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Modeling flow and sediment transport in water bodies and watersheds
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The research focus is on the various modeling aspects of flow and sediment transport in water bodies and watersheds. The interaction of flow with a mobile bed involves a complex process in which various turbulent scales characterized by coherent structures cause a chaotic sediment motion. In many rivers and natural waterways secondary flows that are dominating flow struc-tures bring about more complications. In estuaries and open waterbodies thermal stratification and internal mixing control the flow structure besides the flow interaction with the mobile bed. To adequately model these processes 3D coupled flow and transport models are needed. The research is based on use and adaptation of open source codes for 3D hydrodynamic and sediment transport model known as Estuarine Coastal Ocean Model (ECOMSED) and the Soil and Water Assessment Tool (SWAT) model. A bed load transport model was developed and coupled to ECOMSED. The flow and sediment transport characteristics in a curved channel and a river reach were successfully captured by the model. Improvements in ECOMSED were made to study the effect of wind and basin bathymetry on mixing and flow exchange between two estuaries. Using spectral analysis the hydrological component of SWAT model was investigated for its applicability under limited data conditions in three Ethiopian catchments.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , viii, 21 p.
Series
Trita-LWR. PHD, ISSN 1650-8602 ; 1039
Keyword [en]
Bed load transport model, ECOMSED, Hydrology, Hydrodynamics, Spectral Analysis, SWAT
National Category
Water Engineering
Identifiers
URN: urn:nbn:se:kth:diva-4703ISBN: 978-91-7178-925-9 (print)OAI: oai:DiVA.org:kth-4703DiVA: diva2:13521
Public defence
2008-05-08, F3, Lindstedtvägen 26, Kungliga Tekniska högskolan | Adress SE-100 44 Stockholm | Telefon +46 8 790 60 00, KTH, 10:00
Opponent
Supervisors
Note
QC 20100827Available from: 2008-04-22 Created: 2008-04-22 Last updated: 2010-08-27Bibliographically approved
List of papers
1. 3D flow and sediment transport modeling in curved channels
Open this publication in new window or tab >>3D flow and sediment transport modeling in curved channels
2007 (English)In: 3rd IASTED International Conference on Environmental Modelling and Simulation, EMS 2007: Honolulu, HI: 20 August 2007 through 22 August 2007, 2007, 82-87 p.Conference paper, Published paper (Refereed)
Abstract [en]

A 3D hydrodynamic model coupled with a 2D bed load transport model is used to predict flow and sediment transport in a curved channel. The 3D hydrodynamic model is part of ECOMSED (open source code). ECOMSED has a long history of successful applications to oceanic, coastal, and estuarine waters. However, curved channel applications of the code are scarce. Improvements in the advection scheme of momentum and turbulence, and shear stress partitioning were necessary to reproduce realistic and comparable results in a curved channel. To account for the dynamics of the mobile bed boundary, a model for the bed load transport was included in the code. The model reproduced measured secondary currents, bed shear stress distribution, and erosion-deposition patterns on a curved channel.

Keyword
2D bed load transport model; 3D hydrodynamic model; Curved channel; ECOMSED; Modeling
National Category
Water Engineering
Identifiers
urn:nbn:se:kth:diva-8246 (URN)2-s2.0-38349106483 (Scopus ID)978-0-88986-682-9 (ISBN)
Note
QC 20100827Available from: 2008-04-22 Created: 2008-04-22 Last updated: 2010-08-27Bibliographically approved
2. Three dimensional numerical modelling of flow and sediment transport in rivers
Open this publication in new window or tab >>Three dimensional numerical modelling of flow and sediment transport in rivers
2007 (English)In: International Journal of Sediment Research, ISSN 1001-6279, Vol. 22, no 3, 188-198 p.Article in journal (Refereed) Published
Abstract [en]

The 3D numerical model, ECOMSED (open source code), was used to simulate flow and sediment transport in rivers. The model has a long history of successful applications to oceanic, coastal and estuarine waters. Improvements in the advection scheme, treatment of river roughness parameterization and shear stress partitioning were necessary to reproduce realistic and comparable results in a river application. To account for the dynamics of the mobile bed boundary, a model for the bed load transport was included in the code. The model reproduced observed secondary currents, bed shear stress distribution and erosion-deposition patterns on a curved channel. The model also successfully predicted the general flow patterns and sediment transport characteristics of a 1-km long reach of the River Klaralven, located in the north of the county of Varmland, Sweden.

Keyword
roughness parameterization; numerical models; river flow; sediment transport
National Category
Water Engineering
Identifiers
urn:nbn:se:kth:diva-8247 (URN)000257209800003 ()2-s2.0-35348934992 (Scopus ID)
Note
QC 20100827 Available from: 2008-04-22 Created: 2008-04-22 Last updated: 2010-11-23Bibliographically approved
3. Mixing and exchange processes between two estuaries in Stockholm Archipelago, Sweden
Open this publication in new window or tab >>Mixing and exchange processes between two estuaries in Stockholm Archipelago, Sweden
2008 (English)In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015Article in journal (Other academic) Submitted
Abstract [en]

ECOM, a three-dimensional time dependant hydrodynamic and thermodynamic model, was used to investigate the mixing and exchange processes between Farstaviken and Baggensfjärden estu-aries in Stockholm archipelago during April to November 1997. Possible causes of bottom oxy-gen deficiency in the smaller estuary of Farstaviken were also investigated. The model with an additional boundary condition for the sediment-water heat exchange and modifications to reduce the pressure gradient error successfully produced the observed temperature profiles by allowing a time variable reduction in the magnitude of the observed wind speed. In Farstaviken (during stratification periods) the epilimnion region occupies 2.5%-17.5% of the flow depth. The ex-change process between the two smaller and larger estuaries is different from that observed be-tween larger basins where density driven currents dominate. Here, the process is primarily con-trolled by wind action and tides. On average 5% of the total water volume of Farstaviken is exchanged with Baggensfjärden on daily basis. The bottom oxygen deficiency in Farstaviken during April to November 1997 is partially related to the topography of the basin and the wind sheltering effect. To investigate this issue as well as the sensitivity of mixing to the changes in topography, additional simulations were performed using a modified bathymetry. The original bathymetry was smoothed using the 2D Gaussian filter. The results showed that both the intensi-ties and penetration depths of eddies were increased in comparison with the original bathymetry. The enhanced circulation can also contribute to increase the content of dissolved oxygen near the bottom of Farstaviken.

Keyword
Mixing and flow exchange, Three-dimensional modeling, Wind sheltering, Basin bathymetry, Bottom oxygen deficiency
National Category
Water Engineering
Identifiers
urn:nbn:se:kth:diva-8248 (URN)
Note
QS 20120315Available from: 2008-04-22 Created: 2008-04-22 Last updated: 2017-12-14Bibliographically approved
4. Hydrological modelling of Ethiopian catchments using limited data
Open this publication in new window or tab >>Hydrological modelling of Ethiopian catchments using limited data
2009 (English)In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 23, no 23, 3401-3408 p.Article in journal (Other academic) Published
Abstract [en]

The hydrological component of Soil and Water Assessment Tool (SWAT) model is adapted for Ethiopian catchments based on primary knowledge of the coherence spectrum between dis-charge and runoff. The implication is that only periods longer than about 50 days can be reliably represented in the model based on the available data. An improved method reflecting soil water retention in terms of cumulative evapotranspiration, so that its value is less dependent on soil storage and more dependent on antecedent climate, is used. The improved method is attractive for Ethiopian conditions due to limited soil data availability and the fact that the time-scale of cumulative evaporation can be evaluated over periods longer than 50 days. The spectrum analysis was done on the available nearby climatic data in three watersheds in Ethiopia to analyze the effects of data limitation on the temporal and spatial scales suitable to account for in comparta-mentalized runoff models. The time scales of SWAT for the surface runoff and groundwater flow response were constrained so as to be consistent with the results of the spectrum analysis. The performance of the SWAT model to predict daily stream flow response was compared to the Seasonal Model (SM) and the Original Linear Purturbation Model (OLPM) both of which need previous seasonal behavior of the stream flow.

Keyword
SWAT; SM; OLPM; Spectral analysis; Ethiopian catchments
National Category
Water Engineering
Identifiers
urn:nbn:se:kth:diva-8249 (URN)10.1002/hyp.7470 (DOI)000271452600013 ()2-s2.0-70649107951 (Scopus ID)
Note
QC 20100827. Updated from submitted to published, 20120315. Previous title: Hydrological modeling under limited data conditions in Ethiopian catchmentsAvailable from: 2008-04-22 Created: 2008-04-22 Last updated: 2017-12-14Bibliographically approved

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