Coastline modelling with UNIBEST: Areas close to structures

Coastline modelling with UNIBEST: Areas close to structures

Van der Salm, G.L.S.

Stive, M.J.F. (mentor)
Zijlema, M. (mentor)
Luijendijk, A.P. (mentor)
Huisman, B.J.A. (mentor)
Nipius, K.G. (mentor)

Civil Engineering and Geosciences

Hydraulic Engineering

Coastal Engineering

2013-02-28

Coastline modeling with UNIBEST: Areas close to structures In the world of coastline modeling there are several ways to predict coastline development. One of those is with the use of single line modeling software. This kind of modeling is rather basic, straight forward and fast, but it lacks some detail of different processes taking place. Processes that can have significant impact on the coastline development. This study aims at providing insight in approaches that can be used to model coastline development near structures. The focus of this study will lay on the use of UNIBEST-CL, a single line coastline modeling package, developed by Deltares. Creating a coastline model in UNIBEST-CL is rather user friendly, but if structures are present some extra work needs to be done to get reasonable output from the model. The standard approach of modeling structures in UNIBEST needs extra calculations of local wave climates in the shadow zone of structures. This can be done by hand, using formulations of Kamphuis and it can also be done by using a second modeling package called SWAN. Both these methods result in a more labour intensive calculation. Therefore, a third approach is developed. An automated module is integrated in the package of UNIBEST-CL. This approach uses the same Kamphuis formulations mentioned earlier. The main difference is that it calculates the local wave climates at every cross-shore ray of the UNIBEST model. Within an average model this will generate more local wave climates compared to the manual approach, resulting in more input information. To compare these three different approaches two kinds of models are created. First a theoretical study is carried out. Secondly, the results of the theoretical study are used to be verified in a field case situation. The theoretical study is based on two questions: • How does the Automated Kamphuis approach perform compared to Manual Kamphuis calculations and SWAN calculations? • Which modeling approach is suitable for what kind of conditions? To investigate these questions, a simple, straight coastline is created with three shore normal groynes. This configuration is tested with several changeable parameters, like different bottom profiles, wave conditions (height, period and direction) and cross shore locations of the local wave climates. After the calculations, the results are assessed by using a classification of the width of the transport zone divided by the length of the groynes. Using this classification, the results of all the runs are compared by looking at the resulting transport magnitude and the coastline shape. This leads to a final table that can be used as a recommendation on which approach to use in what kind of situation. The results of the theoretical study are used in a second calculation, to hindcast the coastline changes in a field application case at the beaches of Sitges, Spain. During the field case testing not all variants of the three approaches are used. Only one SWAN approach (50% groyne length) and the Automated Kamphuis are compared. While running this coastline model multiple adjustment of the Automated module were needed. Some programming code in the software needed to be adjusted during the calculations. Finally, the field case resulted in satisfactory results for both approaches. Some conclusions that can be drawn from both the theoretical and the field case study are: • The automated approach functions well compared to the manual approach with local climates at the shoreline. (The module in UNIBEST-CL works properly) • Using a classification ratio of width of transport zone divided by the length of the groyne one of the approaches can be chosen that will give the most optimal result in the specific situation. • If the ratio is very small (e.g. a small width off transport compared to the groyne length) the best approach will be the SWAN approach, because the most processes are taken into account in this situation. • With a larger ratio, Kamphuis, and therefore the Automated approach, will give better results, because it takes the effect of the structure into account, better than the SWAN approach. • The result of the field case shows that the Automated approach also works well in real situations, compared to the outcome of the SWAN approach.

Diffraction
UNIBEST
Coastline Modelling
Structures

http://resolver.tudelft.nl/uuid:f77f32d5-b9ca-47d8-9b43-decbe23c8080

Student theses

master thesis

(c) 2013 Van der Salm, G.L.S.