Changes, perturbations, and responses in geomorphic systems

Phillips, Jonathan D.

doi:10.1177/0309133309103889

Cited by 129 publications

(112 citation statements)

References 44 publications

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“…For example, presented a qualitative conceptual model of landscape evolution in terms of improbable system states, arguing that although deterministic process "laws" act on topography, the actual outcome (i.e., any particular landscape) depends on initial conditions and in particular is sensitive to history. Many other works have similarly generalized complex channel process and response feedbacks to understand morphodynamics (e.g., Fonstad, 2003;Phillips, 2011Phillips, , 2009Phillips, , 1991Chin and Phillips, 2007;Stark and Stark, 2001;Yanites and Tucker, 2010).…”

Section: State Variable Framework For Modeling Morphodynamicsmentioning

confidence: 99%

Gravel threshold of motion: a state function of sediment transport disequilibrium?

Johnson

2016

Earth Surf. Dynam.

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Abstract. In most sediment transport models, a threshold variable dictates the shear stress at which nonnegligible bedload transport begins. Previous work has demonstrated that nondimensional transport thresholds (τ * c ) vary with many factors related not only to grain size and shape, but also with characteristics of the local bed surface and sediment transport rate (q s ). I propose a new model in which q s -dependent τ * c , notated as τ * c(q s ) , evolves as a power-law function of net erosion or deposition. In the model, net entrainment is assumed to progressively remove more mobile particles while leaving behind more stable grains, gradually increasing τ * c(q s ) and reducing transport rates. Net deposition tends to fill in topographic lows, progressively leading to less stable distributions of surface grains, decreasing τ * c(q s ) and increasing transport rates. Model parameters are calibrated based on laboratory flume experiments that explore transport disequilibrium. The τ * c(q s ) equation is then incorporated into a simple morphodynamic model. The evolution of τ * c(q s ) is a negative feedback on morphologic change, while also allowing reaches to equilibrate to sediment supply at different slopes. Finally, τ * c(q s ) is interpreted to be an important but nonunique state variable for morphodynamics, in a manner consistent with state variables such as temperature in thermodynamics.

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Section: State Variable Framework For Modeling Morphodynamicsmentioning

confidence: 99%

Gravel threshold of motion: a state function of sediment transport disequilibrium?

Johnson

2016

Earth Surf. Dynam.

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“…Os trabalhos pioneiros de Brunsden e Thornes (1979);Brunsden (1993;1996;Phillips (2009);Fryirs et al, (2009);Souza (2014); Souza et al, (2014) e Souza e Corrêa (2012;2015), forneceram as bases conceituais e de aplicação desse método, permitindo a realização de diagnósticos para o planejamento ambiental e ecossistemas fluviais.…”

Section: Introductionunclassified

Sensitividade Fluvial Da Drenagem Principal Da Bacia Hidrográfica Do Rio Sagrado - Serra Do Mar Paranaense

Kleina

Santos

2017

Revista Ra'e Ga

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RESUMOA sensitividade fluvial permite reconhecer pontos sujeitos às mudanças na rede de drenagem, identificadas por meio das forças de resistência (capacidade do sistema em resistir a uma alteração do estado inicial) e perturbação (aplicações de energias, como clima, interferências bióticas e antrópicas). Diante do exposto, o presente trabalho tem como objetivo determinar a sensitividade fluvial nas principais drenagens que compõem a bacia hidrográfica do rio Sagrado, localizada em Morretes, na Serra do Mar paranaense. Para obtenção dos resultados, tornou-se necessária a identificação dos estilos e ajustes fluviais, concentração de erosão, conectividade fluvial e evolução da ocupação da terra na bacia. Os dados foram sobrepostos e analisados, evidenciando que as maiores perturbações foram localizadas nos rios Sagrado e Sambaqui, principalmente próximas às planícies, classificadas como alta sensitividade. Diferentemente, rios margeados pelas altas declividades da Serra do Mar, recobertos por vegetação em estágio médio/avançado, situam-se locais com pouca probabilidade de mudanças, sendo denominadas como baixa sensitividade. Assim conclui-se que os terços de rios localizados em planícies possuem poucas resistências e muitas alterações no uso da terra, enquanto que nas altas declividades, em vales fluviais confinados e parcialmente confinados, a sensitividade apresenta-se baixa. PALAVRAS-CHAVE:Resistências; Perturbações; Mudanças; Sistema fluvial. ABSTRACTThe fluvial sensitivity allows to recognize points subject to changes in the drainage network, identified by the resistance forces (ability of the system to withstand a change of the initial state) and disturbance (energy applications such as climate, biotic and anthropic interference). Thus, the research's objective is to map the fluvial sensitivity in the major rivers that compose the Sagrado River watershed, located in Morretes, Serra do Mar, Paraná State. In order to obtain the results, it was necessary to identify the style and fluvial adjustments, erosion concentration, fluvial connectivity and land use evolution in the basin. The data were overlapped and confronted, evidencing that the major disturbances were located in Sagrado and Sambaqui rivers, especially near the plains areas, classified as high sensitivity. In contrast, rivers bordered by high slopes of the Serra do Mar, covered with vegetation in medium/advanced stage, are situated places of probability of minor changes, being named as low sensitivity. So it is concluded that thirds of rivers located in plains have low resistance and a lot of changes in land use, whereas in high declivity, in confined and partially confined fluvial valleys, the sensitivity appears low.

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“…Feedback process analysis is a valuable tool in this respect. Phillips (2009) proposed '4Rs' (recursion, response, resilience, resistance) as a theoretical framework to understand change in geomorphic systems by identifying potential feedbacks, determining their signs, and assessing their relative importance. Lane (2013), by analogy with lessons learned from climate modelling, argued that in geomorphology there is the need for a great number of feedbacks to be identified and appreciated.…”

Section: Introductionmentioning

confidence: 99%

Feedback structure of cliff and shore platform morphodynamics

Payo

Dickson

Walkden³

2014

J Coast Conserv

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It has been suggested that studies of geomorphological systems should identify potential system feedbacks, determine their direction of influence, and assess their relative importance. In this paper we show how a core set of processes and feedback loops can be distilled from existing literature on rock coast morphodynamics. The structure has been represented using Causal Loop Diagrams and a methodology to estimate the strength of a single feedback loop is presented. The backwearing erosion rate (cliff horizontal erosion) has been found to be controlled by at least four feedback loops; three balancing (cliff toe wave energy depletion, ground-water pore pressure diminution and cliff deposit protection) and one positive loop (abrasion enhancement). The downwearing erosion rate (vertical erosion) has been found to be controlled by at least three balancing feedback loops (weathering limited, shear depletion, cover-protection). Mean sea level directly influences the downwearing rate, through the water depth relative to the wave base, and indirectly influences the backwearing erosion rate through the wave energy dissipation that determines the amount of energy reaching the cliff toe. The offshore wave non-linearity parameter is proposed to capture the complex interaction between waves and shore platform geometries. The strength of the cliff toe energy depletion loop is assessed by reasoning on its causal pathway and found to be O(−10 −10 to −10 −4 ) for poorly lithified rock coasts. By understanding how the individual and overall feedback strengths are influenced by different future environmental and human intervention scenarios we could provide better assessment at the time scales needed for coastal management.

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Changes, perturbations, and responses in geomorphic systems

Cited by 129 publications

References 44 publications

Gravel threshold of motion: a state function of sediment transport disequilibrium?

Gravel threshold of motion: a state function of sediment transport disequilibrium?

Sensitividade Fluvial Da Drenagem Principal Da Bacia Hidrográfica Do Rio Sagrado - Serra Do Mar Paranaense

Feedback structure of cliff and shore platform morphodynamics

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