavy metals, the results of some experiments, carried out in the laboratory for this purpose, are shown. These experiments were carried out utilizing broom fibers obtained in different ways and, limitedly to the considered pollutants, showed the high capability of these fibers to reduce their concentrations. The best results were obtained for the broom fibers extracted by a particular chemical-physical process. Moreover, the behaviour of this fiber with time was investigated, determining the kinetic constant of degradation.

Description: The present level of pollution, increasingly involving ground waters, constitutes a serious risk to the environment and also to human health. Therefore the remediation of saturated and unsaturated soils to remove pollutant materials is more and more frequently required. In the present paper, the possibility of removing heavy metals by permeable reactive barrier (PRB) from the groundwater carried out specifically with broom fibers, is investigated. Once shown the economic benefits deriving from the use of this plant, a hydraulic characterization of the broom fiber mass was performed, determining the permeability and the porosity in correspondence to different levels of compactness of the fibers. Having verified the effectiveness of removal of some heavy metals by these fibers, the results of some experiments, carried out in the laboratory for this purpose, are shown. These experiments were carried out utilizing broom fibers obtained in different ways and, limitedly to the considered pollutants, showed the high capability of these fibers to reduce their concentrations. The best results were obtained for the broom fibers extracted by a particular chemical-physical process. Moreover, the behaviour of this fiber with time was investigated, determining the kinetic constant of degradation.