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Recent synthesis of 10 Be-derived denudation rates by Willenbring et al. (2013) suggests that the "fl at" areas of the world, those with average slopes of <~100 m/km and representing ~90% of Earth's land surface, have adequately high rates of denudation to produce most of the sediment transported to the world's oceans. This fi nding is based on the product of interpolated denudation rates (L/T) over the world's drainage areas (L 2 ) using landscape slope as the controlling variable. We suggestdoi:10.1086/498101 fatcat:slovy2cgg5fkrn5gk4aok6ijoq
more »... hat these fi ndings are incorrect on several grounds. First, Willenbring et al. have mixed two related-but differentconcepts: "gross" basin denudation and river sediment discharge. Gross basin denudation (L/T) is an integrated rate of regolith degradation; river sediment discharge (L 3 /T or M/T) is a measure of fl ux in a river, and it cannot be calculated by multiplying denudation rates and watershed areas because this ignores sediment transport through a basin (e.g., Trimble, 1977) . Although Willenbring et al. acknowledge this where they state that such comparisons are "impossible" (p. 345), we are told throughout the paper that their results are related to rates of sediment discharged "to the oceans" (p. 343, 344, 346). Both cannot be true. Second, the denudation estimates presented by the authors-even if they were correct-simply do not add up. For example, the global values reported by Willenbring et al. are substantially lower than all previous estimates of global river sediment discharge (see their table DR2 in GSA Data Repository 2013091). Because global river sediment discharge to the ocean, even before human-caused effects, is ~15-20 Gt/yr, and sediment conveyance losses over time scales characterized by 10 Be are likely equivalent to these rates (Milliman and Farnsworth, 2011) , global gross denudation is likely an order of magnitude greater than the 4.4 Gt/yr estimated by Willenbring et al. These errors become clear when individual basins are examined. For example, the Amazon River receives 2.3-3.1 Gt/yr of sediment from the Andes (Aalto et al., 2006) but discharges only ~1 Gt/yr in the lower river at Obidos (Dunne et al., 1998) . Thus, the ~4 × 10 6 km 2 "fl at" lower basin of the Amazon currently traps a net 1.3-2.1 Gt/yr of sediment. If Willenbring et al. were correct that ~10 mm/kyr of denudation occurred in the fl at Amazonia, then only ~0.1 Gt/yr of sediment would be generated in these lowlands, which is ~4% (at most) of the total "gross" denudation of this basin's steep headwaters. Third, there are important data gaps in both fl at and steep landscapes. For instance, the authors' data set includes no measurements for slopes <11 m/km, which combined represent ~50% of Earth's landscape. To fi ll this data gap, Willenbring et al. extrapolate relationships from higher sloped areas. As such, there was no assessment whether the relationship used was representative of the global conditions in areas that were largely unrepresented in the database, such as the expansive fl at areas in the world's deserts and boreal regions where fl uvial processes are of limited importance. For steep landscapes, the data are limited to only two basins where denudation rates exceed 5000 mm/kyr As such, the data set does not include areas with the highest denudation rates and sediment yields in the world (e.g., Taiwan, New Zealand, Southeast Asia, and southeastern Alaska; Milliman and Farnsworth, 2011) , and this data gap certainly contributes to the underestimation of global denudation. Fourth, while the use of a constant denudation rate for fl at areas of Earth's surface is computationally attractive, this concept is counter to decades of research and basic principles of physics. Strong slope dependencies are found in: (1) reported denudation and erosion rates of the lowerrelief regions of the world over both short-and long-term time scales; (2) the range of geomorphic transport laws and landscape evolution models that successfully mimic morphodynamic patterns over geologic time scales; (3) all sediment transport algorithms, whether at the river-order scale or at the local scale of the hydraulic gradient; and (4) all appropriate experimental laboratory data (e.g., Burbank and Anderson, 2011). These dependencies include both eroding bedrock channels (detachment-limited transport) and alluvial channels and eroding soils (transport limited). Combined, this suggests that a constant sediment production rate for all fl at areas <200 m/km is not justifi ed. Furthermore, many of these fl at areas are net sinks-not sources-of sediment, and they would require "negative" sediment production rates in calculations of discharge "to the ocean" (Willenbring et al., p. 343, 344, 346). While a number of other problems should be discussed (e.g., a model derived from watersheds orders-of-magnitude larger than the grid spacing, incorrect statements about correlations between slope and denudation [p. 344] and residuals summing to zero [p. 344], misrepresentation of watershed sizes in the histogram of their fi gure 1, no assessment of uncertainty, no corrections for fl oodplain storage, elimination of data based on a basin size threshold rather than a morphologic threshold, and a global slope-area curve [their fi gure 3A] with units inconsistent with a continuous distribution function and without data above 250 m/km), length constraints require us to end our discussion here. In conclusion, the methods and fi ndings of Willenbring et al. include incorrect assumptions, insuffi cient data sets, unreliable extrapolations, and computational errors. Combined, this results in overestimation of sediment contributions from "fl at" areas and a gross underestimation of sediment contributions from "steep" areas of the world. The conclusions are therefore invalid.
Loup Guyot planeta. ... Naziano Filizola & Jean Loup Guyot -Agência Nacional de Águas) de um mesmo rio Amazônico (curso principal e os grandes tributários), em concomitância com medições de vazão; ii) amostragens realizadas ...doi:10.25249/0375-7536.2011414566576 fatcat:7d3sgterdfez5ayuszyf6hgp7m
Jean Loup Guyot Fig. 1 . 1 Map of the Amazon drainage basin of Bolivia: sampling points-.; PHICAB gauging stations-*, major cities-.. ... Hydroécologie Quantitative B.P. 220 69336 Lyon Cedex 09, France Jean Gabriel Wasson Table 1 . 1 Data for rivers of the Amazonian drainage basin of Bolivia. ...doi:10.4319/lo.1994.39.2.0452 fatcat:iuawqnikbjd6jlsfav4dnqyjyu
Sediment Transport in Aquatic Environments
Sediment Transport in Aquatic Environments How to reference In order to correctly reference this scholarly work, feel free to copy and paste the following: Naziano Filizola, Jean-Loup Guyot, Hella Wittmann ... , Jean-Michel Martinez and Eurides de Oliveira (2011) . ...doi:10.5772/19948 fatcat:lzpg76esjzgmdph33cwg2z6m4u
., 1997; Guyot et al., 1998] show that the interannual variability of the Amazon river in Manaus, near Obidos, is weakly related to the El Niño Southern Oscilla- tion (ENSO) in the Pacific. ...doi:10.1029/2003gl018741 fatcat:2syus4pgynfrnbypemgttioy4q
oceano, pois fornece aproximadamente, a nível mundial, 17% de água continental (Callède et al. 2010) , 4% de material dissolvido e 3% de material em suspensão para o oceano (Millimam 2001; Filizola e Guyot ... à Tabatinga.Tratamento dos dados físico-químicosO banco de dados do ORE-HYBAM mostram que a vazão foi medida pelo sistema ADCP (Acoustic Doppler Current Profiler) cujo método é detalhado emFilizola e Guyot ...doi:10.1590/1809-4392201402722 fatcat:n6bzlbxjy5donj3zz3uikxkzey
Guyot et al. ... Guyot et al. 1 Journal of South American Earth Sciences 12 (1999) .......... ........................................... tl' ................... ...doi:10.1016/s0895-9811(99)00030-9 fatcat:jachrx2ajrbf7fhsveirknzw64
., 2001) or in some basins of the Andean headwater of the Madeira Basin (Guyot, 1993; Roche & Fernandez, 1988) . ... In some rivers, C-Q relationships shift significantly over the hydrological period: for example, in the Beni basin Guyot (1993) and Moquet et al. (2016) reported a dilutional behavior of major elements ...doi:10.1002/2017wr020591 fatcat:tt765ddvvfhidlpzgsbn2oulea
GUYOT, J. QUINTANILLA, J. CORTÉS, N. ... rios Beni et Mamore à l'amont de Porto Velho), le Rio Madeira reçoit un flux de matières dissoutes de 35-40 106 t an-1 , et un flux de matières particulaires de 223 106 t an-1 (Roche & Fernandez, 1988; Guyot ... Pour la partie brésilienne, ces résultats sont provisoires car la banque de données du DNAEE est en cours de restructuration, et toutes les informations ne sont pas encore saisies (Filizola & Guyot, 1994 ...doi:10.1080/09853111.1993.11105251 fatcat:22s22fp6j5agfdaa6tkow7rxim
Fernandez-Jauregui, 1988; Guyot, 1993 . These highly turbid rivers flowing out from the Andes correspond to white water rivers. ... Ž taken Guyot, 1993 . SPM is made up of clays 57 to . Ž . 76% and quartz 15 to 33% with subordinate amounts of plagioclase and K-feldspar. ...doi:10.1016/s0009-2541(99)00015-7 fatcat:fvoudikcbfcfvbhcnbbedr3z44
La méthode éprouvée des polygones de Thiessen (Thiessen, 1911) (Molinier et al., 1992) et des 1270 mm pour le Rio Negro à Manaus (Guyot et ai, 1994) . ... avait été estimé à 100 000-110 000 m 3 s" 1 dès 1954 (Pardé, 1954) sans aucune mesure complète de débit et réajusté à 166 000 m J s" en 1992 (Molinier et al, 1992) , puis à 169 000 m 3 s"'en 1994 (Guyot ...doi:10.1080/02626660209492933 fatcat:2tw2khfplbb65nvjaxcdqb4vzy
Données 5.1.1 Les mesures à l'entrée amont de l'estuaire de l'Amazone Afin de mettre au point la technique de la mesure à l'estuaire, une première série de jaugeages est faite, en juin 1997 (Guyot et ...doi:10.7202/044688ar fatcat:k4lczp66svbspo4unperavnary
Journal of Hydrology
Molion and de Moraes (1987) and Guyot et al. (1998) found that the association between ENSO and discharges is significant in the north-eastern part of the basin. ... However, Moron et al. (1995) , Guyot et al. (1998) , Uvo et al. (2000) , Liebmann and Marengo (2001) and Ronchail et al. (2002) , coincide in saying that relationships between rainfall or discharge ...doi:10.1016/j.jhydrol.2005.04.004 fatcat:hd34ogqw6bfttjprx5g6wojpru
The impact of a changing climate on the Amazon basin is a subject of intensive research because of its rich biodiversity and the significant role of rainforests in carbon cycling. Climate change has also a direct hydrological impact, and increasing efforts have focused on understanding the hydrological dynamics at continental and subregional scales, such as the Western Amazon. New projections from the Coupled Model Inter-comparison Project Phase 5 ensemble indicate consistent climatic warmingdoi:10.1088/1748-9326/11/1/014013 fatcat:rsvbpqyolbe3vbdvbhqasvrfvu
more »... d increasing seasonality of precipitation in the Peruvian Amazon basin. Here we use a distributed land surface model to quantify the potential impact of this change in the climate on the hydrological regime of the upper Amazon river. Using extreme value analysis, historical and future projections of the annual minimum, mean, and maximum river flows are produced for a range of return periods between 1 and 100 yr. We show that the RCP 4.5 and 8.5 scenarios of climate change project an increased severity of the wet season flood pulse (7.5% and 12% increases respectively for the 100 yr return floods). These findings agree with previously projected increases in high extremes under the Special Report on Emissions Scenarios climate projections, and are important to highlight due to the potential consequences on reproductive processes of in-stream species, swamp forest ecology, and socio-economy in the floodplain, amidst a growing literature that more strongly emphasises future droughts and their impact on the viability of the rainforest system over greater Amazonia.
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