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Ship-Induced Waves and Sediment Transport in Göta River, Sweden

Althage, Jonas LU (2010) In TVVR 10/5021 VVR820 20102
Division of Water Resources Engineering
Abstract
Göta River, in Swedish Göta älv, is Sweden’s largest river as to flow rate. The surrounding river valley landscape is also among the most prone to landslides in the country, with cohesive sediments, including quick clay, as the dominant soil type. Both natural and anthropogenic erosion and sediment transport are occurring in the river, in the latter case induced by for example ship-generated waves.

The ships that navigate Göta River induce erosion of the river banks and bed by the impact of waves and scouring from propeller jets. During ship passages, large increases in turbidity are detected through measurements in the water, which means that the total load of suspended particulate matter in the river increases due to erosion and... (More)
Göta River, in Swedish Göta älv, is Sweden’s largest river as to flow rate. The surrounding river valley landscape is also among the most prone to landslides in the country, with cohesive sediments, including quick clay, as the dominant soil type. Both natural and anthropogenic erosion and sediment transport are occurring in the river, in the latter case induced by for example ship-generated waves.

The ships that navigate Göta River induce erosion of the river banks and bed by the impact of waves and scouring from propeller jets. During ship passages, large increases in turbidity are detected through measurements in the water, which means that the total load of suspended particulate matter in the river increases due to erosion and sediment transport from ship-induced effects.

By digitizing the variation in the water level when ships pass an observation pier, the ship-generated wave properties have been determined. The waves were found to induce bed shear stresses that frequently exceed the estimated bed sediment critical shear stress. The critical shear stress has been estimated by analysing calculated shear stresses and turbidity readings, linking increases of the latter (which translate into an increase in the mass of suspended particulate matter in the water) to the magnitude of the former. Subsequently, the waves do not only contribute to the sediment transport of the river, but it is also established that they erode the river bed and banks. Through basic assumptions and estimations, ship-generated waves are calculated to erode about 40,000 tonnes of bed sediment annually along the full stretch of the Göta River. Moreover, a predicted increase in the bulk transport by ships could double the erosion by the year 2020. This does not consider the fact that the sediment settles after some time, so the calculated erosion is most likely an over-estimation.

The key factor which determines the magnitude of the wave height is the ship velocity relative to the water flow velocity. Other parameters, such as ship draught, ship size, and water depth, do not show a consistent relationship with the recorded maximum wave height. (Less)
Please use this url to cite or link to this publication:
author
Althage, Jonas LU
supervisor
organization
course
VVR820 20102
year
type
H2 - Master's Degree (Two Years)
subject
keywords
turbidity, channel, river, ship-generated waves, sediment transport, erosion, field measurements, shear stress
publication/series
TVVR 10/5021
report number
10/5021
ISSN
1101-9824
language
English
additional info
Examiner: Hans Hanson
id
1755358
date added to LUP
2011-01-04 16:26:00
date last changed
2019-03-27 11:16:51
@misc{1755358,
  abstract     = {Göta River, in Swedish Göta älv, is Sweden’s largest river as to flow rate. The surrounding river valley landscape is also among the most prone to landslides in the country, with cohesive sediments, including quick clay, as the dominant soil type. Both natural and anthropogenic erosion and sediment transport are occurring in the river, in the latter case induced by for example ship-generated waves.

The ships that navigate Göta River induce erosion of the river banks and bed by the impact of waves and scouring from propeller jets. During ship passages, large increases in turbidity are detected through measurements in the water, which means that the total load of suspended particulate matter in the river increases due to erosion and sediment transport from ship-induced effects.

By digitizing the variation in the water level when ships pass an observation pier, the ship-generated wave properties have been determined. The waves were found to induce bed shear stresses that frequently exceed the estimated bed sediment critical shear stress. The critical shear stress has been estimated by analysing calculated shear stresses and turbidity readings, linking increases of the latter (which translate into an increase in the mass of suspended particulate matter in the water) to the magnitude of the former. Subsequently, the waves do not only contribute to the sediment transport of the river, but it is also established that they erode the river bed and banks. Through basic assumptions and estimations, ship-generated waves are calculated to erode about 40,000 tonnes of bed sediment annually along the full stretch of the Göta River. Moreover, a predicted increase in the bulk transport by ships could double the erosion by the year 2020. This does not consider the fact that the sediment settles after some time, so the calculated erosion is most likely an over-estimation.

The key factor which determines the magnitude of the wave height is the ship velocity relative to the water flow velocity. Other parameters, such as ship draught, ship size, and water depth, do not show a consistent relationship with the recorded maximum wave height.},
  author       = {Althage, Jonas},
  issn         = {1101-9824},
  keyword      = {turbidity,channel,river,ship-generated waves,sediment transport,erosion,field measurements,shear stress},
  language     = {eng},
  note         = {Student Paper},
  series       = {TVVR 10/5021},
  title        = {Ship-Induced Waves and Sediment Transport in Göta River, Sweden},
  year         = {2010},
}