scholarly journals Quantification of the morphodynamics and ecological functionality of a Mediterranean river

2018 ◽  
Vol 40 ◽  
pp. 02042
Author(s):  
Margot Chapuis ◽  
Amine Ait Elabas ◽  
Katia Souriguére ◽  
Franck Compagnon ◽  
Vincent Mayen ◽  
...  
Keyword(s):  
Potential Application ◽  
Morphological Evolution ◽  
River System ◽  
Ecological Indicators ◽  
River Systems ◽  
Restoration Project ◽  
Mediterranean River ◽  
Downstream Reach ◽  
Ecological Functionality ◽  
Points Of View

The Var River (South-East France) was extensively modified (channelization, dams…) on the 21th century and is currently undergoing an ambitious restoration project to restore its 'natural' active braiding pattern on the downstream reach of the river. As part of the feedback evaluation of the project, this study aims at: (1) quantifying the morphological evolution of the bed that is recovering from sediment discontinuity; (2) identifying and/or developing hydromorphological and ecological indicators which quantify improvement in the river system from hydrosedimentary and ecological points of view. We used LiDAR and orthophoto datasets and performed analyses for unchannelized braiding rivers [1, 2]. Active width (Wrestored = 242 ± 19 m vs. values ranging from 103 ± 53 to 163 ± 53 m for 'unrestored' reaches) and normalized bed relief index values (BRI*restored = 0,003 ± 0,001 vs. 0,003 ± 0,003 to 0,007 ± 0,004 for 'unrestored' reaches) indicate a combination of low roughness and wide active width. Thus the 'restored' reach shows a different set of indices compared to nearby 'unrestored' reaches, suggesting these tools are promising in discriminating 'restored' vs. 'unrestored' reaches. Adapting existing methods from 'natural' to 'channelized' braiding rivers widened the potential application of the tools developed by Lallias-Tacon [2] to modified braiding river systems.

Chutes and ladders and other games we play with rivers. II. Simulated effects of translocation on white sturgeon

2006 ◽  
Vol 63 (1) ◽  
pp. 176-185 ◽  
Author(s):  
Henriette I Jager
Keyword(s):  
Fish Species ◽  
Simulation Study ◽  
River System ◽  
Genetic Effects ◽  
White Sturgeon ◽  
Acipenser Transmontanus ◽  
River Systems ◽  
Short Segment ◽  
River Fragmentation ◽  
Demographic Effects

Restoring connectivity is viewed as an important recovery option for fish species adversely affected by river fragmentation. This simulation study quantified the genetic and demographic effects of translocation on metapopulations of white sturgeon (Acipenser transmontanus) inhabiting a series of long (source) and short (sink) river segments. Genetic effects were predictable; upstream translocations increased introgression and downstream translocations had no effect. Demographic results suggest that indiscriminant efforts to reconnect populations may do more harm than good. Simulated river systems with high interspersion of long and short segments and a long segment far upstream tended to benefit most from translocation, but only when narrow screening or downstream passage was also provided below the river segment receiving fish. When combined with narrow screening, upstream translocation to a long segment subsidizing several downstream short segments produced the best results. Downstream passage outperformed narrow screening only when the translocation recipient was a short segment in a river system with low interspersion and no long, upstream river segment. This model-based evaluation of reconnection options has helped to refine ideas about restoring populations in fragmented rivers by predicting which options benefit riverine metapopulations as a whole.

scholarly journals ĐẶC ĐIỂM HỆ THỐNG SÔNG CỔ VÀ TÁC ĐỘNG NHÂN SINH DỰA TRÊN KẾT QUẢ MÔ HÌNH TIẾN HÓA TỈ LỆ LỚN KHU VỰC CHÂU THỔ SÔNG HỒNG

2020 ◽  
Vol 19 (4) ◽  
pp. 463-478
Author(s):  
Mai Duc Dong ◽  
Phung Van Phach ◽  
Nguyen Trung Thanh ◽  
Duong Quoc Hung ◽  
Pham Quoc Hiep ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
River System ◽  
River Network ◽  
River Delta ◽  
Red River ◽  
River Systems ◽  
Red River Delta ◽  
The World ◽  
History Of

The Simclast model has been verified and applied effectively in simulating the delta development for some major deltas in the world. In this study, we applied the model Simclast for simulating the history of the Red river delta development in late Pleistocene-Holocene. Results of the model reveal that the mainland of study area had reduced rapidly during transgression period (10,000-8,000 BP). The morphology changed significantly in the paleo-Red and Day river systems, but slightly in the paleo Thai Binh river system. The paleo-river network had been active in upper part before 11,000 BP and then shifted seaward until 2,000 BP. The river-sea interaction causes erosion and accumulation; as a result the morphology changed remarkably. The paleo-Thai Binh river had been inactive until 5,500 BP and then it was active but the morphology had not varied remarkably. The recent coastline generated from Simclast is relatively in accordance with the present coastline.

scholarly journals Feedback Mechanism in Bifurcating River Systems: the Effect on Water-Level Sensitivity

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1915
Author(s):  
Matthijs R.A. Gensen ◽  
Jord J. Warmink ◽  
Fredrik Huthoff ◽  
Suzanne J.M.H. Hulscher
Keyword(s):  
Water Level ◽  
Flood Risk ◽  
River System ◽  
Feedback Mechanism ◽  
Water Levels ◽  
River Systems ◽  
Water Level Variations ◽  
System Water ◽  
Discharge Distribution ◽  
Single Branch

Accurate and reliable estimates of water levels are essential to assess flood risk in river systems. In current practice, uncertainties involved and the sensitivity of water levels to these uncertainties are studied in single-branch rivers, while many rivers in deltas consist of multiple distributaries. In a bifurcating river, a feedback mechanism exists between the downstream water levels and the discharge distribution at the bifurcation. This paper aims to quantify the sensitivity of water levels to main channel roughness in a bifurcating river system. Water levels are modelled for various roughness scenarios under a wide range of discharge conditions using a one-dimensional hydraulic model. The results show that the feedback mechanism reduces the sensitivity of water levels to local changes of roughness in comparison to the single-branch river. However, in the smaller branches of the system, water-level variations induced by the changes in discharge distribution can exceed the water-level variations of the single-branch river. Therefore, water levels throughout the entire system are dominated by the conditions in the largest branch. As the feedback mechanism is important, the river system should be considered as one interconnected system in river maintenance of rivers, flood-risk analyses, and future planning of river engineering works.

scholarly journals Centering the Korle Lagoon: exploring blue political ecologies of E-Waste in Ghana

2019 ◽  
Vol 26 (1) ◽  
pp. 448
Author(s):  
Peter C Little ◽  
Grace Abena Akese
Keyword(s):  
Political Ecology ◽  
Ecological Restoration ◽  
Social Life ◽  
Flood Control ◽  
Risk Mitigation ◽  
Dominant Role ◽  
River System ◽  
Toxic Waste ◽  
Restoration Project ◽  
Political Ecologies

<p>Among emerging studies of the global political economy and ecology of electronic waste (or e-waste), few directly explore the already complex waste trades and materialities in relation to the general political ecology of water, flood control, dredging, and neoliberal ecological restoration. Even fewer focus on how this political-ecological challenge is unfolding in a West African context where ocean-based e-waste trades have played a dominant role. This article engages this particular domain of blue economic critique by focusing on Ghana in general and what we shall call "blue political ecologies of e-waste" in particular. The article focuses on e-waste politics unfolding in and around the Korle Lagoon in Accra, Ghana. The Korle Lagoon is an urban marine space of intensive land use, toxic waste disposal, social life, and urban ecological restoration. Amidst heavy contamination, there are attempts to rehabilitate the lagoon through the Korle Lagoon Ecological Restoration Project, an ecological science and restoration project focused on the Lagoon and its river system in the metropolitan area of Accra. It showcases the neoliberal complexities of ecological restoration. Importantly, situated in a multi-use marine environment, the project also highlights, we argue, a political ecological moment that is both about things 'blue', like water quality concerns, but also about other things non-blue such as contestation over land and housing, 'green' international NGO intervention on e-waste risk mitigation, and desires for new urban ecologies. Drawing on ethnographic research conducted between 2015 and 2018, this article contributes to blue political-ecological research and critique in Africa by asking: how do e-waste politics leak into discussions of the blue economy along the Korle Lagoon in Ghana? What are the promises and prospects of a blue political ecology of e-waste in general, and in Africa in particular?</p><strong>Key Words</strong>: Political ecology, Ghana, e-waste, lagoon contamination, ecological restoration

scholarly journals Long-chain diols in rivers: distribution and potential biological sources

2018 ◽  
Vol 15 (13) ◽  
pp. 4147-4161 ◽  
Author(s):  
Julie Lattaud ◽  
Frédérique Kirkels ◽  
Francien Peterse ◽  
Chantal V. Freymond ◽  
Timothy I. Eglinton ◽  
...  
Keyword(s):  
River Flow ◽  
River System ◽  
18S Rrna Gene ◽  
Rrna Gene ◽  
River Systems ◽  
Eukaryotic Diversity ◽  
Fractional Abundance ◽  
Biological Sources ◽  
Rrna Gene Sequencing ◽  
Long Chain

Abstract. Long-chain diols (LCDs) occur widespread in marine environments and also in lakes and rivers. Transport of LCDs from rivers may impact the distribution of LCDs in coastal environments, however relatively little is known about the distribution and biological sources of LCDs in river systems. In this study, we investigated the distribution of LCDs in suspended particulate matter (SPM) of three river systems (Godavari, Danube, and Rhine) in relation with precipitation, temperature, and source catchments. The dominant long-chain diol is the C32 1,15-diol followed by the C30 1,15-diol in all studied river systems. In regions influenced by marine waters, such as delta systems, the fractional abundance of the C30 1,15-diol is substantially higher than in the river itself, suggesting different LCD producers in marine and freshwater environments. A change in the LCD distribution along the downstream transects of the rivers studied was not observed. However, an effect of river flow is observed; i.e., the concentration of the C32 1,15-diol is higher in stagnant waters such as reservoirs and during seasons with river low stands. A seasonal change in the LCD distribution was observed in the Rhine, likely due to a change in the producers. Eukaryotic diversity analysis by 18S rRNA gene sequencing of SPM from the Rhine showed extremely low abundances of sequences (i.e., < 0.32 % of total reads) related to known algal LCD producers. Furthermore, incubation of the river water with 13C-labeled bicarbonate did not result in 13C incorporation into LCDs. This indicates that the LCDs present are mainly of fossil origin in the fast-flowing part of the Rhine. Overall, our results suggest that the LCD producers in rivers predominantly reside in lakes or side ponds that are part of the river system.

scholarly journals A Billion Years of History within the Grevena-Deskati Watershed

2019 ◽  
Vol 54 (1) ◽  
pp. 20 ◽  
Author(s):  
Dina Ghikas ◽  
Anne Ewing Rassios
Keyword(s):  
River Basin ◽  
River System ◽  
Climatic Conditions ◽  
Geologic History ◽  
River Systems ◽  
High Quality ◽  
River Flows ◽  
Rock Types ◽  
Tectonic Events ◽  
Selection Of

The river system of West Macedonia comprises the headwaters and western extent of the Aliakmon watershed.  This region has a unique and highly complex geologic history (Rassios, 2008; Rassios, 2011), many aspects of which can be inferred by examining conglomerate (river-cobble) formations in the region.  These formations contain all rock types found within the modern-day river basin, as well as some which are not found within today's basin.  River-deposited sediments and cobbles found along today’s Aliakmon and Venetikos River systems trace the courses of ancient river flows, and thus provide information about past climatic conditions and tectonic events.  The sediments making up conglomerate formations in the region are mature, containing cobbles which have been transported, consolidated, eroded and redeposited up to five times (Rassios and Grivas, 1998).  This recycling of cobbles leaves only the most durable rocks while softer rocks are destroyed via abrasion.  Prehistoric peoples availed themselves of this concentrated and convenient selection of high-quality stones for the purpose of fashioning tools and weapons.

scholarly journals The potential of small mountain river systems for paleoenvironmental reconstructions in drylands - An example from the Binaloud Mountains in northeastern Iran

2021 ◽  
Author(s):  
Azra Khosravichenar ◽  
Morteza Fattahi ◽  
Hamideh Amini ◽  
Hans von Suchodoletz
Keyword(s):  
River System ◽  
Large River ◽  
Alluvial Fan ◽  
Small Rivers ◽  
River Systems ◽  
Mountain Ranges ◽  
Geomorphological Mapping ◽  
Fluvial Dynamics ◽  
Local Tectonics ◽  
Numerical Dating

&lt;p&gt;Fluvial sediments are valuable paleoenvironmental archives of the Quaternary. Since besides environmental factors they are also affected by local tectonics or intrinsic processes, large instead of small catchments should be studied. In drylands covering ca. 45% of the global terrestrial surface large river systems are generally missing, and most river systems are small rivers originating from mountain ranges. Their sediments are potentially interesting paleoenvironmental archives, but are often affected by intensive tectonics. During this study, to obtain a robust regional paleoenvironmental signal a small river system in the southwestern Binaloud Mountains in semi-arid NE Iran was exemplarily studied with a combined approach that encompassed both alluvial fan and catchment. By using geomorphological mapping and numerical dating, fluvial aggradation followed by incision was independently identified in larger areas or in different parts of the river system ca. 95&amp;#8211;88 ka, 40 ka, 20 ka, around/after the Pleistocene/Holocene transition and possibly ca. 2.6 ka. These could be linked with regional and over-regional paleoenvironmental data. Furthermore, large boulders on the alluvial fan suggest anthropogenic destabilisation of the catchment during the last decades. Despite strong local tectonics the fluvial dynamics was mostly controlled by paleoenvironmental changes and human activity. This indicates that despite their small size, such river systems form valuable paleoenvironmental archives in drylands where other archive types are largely missing.&amp;#160;&lt;/p&gt;

Duplication

2003 ◽  
Author(s):  
Mary Jane West-Eberhard
Keyword(s):  
Twentieth Century ◽  
Morphological Evolution ◽  
Life Stage ◽  
Divergent Evolution ◽  
Regulatory Change ◽  
Major Theme ◽  
Developmental Processes ◽  
Early Twentieth Century ◽  
Expression Of Genes ◽  
Points Of View

Duplication occurs at all levels of phenotypic organization. It was among the first developmental phenomena to attract the attention of biologists interested in phenotypic transitions during evolution. Duplication and repetition of similar segments, or metamerism, appeared in the writings of Aristotle, Cuvier, Owen, and Darwin, and many early twentieth-century authors discussed it (reviewed in Lauder, 1981). More recently it has become a major theme in discussions of genetic diversification (e.g., Ohno, 1970; Weiss, 1990). Nijhout (1991a) considers iteration or redundancy of parts followed by divergence of the replicates “the major principle of morphological evolution.” But it is not easy to rank modes of origin in order of their importance, because it is so easy to reclassify examples from different points of view. Just as heterochrony can be emphasized by focusing on the timing aspect of any regulatory change (as discussed in chapter 13), duplication can be emphasized by focusing on the iterative aspect of repeated expression at different times, places, or contexts. Phenotypic recombinations classified in these chapters as heterotopy, heterochrony, cross-sex transfers, or correlated shifts could be reclassified as duplications, since many are reexpressions of the same trait in a new place or context without loss of the original trait. Similarly, pleiotropy can be described as the duplicated expression of genes (Hamburger, 1980). This chapter focuses mainly on adjacent duplications that result in serial repetitions—serial homologues, or “iteration” (Nijhout, 1991a). Heterotopy, or nonadjacent duplication within the same individual and life stage, is discussed in chapter 14, even though the separation is somewhat arbitrary. The differences in position and surroundings that result in differences in phenotypic pattern are, in their effects, regulatory differences, and it is just such local differences that cause developmental processes to diverge. It is a difference in regulation, then, that causes duplicates to diverge phenotypically and ultimately renders them subject to diverging selection and divergent evolution. One could reason from this that divergence between duplicates is virtually inevitable given enough time, because the local developmental environments on all sides of duplicate parts would rarely be absolutely identical over long periods.

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