Treating causes not symptoms: restoration of surface - groundwater interactions in rivers

2009 ◽  
Vol 60 (9) ◽  
pp. 976 ◽  
Author(s):  
Tamao Kasahara ◽  
Thibault Datry ◽  
Michael Mutz ◽  
Andrew J. Boulton
Keyword(s):  
River Restoration ◽  
Fluvial Geomorphology ◽  
Hydraulic Gradient ◽  
River Ecosystem ◽  
Ecological Connectivity ◽  
Alluvial Rivers ◽  
Vertical Hydraulic Gradient ◽  
Groundwater Exchange ◽  
Sediment Permeability ◽  
Flushing Flows

Many river restoration projects seek to address issues associated with impaired hydrological and ecological connectivity in longitudinal (e.g. effects of dams, weirs) or lateral (e.g. alienated floodplain) dimensions. Efforts to restore the vertical dimension of impaired stream–groundwater exchange are rare, hampered by limited understanding of the factors controlling this linkage in natural alluvial rivers. We propose a simplified two-axis model of the ‘primary drivers’ (sediment structure and vertical hydraulic gradient) of stream–groundwater exchange that acknowledges their interaction and provides a practical template to help researchers and river managers pose hypothesis-driven solutions to restoration of damaged or lost vertical connectivity. Many human activities impact on one or both of these drivers, and we review some of the tools available for treating the causes (rather than symptoms) in impacted stream reaches. For example, creating riffle-pool sequences along stream reaches will enhance vertical hydraulic gradient, whereas flushing flows can remove clogging layers and sustain sediment permeability. Our model is a first step to specifying mechanisms for recovery of lost vertical connectivity. Assessing results of river restoration using this approach at reach to catchment scales will provide scientific insights into the interplay of hydrology, fluvial geomorphology and river ecosystem function at appropriately broad scales.

scholarly journals Fluvial Geomorphology and River Management

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1608
Author(s):  
Salvatore Ivo Giano
Keyword(s):  
Human Activities ◽  
River Restoration ◽  
Fluvial Geomorphology ◽  
Landscape Evolution ◽  
River Management ◽  
Special Issue ◽  
Fluvial Systems ◽  
The Impact

This Special Issue deals with the role of fluvial geomorphology in landscape evolution and the impact of human activities on fluvial systems, which require river restoration and management [...]

How environmental stress leads to alternative microbiota states in a river ecosystem: A new insight into river restoration

2021 ◽  
pp. 117538
Author(s):  
Jiahui Shang ◽  
Wenlong Zhang ◽  
Xinqi Chen ◽  
Yi Li ◽  
Lihua Niu ◽  
...  
Keyword(s):  
Environmental Stress ◽  
River Restoration ◽  
River Ecosystem ◽  
Insight Into

scholarly journals Flow and wake characteristics associated with large wood to inform river restoration

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Isabella Schalko ◽  
Ellen Wohl ◽  
Heidi M. Nepf
Keyword(s):  
Habitat Suitability ◽  
River Restoration ◽  
Recirculation Zone ◽  
Habitat Diversity ◽  
Turbulence Level ◽  
Large Wood ◽  
River Ecosystem ◽  
Mean Velocity ◽  
Physical Model Tests ◽  
Channel Center

AbstractWood is an integral part of a river ecosystem and the number of restoration projects using log placements is increasing. Physical model tests were used to explore how the wood position and submergence level (discharge) affect wake structure, and hence the resulting habitat. We observed a von-Kármán vortex street (VS) for emergent logs placed at the channel center, while no VS formed for submerged logs, because the flow entering the wake from above the log (sweeping flow) inhibited VS formation. As a result, emergent logs placed at the channel center resulted in ten times higher turbulent kinetic energy compared to submerged logs. In addition, both spatial variation in time-mean velocity and turbulence level increased with increasing log length and decreasing submergence level. Submerged logs and logs placed at the channel side created a greater velocity deficit and a longer recirculation zone, both of which can increase the residence time in the wake and deposition of organic matter and nutrients. The results demonstrate that variation in log size and degree of submergence can be used as a tool to vary habitat suitability for different fish preferences. To maximize habitat diversity in rivers, we suggest a diverse large wood placement.

Numerical and experimental study of the vertical distribution of velocity and hydraulic gradient in the capillary fringe

2021 ◽  
Author(s):  
Ali Mahdavi Mazdeh ◽  
Stefan Wohnlich
Keyword(s):  
Hydraulic Conductivity ◽  
Vertical Distribution ◽  
Water Content ◽  
Middle Part ◽  
Hydraulic Gradient ◽  
Upward Movement ◽  
Capillary Fringe ◽  
Gradient Profile ◽  
Vertical Hydraulic Gradient ◽  
The Vertical Distribution

<p>Capillary fringe plays an important role in the fate and transport of infiltrated solutes from agricultural lands. In this study, flow patterns and the vertical distribution of the velocity and hydraulic gradient inside the capillary fringe were investigated using FEFLOW calibrated by experimental data. An experimental box along with a real sample of capillary fringe from the study area (Sand and clay pit Brüggen, Germany) was used for the experiments. The dimension of the filled part of the box was 0.75 m long, 0.55 m high, and 0.150 m wide. To maintain a constant hydraulic gradient throughout the experiments the upstream and downstream groundwater levels were fixed to 7 cm and 3 cm, respectively. The horizontal velocity at different points inside the capillary fringe and the vadose zone was measured by injecting the fluorescent dye tracer (Uranin). At the end of the experiments, the soil samples are collected from different parts of the box for water content measurement. The results indicate that FEFLOW successfully estimates water content, overall flow pattern, and more importantly horizontal movement inside the capillary fringe. The streamlines are parallel to the groundwater table in the middle part.  Based on both experimental and numerical results, while there is a downward movement near the outflow, an upward movement was seen near the inflow. In previous studies, the velocity profile inside the capillary fringe was estimated using Darcy’s law, unsaturated hydraulic conductivity, and constant hydraulic gradient. The detailed comparison of measured water content and velocity with numerical modeling results showed that the constant hydraulic gradient assumption above the water table in previous studies is not valid. The vertical hydraulic gradient profile calculated by FEFLOW showed that the hydraulic gradient at the middle part of the box changes from 0.042 to 0.03. Moreover, the shape of the vertical hydraulic gradient profile is a function of the location in the box and soil type.</p><p><strong>Keywords: </strong>Solute transport, Unsaturated zone, Streamline, Pore velocity, Hydraulic conductivity, FEFLOW</p>

A Retrospective Benefit-Cost Analysis on the Elwha River Restoration Project

2019 ◽  
Vol 11 (1) ◽  
pp. 76-100
Author(s):  
Allen Bellas ◽  
Lea Kosnik
Keyword(s):  
Cost Analysis ◽  
River Restoration ◽  
River Ecosystem ◽  
Elwha River ◽  
Benefit Cost Analysis ◽  
Current State ◽  
Ex Post ◽  
Original Analysis ◽  
The Cost ◽  
Benefit Cost

AbstractIn 1992, Congress passed The Elwha River Ecosystem and Fisheries Restoration Act with the goal of “full restoration of The Elwha River Ecosystem and native anadromous fisheries.” As part of that act, the federal government was required to produce a benefit-cost analysis on dam removal of the Elwha and Glines Canyon dams, which was published in 1994. This article revisits that initial 1994 benefit-cost analysis; background on its methods and assumptions is given, comparisons are made to current state-of-the-art techniques in benefit-cost analysis, and an ex post benefit-cost analysis of the project is conducted for comparison purposes. We find that the cost and scope of the project exceeded original expectations, the cost of the foregone electricity generation was less than expected, and that anticipated recreational and fisheries benefits were both delayed, and lower, than expected. Furthermore, issues such as the value of hatchery-spawned versus wild anadromous fish seem not to have been anticipated in the original analysis, highlighting the fact that in doing an ex ante analysis, researchers must expect that unexpected factors may influence the ex post results of any project.

Running water: fluvial geomorphology and river restoration

2002 ◽  
pp. 133-152 ◽  
Author(s):  
Malcolm D. Newson ◽  
John Pitlick ◽  
David A. Sear
Keyword(s):  
River Restoration ◽  
Fluvial Geomorphology ◽  
Running Water
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