Living breakwaters are designed to protect the coast against flooding and erosion, whilst at the same time they enhance the local ecological system by incorporating natural reef components. This study investigates the design of a modular artificial reef developed by the company called Reefy. Reefy breakwaters will consist of interlocking blocks with holes inside and rounded corners. For the configuration of the breakwater no proper design guidelines exist yet which incorporate both the hydrodynamic and ecological functionalities, as both this field of engineering and this reef system are relatively new. Therefore, this study aims to provide insight and develop preliminary design guidance on how to design a hybrid living breakwater from Reefy blocks under wave loading. 
To this end, an experimental study was performed in the Eastern Scheldt wave flume of Deltares investigating the impact of different design variables on both the 2D hydrodynamicand ecological performance under wave loading, in shallow water conditions. Both irregularand regular wave conditions are tested. This thesis focuses on submerged structures and therefore the freeboard is defined to be positive for submerged structures. In total, 15 different designs are tested amongst which 7 are 2DV configurations and the other 8 are complex 3D configurations. Single as well as double 3D structures are tested and the space between a double structure is referred to as ”channel”.
For the hydrodynamic performance, the impact of several design variable on the transmission coefficient (Kt) and reflection (Kr) is quantified. In this study, Kt is defined as the transmitted waveheight behind the structure divided by the incoming waveheight at the same location without a structure. These coefficients are based on the incident wave signals. As most of these tests had shallow water conditions, with large Ursell numbers, the usual methods to determine the incoming wave did not work. Therefore, to obtain the incoming wave signal, a new method was used, based on a combination of the existing techniques. Lastly, from the irregular waves the transmitted- and reflected energy density spectra are investigated and compared to the results from the regular waves. The results of this study reveal that for the same number of blocks, a more complex structure can be built without making a compromise in the hydrodynamic performance parameters.  Furthermore, the existing formulae for the Kt and Kr are compared to results of the hydrodynamic performance as measured. The ones with the best correlation are optimized using a non linear regression analysis. 
For the ecological performance, the stream-wise peak velocities are investigated in the wake behind the structure and in the channel. The performance is investigated based on a tranquility index Tr. Tr increases if the flow is more tranquil. The outcomes of Tr showed that in general, Tr increases for an increase in the design variables that were inversely proportional related to Kt .
In conclusion, the performed tests and analysis provide insight into relevant physical processes and design parameters for artificial reefs, and therefore assists the designer of artificial reefs.

The goal of this study is to examine the feasibility of this solution, from a water quality and hydraulic point of view. Firstly, the current state of the three water bodies was investigated and a stakeholder analysis was conducted to look into the social and political context. Secondly, the effect of the solution on the water quality in the WL and TLR was researched. The most important water quality parameters were qualitatively discussed and after that, the quantitatively changes in the WL were modelled. A convection-diffusion model was set up for different parameter concentrations in R. The initial parameter concentrations were gathered by field measurements and extensive online research. The water quality assessment shows that the Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), turbidity and Total Suspended Solids (TSS) concentrations in the RR have a better value than in the WL. The model itself shows for every parameter that after 100 days of mixing the water is not completely mixed in the WL. The water in the TLR is flushed with WL water and its quality is therefore more or less equal to WL water. It is concluded that the proposed solution improves the water quality in the WL and the TLR. However, long and frequent mixing is necessary for the WL water to reach the RR water quality level. Thirdly, a hydraulic analysis was carried out by investigating the hydrological and geometrical characteristics of the three water bodies. Thereafter, the hydraulic impact was examined by comparing six different flushing scenarios.The flow, water depth and sediment transport rates for different time intervals were modelled in R over the distance of the TLR. A Multi Criteria Analysis was done to interpret the results on the consequences in the TLR. The outcome of the optimum scenario is when the gate has an opening height of 5%. The total transported sediment volume is significantly larger in this scenario, which is beneficial. From a hydraulic perspective the proposed solution is feasible for all water bodies. However, more extensive research on for example the impact on the hydraulics in the TLR is needed to get more conclusive results. As a spin-off, our project (co-)developed educational tools that can be used within the HUNRE curriculum and as awareness raising activities in Hanoi with citizens, schools and the like. Fieldwork with Vietnamese students was conducted to start with building a data base on water quality of the water bodies in Hanoi. The tools that are created are manuals, instruction videos and an introduction lecture. Furthermore, the database, that is built, can be extended with more fieldwork in the future. The extent to which the educational tools and the database integrate in the study program of HUNRE remains unsure, however the awareness among Vietnamese students on the importance of water quality has increased. Furthermore, the OKP project strives to realize the integration of the educational tools in the future. Therefore, this research objective is expected to be achieved.

Dit onderzoek is uitgevoerd om meer inzicht te verkrijgen over de de invloed van ondergrondse waterberging (owb) systemen op warmte- koudeopslag (wko) systemen. Meer specifiek is er onderzoek gedaan naar de situatie in Utrecht. In Utrecht zijn meerdere wko-systemen aanwezig en de Gemeente heeft plannen geformuleerd om in de buurt hiervan een plantsoen aan te leggen om hemelwater op te vangen en in de ondergrond te bergen. In deze studie is de invloed van deze owb op de omliggende wko-systemen onderzocht. Bij het bepalen van de invloed van een owb-systeem is zijn de neerslag- en ontwerp dimensies variabel.

Het onderzoek is gestart met de inventarisatie van de bodem in Utrecht. Hierbij is gekeken naar eigenschappen die van belang zijn voor de toepassing van beiden systemen. De bodem in Utrecht is opgebouwd uit twee verschillende typen lagen: de scheidende klei- en veenlagen en de watervoerende zandpakketten (aquifers). De dikte van de eerste scheidende laag is ca. 4 meter en de dikte van de eerste aquifer is ca. 40 meter. Met deze opbouw kan water in de aquifer worden geborgen zonder dat dit voor wateroverlast op het maaiveld (mv) zorgt.

De bodemenergiesystemen rondom het plantsoen betreffen die van de Jaarbeurs en de Rabobank. De omvang van de bron (het volume in de aquifer waar warme of koude wordt opgeslagen) is onderverdeeld in de thermische- en de hydraulische omvang en de vorm is cilindervormig beschouwd.
Alle bronnen hebben een filterlengte van 18 meter die begint op 8 meter -mv. De grootte van de type bronnen en de grondwaterstromingsrichting verschillen per seizoen door de warmte- en koude vraag en beschikbaarheid.

Voor de ondergrondse waterberging zijn de KNMI-neerslaggegevens van de Bilt sinds 2000 geanalyseerd en is het gemiddelde neerslag per meteorologisch seizoen bepaald. Het percentage hiervan dat beschikbaar komt voor owb is op basis van drie verschillende scenario’s bepaald met als variabelen het verharde oppervlakte en het percentage van de neerslag dat op verhard oppervlakte
valt én naar het owb-systeem wordt geleid. Voor iedere scenario is de minimale afstand tussen de owb-bron en de wko-systemen bepaald aan de hand van (1) de hydraulische straal, (2) de zuurstof spreiding en (3) de radiaal afgelegde afstand van het infiltratiewater. De afgelegde afstand van het infiltratiewater is bepaald op de tijd die nodig is voor de bodem om alle zuurstof om te zetten op 25 meter van de put. De grootste waarde van (1), (2) en (3) is maatgevend genomen.

Uit de resultaten van het onderzoek blijkt de hydraulische straal van de owb in geen enkel scenario te overlappen met de wko-bronnen. Dit geldt ook voor de zuurstofspreiding op basis van zowel een lineair- als een exponentieel verband tussen de zuurstofconcentratie en afstand van de owb-put.
Afhankelijk van de ontwerpdimensies en het scenario overlapt de radiale afstand afgelegd door het infiltratiewater wel met de wko-bronnen en wordt de installatie van een owb-systeem afgeraden.