Factors influencing the recession rate of Niagara Falls since the 19th century

Hayakawa, Yuichi S.; Matsukura, Yukinori

doi:10.1016/j.geomorph.2009.04.011

Cited by 24 publications

(17 citation statements)

References 32 publications

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“…Furthermore, the knickpoint reinforcements were only a temporary feature as they were ripped out by flooding in March 1936. While waterfall lip shape, length and height are thought to be influential in affecting waterfall retreat rates 38 , other studies have highlighted bedrock structure and fracture geometry as playing a fundamental role in block stability 36,39 , knickpoint morphology and retreat rate 6,11,20,40 . In this example, the slowdown in retreat rate appears to mirror the timing of when the knickpoint interacts spatially with the area dominated by anti-flow oriented fracture sets, implying that that structural differences along the gorge, with local predominance of fracture sets dipping against the flow, became significant in suppressing the retreat progression 30 (Fig.…”

Section: Discussionmentioning

confidence: 99%

Exceptional river gorge formation from unexceptional floods

et al. 2015

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An understanding of rates and mechanisms of incision and knickpoint retreat in bedrock rivers is fundamental to perceptions of landscape response to external drivers, yet only sparse field data are available. Here we present eye witness accounts and quantitative surveys of rapid, amphitheatre-headed gorge formation in unweathered granite from the overtopping of a rock-cut dam spillway by small-moderate floods (B100-1,500 m 3 s À 1 ). The amount of erosion demonstrates no relationship with flood magnitude or bedload availability. Instead, structural pattern of the bedrock through faults and joints appears to be the primary control on landscape change. These discontinuities facilitate rapid erosion (4270 m headward retreat; B100 m incision; and B160 m widening over 6 years) principally through fluvial plucking and block topple. The example demonstrates the potential for extremely rapid transient bedrock erosion even when rocks are mechanically strong and flood discharges are moderate. These observations are relevant to perceived models of gorge formation and knickpoint retreat.

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Section: Discussionmentioning

confidence: 99%

Exceptional river gorge formation from unexceptional floods

et al. 2015

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“…To test this hypothesis, as well as the potential of gravitational collapses of rock blocks on the cliff, we conducted a stability analysis on the cliff face by using a cantilever beam model that incorporates notch development beneath a cliff and associated stress distribution by rotational moment inside the cliff (Figure 4) [35][36][37][38][39]. The application of a cantilever beam model for waterfall cliff face has also been verified in the case of Niagara Falls [22]. In this model, the maximum bending stress σ max inside a cliff is given as where M is the bending moment and Z is the modulus of the section.…”

Section: Stability Analysis Model Of Undercut Cliffmentioning

confidence: 99%

“…However, for knickpoints with either vertical or degraded faces, shear stress of water flow, including gradual abrasion on the waterfall lip, is also an important factor in the erosion of waterfalls [9]. A model that includes this factor, even without considering undercut erosion, effec-tively explains the erosion rate of Niagara Falls [22]. A wide variety of waterfall erosion types has been documented for various waterfalls.…”

Section: Introductionmentioning

confidence: 99%

Stability Analysis of Cliff Face around Kegon Falls in Nikko, Eastern Japan: An Implication to Its Erosional Mechanisms

Hayakawa¹

2013

IJG

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A waterfall highlights the locus of active fluvial erosion of bedrock, and its mechanism has been the subject of several studies; however, erosional processes remain to be clarified for specific rock structures composing a waterfall. Herein, the detailed morphology of cliffs around a waterfall is examined by a terrestrial laser scanning (TLS) approach to analyze erosional processes occurring in the cliffs. The study site is Kegon Falls in Japan, which has a vertical drop of surface water from the top of its cliff and groundwater outflows from its lower portion. The entire cliff is mostly overhanging and minor rockfalls are often observed. The latest major rockfall occurred in 1986, causing an approximate 8-m upstream shift of the waterfall lip. From the point cloud obtained by TLS measurement, a digital elevation model on a vertical plane was generated, and cross-sectional profiles were extracted. A distinct 5-to 10-m depression was found at the bottom of the upper andesite layer of the waterfall cliff, which appears to have been formed by freeze-thaw and wet-dry weathering following the upstream shift of the surface water drop. Stability analysis of the waterfall cliff with an undercutting notch indicates that the igneous rock composing the cliff is sufficiently strong to maintain its current overhanging shape and that catastrophic collapse of the entire waterfall face rarely occurs. Following the formation of the depression, the upper cliff face appears to have been gradually eroded by gravitational collapses of relatively small blocks bounded by columnar and platy joints.

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“…El aumento de la distancia que retroceden los knickpoints con respecto al área de drenaje, estimado por el ajuste de la curva potencial, sugiere que la propagación puede darse en un rango amplio de cuencas (Figura 5 en Loget y van den Driessche, 2009). La velocidad del retroceso registrada es del orden de 10 -3 m/a (Hayakawa y Matsukura, 2003) hasta valores excepcionalmente altos de ~1 m/a para las cataratas del Niágara (Gilbert, 1907;Hayakawa y Matsukura, 2009). Los resultados obtenidos hasta el momento permiten confirmar que existe una deTabla 1.…”

Section: Modelos Empíricosunclassified

“…Otros mecanismos de formación resultan de procesos heredados en el relieve, como es el caso de la erosión glacial (e. g., von Engeln, 1940;Hayakawa y Matsukura, 2009).…”

Section: Introductionunclassified

Estado actual del conocimiento, clasificación y propuesta de inclusión del término knickpoint en el léxico geológico- geomorfológico del español

Castillo¹,

Lugo-Hubp²

2011

BSGM

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ResumenEl término knickpoint se utiliza comúnmente en geomorfología, principalmente en lengua inglesa, para denominar aquellas rupturas bruscas de la pendiente del lecho de un río a lo largo de su perfil longitudinal. Los knickpoints son expresión del desequilibrio de un sistema fluvial y pueden estar presentes tanto en ríos aluviales como en ríos en lecho rocoso. Los avances en geomorfología fluvial y evolución del paisaje indican que los knickpoints resultan de distintos procesos tectónicos, climáticos y geomorfológicos. No obstante, no existe hasta ahora una definición formal del término. El uso actual del concepto de knickpoint no proporciona información alguna sobre los mecanismos de su formación y por lo tanto, se refiere a la morfología del lecho fluvial. La acotación del término en español es necesaria, ya que éste ha sido utilizado, pero no ha sido definido de manera formal. En el presente estudio se hace una revisión del término y se realiza una clasificación de los knickpoints con base en un criterio genético, del cual se reconocen cinco tipos: glacial, litológico, tectónico, eustático y glacio-isostático (o glacioeustático). Se propone aquí la inclusión del término en el léxico geológico y geomorfológico del español, agregando un adjetivo calificativo que defina el origen.Palabras clave: knickpoint (punto de inflexión), desequilibrio, perfil longitudinal, sistema fluvial, ríos en lecho rocoso. Abstract The term knickpoint is commonly used in geomorphology to distinguish any abrupt change in the channel

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Factors influencing the recession rate of Niagara Falls since the 19th century

Cited by 24 publications

References 32 publications

Exceptional river gorge formation from unexceptional floods

Exceptional river gorge formation from unexceptional floods

Stability Analysis of Cliff Face around Kegon Falls in Nikko, Eastern Japan: An Implication to Its Erosional Mechanisms

Estado actual del conocimiento, clasificación y propuesta de inclusión del término knickpoint en el léxico geológico- geomorfológico del español

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