scholarly journals Best Fit and Selection of Theoretical Flood Frequency Distributions Based on Different Runoff Generation Mechanisms

Water ◽  
2010 ◽  
Vol 2 (2) ◽  
pp. 239-256 ◽  
Author(s):  
Vito Iacobellis ◽  
Mauro Fiorentino ◽  
Andrea Gioia ◽  
Salvatore Manfreda
Keyword(s):  
Flood Frequency ◽  
Runoff Generation ◽  
Frequency Distributions ◽  
Generation Mechanisms ◽  
Best Fit ◽  
Selection Of

scholarly journals Threshold effects in catchment storm response and the occurrence and magnitude of flood events: implications for flood frequency

2007 ◽  
Vol 11 (4) ◽  
pp. 1515-1528 ◽  
Author(s):  
D. I. Kusumastuti ◽  
I. Struthers ◽  
M. Sivapalan ◽  
D. A. Reynolds
Keyword(s):  
Surface Runoff ◽  
Rainfall Variability ◽  
Temporal Frequency ◽  
Flood Frequency ◽  
Storm Events ◽  
Rainfall Runoff ◽  
Runoff Generation ◽  
Frequency Curve ◽  
Generation Mechanisms ◽  
Frequency Curves

Abstract. The aim of this paper is to illustrate the effects of selected catchment storage thresholds upon runoff behaviour, and specifically their impact upon flood frequency. The analysis is carried out with the use of a stochastic rainfall model, incorporating rainfall variability at intra-event, inter-event and seasonal timescales, as well as infrequent summer tropical cyclones, coupled with deterministic rainfall-runoff models that incorporate runoff generation by both saturation excess and subsurface stormflow mechanisms. Changing runoff generation mechanisms (i.e. from subsurface flow to surface runoff) associated with a given threshold (i.e. saturation storage capacity) is shown to be manifested in the flood frequency curve as a break in slope. It is observed that the inclusion of infrequent summer storm events increases the temporal frequency occurrence and magnitude of surface runoff events, in this way contributing to steeper flood frequency curves, and an additional break in the slope of the flood frequency curve. The results of this study highlight the importance of thresholds on flood frequency, and provide insights into the complex interactions between rainfall variability and threshold nonlinearities in the rainfall-runoff process, which are shown to have a significant impact on the resulting flood frequency curves.

scholarly journals Probability distribution of flood flows in Tunisia

2008 ◽  
Vol 12 (3) ◽  
pp. 703-714 ◽  
Author(s):  
H. Abida ◽  
M. Ellouze
Keyword(s):  
Goodness Of Fit ◽  
Flood Frequency ◽  
Northern Tunisia ◽  
Frequency Distributions ◽  
Generalized Pareto ◽  
Southern Tunisia ◽  
Pearson Type ◽  
L Moments ◽  
Homogeneous Regions ◽  
Best Fit

Abstract. L (Linear) moments are used in identifying regional flood frequency distributions for different zones Tunisia wide. 1134 site-years of annual maximum stream flow data from a total of 42 stations with an average record length of 27 years are considered. The country is divided into two homogeneous regions (northern and central/southern Tunisia) using a heterogeneity measure, based on the spread of the sample L-moments among the sites in a given region. Then, selection of the corresponding distribution is achieved through goodness-of-fit comparisons in L-moment diagrams and verified using an L moment based regional test that compares observed to theoretical values of L-skewness and L-kurtosis for various candidate distributions. The distributions used, which represent five of the most frequently used distributions in the analysis of hydrologic extreme variables are: (i) Generalized Extreme Value (GEV), (ii) Pearson Type III (P3), (iii) Generalized Logistic (GLO), (iv) Generalized Normal (GN), and (v) Generalized Pareto (GPA) distributions. Spatial trends, with respect to the best-fit flood frequency distribution, are distinguished: Northern Tunisia was shown to be represented by the GNO distribution while the GNO and GEV distributions give the best fit in central/southern Tunisia.

scholarly journals Threshold effects in catchment storm response and the occurrence and magnitude of flood events: implications for flood frequency

2006 ◽  
Vol 3 (5) ◽  
pp. 3239-3277 ◽  
Author(s):  
D. I. Kusumastuti ◽  
I. Struthers ◽  
M. Sivapalan ◽  
D. A. Reynolds
Keyword(s):  
Surface Runoff ◽  
Rainfall Variability ◽  
Temporal Frequency ◽  
Flood Frequency ◽  
Storm Events ◽  
Rainfall Runoff ◽  
Runoff Generation ◽  
Frequency Curve ◽  
Generation Mechanisms ◽  
Frequency Curves

Abstract. The aim of this paper is to illustrate the effects of selected catchment storage thresholds upon runoff behaviour, and specifically their impact upon flood frequency. The analysis is carried out with the use of a stochastic rainfall model, incorporating rainfall variability at intra-event, inter-event and seasonal timescales, as well as infrequent summer tropical cyclones, coupled with deterministic rainfall-runoff models that incorporate runoff generation by both saturation excess and subsurface stormflow mechanisms. Changing runoff generation mechanisms (i.e. from subsurface flow to surface runoff) associated with a given threshold (i.e. saturation storage capacity) are shown to be manifested in the flood frequency curve as a break in slope. It is observed that the inclusion of infrequent summer storm events increases the temporal frequency occurrence and magnitude of surface runoff events, in this way contributing to steeper flood frequency curves, and an additional break in the slope of the flood frequency curve. The results of this study highlight the importance of thresholds on flood frequency, and provide insights into the complex interactions between rainfall variability and threshold nonlinearities in the rainfall-runoff process, which are shown to have a significant impact on the resulting flood frequency curves.

scholarly journals Effects of runoff thresholds on flood frequency distributions

2008 ◽  
Vol 5 (2) ◽  
pp. 903-933 ◽  
Author(s):  
A. Gioia ◽  
V. Iacobellis ◽  
S. Manfreda ◽  
M. Fiorentino
Keyword(s):  
River Basin ◽  
Test Site ◽  
Flood Frequency ◽  
Model Parameters ◽  
Runoff Generation ◽  
Antecedent Soil Moisture ◽  
Frequency Distributions ◽  
Basin Scale ◽  
Modelling Assumptions ◽  
New Formulation

Abstract. Runoff generation during extreme floods usually occurs whenever rainfall forcing exceeds a given threshold. In many cases, different thresholds may be identified as responsible of the hydrological losses during ordinary events or extraordinary events at the basin scale. Such thresholds are shown to be related to the dynamics of soil saturation of the river basin and to account for the high skewness of their annual flood distributions. In basins where ordinary floods are mostly due to a small portion of the surface which is particularly prone to produce runoff, depending on permeability of a river basin and its antecedent soil moisture conditions, severe rainfall may exceed a basin-wide soil storage threshold and produce the so-called outlier events responsible of the high skewness of floods distributions. In this context, the derived theoretical model based on the concept of variable contributing area to peak flow proposed by Iacobellis and Fiorentino (2000) was generalized with the aim of incorporating such kind of dynamics in the description of the phenomena. The work produced a new formulation of the derived distribution where the two runoff components are explicitly considered. The present work was validated by using as test site a group of basins belonging to Southern Italy and characterized by flood distributions with high skewness. The application of the proposed model provided a good fitting to the observed distributions. Moreover, model parameters were found to be strongly related to physiographic basin characteristics giving consistency to the modelling assumptions.

scholarly journals Probability distribution of flood flows in Tunisia

2007 ◽  
Vol 4 (2) ◽  
pp. 957-981 ◽  
Author(s):  
H. Abida ◽  
M. Ellouze
Keyword(s):  
Goodness Of Fit ◽  
Flood Frequency ◽  
Northern Tunisia ◽  
Frequency Distributions ◽  
Generalized Pareto ◽  
Southern Tunisia ◽  
Pearson Type ◽  
L Moments ◽  
Homogeneous Regions ◽  
Best Fit

Abstract. L (Linear) moments are used in identifying regional flood frequency distributions for different zones Tunisia wide. 893 site-years of annual maximum stream flow data from a total of 37 stations with an average record length of 24.14 years are considered. The country is divided into two homogeneous regions (northern and central/southern Tunisia) using a heterogeneity measure, based on the spread of the sample L-moments among the sites in a given region. Then, selection of the corresponding distribution is achieved through goodness-of-fit comparisons in L-moment diagrams and verified using an L-moment based regional test that compares observed to theoretical values of L-skewness and L-kurtosis for various candidate distributions. The distributions used, which represent five of the most frequently used distributions in the analysis of hydrologic extreme variables are: (i) Generalized Extreme Value (GEV), (ii) Pearson Type III (P3), (iii) Generalized Logistic (GLO), (iv) Generalized Normal (GN), and (v) Generalized Pareto (GPA) distributions. Spatial trends, with respect to the best-fit flood frequency distribution, are distinguished: Northern Tunisia was shown to be represented by the GEV distribution while the GLO distribution gives the best fit in central/southern Tunisia.

scholarly journals Regional analysis of runoff thresholds behaviour in Southern Italy based on theoretically derived distributions

2011 ◽  
Vol 26 ◽  
pp. 139-144 ◽  
Author(s):  
M. Fiorentino ◽  
A. Gioia ◽  
V. Iacobellis ◽  
S. Manfreda
Keyword(s):  
Frequency Distribution ◽  
Southern Italy ◽  
Regional Analysis ◽  
Flood Frequency ◽  
Annual Maximum ◽  
Runoff Generation ◽  
Frequency Distributions

Abstract. The analysis of runoff thresholds and, more in general, the identification of main mechanisms of runoff generation controlling the flood frequency distribution is investigated, by means of theoretically derived flood frequency distributions, in the framework of regional analysis. Two nested theoretically-derived distributions are fitted to annual maximum flood series recorded in several basins of Southern Italy. Results are exploited in order to investigate heterogeneities and homogeneities and to obtain useful information for improving the available methods for regional analysis of flood frequency.

Challenges for Application of the Derived Distribution Approach to Flood Frequency

2021 ◽  
Author(s):  
Ross Woods ◽  
Yanchen Zheng ◽  
Roberto Quaglia ◽  
Giulia Giani ◽  
Dawei Han ◽  
...  
Keyword(s):  
Data Analysis ◽  
Water Balance ◽  
Flood Frequency ◽  
Alternative Methods ◽  
Rainfall Runoff ◽  
Runoff Generation ◽  
Distribution Method ◽  
Event Scale ◽  
Continuous Simulation ◽  
Generation Mechanisms

<p>Flood estimation in ungauged basins is important for flood design, and for improving our understanding of the sensitivity of flood magnitude to changes in climate and land cover. Flood estimates by current methods (e.g. statistical regression, unit hydrograph) have high uncertainty, even in places with dense observing networks (e.g. +/- 50-100% in the UK). Reductions in this uncertainty are being sought by using alternative methods, such as continuous simulation using hydrological models (spatially-distributed or lumped), and event-scale derived distribution approaches. The very significant challenges for reliable application of continuous simulation models in ungauged catchments are well described in the literature.</p><p>The event-scale derived distribution approach also has challenges, which we explore below. The derived distribution approach at the event scale typically combines the following elements: a stochastic rainfall model, an event-scale rainfall-runoff model (including “losses” and a “baseflow” component), and a runoff routing model. In principle, every element of this approach may be considered as a (seasonally varying) random variable. The flood peak distribution is obtained by integrating over joint distributions of the model elements.</p><p>First challenge: what is the physical basis for estimating the event runoff coefficient? In the 1970s, this was addressed using infiltration theory, but other runoff generation mechanisms are often more important. How do we connect our knowledge of seasonal water balance and runoff generation processes to the probability distribution of event runoff coefficients, and its seasonal variation? We suggest (i) begin with locations which are dominated by a small number of runoff generation mechanisms (ii) make use of existing theory on links between climate, catchment characteristics and seasonal water balance (iii) adapt relevant simple concepts of runoff generation which link seasonal water balance to runoff generation.</p><p>Second challenge: how do we parsimoniously quantify the impacts of within-storm temporal rainfall patterns on the flood hydrograph? Existing approaches use stochastic rainfall models to explicitly generate (hourly) time series of rainfall; since catchments damp out high frequency forcing, we suggest that these rainfall series often contain excessive temporal detail and obscure the most informative interactions between rainfall and catchment response. We propose that we use stochastic models that can generate hydrologically relevant attributes of rainfall events (e.g. intensity/depth/duration, spatial and temporal moments), and then apply rainfall-runoff transformations which operate on rainfall moments, and do not require excess detail in temporal (or spatial) patterns of rainfall.</p><p>Third challenge: What is an event? This is no problem for theoretical models, but it is hard as a data analysis question, and we need data analysis to implement and evaluate the derived distribution method. The event identification methods of engineering hydrology are subjective, require manual intervention and are poorly suited for large sample hydrology! We suggest the answer lies in the catchment’s response time.</p><p>The underlying conceptual framework to link seasonal climate and hydrology to floods is already available (Sivapalan et al, 2005). What these challenges require is that we integrate and apply more of our existing hydrological concepts and knowledge to implement the process-based theory of flood frequency. </p>

scholarly journals Runoff thresholds in derived flood frequency distributions

2008 ◽  
Vol 12 (6) ◽  
pp. 1295-1307 ◽  
Author(s):  
A. Gioia ◽  
V. Iacobellis ◽  
S. Manfreda ◽  
M. Fiorentino
Keyword(s):  
Source Area ◽  
Infiltration Rate ◽  
Flood Frequency ◽  
Model Parameters ◽  
Runoff Generation ◽  
Frequency Model ◽  
Frequency Distributions ◽  
Proposed Model ◽  
Basin Scale ◽  
New Formulation

Abstract. In general, different mechanisms may be identified as responsible of runoff generation during ordinary events or extraordinary events at the basin scale. In a simplified scheme these mechanisms may be represented by different runoff thresholds. In this context, the derived flood frequency model, based on the effect of partial contributing areas on peak flow, proposed by Iacobellis and Fiorentino (2000), was generalized by providing a new formulation of the derived distribution where two runoff components are explicitly considered. The model was tested on a group of basins in Southern Italy characterized by annual maximum flood distributions highly skewed. The application of the proposed model provided good results in terms of descriptive ability. Model parameters were also found to be well correlated with geomorphological basin descriptors. Two different threshold mechanisms, associated respectively to ordinary and extraordinary events, were identified. In fact, we found that ordinary floods are mostly due to rainfall events exceeding a threshold infiltration rate in a small source area, while the so-called outlier events, responsible of the high skewness of flood distributions, are triggered when severe rainfalls exceed a threshold storage in a large portion of the basin.

scholarly journals Regional parent flood frequency distributions in Europe – Part 1: Is the GEV model suitable as a pan-European parent?

2014 ◽  
Vol 18 (11) ◽  
pp. 4381-4389 ◽  
Author(s):  
J. L. Salinas ◽  
A. Castellarin ◽  
A. Viglione ◽  
S. Kohnová ◽  
T. R. Kjeldsen
Keyword(s):  
Statistical Model ◽  
Frequency Distribution ◽  
Climatic Factors ◽  
Extreme Value ◽  
Flood Frequency ◽  
Generalized Extreme Value Distribution ◽  
Statistical Hypothesis ◽  
Generalized Extreme Value ◽  
Frequency Distributions ◽  
Hypothetical Scenario

Abstract. This study addresses the question of the existence of a parent flood frequency distribution on a European scale. A new database of L-moment ratios of flood annual maximum series (AMS) from 4105 catchments was compiled by joining 13 national data sets. Simple exploration of the database presents the generalized extreme value (GEV) distribution as a potential pan-European flood frequency distribution, being the three-parameter statistical model that with the closest resemblance to the estimated average of the sample L-moment ratios. Additional Monte Carlo simulations show that the variability in terms of sample skewness and kurtosis present in the data is larger than in a hypothetical scenario where all the samples were drawn from a GEV model. Overall, the generalized extreme value distribution fails to represent the kurtosis dispersion, especially for the longer sample lengths and medium to high skewness values, and therefore may be rejected in a statistical hypothesis testing framework as a single pan-European parent distribution for annual flood maxima. The results presented in this paper suggest that one single statistical model may not be able to fit the entire variety of flood processes present at a European scale, and presents an opportunity to further investigate the catchment and climatic factors controlling European flood regimes and their effects on the underlying flood frequency distributions.

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