Increased Bed Erosion Due to Ice

Zabilansky, Leonard J.; Hains, Decker B.; Remus, John I.

doi:10.1061/40836(210)16

Cited by 12 publications

(21 citation statements)

References 5 publications

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“…It has previously been stated that ice cover causes pressurized flow conditions, which increases shear stress and bed erosion (Zabilansky et al ., ). Even without ice cover, the simulations with ST scaling set to 1 predicted greater erosion during the summer than was actually surveyed, and, therefore, the model performance cannot be explained by the absence of ice.…”

Section: Discussionmentioning

confidence: 97%

Surveyed and modelled one‐year morphodynamics in the braided lower Tana River

Lotsari

Wainwright²,

Corner

et al. 2013

Hydrological Processes

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Field measurements and morphodynamic simulations were carried out along a 5‐km reach of the sandy, braided, lower Tana River in order to detect temporal and spatial variations in river bed modifications and to determine the relative importance of different magnitude discharges on river bed and braid channel evolution during a time span of one year, i.e. 2008–2009. Fulfilling these aims required testing the morphodynamic model's capability to simulate changes in the braided reach. We performed the simulations using a 2‐D morphodynamic model and different transport equations. The survey showed that more deposition than erosion occurred during 2008–2009. Continuous bed‐load transport and bed elevation changes of ±1 m, and a 70–188‐m downstream migration of the thalweg occurred. Simulation results indicated that, during low water periods, modifications occurred in both the main channel and in other braid channels. Thus, unlike some gravel‐bed rivers, the sandy lower Tana River does not behave like a single‐thread channel at low discharge. However, at higher discharge, i.e. exceeding 497 m3/s, the river channel resembled a single‐thread channel when channel banks confined the flow. Although the spring discharge peaks caused more rapid modifications than slower flows, the cumulative volumetric changes of the low water period were greater. The importance of low water period flows for channel modifications is emphasized. Although the 2‐D model requires further improvements, the results were nevertheless promising for the future use of this approach in braided rivers. Copyright © 2013 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 97%

Surveyed and modelled one‐year morphodynamics in the braided lower Tana River

Lotsari

Wainwright²,

Corner

et al. 2013

Hydrological Processes

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“…In many regions, the river ice exists for a significant part of the year and induces geomorphological changes (Zabilansky et al ., ; Turcotte et al ., ). An unresolved issue is whether river ice has an evident effect on channel morphology (Ettema and Kempema, ), and the influence of ice cover on river bed morphology is not fully examined.…”

Section: Introductionmentioning

confidence: 97%

“…Already, in the 1970s, it was found that under ice cover, the sediment transport rate was reduced, mainly because of the lower velocities (Sayre and Song, ). On the other hand, a fixed ice cover may intensify bed erosion (Zabilansky et al ., ), especially if a bankfast and rough ice cover is restrained from responding vertically to changes in discharge. The average water velocity is reduced by the additional ice–water boundary.…”

Section: Introductionmentioning

confidence: 99%

River ice cover influence on sediment transportation at present and under projected hydroclimatic conditions

et al. 2015

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Abstract:A large number of rivers are frozen annually, and the river ice cover has an influence on the geomorphological processes. These processes in cohesive sediment rivers are not fully understood. Therefore, this paper demonstrates the impact of river ice cover on sediment transport, i.e. turbidity, suspended sediment loads and erosion potential, compared with a river with ice-free flow conditions. The present sediment transportation conditions during the annual cycle are analysed, and the implications of climate change on wintertime geomorphological processes are estimated. A one-dimensional hydrodynamic model has been applied to the Kokemäenjoki River in Southwest Finland. The shear stress forces directed to the river bed are simulated with present and projected hydroclimatic conditions. The results of shear stress simulations indicate that a thermally formed smooth ice cover diminishes river bed erosion, compared with an ice-free river with similar discharges. Based on long-term field data, the river ice cover reduces turbidity statistically significantly. Furthermore, suspended sediment concentrations measured in ice-free and icecovered river water reveal a diminishing effect of ice cover on riverine sediment load. The hydrodynamic simulations suggest that the influence of rippled ice cover on shear stress is varying. Climate change is projected to increase the winter discharges by 27-77% on average by 2070-2099. Thus, the increasing winter discharges and possible diminishing ice cover periods both increase the erosion potential of the river bed. Hence, the wintertime sediment load of the river is expected to become larger in the future.

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“…The constricted flow area due to the ice cover can result in higher velocities, increased turbulence, and scour of erodible bed material (Zabilansky et al 2006). Through the Chamberlain Bridge, the slope steepens and velocities greater than 10 ft/s can be seen during open water flow.…”

Section: Ice Impacts Resulting From Merrimack Village Dam Removalmentioning

confidence: 99%

Evaluation of Dam Decommissioning in an Ice-Affected River: Case Study

Vuyovich¹,

White²

2007

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Many dams across the United States are being decommissioned as a result of structural deficiencies or a desire to restore fish passage and to restore the natural stream. On northern rivers, dam removal affects the river ice processes and can result in increased ice jams and ice jam-related flooding. An analysis of the river system prior to dam removal is often necessary to ensure that increased ice jams, flooding, and damages do not result. This case study presents the types of analyses needed to investigate the ice impacts of the potential removal of the Merrimack Village Dam on the Souhegan River in Merrimack, New Hampshire. Of particular interest were the potential impacts to the historic Chamberlain Bridge. A HEC-RAS hydraulic model was used to estimate the ice jam thickness and resulting water surface profiles with and without an ice jam in place for both the pre-and post-dam-removal conditions. The results of this analysis indicate that removing the Merrimack Village Dam will not pose significant risk to the Chamberlain Bridge or to the area downstream.

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Increased Bed Erosion Due to Ice

Cited by 12 publications

References 5 publications

Surveyed and modelled one‐year morphodynamics in the braided lower Tana River

Surveyed and modelled one‐year morphodynamics in the braided lower Tana River

River ice cover influence on sediment transportation at present and under projected hydroclimatic conditions

Evaluation of Dam Decommissioning in an Ice-Affected River: Case Study

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