Rehabilitation of Holwerd

Rehabilitation of Holwerd

Moreno, A.J.
Kar, A.
De Queiroz, B.
Rada Mora, M.B.
Disanayaka Mudiyanselage, S.S.J.
Arefin, S.S.

Hofland, B. (mentor)

Civil Engineering and Geosciences

Hydraulic Engineering

Masterproject CiTG CEG 4061 - 09

2016-06-06

Holwerd is a village located at the coast of the Wadden Sea. Decisions made in the past have affected the town in a negative manner leading to an impoverishment of the region. Therefore, we were tasked with rehabilitating the city of Holwerd by establishing the connection with the sea and making the goal (Holwerd aan Zee) of the inhabitants come into a reality. In order to prioritize the different actions required to achieve the objective, a survey was conducted. Hence, a clearer view of what people are attracted to when choosing a destination is obtained. It was found that the most attractive option is the one that includes recreational elements (proximity to the sea restaurants and bars, hotels...), natural elements (parks, open spaces...) as well as cultural elements (museums, architecture…). Due to the high cost of this alternative, the project is divided into phases. In addition, an environmental impact assessment was conducted to ensure a well-balanced project implementation. In this multidisciplinary project, the focus is mainly on the construction of the navigational channel through the dike connecting to a buffer lake. Together with the channel, the implementation of a sluice in the opening of the dike is also analysed. Through a multi-criteria evaluation each alternative of channel alignment and gates is assessed. These multi-criteria analyses determined that the optimal solution is to connect the navigational channel to a fresh water source where a canal and a small marina were already present. Regarding the type of gate, it resulted that the folding gate made of timber was the most suitable to be installed both in the dike side and in the inner side blocking the salt water flowing further into the fresh water. The design of the channel was developed in such a way that an ebb-dominance tendency is present. The exporting of sediment was checked by using a one-dimensional model with a sinusoidal symmetric tide. The gate prototype was also modelled to ensure the structure can resist the different water levels. Regarding the dredged material of the channel, two proposals are evaluated in order to find a beneficial use of the remaining volume. A nourishment and development of salt marshes in Visbuurt (adjacent town of Holwerd) as well as the creation of the silt islands and development of salt marshes in Holwerd are studied. The dredging operation is also described. Finally, additional research and data collection are recommended prior to further action.

http://resolver.tudelft.nl/uuid:4db0aee4-40dc-4bfa-bae9-7be0916e4859

53.38111, 5.89500

Student theses

student report

(c) 2016 The Authors