scholarly journals Development of an automated desktop procedure for defining macro-reaches for river longitudinal profiles

Water SA ◽  
2007 ◽  
Vol 32 (3) ◽  
Author(s):  
LH Dollar ◽  
ESJ Dollar ◽  
J Moolman
2020 ◽  
Vol 90 (11) ◽  
pp. 1581-1600
Author(s):  
Luke A. Pettinga ◽  
Zane R. Jobe

ABSTRACT Submarine landscapes, like their terrestrial counterparts, are sculpted by autogenic sedimentary processes toward morphologies at equilibrium with their allogenic controls. While submarine channels and nearby, inter-channel continental-margin areas share boundary conditions (e.g., terrestrial sediment supply, tectonic deformation), there are significant differences between the style, recurrence, and magnitude of their respective autogenic sedimentary processes. We predict that these process-based differences affect the rates of geomorphic change and equilibrium (i.e., graded) morphologies of submarine-channel and continental-margin longitudinal profiles. To gain insight into this proposed relationship, we document, classify (using machine learning), and analyze longitudinal profiles from 50 siliciclastic continental margins and associated submarine channels which represent a range of sediment-supply regimes and tectonic settings. These profiles tend to evolve toward smooth, lower-gradient longitudinal profiles, and we created a “smoothness” metric as a proxy for the relative maturity of these profiles toward the idealized equilibrium profile. Generally, higher smoothness values occur in systems with larger sediment supply, and the smoothness of channels typically exceeds that of the associated continental margin. We propose that the high rates of erosion, bypass, and deposition via sediment gravity flows act to smooth and mature channel profiles more rapidly than the surrounding continental margin, which is dominated by less-energetic diffusive sedimentary processes. Additionally, tectonic deformation will act to reduce the smoothness of these longitudinal profiles. Importantly, the relationship between total sediment supply and the difference between smoothness values of associated continental margins and submarine channels (the “smoothness Δ”) follows separate trends in passive and active tectonic settings, which we attribute to the variability in relative rates of smoothness development between channelized and inter-channel environments in the presence or absence of tectonic deformation. We propose two endmember pathways by which continental margins and submarine channels coevolve towards their respective equilibrium profiles with increased sediment supply: 1) Coupled Evolution Model (common in passive tectonic settings), in which the smoothness Δ increases only slightly before remaining static, and 2) Decoupled Evolution Model (common in active tectonic settings), in which the smoothness Δ increases more rapidly and to a greater final value. Our analysis indicates that the interaction of the allogenic factors of sediment supply and tectonic deformation with the autogenic sedimentary processes characteristic of channelized and inter-channel areas of the continental margin may account for much of the variability between coevolution pathways and depositional architectures.


2020 ◽  
Vol 14 (02) ◽  
pp. 71-92
Author(s):  
Adriana cassiano Silva ◽  
Osvaldo Girão da Silva

Os estilos fluviais refletem a fisiografia estrutural da rede de drenagem controladas pelos estratos rochosos, retratando na paisagem sua dinâmica, assim como os padrões de canais, que podem ser alterados por processos geomorfológicos, climáticos e antrópicos. O quadro dos estilos fluvial fornece um modelo geomorfológico dos processos espaciais e temporais biofísicos para gestão e planejamento das bacias hidrográficas. O presente trabalho teve como objetivo analisar as influências do comportamento no canal da bacia do rio Una localizado no Nordeste do Estado de Pernambuco, a partir da investigação das feições da drenagem como reflexo da transferência de matéria e energia entre distintos compartimentos e setores do ambiente fluvial.  A metodologia proporcionou uma visão geral de toda área analisada, a partir da avaliação do índice de sinuosidade, mapeamento dos estilos e das feições fluviais, perfis longitudinais e trabalhos de observação em campo. Assim, constatou-se que a influência estrutural na rede de drenagem da referida bacia comandou a retilineidade do canal Una, com quebra no gradiente topográfico, inflexão do canal e vales encaixados. Nesse ambiente, verificou-se que a produção e deposição dos sedimentos estão vinculados as influências do clima tropical. Palavras-Chave: Feição Fluvial; Estrutura; Instabilidade; Deposição de Sedimentos.   ANALYSIS OF PATTERNS AND CHANNEL STYLE FROM THE LANDSCAPE GEOMORPHOLOGICAL FLUVIAL IN RIVER BASIN UNA/ PE Abstract The river styles reflect the structural physiography drainage network controlled by the rock strata, depicting the landscape dynamics, as well as channel patterns, which can be changed by geomorphological, climatic and anthropogenic processes. The fluvial styles of the table provides a geomorphological model of spatial processes and biophysical time for planning and management of river basins. This study aimed to analyze the influence of behavior on the channel of the river basin Una located in the northeastern state of Pernambuco, from the investigation of drainage features reflecting the transfer of matter and energy between different compartments and sections of the river environment. The methodology provided an overview of the whole analyzed area, from the evaluation of the sinuosity index, mapping styles and river features, longitudinal profiles and field observation work. Thus, it was found that the structural influence on the basin drainage network commanded the straightness of Una channel, breaking the topographic gradient, channel inflection and enclosed valleys. In this environment, it found that the production and deposition of sediments are bound influences the tropical climate. Keywords: Fluvial feature, structure, Instability, Deposition of Sediments.   ANÁLISIS DE PATRONES Y CANALES DE ESTILOS DE PAISAJE DEL RÍO GEOMORFOLÓGICO EN UNA DE CUENCA / PE Resumen Los estilos de los ríos reflejan la red estructural de drenaje fisiografía controlado por los estratos de roca, que representa la dinámica del paisaje, así como los patrones de canal, que puede ser cambiado por procesos geomorfológicos, climáticos y antropogénicos. Los estilos fluviales de la tabla proporciona un modelo geomorfológico de los procesos espaciales y el tiempo biofísico para la planificación y gestión de las cuencas hidrográficas. Este estudio tuvo como objetivo analizar la influencia del comportamiento en el canal de la cuenca del río Una ubicada en el nororiental estado de Pernambuco, a cercar de la investigación de las características de drenaje que refleja la transferencia de materia y energía entre los distintos compartimentos y secciones del entorno del río. La metodología proporciona una visión general de toda la zona analizada, de la evaluación del índice de sinuosidad, la cartografía de estilos y características de ríos, perfiles longitudinales y trabajos de observación de campo. Por lo tanto, se encontró que la influencia estructural en la red de drenaje cuenca mandó la rectitud de canal Una, rompiendo el gradiente topográfico, la inflexión del canal y valles cerrados. En este entorno, se encontró que la producción y deposición de sedimentos están obligados influencias del clima tropical. Palabras clave: río de funciones; la estrutura; la inestabilidad; la deposición de sedimentos.


2001 ◽  
Vol 13 (7) ◽  
pp. 892-909 ◽  
Author(s):  
Peter Garrard ◽  
Matthew A. Lambon Ralph ◽  
Peter C. Watson ◽  
Jane Powis ◽  
Karalyn Patterson ◽  
...  

Two types of theoretical account have been proposed to explain the phenomenon of category-specific impairment in tests of semantic memory: One stresses the importance of different cortical regions to the representation of living and nonliving categories, while the other emphasize the importance of statistical relationships among features of concepts belonging to these two broad semantic domains. Theories of the latter kind predict that the direction of a domain advantage will be determined in large part by the overall damage to the semantic system, and that the profiles of patients with progressive impairments of semantic memory are likely to include a point at which an advantage for one domain changes to an advantage for the other. The present series of three studies employed semantic test data from two separate cohorts of patients with probable dementia of Alzheimer's type (DAT) to look for evidence of such a crossover. In the first study, longitudinal test scores from a cohort of 58 patients were examined to confirm the presence of progressive semantic deterioration in this group. In the second study, Kaplan-Meier survival curves based on serial naming responses and plotted separately for items belonging to living and nonliving domains indicated that the representations of living concepts (as measured by naming) deteriorated at a consistently and significantly faster rate than those of nonliving concepts. A third study, carried out to look in detail at the performance of mildly affected patients, employed an additional cross-sectional cohort of 20 patients with mild DAT and utilized a graded naming assessment. This study also revealed no evidence for a crossover in the advantage of one domain over the other as a function of disease severity. Taken together with the model of anatomical progression in DAT based on the work of Braak and Braak (1991), these findings are interpreted as evidence for the importance of regional cerebral anatomy to the genesis of semantic domain effects in DAT.


Geosphere ◽  
2011 ◽  
Vol 7 (2) ◽  
pp. 313-332 ◽  
Author(s):  
J. A. Covault ◽  
A. Fildani ◽  
B. W. Romans ◽  
T. McHargue

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