Search results for "Return period"
showing 10 items of 18 documents
Rainfall erosivity over the Calabrian region
1997
Abstract Following the results of a study carried out for the neighbouring Sicilian region, this paper reports a study of the applicability of the annual value, Faj, of the Arnouldus index to represent the erosion risk in Calabrian region. Firstly, By using 214 values of the mean annual value of the erosivity index, FF, and a Kriging interpolation method, an isoerosivity map is plotted. Then, in order to predict the erosion risk for an event of any return period, the probability distribution of the Faj index is studied. An in situ statistical analysis, carried out by using candidate distributions with two parameters (Gauss, LN2, EV1 and Weibull distribution), showed that the EV1 and LN2 law…
The influence of geomorphological position and vegetation cover on the erosional and hydrological processes on a Mediterranean hillslope
1998
Soil erosion and runoff rates are assumed to be highly dependent on slope position. However, little knowledge exists about the hydrogeomorphological processes at the pedon scale that support this idea. In order to assess the hydrological and erosional behaviour of soils at different slope positions, simulated rainfall experiments (55 mm was applied during one hour) were carried out on a south-facing slope with underlying limestone in south-east Spain. In the mean terms, the erosion rates (9 g m2 hr−1) and the runoff coefficients (12%) were very low at the scale of measurement (0·25 m2). The slope position does not affect erosion rates when the measurements are carried out under extreme dry …
Multi-year drought frequency analysis at multiple sites by operational hydrology - A comparison of methods
2006
Abstract This paper compares two generators of yearly water availabilities from sources located at multiple sites with regard to their ability to reproduce the characteristics of historical critical periods and to provide reliable results in terms of the return period of critical sequences of different length. The two models are a novel multi-site Markov mixture model explicitly accounting for drought occurrences and a multivariate ARMA. In the case of the multisite Markov mixture model parameter estimation is limited to a search in the parameter space guided by the value of parameter λ to show the sensitivity of the model to this parameter. Application to two of the longest time series of …
Statistical distribution of soil loss and sediment yield at Sparacia experimental area, Sicily
2010
Abstract An analysis of the statistical distribution of event soil loss was carried out using the data collected in the period 1999–2008 at the microplots and plots of the Sparacia experimental area (Sicily, Italy). For a given microplot size, the analysis allowed to establish that the soil loss frequency distribution was skewed. Using the soil loss normalized by the event mean value, the analysis also showed that the frequency distributions corresponding to different microplot and plot sizes were overlapping, i.e. all distributions were extracted by the same statistical population. The developed analysis allowed to suggest that the soil loss of a given return period can be estimated using …
A diachronic analysis of estuarine turbidity due to a flood following an extreme rainfall event
2011
During floods following rainfall events characterized by long return period, rivers bring to their mouths the higher concentration of sediments. This paper deals with a qualitative assessment of coastal water and turbidity load in estuarine waters as a consequence of an intense rainfall event occurred on the 16t h and 17 th September 2003 in the eastern part of Sicily. Although empirical relationships to estimate turbidity using remote sensing can be found in literature, however models parameters need to be calibrated through in situ measures acquired via intensive field campaigns. The algorithm used within this research was calibrated using field data acquired during three periods in 2008 …
Selection of the Optimal Design Rainfall Return Period of Urban Drainage Systems
2014
Abstract The aim of this work is to define a methodology to identify the optimal rainfall return period for the design of urban drainage systems. The choice of the optimal return period is made minimizing the total costs of the system: the sewer network is dimensioned for a set of possible design rainfall return periods, and the corresponding construction, maintenance and operation costs are evaluated. For each scenario, the total expected damage from flooding caused by rainfall events with return period greater than the design one is then estimated by hydraulic simulation. This methodology has been applied to a small urban catchment in Palermo (Italy).
A review of estimating population exposure to sea-level rise and the relevance for migration
2020
Abstract This review analyses global or near-global estimates of population exposure to sea-level rise (SLR) and related hazards, followed by critically examining subsequent estimates of population migration due to this exposure. Our review identified 33 publications that provide global or near-global estimates of population exposure to SLR and associated hazards. They fall into three main categories of exposure, based on definitions in the publications: (i) the population impacted by specified levels of SLR; (ii) the number of people living in floodplains that are subject to coastal flood events with a specific return period; and (iii) the population living in low-elevation coastal zones. …
Multivariate statistical analysis for water demand modelling: implementation, performance analysis, and comparison with the PRP model
2015
Water demand is the driving force behind hydraulic dynamics in water distribution systems. Consequently, it is crucial to accurately estimate the actual water use to develop reliable simulation models. In this study, copula-based multivariate analysis was proposed and used for demand prediction for a given return period. The analysis was applied to water consumption data collected in the water distribution network of Palermo (Italy). The approach produced consistent demand patterns and could be a powerful tool when coupled with water distribution network models for design or analysis problems. The results were compared with those obtained using a classical water demand model, the Poisson re…
Effects of hydrological events on morphological evolution of a fluvial system
2018
Abstract This study quantifies morphological evolution of the Dez River, Iran, from 1955 to 2016. The approach uses a sequence of Landsat images, aerial photos, and topographic maps. In addition, the hydrological data including average daily discharge and yearly maximum discharge at the Dezful hydrological station for the period (1955–2016) were used. The study reach was divided into 48 meander loops from upstream to downstream. Active channel width (w) was determined at 10 m intervals and changes assessed along the study reach of the Dez River. Morphological indices including sinuosity index; straight meander length; centerline flow length; erosion area; erodible length channel migration; …
Rockburst induced ground motion—a comparative study
2004
Abstract While rockbursts from underground copper mining in Western Poland normally produce surface peak ground accelerations (PGA) and velocities of 0.05–0.1 g and 1–3 cm/s, occasionally these peak motions may exceed 0.15 g and 10 cm/s, respectively. These larger motions are of considerable concern and an investigation has been undertaken to define the nature of these larger induced ground motions. This paper compares these rockburst motions with low intensity earthquakes. Various strong motion parameters such as PGA, peak ground velocity (PGV) and displacements as well as strong motion duration, Arias intensity, Fourier and response spectra are compared with those from earthquakes. It is …