As a result of the unabated growth in plastic usage worldwide, their abundance in the marine environment has steadily increased over the last few decades. Nowadays, plastic litter is observed across all oceans and shores. Due to their wide spread and adverse effects on ecology, economy and potentially human health, plastic pollution has been recognized as a worldwide environmental and ecological threat. For these reasons, it is important to reduce and mitigate the abundance of plastic litter in the marine environment. As marine plastic litter predominately originates from near the coast, it is critical to study the plastic behaviour in coastal waters. However, there is considerable uncertainty regarding what factors are influencing the trajectories, distribution and deposition sites of plastic litter. Along with complex physical processes and scarcity of empirical data, there is currently little knowledge and understanding on the transport and fate of plastics in coastal waters.

With the aim of obtaining more insight into plastic behaviour, the present study intends to examine the most important processes and quantify the effects of parameter uncertainty on modelling the transport and fate of buoyant macroplastic in coastal waters. The transport and fate of plastics is modelled by combining hydrodynamics with particle tracking concepts. For the simulations the Delft3D software Suite was used, where a Delft3D-FLOW model of the southern North Sea (ZUNO-DD) was coupled to Delft3d-PART. The model calculates how the position of plastic particles evolves in time from their release until the end of the simulation. In this study, model simulations are used as a numerical tool for exploring the relative influence of current uncertainties inherent in process parameters and data inputs on model results. A set of scenarios were defined by changing parameter values on at a time. By studying the changes in particle trajectories and shoreline deposition areas, a better understanding of their relative importance was obtained.

The modelling results imply that the effect of windage and release location are the most important parameters. Further, it is observed that dominating driving mechanisms may change with varying forcing conditions and object characteristics. Other factors such as small-scale processes and moment of release may impact particle trajectories and fate. However, the relative influence of these processes is less significant and therefore considered less critical. Adopting the findings of this thesis into decision making policy can support emergency response operations and monitoring strategies.

The research on plastic behaviour in the coastal environment is still in its early stage, and much has yet to be revealed. Therefore, further improve understanding of buoyant macroplastic behaviour is required. Validation of the results presented in this study is limited due to the scarcity of empirical data. Thus, further research should be directed towards collecting more field data. Further, it is recommended that effort is put into parametrizing accurately the effect of windage. Furthermore, expanding numerical simulations should be
expanded to a range of conditions and coastal environments so that trends can be compared and highlighted, but also allows for exploring new hypotheses.

For the past years large quantities of plastic waste have been accumulating on the beaches in Southwest Bali. This has economical, environmental and health implications in this area. This event mainly occurs between December to March. The objective of this report is to map the plastic waste problem in Southwest Bali and look for efficient solutions to mitigate plastic washing ashore at its beaches. To reach this objective the main drivers for the plastic waste accumulation are investigated. Furthermore, research on the distribution and composition is provided. The local waste management system and its shortcomings are assessed. Personal waste treatment is analyzed using a survey. Background information on the problem was gathered with the use of a literature study and area analysis. A conceptual model is introduced to reach the research objective. This conceptual model is a schematization, in order to better understand the research area and the behavior of the plastic in the case area. In order to quantify the model further research is required. This consist of four research disciplines. Namely, ocean, boundaries and bottom; river measurements; beach measurements and waste management & social studies. Via literature studies and interviews, research on the ocean, boundaries and bottom is performed. Three rivers where measured over the course of 2 months. Research was done to determine river parameters. Plastics were caught by a manta trawl and visual waste counting was performed to understand the plastic flux in rivers. Research on the beaches was done on the composition and quantity of various plastic sources namely oceanic, terrestrial and river inputs. Via interviews with local stakeholders the waste management system the case area is mapped. With the use of a survey, personal awareness and motivation among plastic pollution is analyzed. The plastic accumulation is largely dependent on the climate and local waste treatment. As waste management facilities are lacking and local awareness and motivation is limited, large quantities of plastic enter local rivers. Together with increased rain conditions large quantities of plastic end up in the ocean. Wind then transports plastic waste towards the beaches. This debris is mainly 'pushed' towards the beaches in Southwest Bali due to the coastal shape. During the research single use plastics are found to be the most common plastic type. Four solutions are proposed to reduce the plastic accumulation in the beaches of Southwest Bali. Intercepting plastics in rivers prevents further dispersion into the ocean and thus limits plastics accumulating on the beaches. Improved waste management could tackle the source of plastics pollution and reduce the amount of plastics entering our nature. Increased education on plastic pollution can result in improved personal waste management, especially in remote areas. As a lot of stakeholders are involved in the problem an improved communication network is desired in order to achieve a combined goal and work more efficiently.

Dit BSc eindwerk is opgesteld om de optimale verticale afstand tussen de warmte- en koudebron van monobronnen te onderzoeken. Hiervoor is kennis over grondwaterstromingen en stijghoogteveranderingen vereist. Deze zijn beide afhankelijk van de systeemdimensies en lokaal geldende bodemkarakteristieken.
In dit rapport is onderzocht hoe de systeemdimensies en bodemparameters de optimale bronscheiding van monobronnen beïnvloed. Doormiddel van een varierende capaciteitsrage van 2.5 – 50 m3/h zijn verschillende monbronnen gesimuleerd onder anisotropie-waarde 2, 5 en 10. Daarnaast is onderzocht hoe de systeemdimensies afhankelijk zijn van de dikte van de aquifer en voor welke dimensies geldt dat warmteverliezen geminimaliseerd worden.
Uit de simulatie volgde dat de optimale bronscheiding profijt heeft van een hoge anisotropie en lange filterlengte. De filterlengte is echter weer van invloed op de vorm van de thermische bel en zo ook bepalend voor warmteverliezen. Bij een hoger vergund volume moeten een langere bronscheiding gehanteerd worden. Een verhoging van het volume gaat gepaard met een minder sterke toename in warmteverliezen. Er geldt dus dat voor grotere systemen een hoger rendement behaald kan worden.
In 5.3 zijn de systeemdimensies gegeven voor minimale systeemlengte en in 5.4 de dimensies voor minimale warmteverliezen.