Regional flood frequency analysis in arid and semi-arid areas

Farquharson, F. A. K.; Meigh, Jeremy; Sutcliffe, J. V.

doi:10.1016/0022-1694(92)90132-f

Cited by 150 publications

(108 citation statements)

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“…US Department of the Interior, Bureau of Reclamation, 1977Reclamation, , 1987Sutcliffe, 1978). Recently, several studies have shown that floods seem to have heavier tails than a Gumbel distribution (Farquharson et al, 1992;Turcotte, 1994;Turcotte & Malamud, 2003). Other studies (Wilks, 1993;Koutsoyiannis & Baloutsos, 2000;Sisson et al, 2003) have extended the scepticism for the Gumbel distribution to the case of rainfall extremes, showing that it underestimates seriously the largest extreme rainfall amounts.…”

Section: Introductionmentioning

confidence: 99%

Statistics of extremes and estimation of extreme rainfall: I. Theoretical investigation / Statistiques de valeurs extrêmes et estimation de précipitations extrêmes: I. Recherche théorique

Koutsoyiannis

2004

Hydrological Sciences Journal

196

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The Gumbel distribution has been the prevailing model for quantifying risk associated with extreme rainfall. Several arguments including theoretical reasoning and empirical evidence are supposed to support the appropriateness of the Gumbel distribution. These arguments are examined thoroughly in this work and are put into question. Specifically, theoretical analyses show that the Gumbel distribution is quite unlikely to apply to hydrological extremes and its application may misjudge the risk, as it underestimates seriously the largest extreme rainfall amounts. Besides, it is shown that hydrological records of typical length (some decades) may display a distorted picture of the actual distribution, suggesting that the Gumbel distribution is an appropriate model for rainfall extremes while it is not. In addition, it is shown that the extreme value distribution of type II (EV2) is a more consistent alternative. Based on the theoretical analysis, in the second part of this study an extensive empirical investigation is performed using a collection of 169 of the longest available rainfall records worldwide, each having 100-154 years of data. This verifies the inappropriateness of the Gumbel distribution and the appropriateness of EV2 distribution for rainfall extremes.Key words design rainfall; extreme rainfall; generalized extreme value distribution; Gumbel distribution; hydrological design; hydrological extremes; probable maximum precipitation; risk Statistiques de valeurs extrêmes et estimation de précipitations extrêmes: I. Recherche théoriqueRésumé La distribution de Gumbel a longtemps été le modèle régnant pour la quantification du risque associé aux précipitations extrêmes. Plusieurs arguments comprenant à la fois un raisonnement théorique et des faits empiriques sont censés soutenir la pertinence de la distribution de Gumbel. Ces arguments sont examinés exhaustivement dans ce travail et sont mis en question. Spécifiquement, des analyses théoriques montrent que la distribution de Gumbel est peu susceptible de s'appliquer aux valeurs extrêmes de variables hydrologiques et que son application peut conduire à une mauvaise estimation du risque par une sérieuse sous-estimation des plus grandes valeurs extrêmes de précipitations. En outre, il est montré que les séries hydrologiques de longueur typique (quelques décennies) peuvent montrer une image déformée de la distribution réelle, ce qui suggère que la distribution de Gumbel est le modèle approprié pour les précipitations extrêmes alors qu'elle ne l'est pas. En outre, on montre que la distribution de valeurs extrêmes du type II (EV2) est une alternative plus cohérente. Dans la deuxième partie de cette étude, une recherche empirique étendue est effectuée, en se basant sur l'analyse théorique, avec une collection de 169 séries de précipitations, parmi les plus longues de celles qui sont disponibles dans le monde entier, comportant chacune 100-154 ans de données. Ceci permet de vérifier la non-pertinence de la distribution de Gumbel et la pertinence de la dist...

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Section: Introductionmentioning

confidence: 99%

Statistics of extremes and estimation of extreme rainfall: I. Theoretical investigation / Statistiques de valeurs extrêmes et estimation de précipitations extrêmes: I. Recherche théorique

Koutsoyiannis

2004

Hydrological Sciences Journal

196

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“…RFFAs employing climatic and catchment indices to estimate the mean annual flood (MAF) have now been undertaken in a large number of arid, semiarid, subtropical and tropical countries to provide a set of flood estimation methods which should be of immediate practical use (Farquharson et al, 1987(Farquharson et al, , 1992Meigh et al, 1993Meigh et al, , 1997. These papers summarize all the MAF prediction equations and dimensionless flood frequency curves derived for the regions and countries of study, including a number of developing countries: Brazil, Rio Grande do Sul; India, Kerala; Indonesia, Java and Sumatra; Malawi; Namibia; Papua New Guinea; The Philippines; Sri Lanka; Swaziland; Thailand; Zimbabwe (Institute of Hydrology, 1986), and parts of Iran, Jordan, Kenya and Korea.…”

Section: Catchment-based Methods Of Flood Estimationmentioning

confidence: 99%

“…For the RFFAs conducted in the arid and semiarid countries, data from gauged catchments were used to derive regression relationships between MAF and basin area (AREA) and mean annual rainfall (MAR) as the two independent variables (Farquharson et al, 1992). These equations provide a preliminary means of estimating the index flood (MAF) for ungauged rivers in Iran, Saudi Arabia and Yemen, Australia (Queensland), South Africa and Botswana.…”

Section: Catchment-based Methods Of Flood Estimationmentioning

confidence: 99%

“…A combined regression equation and growth curve for all warm arid zones studied permits the flood magnitude with a known risk of exceedance to be derived within warm arid zones of the world (annual basin rainfall < 600 mm) even where local flow data are currently unavailable. Farquharson et al (1992) also make the important observation that the 5-year flood may be a more appropriate scaling factor for the dimensionless growth curves in arid zones due to the problem of low or zero annual maxima in a number of years.…”

Section: Catchment-based Methods Of Flood Estimationmentioning

confidence: 99%

“…It expresses the likely deviation of the estimates from the "true" values. Given a. fsee of 2.0, the "true" MAF is likely to fall within the range of twice to half the MAF estimate given by the regression equation (Farquharson et al, 1992). The aim of any flood analysis is to maximize R 2 and minimize fsee.…”

Section: Applications Of the Channel-geometry Methods Javamentioning

confidence: 99%

See 2 more Smart Citations

Flood discharge estimation from river channel dimensions: results of applications in Java, Burundi, Ghana and Tanzania

Wharton

Tomlinson²

1999

Hydrological Sciences Journal

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The channel-geometry method is an indirect method of flood estimation which relies on the development of relations between flood discharges, measured at gauging stations, and channel dimensions, measured from natural river reaches in the vicinity of the gauge. Channel-geometry equations enable flood discharges to be estimated at ungauged locations on natural streams from measurements of channel size and by combining the index flood estimate (usually the mean annual flood) with regional flood growth factors. This paper reports on channel-geometry equations which have been developed and applied in four developing, tropical countries as part of hydrological investigations for road design and flood risk assessment (Java), irrigation and hydropower development (Burundi), design of all-weather roads (Ghana), and rehabilitation of railway bridges (Tanzania). The applications demonstrate the benefits of the channel-geometry method in situations where data on catchment characteristics are limited or may not offer the most appropriate basis for flood discharge estimation.

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Flash-flood and bedload dynamics of desert gravel-bed streams

Reid¹,

Laronne²,

Powell³

1998

Hydrol. Process.

105

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Abstract:Comparatively little is known about the hydrology of desert¯ash-¯oods despite the extent of the world's drylands. There is even less known about their sedimentary behaviour and particularly about the movement of coarse material as bedload. The results of an intense ®eld monitoring programme carried out on an ephemeral gravel-bed stream in the northern Negev Desert are presented. In this semi-arid setting,¯ow duration analysis indicates that the channel is hydrologically active for 2% of the time, or about seven days per year, and that overbank¯ow can be expected for only 0 . 03% of the time Ð about three hours per year. Multipeaked¯ood hydrographs are the norm, re¯ecting many factors including the arrival of separate slugs of discharge from contributing subcatchments. The passage of the initial¯ood bore is surprisingly slow, but the rising limb of thē ood hydrograph is rapid with a median time of rise of 10 minutes, in keeping with expected¯ash-¯ood behaviour. Bedload¯ux is high, averaging 2Á67 kg s À1 m À1 during the period that the channel carries¯ow. This gives very high bedload sediment yield despite the infrequent and short duration of¯ood¯ows and matches the high yield of suspended sediment. The relationship between bedload¯ux and boundary shear stress is simple, in contrast with perennial gravel-bed streams, and the exponent of the log±log relationship is 1 . 52. Of great value is that the behaviour of the Nahal Eshtemoa corroborates a pattern established by the authors previously in a smaller tributary stream. #

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Regional flood frequency analysis in arid and semi-arid areas

Cited by 150 publications

References 1 publication

Statistics of extremes and estimation of extreme rainfall: I. Theoretical investigation / Statistiques de valeurs extrêmes et estimation de précipitations extrêmes: I. Recherche théorique

Statistics of extremes and estimation of extreme rainfall: I. Theoretical investigation / Statistiques de valeurs extrêmes et estimation de précipitations extrêmes: I. Recherche théorique

Flood discharge estimation from river channel dimensions: results of applications in Java, Burundi, Ghana and Tanzania

Flash-flood and bedload dynamics of desert gravel-bed streams

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