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Coastal Erosion in Maputo, Mozambique. Governing processes and mathematical modeling

Björnberg, Sofie LU and Wahlström, Siri LU (2012) VVR820 20122
Division of Water Resources Engineering
Abstract
Erosion of coastal areas is experienced in many countries around the world. The natural beach dynamics is caused by hydrodynamic processes, variations in sediment transport rates and frequency of storm events but anthropogenic influences may also contribute to an increased erosion/accretion of the shoreline. Maputo city, located in the southeastern part of Mozambique, have during the last decays experienced erosion of primarily the eastern coastline.

The research of coastal hydraulics at the Eduardo Mondlane University in Maputo is currently supported by the Department for Water Resources Engineering at Lund University. This thesis can therefore be regarded as a contribution to the analysis of the hydrodynamics and sediment transport... (More)
Erosion of coastal areas is experienced in many countries around the world. The natural beach dynamics is caused by hydrodynamic processes, variations in sediment transport rates and frequency of storm events but anthropogenic influences may also contribute to an increased erosion/accretion of the shoreline. Maputo city, located in the southeastern part of Mozambique, have during the last decays experienced erosion of primarily the eastern coastline.

The research of coastal hydraulics at the Eduardo Mondlane University in Maputo is currently supported by the Department for Water Resources Engineering at Lund University. This thesis can therefore be regarded as a contribution to the analysis of the hydrodynamics and sediment transport processes in Maputo bay.

Aim:
The aim of this master thesis is to evaluate the governing processes of the historical erosion along the eastern coastline of Maputo, Mozambique. The cause of the coastal erosion along Costa do Sol will be evaluated and a quantification of the sediment transport rates along the coast will be analyzed. Finally the historical shoreline evolution is attempted to be reproduced in the one-line numerical model GENESIS.

Method:
The thesis work was initiated in august 2012 with a literature review of general theory. Afterwards information of local conditions, wind data and historical aerial photographs were collected from different departments of the Eduardo Mondlane University and National Institutions in Maputo. Information of historical erosion problems and carried out protection measures were gathered through interviews with the Maputo municipality. The collected wind data were used to calculate the wind generated wave climate affecting the study stretch. The current conditions around Costa do Sol were investigated during several field studies where the focuses were to identify the problem areas and to perform cross-shore surveys as well as sediment sampling. Finally, the historical evolution of Costa do Sol as an effect of the long-term erosion was modeled and calibrated using the one-line numerical model GENESIS.

Conclusion:
The analysis showed that the shoreline has successively retreated over the time period 1969 to 2012 where an increase in erosion was noticed between 2000 and 2012. The sudden increase in erosion is likely to have been triggered by some anthropogenic factor or large storm event.

This thesis concludes that the erosion along Costa do Sol is not likely to be explained by gradients in the longshore sediment transport only. The modeled net sediment transport and associated gradients were low in all of the model runs and the calculated resulting shoreline change was small. What other factors or combination of factors that contributes to the erosion needs to be investigated further.

The municipality’s future plans for the Costa do Sol will generate more constructions along the beach. Our recommendation is not to further exploit the area but instead focus on repair of existing structures and beach nourishment.

On a national level Mozambique officially applies integrated coastal zone management but no traces of this are experienced on a municipal level. It is our recommendation that a more holistic plan of how to produce a more coherent management plan that will provide both a secure and healthy beach in the future will be produced and implemented on a local level. (Less)
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author
Björnberg, Sofie LU and Wahlström, Siri LU
supervisor
organization
course
VVR820 20122
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Maputo, Mozambique, coastal erosion, waves, wind, sediment transport, GENESIS, modeling, protective measures, shoreline evolution, coastal management
report number
TVVR-12/5022
ISSN
1101-9824
language
English
id
3357759
date added to LUP
2013-01-09 13:44:56
date last changed
2013-01-09 13:44:56
@misc{3357759,
  abstract     = {Erosion of coastal areas is experienced in many countries around the world. The natural beach dynamics is caused by hydrodynamic processes, variations in sediment transport rates and frequency of storm events but anthropogenic influences may also contribute to an increased erosion/accretion of the shoreline. Maputo city, located in the southeastern part of Mozambique, have during the last decays experienced erosion of primarily the eastern coastline. 

The research of coastal hydraulics at the Eduardo Mondlane University in Maputo is currently supported by the Department for Water Resources Engineering at Lund University. This thesis can therefore be regarded as a contribution to the analysis of the hydrodynamics and sediment transport processes in Maputo bay.

Aim: 	
The aim of this master thesis is to evaluate the governing processes of the historical erosion along the eastern coastline of Maputo, Mozambique. The cause of the coastal erosion along Costa do Sol will be evaluated and a quantification of the sediment transport rates along the coast will be analyzed. Finally the historical shoreline evolution is attempted to be reproduced in the one-line numerical model GENESIS.

Method:	
The thesis work was initiated in august 2012 with a literature review of general theory. Afterwards information of local conditions, wind data and historical aerial photographs were collected from different departments of the Eduardo Mondlane University and National Institutions in Maputo. Information of historical erosion problems and carried out protection measures were gathered through interviews with the Maputo municipality. The collected wind data were used to calculate the wind generated wave climate affecting the study stretch. The current conditions around Costa do Sol were investigated during several field studies where the focuses were to identify the problem areas and to perform cross-shore surveys as well as sediment sampling. Finally, the historical evolution of Costa do Sol as an effect of the long-term erosion was modeled and calibrated using the one-line numerical model GENESIS. 

Conclusion: 	
The analysis showed that the shoreline has successively retreated over the time period 1969 to 2012 where an increase in erosion was noticed between 2000 and 2012. The sudden increase in erosion is likely to have been triggered by some anthropogenic factor or large storm event. 

This thesis concludes that the erosion along Costa do Sol is not likely to be explained by gradients in the longshore sediment transport only. The modeled net sediment transport and associated gradients were low in all of the model runs and the calculated resulting shoreline change was small. What other factors or combination of factors that contributes to the erosion needs to be investigated further.

The municipality’s future plans for the Costa do Sol will generate more constructions along the beach. Our recommendation is not to further exploit the area but instead focus on repair of existing structures and beach nourishment. 
 
On a national level Mozambique officially applies integrated coastal zone management but no traces of this are experienced on a municipal level. It is our recommendation that a more holistic plan of how to produce a more coherent management plan that will provide both a secure and healthy beach in the future will be produced and implemented on a local level.},
  author       = {Björnberg, Sofie and Wahlström, Siri},
  issn         = {1101-9824},
  keyword      = {Maputo,Mozambique,coastal erosion,waves,wind,sediment transport,GENESIS,modeling,protective measures,shoreline evolution,coastal management},
  language     = {eng},
  note         = {Student Paper},
  title        = {Coastal Erosion in Maputo, Mozambique. Governing processes and mathematical modeling},
  year         = {2012},
}