In July 2021 severe flooding occurred in the South of Limburg, Belgium, and Germany due to heavy precipitation. Extreme precipitation events like this are expected to occur more often in our changing climate. Urbanization is thought to be another contributing factor to the July 2021 flood event. The Netherlands is expected to increase urbanization as a solution to its housing shortage. To make room for urbanization, while minimizing the effect of climate change, the government wants to make ”water and soil leading”, Water en Bodem Sturend, in the decision-making about the layout of the Netherlands.

Therefore, the goal of this research is to investigate the best suitable subcatchment for the construction of new residential houses within the Geul catchment, in terms of flooding. The July 2021 flood event is used as a reference. The first step was to investigate the hydrological response of the Geul catchment. Secondly, this hydrological response was modelled by the semi-distributed hydrological models HBV coupled to D-RR and by the distributed model Wflow_sbm. HBV and D-RR are set up in this research, while Wflow_sbm is adopted from Klein (2022) and Bouaziz (2022). The hydrological models are coupled to the Geul hydrodynamic model D-HYDRO of Hulsman, Weijers, Verstegen, and Goedbloed (2023). The building plans in the Geul catchment were investigated and scenarios were constructed. These scenarios were simulated in the hydrological models. This method resulted in a workflow that can be found in Idsinga (2024). The workflow can be applied on analyses of different land cover types.

The modelled hydrographs showed differences between the hydrological models. Each model better describes one part of the hydrological response compared to the other. HBV and D-RR better represent the subsurface flow and describe the hydrological response during consecutive precipitation events. Wflow_sbm represents the overland flow flux better and therefore describes the hydrological response during the July 2021 flood event. The modelled flood extents during the July 2021 flood event are also compared to the estimated extent by Slager, de Moel, and de Jong (2021). Wflow_sbm showed better similarity to the measured flood extent than HBV and D-RR. The Province of Limburg wants to build 18,730 new houses in the South of Limburg. This results in an increase of 6 km2 paved area. In this research, this increase is applied to different locations in the Geul catchment. Next, the impact of completely paved subcatchments was investigated. The relatively small 6 km² increase in paved area did not result in different discharge behaviour and the total area of the flood extent showed a small difference. However, it impacted the flooded paved area. Building far from the river on the hills resulted in no increase in the flooded paved area. New houses in the valleys, close to the river, are more exposed to flooding. In the Meerssen subcatchment, the added paved area was responsible for 95% of the total increase in the flooded paved area. This was also the case in the Gulp subcatchment, where about 90% of the increase in flooded paved area came from the added paved area.

The Meerssen subcatchment is the most vulnerable to flooding. This subcatchment contains the most paved area and more runoff will result in a more flooded paved area. A completely paved Gulp subcatchment results in a less flooded paved area than building 6 km2 close to the Geul in the Meerssen subcatchment. When the Belgians build new houses in the Sippenaeken subcatchment, the Netherlands will receive more water during an extreme event such as in July 2021.

The letter Water en Bodem Sturend states that new houses must be built in sensible locations. In this research, the location of new houses is found to be important for the hydrological response. Building close to the river results in a more flooded paved area than building far from the river. The Gulp subcatchment is the least vulnerable to flooding and can be considered the best building location for new houses among the three investigated subcatchments.

Kelp Blue is a company whose top priority is the well-being of the planet. Through the cultivation of giant kelp on offshore farms, they create several sustainable products, new job opportunities in regions where they are needed, enhance biodiversity in the water, and above all, sequester tons of CO2 from the air. The start-up is still in its research and development phase, but plans to be building farms on a large scale in just a few years. Despite their knowledge in engineering, the company still needs consulting on certain elements. Therefore the company invited a group of students from the Delft University of Technology to Lüderitz, Namibia for a consultancy project. The project involved creating a procedure for the company to scale up in a sustainable manner. The students decided that this complex problem should be divided into sub-problems. One workstream focused on reducing the carbon emissions during upscaling, while the other workstream focused on analyzing and improving the company’s current design and installation of the farms. Following, both parts of the project are shortly summarized: Part I: Improving the company’s current design Kelp Blue is currently in the pilot phase, in which they’re installing their first large giant kelp farms. Before, they were focusing on the complete installation, including planting the kelp on the submerged netting structure, and the review of this. For the company’s commercial phase, where they want to be able to place farms daily on a large scale, designs were still developed and analyzed. For the commercial phase, this workstream made a new design and installation method. It required an installation where buoys would need to be submerged, the structure locked in place at the desired depth, without the use of scuba divers or remote operated vehicles. Despite the fact that these requirements were challenging, an outstanding result was achieved. The main problem was divided into subproblems, and for each of those a suitable solution was created. Hopes are that the company will consider the given advice as helpful and maybe implement some parts of (or the whole) new design. Part II: Reducing carbon emissions during upscaling First, interviews and desk research were conducted to get a good idea of the challenge of sustainability. This included reading reports, speaking with employees, policy makers and experts with experience within the area. With this information, the challenge could be mapped out and the solution space became clear in terms of legislation and technical possibilities. Climate information was also requested that could later be used to run simulations. During the determination of the possible solutions, research was done on the realistic possibilities, where eventually the use of either solar or wind energy was most appropriate. After conducting a multi-criteria analysis that was put together with the management of Kelp Blue, investing in a solar plant proved to be the most appropriate solution.

Hydrological models are used for all kinds of water management applications. Detailed hydrological simulations are needed to solve the hydrological problems of the 21st century, especially in developing countries. However, sufficient hydrological and meteorological data is often not available. The use of remote sensing (RS) datasets may offer a solution to this problem. RS datasets can perfectly be applied in distributed conceptual hydrological models. In this study, several RS datasets are applied in the calibration of a distributed conceptual hydrological model, and the influence of this approach on the overall model performance is assessed. The RS data applied in this study include terrestrial water storage anomaly (TWSA) data, normalized difference vegetation index (NDVI) data, and soil moisture (SM) data. Also the input and forcing data for the hydrological model consists of datasets based on satellite observations. This data is used in a wflow hbv model, which is applied to the Volta basin in Western Africa as a case-study. In this study, not only the effect of including RS data in the calibration of a distributed hydrological model on streamflow is assessed, but also the effect on a set of internal components of the system, directly related to the datasets used for calibration. These internal stocks and fluxes are the TWSA, the actual evapotranspiration (AET) and the amount of soil moisture in the unsaturated zone. Together with streamflow, the assessment of these stocks and fluxes make up the overall model performance of the system. The effect on the overall model performance is examined using different scenarios, in which different combinations of datasets are used for calibration. Not the absolute values, but the spatiotemporal patterns of the remote sensing datasets are used for model assessment. This is done using the spatial pattern efficiency metric (ESP ). Model optimization was done using the Dynamically Dimensioned Search (DDS) algorithm. The results show that the hydrological model developed for this case-study is already able to simulate streamflow and the temporal patterns of the RS datasets quite well, when it is calibrated on streamflow only. However, the spatial pattern representation of the RS datasets was found to be inadequate and the differences in streamflow simulation performance for the different subcatchments is large. When SM or TWSA data was added to the calibration procedure, the temporal and spatial pattern representations only changed minimally, which is attributed to limited model complexity and flexibility. However, generally a trade-off effect was observed in which the spatial and temporal pattern representation improved, but the streamflow performance decreased. This effect was stronger for the addition of the SM dataset to the calibration than for the addition of TWSA dataset. Although there is definitely a strong connection between NDVI and AET, the physical relation between the two variables was found to be too weak to be used for hydrological model calibration, even when only the spatial and temporal pattern information was used. The overall model performance did improve most in the calibration catchments in the scenario in which Q, SM and TWSA data were combined in the calibration procedure, but the differences with the baseline scenario were only small. For the streamflow performance however, the differences between the scenarios are quite significant. It was shown that calibrating a hydrological model on the spatial and temporal patterns of RS data only (non-Q calibration) can accurately represent the temporal pattern of streamflow observations, but not the magnitude of the flow values. It is recommended to repeat this study using a more complex and more flexible model setup, which allows the model to use the freedom it is given to better represent the spatial patterns observed with RS.

The purpose of this MSc thesis is to do an experimental study into the spatial and temporal variation of rocking armour units. Armour units on a breakwater slope under wave loading can sometimes start to move back and forth, this phenomenon is known as rocking. Rocking can lead to significant impacts between armour units, which can result in breakage. This is especially important for single layer armour units, like the Xbloc. The development of the smart Xbloc makes it possible to measure accelerations and angular velocity with a stand alone sensors at a sampling frequency of around 100 Hz. The current literature does not provide the spatial distribution of the number of impacts and the impact velocities due to rocking. Furthermore, only limited knowledge is available on the distribution in time. The research aim of this thesis is: Determining the spatial and temporal distribution of the number of moving armour units, the number of impacts and the impact velocity of rocking armour units. To achieve this aim a physical scale model was set up and model tests have been performed with 10 smart Xbloc units to measure rocking. The collected data, analysis and results provide a unique look into the behaviour of single layer armour units. The results can be used to validate rocking models and provide valuable statistical information on the number of impacts and the impact velocities.

Heavy rainfall, combined with expanding (unplanned) urban settlements in flood prone areas, expose Dar es Salaam (Tanzania) to the risks of flooding. The urbanisation is so rapid in many areas that it is not beneficial to carry out expensive surveys which are quickly out of date. The work carried out by community-mapping project Dar Ramani Huria (Swahili for "Open map") aims to make a detailed map of Dar es Salaam, to enable the hydrologic models to approach the real situation more closely. However, the surveying methods used until recently are not sufficiently accurate. However, an alternative emerges in the form of community members using a low-cost, dual-frequency global navigation satellite system (GNSS) receiver during surveys. However, before this receiver can be implemented a detailed research has to be done. In this thesis the horizontal and vertical performance of the U-blox ZED-F9P receiver in Delft (the Netherlands) and Dar es Salaam is studied. The research is divided into two parts: performance and case study. For the performance study a series of post-processed kinematic (PPK) experiments were conducted in Delft and Dar es Salaam. The experiments have been designed in order to provide a variety of location, antenna-performance, baseline length, software package and movability. In addition, two re-initialisation experiments were conducted to measure how fast the interrupted GNSS signal is regained by the receiver. The case study focused on the desirability and feasibility, mainly focussing on accuracy, of implementation in the project of Dar Ramani Huria. Structured and unstructured interviews with employees of the Humanitarian OpenStreetMap Team (HOT) Tanzania were held to find out the requirements of implementation. The positioning performance of the receiver varies between the different experiments. The conclusions regarding the positioning performance are based on the scatter plots in the horizontal plane and the positioning over time for the three separate directional components; East, North and Up. The values for the horizontal performance (RMS East, RMS North) and for the vertical performance (RMS Up) of the fix solutions insofar as they fall inside the 95% confidence ellipse are decisive. Only the relevant experiments, namely those who can map a larger area with a single reference station are taken into consideration. The horizontal positioning performance ranges from 1.13 till 16.83 However the latter, high value is from the 9 baseline Dar es Salaam experiment with a very low percentage of fixed solutions. If we disregard the experiments with low percentage of fixed solutions then the horizontal positioning performance ranges van 1.13 till 9.42. The vertical positioning performance shows less accuracy ranging from 3.56 till 14.75. If we compare this performance with the requirements for Dar Ramani Huria’s project, even the strictest of 2cm, the performance is more than adequate according to the "few cm accuracy" requirement. The experiment with the high-end antenna shows with values 2.44mm (RMS East) and 3.42mm (RMS North) the best horizontal and with the value 3.75$mm(RMS Up) the best vertical performance. Another factor influencing the performance is the location, in particular the aspect of atmospheric delay that varies between Dar es Salaam and Delft. This research thesis concludes that the implementation of the receiver in Dar Ramani Huria's project is well possible and that the performance of the receiver is adequate. This conclusion is confirmed by what is actually occurring in the field: HOT Tanzania and Dar Ramani Huria already started using the GNSS receiver and carrying out surveys with this receiver.

Fog harvesting is a sustainable drinking water solution for arid climates. Previous studies have developed an analytical model to predict the fog water collection efficiency as a product of aerodynamic and deposition efficiency as independent factors. In this study, we tested the assumption that deposition efficiency stays unchanged when the geometry of the fog catcher is adjusted. We assessed the collection efficiency of both straight and curved fog water collectors using computational fluid dynamics models and performed controlled experiments in a climatic wind tunnel on sample fog water collectors. The analytical model disregards convex fog harvesters because their lower drag coefficient reduces the aerodynamic efficiency of the fog harvester. The results of the CFD models show that efficiency can be doubled if fog catchers are built convex facing the wind. The wind tunnel experiments support the results from the CFD models. The results of this study show that for convex fog harvesters, although less fog passes through the net, the deposition efficiency increases resulting in a net increase of water collection.