1,354,140 research outputs found
"Comparison of a 1D and a 2D Hydraulic Model in Flood Risk Assessment"
No full textTraditionally flood risk assessments have been developed from one-dimensional models, which are capable of calculating flood levels and discharges quite accurately in applications where the flow path is mainly linear. In fact, physical phenomena involved in the process of describing exchanges of flows with the floodplains make this procedure questionable in urban areas, where the flow paths are usually complex. More recently 2D models have been introduced to overcome these problems. In this study we discuss the capability of one-dimensional modeling (HEC-RAS v.4.0) and compare simulation results with those from a two-dimensional finite element model (River 2D), in order to determine the strengths and weaknesses of the different approaches. These practical implications are analyzed and illustrated on a case study on the terminal reach of the River Pescara, Italy. The results of this study can provide useful information in determining which tool to use and which aspects to consider in order to make more reliable analyses of flooding processes in urban areas
RIVER REHABILITATION FOR FLOOD PROTECTION: A SUSTAINABLE SOLUTION (VOMANO RIVER’S MOUTH CASE STUDY, CENTRAL ITALY)
No full textRivers are highly sensitive to long-term and intensive human activities on their floodplains,
which usually lead to fundamental transformations of fluvial morphology and changes in the character
and intensity of flood events. In the last years it has been registered a growing interest at both strategic
and operational levels amongst river managers in Europe in developing wetland rehabilitation schemes
for flood risk mitigation and biodiversity protection.
The paper illustrates a sustainable flood mitigation plan in urban context through destroyed floodplain
rehabilitation, based on a geomorphic approach, for the Vomano River’s mouth, central Italy: an example
on how the analysis of historical information can be a useful tool for identifying a preliminary guiding
image for the rehabilitation process, to be then verified by means of hydraulic modeling
Analisi sperimentale sull’erosione prodotta a valle di grandi dighe
No full textL’erosione a valle di grandi dighe è dovuta all’impatto dei getti ad alta velocità uscenti dagli organi di sfioro delle strutture di ritenuta. Ai fini della scelta del dispositivo di dissipazione è opportuno stimare già in fase di progettazione preliminare la geometria dello scavo e la sua configurazione di equilibrio, in modo da evitare lo scalzamento delle fondazioni della diga e la destabilizzazione dei versanti. Gli AA. riferiscono sui risultati sperimentali, condotti su un modello in similitudine di Froude, per cinque diverse condizioni di esercizio, sull’erosione prodotta al piede di una diga con dissipatore a salto di sci; viene inoltre discussa l’applicabilità delle formule empiriche presenti in letteratura e i risultati comparati in termini di profondità di scavo di equilibrio.Scour downstream of large dams is due to high-velocity jet impact issuing from water releasing structures. The geometry of the hole and the equilibrium scour depth should be carefully estimated in the design phase to prevent undermining of the dam's foundation or side slopes during the operation lifetime. The paper presents an analysis of a dam plunge pool, making use of laboratory observations on a small-scale model in Froude similitude, under different flow conditions, to perform a comparative analysis between scour estimation methods. The application of empirical formulas specifically to ski-jump jets is discussed and results are compared in terms of ultimate scour depth
Remote monitoring system for the Gran Sasso aquifer
No full textThe possibility of using as drinking water the huge groundwater resources stored in the Gran Sasso Massif (Abruzzo Region, Italy) and collected by means of drainage works in the highway tunnels connecting the cities of L’Aquila and Teramo is dependent on water hygienic safety in terms of avoiding risks of contamination deriving from traffic accidents involving hazardous materials spills. This paper describes the hydraulic security devices and the automatic control system which are able to delay the introduction of the drained water to the supply networks, allowing a sufficient time for detecting any possible contamination and then evacuating the polluted water
Effects of wildfires on peak discharges in watersheds
No full textIt is acknowledged that wildfires can alter hydrologic processes in watersheds, increasing runoff peak discharge, which is one of the most important hydrological variables used in water resources applications. Then it is evident that usual rainfall-runoff methods should be modified in some of their components in order to model the different watershed response in burned condition. This paper contains some considerations on the estimation of the SCS runoff Curve Number, needed for the calculation of peak discharge in the small urban basin of San Giuliano in L’Aquila (Italy), which has been recently affected by a wildfire, causing a significant reduction in the forest cover
Implementing the Floods Directive: uncertainties in damage modelling
No full textRisk assessments, as emphasized by the Floods Risk Directive, are becoming the basis for a rational decision-making in planning and designing flood risk reduction measures throughout Europe. In this context, the estimation of flood damages in quantitative terms is a key issue for implementing the Directive, as risk is expressed as a combination of the likelihood of flood occurrence and the impact associated with the event. However damage estimates are still affected by high uncertainty, mainly related to the use of depth-damage functions and methodological differences between the existing models; in addition, for some countries, like Italy, where there are no specific curves, a transfer of damage models from other areas is required, adding extra uncertainty in the modelling process. The present paper investigates the reliability of estimates of potential direct flood damage, comparing the influence of hazard and damage components in risk assessments; this is obtained by varying one factor at a time and using different damage models available in literature, in two case studies of cost-benefit analysis for flood detention basin systems. The results show that the total uncertainty is mainly related to the use of the depth-damage curves, whilst hazard modelling has minor influence
Flood risk mitigation through river rehabilitation
No full textRivers are highly sensitive to long-term and intensive human activities on their floodplains, which usually lead to fundamental transformations of fluvial morphology and changes in the character and intensity of flood events. In the last years it has been registered a growing interest at both strategic and operational levels amongst river managers in Europe in developing wetland rehabilitation schemes for flood risk mitigation and biodiversity protection. But the main difficulties in restoring floodplains lie partly in human activities for industrial, agricultural and residential purposes settled on river corridors; certainly, an optimal balance between nature rehabilitation goals and other societal interests, can provide considerable benefits for many actor groups spanning a variety of policy fields.
The paper illustrates a sustainable flood mitigation plan in urban context through destroyed floodplain rehabilitation for the Vomano River’s mouth, central Italy
Global effects of wildfires on runoff peak discharges
No full textIt is acknowledged that wildfires can alter hydrologic processes in watersheds, increasing runoff peak discharge, which is one of the most important hydrological variables used in water resources applications. Then it is evident that usual rainfall-runoff methods should be modified in some of their components in order to model the different watershed response in burned condition. This paper contains some considerations on the estimation of the SCS runoff Curve Number, needed for the calculation of peak discharge in the small urban basin of San Giuliano in L’Aquila (Italy), which has been recently affected by a wildfire, causing a significant reduction in the forest cover
A New Tool to Estimate Inundation Depths by Spatial Interpolation (RAPIDE): Design, Application and Impact on Quantitative Assessment of Flood Damages
No full textRapid tools for the prediction of the spatial distribution of flood depths within inundated areas are necessary when the implementation of complex hydrodynamic models is not possible due to time constraints or lack of data. For example, similar tools may be extremely useful to obtain first estimates of flood losses in the aftermath of an event, or for large-scale river basin planning. This paper presents RAPIDE, a new GIS-based tool for the estimation of the water depth distribution that relies only on the perimeter of the inundation and a digital terrain model. RAPIDE is based on a spatial interpolation of water levels, starting from the hypothesis that the perimeter of the flooded area is the locus of points having null water depth. The interpolation is improved by (i) the use of auxiliary lines, perpendicular to the river reach, along which additional control points are placed and (ii) the possibility to introduce a mask for filtering interpolation points near critical areas. The reliability of RAPIDE is tested for the 2002 flood in Lodi (northern Italy), by comparing the inundation depth maps obtained by the rapid tool to those from 2D hydraulic modelling. The change of the results, related to the use of either method, affects the quantitative estimation of direct damages very limitedly. The results, therefore, show that RAPIDE can provide accurate flood depth predictions, with errors that are fully compatible with its use for river-basin scale flood risk assessments and civil protection purpose
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