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Delft University of Technology

1. Borsje, Ruben (author). Assessing current patterns behind hybrid dams: Demak, Indonesia.

Degree: 2017, Delft University of Technology

The Demak coastal area faces severe erosion problems. The main cause of the erosion of the coastline, which is at some places as high as 1.5 km of land, is the deforestation of the green belt of mangroves for the purpose of building fishponds. This has disturbed the delicate sediment balance in the area drastically. The BioManCO project aims to develop a bio-morphodynamic model for mangrove mudcoasts like the coast of Demak, which will eventually be used to identify the conditions under which restoration of the sediment balance may lead to autonomous reforestation of a sustainable mangrove green belt and thus the natural coastal protection. A measure to restore this sediment balance that is already being implemented in the area is the construction of semi-permeable dams. It is not clear yet however, why some of these dams work as intended and why some do not. In an earlier study a 2DH model has been set up to better understand and optimise the design of these structures using the large-scale morphodynamics of the area. A large obstacle that the development of this model and the BioManCO model faces however, is the scarcity of data in these areas. The flow patterns around these semi-permeable dams have been identified in the model, but cannot yet be verified. The aim of this thesis is to visualise flow patterns around and the permeability of a selected dam in the field to be able to get a better understanding of the hydrodynamics of the area. As the coastal area of Demak is quite remote, low-tech drifters will be used for this purpose, made only of locally available, inexpensive materials. They will be released at different locations at different moments in the tidal cycle. Data acquisition will take place by visual observation and by a camera attached to a drone. An algorithm will be developed to process the data digitally. It will automatically detect the drifters in the images taken by the drone. Using several Ground Control Points, of which the GPS-coordinates are known, the images can be rectified, so that the relation between the pixels in every image and their location in the real world is known. Using this information and the pixel-coordinates of the detected drifters, the paths of the drifters can be extracted from the images in real-world coordinates. From these paths, flow velocites can be deduced. The permeability of the dam will be assessed by releasing milk into the flow in several configurations during which data will be acquired by means of a GoPro camera mounted above the semi-permeable dam. The results show, that tide is the main driving force behind the flow patterns around the dam focused on in this research. During falling tide, a circulation pattern can be seen, which is caused by a combination of the local bathymetry and a wind driven mass transport over the plot. The flow patterns however do not resemble the patterns found in earlier model runs of the area. The cause of this is thought to be the combination of simplifications in the model and the permeability of the dams,… Advisors/Committee Members: Tas, Silke (mentor), Reniers, Ad (graduation committee), Winterwerp, Han (graduation committee), Aarninkhof, Stefan (graduation committee), Delft University of Technology (degree granting institution).

Subjects/Keywords: Building with Nature; drifters; drone; image rectification; mangroves; mud coast; erosion; hybrid dam; permeable dam; current pattern; visualisation; BioManCO

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Borsje, R. (. (2017). Assessing current patterns behind hybrid dams: Demak, Indonesia. (Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:6a278ea7-b30a-430c-90fb-a3244698995b

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Borsje, Ruben (author). “Assessing current patterns behind hybrid dams: Demak, Indonesia.” 2017. Thesis, Delft University of Technology. Accessed October 22, 2020. http://resolver.tudelft.nl/uuid:6a278ea7-b30a-430c-90fb-a3244698995b.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Borsje, Ruben (author). “Assessing current patterns behind hybrid dams: Demak, Indonesia.” 2017. Web. 22 Oct 2020.

Vancouver:

Borsje R(. Assessing current patterns behind hybrid dams: Demak, Indonesia. [Internet] [Thesis]. Delft University of Technology; 2017. [cited 2020 Oct 22]. Available from: http://resolver.tudelft.nl/uuid:6a278ea7-b30a-430c-90fb-a3244698995b.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Borsje R(. Assessing current patterns behind hybrid dams: Demak, Indonesia. [Thesis]. Delft University of Technology; 2017. Available from: http://resolver.tudelft.nl/uuid:6a278ea7-b30a-430c-90fb-a3244698995b

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


Delft University of Technology

2. Borsje, Ruben (author). Wave-Driven Set-Up of Fluid Mud: Demak, Indonesia.

Degree: 2019, Delft University of Technology

Demak is a regency within the province of Central Java, Indonesia, with a mud-mangrove coast bordering the Java Sea. The region is facing a rapid retreat of the coastline, threatening the livelihood of a large part of the population. The main cause of the erosion is the deforestation of the green belt of mangroves. This has disturbed the delicate sediment balance in the area drastically. This MSc thesis was carried out within BioManCO. This is a project of Delft University of Technology and Universitas Diponegoro and aims to develop a bio-morphodynamic model for mangrove-mud coasts. This will eventually be used to identify the conditions under which autonomous reforestation of a sustainable mangrove green belt will take place, restoring the natural coastal protection. Semi-permeable dams are already being implemented to restore the sediment balance in the area. In this approach, however, the existence of a fluid mud layer is neglected. The observation of relatively steep slopes of the interface between mud and water indicates potential mud transport within the mud layer. Such a transport would contribute to the shoreward flux of sediment and thus to the restoration of the coastal profile. If a hybrid dam is implemented, it will block the flow of sediment and might therefore defy its own purpose; attenuating flow and waves in order to capture sediment and restore the eroded coastal profile. The objective of this thesis is to assess wave damping as a driving mechanism for set-up of the fluid mud layer at the coast of Demak and to identify under what conditions such a set-up can exist. Significant attenuation of waves can be achieved by viscous dissipation of wave energy in the mud layer. The set-up of the fluid mud interface is hypothesised to be balancing the wave force resulting from the reduction of wave energy in shoreward direction. To gain insight in the damping of waves and, more generally, in the dynamics of the coastal system of Demak, a field campaign has been carried out. Based on these measurements a SWAN-Mud model has been set up and has been coupled to an idealised model that calculates the equilibrium slope based on modelled wave-damping. The field observations show that the interface level is indeed sloping upwards towards the coast. This slope, however, does not seem to change significantly during the field campaign, indicating that the occurring waves are not able to move the layer. A strong daily variation in wave height and period, dependent on the prevailing wind system, is observed. SWAN-Mud is able to reproduce these measurements convincingly, even with the simple schematisation used in this thesis. The damping of the waves is influenced by the water depth and the wave period, and to a lesser extent by the wave height. It is also strongly dependent on the thickness and viscosity of the mud layer. The use of a fluid mud module to model the dissipation of waves at the coast of Demak is proven to be necessary. The developed conceptual model assumes a balance between the wave force in the mud layer… Advisors/Committee Members: Reniers, Ad (mentor), van Maren, Bas (mentor), Winterwerp, Han (graduation committee), de Schipper, Matthieu (graduation committee), Tas, Silke (graduation committee), Delft University of Technology (degree granting institution).

Subjects/Keywords: fluid mud; Building with Nature; mud coast; erosion; sediment transport; Wave Attenuation; wave damping; radiation stress; fieldwork; SWAN; SWAN-Mud; viscous damping; indonesia; Demak; mud; conceptual model; hybrid dam

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Borsje, R. (. (2019). Wave-Driven Set-Up of Fluid Mud: Demak, Indonesia. (Masters Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:d51e770e-37ad-4c02-8cbf-c5abceaccc39

Chicago Manual of Style (16th Edition):

Borsje, Ruben (author). “Wave-Driven Set-Up of Fluid Mud: Demak, Indonesia.” 2019. Masters Thesis, Delft University of Technology. Accessed October 22, 2020. http://resolver.tudelft.nl/uuid:d51e770e-37ad-4c02-8cbf-c5abceaccc39.

MLA Handbook (7th Edition):

Borsje, Ruben (author). “Wave-Driven Set-Up of Fluid Mud: Demak, Indonesia.” 2019. Web. 22 Oct 2020.

Vancouver:

Borsje R(. Wave-Driven Set-Up of Fluid Mud: Demak, Indonesia. [Internet] [Masters thesis]. Delft University of Technology; 2019. [cited 2020 Oct 22]. Available from: http://resolver.tudelft.nl/uuid:d51e770e-37ad-4c02-8cbf-c5abceaccc39.

Council of Science Editors:

Borsje R(. Wave-Driven Set-Up of Fluid Mud: Demak, Indonesia. [Masters Thesis]. Delft University of Technology; 2019. Available from: http://resolver.tudelft.nl/uuid:d51e770e-37ad-4c02-8cbf-c5abceaccc39

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