Until now, an extensive design method for mild slopes has not been available. The aim of this thesis is to understand the stability of rock on mild slopes under wave attack for impermeable cores in order to optimize designs. Physical model tests have been executed to study this stability for a 1:8 slope. Mossinkoff (2019) executed physical model tests for a 1:10 slope and a re-analysis of these tests is included in this thesis as well. Damage caused by entrained rocks is quantified by damage parameters using stereophotogrammetry and coloured rocks in strips. In this study, the influence of several hydraulic and structural parameters on damage parameters has been investigated for mild slopes. A positive correlation has been found between the significant wave height and the damage parameters. Besides this, based on the analysis it can be concluded that the wave steepness and damage parameters are negatively correlated. An increase in layer thickness of the rocks does not seem to increase the stability of rock on mild slopes. However, the slope angle does have an effect on the stability as a milder slope is associated with less damage. Another conclusion is that more damage continues to be observed even after 15 000 waves. Based on the results of the physical model tests, a design formula is developed for mild slopes to be able to increase efficiency in designs of coastal structures for these mild slopes. This study also provides evidence that rocks on mild slopes have different characteristics of damage and damage development compared to steep slopes. The largest share of entrained rocks transport in upward direction and rocks on mild slopes seem to be more mobile compared to steep slopes. This suggested that it might be more efficient to study the moment when the filter layer or the core becomes visible instead of the static stability of rock within the armour layer itself.

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.