6,363 research outputs found
Estimation of flood warning runoff thresholds in ungauged basins with asymmetric error functions
No full textIn many real-world flood forecasting systems, the runoff thresholds for
activating warnings or mitigation measures correspond to the flow peaks with
a given return period (often 2 years, which may be associated with the
bankfull discharge). At locations where the historical streamflow records
are absent or very limited, the threshold can be estimated with
regionally derived empirical relationships between catchment descriptors and
the desired flood quantile. Whatever the function form, such models are
generally parameterised by minimising the mean square error, which assigns
equal importance to overprediction or underprediction errors.
Considering that the consequences of an overestimated warning threshold
(leading to the risk of missing alarms) generally have a much lower level of
acceptance than those of an underestimated threshold (leading to the
issuance of false alarms), the present work proposes to parameterise the
regression model through an asymmetric error function, which penalises the overpredictions more.
The estimates by models (feedforward neural networks) with increasing degree
of asymmetry are compared with those of a traditional, symmetrically trained
network, in a rigorous cross-validation experiment referred to a database of
catchments covering the country of Italy. The analysis shows that the use of
the asymmetric error function can substantially reduce the number and extent
of overestimation errors, if compared to the use of the traditional square
errors. Of course such reduction is at the expense of increasing
underestimation errors, but the overall accurateness is still acceptable and
the results illustrate the potential value of choosing an asymmetric error
function when the consequences of missed alarms are more severe than those
of false alarms
ANALISI DEI CONSUMI IDROPOTABILI SUL TERRITORIO ROMAGNOLO: LA CRISI DEL 2011-2012 E MODELLAZIONE DELL’INFLUENZA STAGIONALE DI FATTORI CLIMATICI E TURISTICI
No full textAsymmetric Error Functions for Reducing the Underestimation of Local Scour around Bridge Piers: Application to Neural Networks Models
No full textArtificial Neural Networks (ANN) have been recently proposed for predicting the maximum expected scour depth at piers: they generally provide accurate predictions but tend to issue high percentages of underpredictions, due to the use of a symmetric error function in the procedure used for their parameterization.
A novel error function is here proposed for optimizing neural networks, giving more weight to underestimation than to overestimation discrepancies, in order to obtain safer design predictions. The performances of the proposed model on an independent set of field records are compared with those of a conventionally trained neural network and with those of a set of widely used formulae.
The asymmetric error function – that might be applied to optimize any other model or equation, as a proficient alternative to the use of envelope curves – allows to obtain predictions that are closer to the measurements than those issued by the traditional formulae, substantially reducing the extent of unnecessary over-design and, at the same time, the percentage of severe underestimations is comparable with those of the safest formulae
Hydrological Sciences Journal
No full textHydrological Sciences Journal is the official journal of the International Association of Hydrological Sciences (IAHS) and provides a forum for original papers and for the exchange of information and views on significant developments in hydrology worldwide.
The scope of the journal includes:
•the hydrological cycle on the Earth
•surface water, groundwater, snow and ice, in all their physical, chemical and biological processes, their interrelationships, and their relationships to geographical factors, atmospheric processes and climate, and Earth processes including erosion and sedimentation
•hydrological extremes and their impact
•measurement, mathematical representation and computational aspects of hydrological processes
•hydrological aspects of the use and management of water resources and their change under the influence of human activity
•water resources systems, including the planning, engineering, management and economic aspects of applied hydrology
The Summer School ‘Sustainability in communication and education. Spreading the word, creating awareness’. An introduction
No full textIntroduction to the book of abstracts of the summer school 'Sustainability in communication and education. Spreading the word, creating awareness
Encuentros con Elena Poniatowska
No full textThe author analyzes testimonial literature from the perspective of female literature through his meeting with Elena Poniatowska. An analysis of reality vs. Fiction in Elena, Jesusa and Tinisima.El autor analiza, desde su encuentro con Elena Poniatowska, la vertiente de la literatura testimonial como literatura de mujeres. Un análisis interior de la relación entre realidad y ficción, entre Elena, Jesusa o Tinísima
APPLICAZIONE DI UNA FUNZIONE D’UTILITA’ PER LA PARAMETRIZZAZIONE DI UN MODELLO AFFLUSSI-DEFLUSSI A FINI DI ALLERTAMENTO
No full textPiù energia per gli utenti, più acqua per l'ambiente: scenari di ibridizzazione idroelettrico-fotovoltaico per un invaso pre-alpino
No full textGestione sostenibile delle risorse idriche e cambiamento climatico: ottimizzazione delle regole di derivazione dall’invaso di Ridracoli
No full text- …
