A conectividade de sedimentos pode ser entendida como a transferência de sedimentos entre diferentes compartimentos da paisagem através das relações entre seus componentes. Isso ocorre, principalmente, por meio da interação entre processos hidrológicos e sedimentológicos, os quais, por sua vez, são controlados por características geomorfológicas. O tema vem se tornando fundamental para o entendimento da dinâmica dos sedimentos em uma bacia hidrográfica, pois avalia a transferência dos sedimentos de maneira integrada e inovadora, considerando diferentes processos e características, diferindo das demais metodologias de estudo da dinâmica da paisagem. Consequentemente, muitas metodologias diferentes foram desenvolvidas em todo o mundo para avaliar a conectividade de maneira quantitativa e qualitativa. No entanto, entre esses estudos, diferentes terminologias foram adotadas. Grande parte das metodologias avalia a conectividade dos sedimentos a partir de aspectos estruturais (geomorfológicos) que distribuem no espaço as relações entre os componentes do sistema. Atualmente, são sugeridas abordagens utilizando aspectos funcionais (hidrológicos), que trazem dependência temporal para a conectividade. Entretanto, poucas metodologias inseriram as características do próprio sedimento nesta avaliação. Em relação aos estudos brasileiros, poucas investigações sobre conectividade foram realizadas, surgindo a necessidade de trabalhos considerando as características físicas das bacias brasileiras. A partir disso, a presente revisão discute, inicialmente, os diferentes conceitos de conectividade utilizados atualmente. Em seguida, resume e discute as metodologias desenvolvidas para avaliar a conectividade dos sedimentos, destacando as propriedades estruturais e funcionais relevantes para o estudo da conectividade. Adicionalmente, estudos de conectividade desenvolvidos em território brasileiro são apresentados. Conclui-se que, somente a partir de estudos que levem em conta a interação entre geomorfologia, hidrologia e sedimentologia, será possível uma avaliação integral da conectividade dos sedimentos. Ademais, a conectividade se apresenta como uma potencial ferramenta para o gerenciamento de bacias hidrográficas, trazendo avanços no entendimento da dinâmica dos sedimentos e, consequentemente, na evolução da paisagem.
<p>The hillslope-channel coupling has a fundamental role in sediment control of a catchment, especially when the catchment is prone to mass movements. Debris flow is a type of mass movements that provides an important sediment contribution to a channel, which is influenced by hillslope-channel coupling degree. This coupling can be represented by the connectivity, a concept utilized as an approach to many queries regarding water and/or sediment transport through methodologies which relates a river with its drainage area. In this regard, this study addresses the representation of debris flow in terms of connectivity. We applied a debris flow computational modelling (DFM) and an index of connectivity (IC) in Mascarada catchment, south Brazil, where hundreds of mass movements were triggered in 2017, to evaluate the potential, limitations and capacity of IC to represent patterns of mass movements&#8217; connectivity. The IC is calculated for each cell of the catchment&#8217;s digital elevation model (DEM) (horizontal resolution of 1 m) in relation to the drainage network. Therefore, the IC represents the lateral connectivity (hillslope-channel) and its capacity to mobilize sediment to the channel. The DFM utilizes the Multiple Flow Direction to distribute volumes of a fluid with a determined kinematic viscosity through a slope, originated from initiation areas with a depth pre-determined by the user. The model utilizes uniform and steady flow solutions for Newtonian fluid, considering a rectangular channel. The DFM simulated the observed debris flow reasonably well, with an accuracy of 68%. However, since the simulation reached the channel and carried the volumes beyond the observed debris flow scar, it presented an overestimation area of 65%. When relation the simulated debris flow paths with the IC, we observed a superposition between those paths and high IC values. Also, the results showed a pixel-by-pixel positive linear correlation between high flow depths (representing convergence of flow) and IC, with values varying from 0,1 and 0,5. Only one of the nine simulated debris flow did not reach the channel and it had the lowest mean IC value along its flow path. Simulated debris flow that reached the channel showed high hillslope-channel connectivity, denoting the important role of high magnitude sediment transport events in sediment connectivity. Therefore, the IC was capable to represent and indicate patterns of debris flow that reached the channel. Though, the results also indicated that IC must be carefully interpreted when employed to understand debris flow and related processes &#8211; some areas have high fluid depth due to low connectivity, but others have high depth in response of convergence of flow due to highly connected areas. In this regard, an integration of connectivity and debris flow modelling tools can by an important step to understand sediment connectivity and to represent patterns of high magnitude mass movements events.</p>
Hydrological and sedimentological dynamics are controlled by hillslope‐channel (de)coupling, which is influenced by several natural and anthropogenic factors. However, studies on sediment connectivity are recent and present numerous challenges to be overcome. Furthermore, there is a need to explore and identify sediment connectivity governing processes and phenomena. In this study, hydrological monitoring and indices application were used to access aspects of sediment connectivity in a small catchment (0.89 km2), located on a plateau in southern Brazil. The indices are a combination of variables conceptually known as controllers of the spatial and temporal organization of sediment flows in the system. The application of these tools proved to be relevant for the characterization of structural and functional connectivity of the study area. The tools applied were structural index of connectivity (IC); index of hydrosedimentological connectivity (IHC), based on observed events; field connectivity index (FIC). The characterization of structural connectivity highlighted natural sinks and blankets zones as the main elements of disconnection in the catchment. The functional connectivity was evaluated for five distinct magnitude events, the results showed a higher influence of sediment availability and antecedent moisture conditions than the other structural factors. The FIC validated the theoretical indices in the study area and highlighted the importance of coupling thresholds between the numerous sediment sources in a known event.
<p>Trails are one of the main places for ecotourism practitioners&#8217; activities. Many of them are located close to watercourses, and it is often necessary for practitioners to cross them. This often leads to dangerous situations, since critical conditions of water stages and flow velocity can make people lose their walking stability. One way to quantify these hazards is the hazard index (HI) which, in general, is defined as the product of the flow velocity by its depth (Stephenson, 2002). Although many studies have been carried out to determine the HI values as safety limits for people exposed to water flows, none of them analyzed the natural river conditions like those encountered during an ecotourism trail. In these environments, locomotion is hampered due to the surface which is usually highly irregular and often contains slippery rocks and sediments. Thus, that there is a gap related to the HI analysis in natural rivers, and more research becomes necessary, since more people have sought to carry out activities related to ecotourism. The main objective of this research is to apply HI approach in natural rivers so that its results can be utilized in the management of trails containing watercourses crossing. Initially, a bibliographic review was carried out, where some important concerns related to people's loss of stability were analyzed. The results of the bibliographic review were organized within a summary table which permits verifying variables with stronger influence on people's stability, during these walks. After this first stage, three mountain trails located in the Aparados da Serra National Park, in southern Brazil, were selected for field measurements. In all of these trails, measurements of flow depth and velocity were carried out using a small current meter and the granulometry of the river sediments was measured through an adaptation of the Pebble Count method. The measurements were taken at all points where tourists cross the riverbed during the trails, i.e., 23 measurement sites in total. The analysis of these data resulted in preliminar information: (i) an easy-to-interpret diagram that indicates the thresholds values of HI in natural rivers, named Hazard Index Diagram of Natural River (HIDNR); and (ii) list of the main variables responsible for people's loss of stability, in order to contribute to the safety of ecotourism practitioners. One of the next steps of the work is to analyze how the sediment transport and connectivity behaviour could give us insights about hazard levels.</p> <p>REFERENCES</p> <p>STEPHENSON, D. (2002). Integrated flood plain management strategy for the Vaal.&#160;Urban Water, v. 4, n. 4, p. 423-428.</p>
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.