Very high rates of bedload sediment transport by ephemeral desert rivers

Laronne, Jonathan B.; Reid, lan

doi:10.1038/366148a0

Cited by 220 publications

(165 citation statements)

References 13 publications

Supporting

Mentioning

155

Contrasting

Order By: Relevance

“…Also, it is the large volume of floods which accounts for most of the suspended sediment yield (Alexandrov et al 2009). However, it is the high discharges associated with high peak discharges, which give rise to exceptionally large fluxes of bed load (Laronne and Reid 1993). A shift to more frequent and larger major RST-generated flood events may, therefore, give rise to an increase of the bed-load fraction in Mediterranean and semi-arid systems, whereby the response will become more typical of that in arid to hyper-arid systems (Laronne and Wilhelm 2001).…”

Section: Discussionmentioning

confidence: 99%

Red Sea Trough flood events in the Negev, Israel (1964–2007)

Shentsis

Laronne

Alpert

2012

Hydrological Sciences Journal

Self Cite

View full text Add to dashboard Cite

Results of a comprehensive synoptic-hydrological analysis of major flood events in the Negev are presented. A low threshold for major flood data was set to be the 10-year recurrence interval of peak discharge and/or flood volume magnitude. Altogether, 75 major flood events, or 133 hydrometrically monitored floods, were extracted. These events were categorized according to synoptic oriented classes by verification of the paired databases of: (a) floods in the study area, and (b) synoptic systems over the Eastern Mediterranean. For the study area, two of the most frequent flood-generating synoptic systems are the autumn Red Sea Trough (RST), 31%, and winter cyclones, 49%. The entire RST series consists of 24 major flood events (55 floods). The synoptic definition was corroborated by analysing the specific form of flood hydrographs and the ratio of flood volume to peak discharge. Regional analysis shows increased contribution of RST events southwards from 30% to 90% with a respective decrease in the number of cyclone events. By comparing two 22-year sub-periods (1964-1985 and 1986-2007), a positive trend in the frequency and magnitudes of RST flood events is discerned. There is also an increased tendency for the occurrence of cyclone floods.Key words floods; synoptic system; Red Sea Trough (RST); climate change; Negev; Arava; Dead Sea; Mediterranean Crues dans le Néguev, Israël (1964-2007) dues à des dépressions sur la Mer RougeRésumé Nous présentons les résultats d'une analyse exhaustive synoptique/hydrologique des crues majeures dans le Néguev (1964Néguev ( -2007. Le seuil inférieur pour les crues majeures a été défini comme le débit de pointe ou le volume de la crue de récurrence 10 ans. Au total, 75 crues majeures, ou 133 crues observées hydrométriquement, ont été extraites. Ces événements ont été classifiés selon des classes synoptiques par vérification des bases de données appariées : (a) des crues dans la zone d'étude, et (b) des systèmes synoptiques sur la Méditerranée orientale. Pour la zone d'étude, deux des systèmes synoptiques générant le plus fréquemment des crues sont les dépressions sur la Mer Rouge (DMR) en automne, 31%, et les cyclones d'hiver, 49%. La série DMR complète est constituée de 24 crues majeures (55 crues). La définition synoptique a été corroborée par l'analyse de la forme spécifique des hydrogrammes de crues et le rapport entre volume et débit de pointe des crues. L'analyse régionale montre une contribution des événements DMR augmentant de 30% à 90% vers le Sud avec une diminution correspondante du nombre d'événements cycloniques. En comparant deux sous-périodes de 22 ans (1964-1985 et 1986-2007), on discerne une tendance positive dans la fréquence et la magnitude des crues DMR. Il ya aussi une tendance croissante à l'apparition de crues d'origine cyclonique.

show abstract

Section: Discussionmentioning

confidence: 99%

Red Sea Trough flood events in the Negev, Israel (1964–2007)

Shentsis

Laronne

Alpert

2012

Hydrological Sciences Journal

Self Cite

View full text Add to dashboard Cite

show abstract

“…However, this conclusion was mainly based on data from temperate mountainous regions. Laronne and Reid (1993) reported that bedload transport in semi-arid ephemeral rivers is much more efficient than in their perennial counterparts of humid zones. Bedload may therefore contribute substantially to the total SSY of semi-arid tropical catchments.…”

Section: Sediment Export Rates and Scale Dependencymentioning

confidence: 99%

Sediment dynamics and the role of flash floods in sediment export from medium-sized catchments: a case study from the semi-arid tropical highlands in northern Ethiopia

et al. 2010

View full text Add to dashboard Cite

Purpose The Ethiopian highlands are a fragile environment, characterized by steep slopes, intense rainfall, a sparse vegetation cover and the occurrence of flash floods. Although important efforts have been made to mitigate the ongoing soil erosion and land degradation problems, the sediment dynamics at medium-sized catchment scale (100-10,000 km²)are not fully understood. Therefore, this study aims to provide a better of sediment export processes and the importance of flash flood events in semi-arid tropical catchments. 2Methods Measuring campaigns were conducted in 10 subcatchments of the Geba, a tributary of the Tekeze, representative of the northern Ethiopian highlands. During 2 to 4 rainy seasons, the rivers were sampled for their suspended sediment concentration (SSC) and runoff discharge.Results and discussion Variations in SSC and sediment grain-size distribution indicate changes in sediment supply during the rainy season, due to the depletion of readily available sediments and the development of a vegetation cover.Also during flood events, changes in sediment supply are observed. Sediment yields (i.e. 497-6,543 t km -2 yr -1 ) are higher than suggested by previous studies and correlate with rainfall depth. The majority of sediment export occurs during a few short but intense flash floods. No clear effect of implemented soil and water conservation measures could be detected in the sediment yields of the catchments.Conclusions Sediment export rates in the Ethiopian highlands are high, are characterized by important changes in sediment supply and are mainly controlled by the occurrence and magnitude of flash flood events. Mitigation measures to reduce sediment yield at the catchment scale should therefore not only focus on the reduction of hillslope erosion rates, but also on the magnitude of these floods.

show abstract

“…This is part of a wider investigation of sediment transport processes in dryland ephemeral streams [Laronne and Reid, 1993;Laronne et al, 1994;Reid and Laronne, 1995;Reid et al, 1996Reid et al, , 1998b. The data have been collected using a permanently installed sediment transport monitoring station.…”

Section: Introductionmentioning

confidence: 99%