scholarly journals Widespread dieback of riparian trees on a dammed ephemeral river and evidence of local mitigation by tributary flows

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2622 ◽  
Author(s):  
Caitlin M. S. Douglas ◽  
Mark Mulligan ◽  
Xavier A. Harrison ◽  
Joh R. Henschel ◽  
Nathalie Pettorelli ◽  
...  
Keyword(s):  
Channel Flow ◽  
River Flow ◽  
Main Channel ◽  
Riparian Trees ◽  
Ephemeral Rivers ◽  
Riparian Tree ◽  
Tree Dieback ◽  
Anthropogenic Threats ◽  
Individual Trees ◽  
Key Resources

Ephemeral rivers act as linear oases in drylands providing key resources to people and wildlife. However, not much is known about these rivers’ sensitivities to human activities. We investigated the landscape-level determinants of riparian tree dieback along the Swakop River, a dammed ephemeral river in Namibia, focusing on the native ana tree (Faidherbia albida) and the invasive mesquite (Prosopisspp.). We surveyed over 1,900 individual trees distributed across 24 sites along a 250 km stretch of the river. General linear mixed models were used to test five hypotheses relating to three anthropogenic threats: river flow disruption from damming, human settlement and invasive species. We found widespread dieback in both tree populations: 51% mortality in ana tree, with surviving trees exhibiting 18% canopy death (median); and 26% mortality in mesquite, with surviving trees exhibiting 10% canopy death. Dieback in the ana tree was most severe where trees grew on drier stretches of the river, where tributary flow was absent and where mesquite grew more abundantly. Dieback in the mesquite, a more drought-tolerant taxon, did not show any such patterns. Our findings suggest that dieback in the ana tree is primarily driven by changes in river flow resulting from upstream dam creation and that tributary flows provide a local buffer against this loss of main channel flow. The hypothesis that the invasive mesquite may contribute to ana tree dieback was also supported. Our findings suggest that large dams along the main channels of ephemeral rivers have the ability to cause widespread mortality in downstream riparian trees. To mitigate such impacts, management might focus on the maintenance of natural tributary flows to buffer local tree populations from the disruption to main channel flow.

Riparian tree fall directionality and modeling large wood recruitment to streams

2006 ◽  
Vol 36 (5) ◽  
pp. 1243-1254 ◽  
Author(s):  
Daniel J Sobota ◽  
Stanley V Gregory ◽  
John Van Sickle
Keyword(s):  
Pacific Northwest ◽  
Field Data ◽  
Riparian Forest ◽  
Large Wood ◽  
Riparian Trees ◽  
The Pacific ◽  
Riparian Tree ◽  
Individual Trees ◽  
Fall Direction ◽  
Recruitment Model

Directionality of tree fall in riparian forests can strongly influence predictions of large wood recruitment to streams, yet accuracy of this model parameter has rarely been assessed with field data. We measured fall directions of 1202 riparian trees distributed among 21 stream sites across the Pacific Northwest, USA. Fall directions were oriented towards the stream at 16 sites, upstream at four sites, and not distinguishable from random at one site. Average tree fall direction across sites was correlated with valley constraint (Spearman r = –0.53; p = 0.02), but variability of fall directions was not correlated with this variable. When grouped by species (six conifers and one deciduous), individual trees exhibited stronger tendency to have fallen towards the channel on steep hillslopes (>40%) than on moderately sloped landforms (<40%). Integration of field data into an established recruitment model indicated that 1.5 to 2.4 times more large wood (by number of tree boles) would be recruited to stream reaches with steep hillslopes than to reaches with moderate side slopes or flat banks, if riparian forest conditions are assumed to be constant. We conclude that stream valley topography should be considered in models that use tree fall directions in predictions of large wood recruitment to streams.

scholarly journals Hydraulic Evaluation of the Levee System Evolution on the Kurobe Alluvial Fan in the 18th and 19th Centuries

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4406
Author(s):  
Tadaharu Ishikawa ◽  
Hiroshi Senoo
Keyword(s):  
Channel Capacity ◽  
Flood Control ◽  
River Flow ◽  
Global Climate ◽  
Flow Simulation ◽  
Japan Sea ◽  
Main Channel ◽  
Alluvial Fan ◽  
Flood Peak ◽  
Levee System

The development process and flood control effects of the open-levee system, which was constructed from the mid-18th to the mid-19th centuries, on the Kurobe Alluvial Fan—a large alluvial fan located on the Japan Sea Coast of Japan’s main island—was evaluated using numerical flow simulation. The topography for the numerical simulation was determined from an old pictorial map in the 18th century and various maps after the 19th century, and the return period of the flood hydrograph was determined to be 10 years judging from the level of civil engineering of those days. The numerical results suggested the followings: The levees at the first stage were made to block the dominant divergent streams to gather the river flows together efficiently; by the completed open-levee system, excess river flow over the main channel capacity was discharged through upstream levee openings to old stream courses which were used as temporary floodways, and after the flood peak, a part of the flooded water returned to the main channel through the downstream levee openings. It is considered that the ideas of civil engineers of those days to control the floods exceeding river channel capacity, embodied in their levee arrangement, will give us hints on how to control the extraordinary floods that we should face in the near future when the scale of storms will increase due to the global climate change.

Land water linkages: influences of riparian deforestation on lake thermocline depth and possible consequences for cold stenotherms

1997 ◽  
Vol 54 (6) ◽  
pp. 1299-1305 ◽  
Author(s):  
Robert France
Keyword(s):  
Thermal Stratification ◽  
Lake Trout ◽  
Salvelinus Namaycush ◽  
Thermocline Depth ◽  
Experimental Lakes Area ◽  
Northwestern Ontario ◽  
Riparian Trees ◽  
Tree Removal ◽  
Riparian Tree ◽  
Land Water

The purpose of the present study was to determine if riparian deforestation would expose lake surfaces to stronger winds and therefore bring about deepening of thermoclines and resulting habitat losses for cold stenotherms such as lake trout (Salvelinus namaycush). Removal of protective riparian trees through wind blowdown and two wildfires was found to triple the overwater windspeeds and produce thermocline deepening in two lakes at the Experimental Lakes Area. A survey of thermal stratification patterns in 63 northwestern Ontario lakes showed that lakes around which riparian trees had been removed a decade before through either clearcutting or by a wildfire were found to have thermocline depths over 2 m deeper per unit fetch length compared with lakes surrounded by mature forests. Riparian tree removal will therefore exacerbate hypolimnion habitat losses for cold stenotherms that have already been documented to be occurring as a result of lake acidification, eutrophication, and climate warming.

scholarly journals Laboratory Study of Weir Height and Location Effect in a Main Channel on the Branching Channel Flow

2013 ◽  
Vol 21 (4) ◽  
pp. 38-45
Author(s):  
Safiya Usama Ahmed Al-Neelah ◽  
Moayad Sa ◽  
ad Allah Khaleel
Keyword(s):  
Channel Flow ◽  
Laboratory Study ◽  
Main Channel ◽  
Weir Height

scholarly journals Experimental Study of Submerged Vanes in Intakes under Sediment Feeding Conditions

2018 ◽  
Vol 40 ◽  
pp. 03016
Author(s):  
Aslı Bor Türkben
Keyword(s):  
Water Intake ◽  
River Flow ◽  
Flow Direction ◽  
Main Channel ◽  
Bed Topography ◽  
Before And After ◽  
Submerged Vane ◽  
Solid Discharge ◽  
Submerged Vanes ◽  
Intake Structure

Sediment is transported along the river flow and deposited in the mouth of the intake structure over time and reducing the water intake capacity. Nowadays, many water intake structures lose their function and are closed to operation. To deal with this problem, recently, submerged vane application has offered a practical and economical solution. The aim of this study was to evaluate the efficiency of three vane installations under sediment feeding conditions by comparing the bed topography before and after vanes were installed. For that purpose, experiments were carried out in a laboratory channel running for 90-degree intake angle. Three vanes were installed in one column at near the intake entrance. The vanes dimensions were equal to; 3cm height, 12cm long, 10 mm thick, and aligned with α = 20° angle to flow direction. The tests were run until equilibrium was reached, i.e. when the outgoing solid discharge was equal or larger than 90% of the incoming. Once the bed topography remained stable, bed and water level surfaces were measured. tests were carried out by feeding sediment from upstream of the main channel.

Effect of Western the Fourth Phase Project on Hydrodynamic Condition for Shijiu Port in Rizhao

2012 ◽  
Vol 204-208 ◽  
pp. 2369-2373
Author(s):  
Jia Rui Li ◽  
Die Shuang Yu
Keyword(s):  
Channel Flow ◽  
Water Area ◽  
Main Channel ◽  
Hydrodynamic Condition ◽  
Port Area ◽  
Before And After ◽  
Project Construction ◽  
Sheltering Effect ◽  
Sea Area ◽  
Flow Velocities

A hydrodynamic model of Shijiu port and its adjacent sea area was built to discuss the effect of western the fourth phase project on the flow condition for Shijiu port area. The results show that with the sheltering effect of breakwaters, flow velocity values are small inside the breakwaters. The water area near the project is affected more by the project construction. The flow velocities there are faster after the project construction than before it. In the main channel, flow velocities outside the breakwaters almost have no difference before and after the project. The project construction doesn’t have significant effect on it.

Numerical modelling of ice jam resistance to main channel flow

1995 ◽  
Vol 21 (11) ◽  
pp. 1109-1120 ◽  
Author(s):  
Raafat G. Saadé ◽  
Amruthur ◽  
S. Ramamurthy ◽  
Michael S. Troitsky
Keyword(s):  
Numerical Modelling ◽  
Channel Flow ◽  
Main Channel ◽  
Ice Jam ◽  
Jam Resistance

Lake Eyre golden perch (Macquaria sp.) spawning and recruitment is enhanced by flow events in the hydrologically variable rivers of Lake Eyre Basin, Australia

2015 ◽  
Vol 66 (9) ◽  
pp. 822 ◽  
Author(s):  
B. J. Cockayne ◽  
D. Sternberg ◽  
D. W. Schmarr ◽  
A. W. Duguid ◽  
R. Mathwin
Keyword(s):  
Channel Flow ◽  
River Flow ◽  
Arid Zone ◽  
Close Association ◽  
Management Strategies ◽  
Low Flow ◽  
Class Strength ◽  
Floodplain Inundation ◽  
Semi Arid ◽  
Age Estimates

Understanding the links between fish recruitment and riverine flows is integral for setting priorities for river-management strategies, particularly in hydrologically variable and unpredictable arid and semi-arid zone rivers. In the present study, we used daily and annual otolith age estimates to identify relationships between riverine flow and spawning and recruitment of Lake Eyre golden perch (Macquaria sp.); an endemic fish of the Lake Eyre Basin, central Australia. We found a close association between Lake Eyre golden perch spawning and periods of increased river flow, with most of spawning occurring 0–35 days after the start of these flow events. Spawning occurred throughout the year but was commonly observed during the first flow events proceeding consecutive months of no-flow when water temperatures exceeded 26°C. Spawning was not dependent on floodplain inundation, with most spawning occurring during within-channel flow events. Annual average year-class strength was related to the number of flow events per year, but not total annual discharge, or the number of low-flow days per year. These results highlight the importance of natural within-channel flow patterns to Lake Eyre golden perch spawning and recruitment and demonstrate the importance of maintaining the natural flow regime of Australia’s arid- and semi-arid-zone rivers.

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