In Dutch polders, numerous structures like bridges, weirs, culverts, and pumping stations have
been constructed over centuries to manage water levels. These structures play a crucial role in
maintaining water levels within predefined targets. The flat topography of the Dutch landscape
combined with the collective impact of head losses, induced by these structures may result in
flooding of polders during high runoff scenarios. Over time, culverts and bridges may
underperform due to alterations in the water system, increased pressure from climate change,
evolved design rules, insufficient maintenance, and shifts in land use.
A challenge is the potential hydraulic underperformance of structures and the need for their
premature replacement, which is costly. Waiting until the end of their technical lifespan may
contribute to floods. Therefore this thesis focuses on improving existing structures to mitigate
the need for replacement, specifically by streamlining inlet and outlet openings to reduce
energy losses. This leads to the research question of this thesis: “How can the head loss over
existing (too tight) culverts be minimised by adding an inlet or outlet profile and does this lead
to a substantial enhancement in the performance of these culverts, providing a practical option
to postpone the replacement of underperforming culverts?”
To answer this question, the problem is explored by looking into the fundamentals of energy
losses, including entrance losses, friction losses, and exit losses. This gives an understanding of
the conditions under which these losses manifest. However, these basic calculations have
inherent limitations due to their reliance on predefined coefficients. This renders them
inadequate for evaluating the effects of introducing new profiles onto an existing structure.
To overcome this, a flume experiment has been performed to verify whether it is possible to
measure water level differences for various profiles at the culvert entrance and exit. With a 3D
Computational Fluid Dynamics (CFD) model (OpenFOAM), flows around different culverts
are simulated. The results of the CFD model are compared to the flume experiment, after
which the CFD model is used to simulate a variety of scenarios, with different profiles, culvert
dimensions, velocities, and water depths.
As such, this thesis addresses challenges and uncertainties in quantifying head losses in culvert
structures through experimental methods and CFD modelling. Experimental setups struggle
with controlling all flow-influencing parameters, while CFD modelling offers flexibility but
requires careful consideration of uncertainties and limitations. The discussion emphasizes the
complexities of comparing experimental and model results, highlighting trade-offs and
uncertainties in each approach.
The conclusion answers the central research question, confirming that specific profiles added to
culverts can significantly reduce entrance losses up to 65%, thereby lowering headwaters for a
constant discharge.
The recommendations section outlines possibilities for further research, including optimizing
profile dimensions and conducting sensitivity analyses of influential parameters. Practical
recommendations involve aligning large-diameter concrete culverts with the socket end in the
flow direction and integrating groove or rounded profiles during construction for cost-effective
inlet loss reduction.

The Province of South Holland is conducting a heritage project to explore the historical significance of barge canals and their future role in a changing climate. This thesis aims to address the water challenges posed by increased floods and droughts caused by climate change through the implementation of a water buffersystem. The buffer should allow the region to serve as a drainage during storms and retain water during droughts, considering the projected climate conditions in 2100. The study focuses on a large case study area, the heart of South Holland, which is enveloped by barge canals and divided into three water boards. A water balance model, calibrated using existing pump time series, is utilized to simulate water flows at the polder level. The model demonstrates sufficient accuracy for predicting larger spatial and seasonal scales within the jurisdiction of the water boards. Future conditions are simulated in the model by incorporating KNMI scenarios. However, the scenarios underestimate the occurrence of droughts, resulting in an underestimation of polder inlet and an overestimation of outlet. 
An above-average extreme climate change scenario is used to compensate for these biases. Combining the model output with long term statistical storm and drought forecasts, this leads to a more realistic buffer design capacity. If the reservoirs can be operated as prescribed, the primary hydrological purposes of the natural water buffers can complement each other. The first criterion consists of the buffering of the increased inequality of net inflow distribution throughout an average expected year, for which 20 million m³ with an additional top layer of 115 mm would be necessary. The second criterion entails the draining of the increase of intense precipitation events. 7.5 million m³ would be necessary to drain the extra precipitation of a 1000 year return period storm event. Thirdly, the buffers should be able to provide water, compensating for the aggravation of drought conditions. 34 million m³ should suffice to compensate for the aggravation of droughts with a return period of 2 years and longer. As the criteria are conditionally compatible, 34 million m³ is the net minimum required buffering capacity for the center of South Holland. 
The final optimal buffering strategy entails the realization of a large buffer in the Noordplaspolder, connecting the Rotte and the Hoogeveensche Vaart, and of a smaller buffer in Schieveen. It also requires the expansion of the water reservoirs in the Eendragtspolder and Berkel. The larger buffer will feature a deeper canal, permanently submerged, linking the Rotte and the Hoogeveensche Vaart, which in turn will connect to the nearby boezem water network. The Noordplaspolder and Eendragtspolder will buffer the area of the two water boards Rijnland and Schieland and the Krimpenerwaard that are inside the case study area, Schieveen and Berkel will buffer Delfland. The Schie and the Vliet will play important roles as water carriers between Delfland and its neighboring water boards and the Nieuwe Maas. This strategy not only addresses water management but also offers recreational, historical, and ecological opportunities. It revives the functions of old barge canals, the Vliet and the Schie, and restores the connection between the Rotte and the Hoogeveensche Vaart, adding to the solution's historical value.

Indonesia faces the challenge of attaining renewable energy goals and reducing carbon emissions by 29% by 2030. Despite a renewable energy goal of 23% of the national energy mix by 2025, only 14% of electricity production is projected to be generated from renewable sources by 2023. Accelerated deployment of renewable energy solutions is required to achieve these goals.

Indonesia has abundant renewable energy sources, such as hydropower, solar, and wind. Yet, a challenge arises from the difference between the electricity demand and supply patterns of these sources, which do not match throughout the day. Fluctuating energy supply patterns and variable energy demand necessitate using efficient Energy Storage Systems (ESS) to bridge the gap.

With its extensive coastline, Indonesia can potentially explore single reservoir Seawater Pumped Hydro Storage (SPHS), a variant of Pumped Hydro Energy Storage (PHES), as an alternative to solve these challenges. Similar to an enormous rechargeable battery, the reservoir in an SPHS system functions as an energy storage system. The system works by pumping up the seawater to the reservoir to store surplus energy during periods of ample supply and discharging it to generate electricity through a hydropower plant during periods of high electricity demand. This research aims to identify the ideal locations for SPHS systems in coastal areas of Indonesia. A Python GIS algorithm was developed to automate the selection process. The identified SPHS sites are then evaluated economically to ascertain their viability. The study concludes by comparing the carbon reduction potential of these systems to Indonesia's carbon emission reduction goals.

The research reveals 609 potential SPHS sites across Indonesia, with a total peak power that can be regenerated of technically potential sites of 29 Gigawatt-peak (GWp). Among these, 297 locations are deemed economically feasible, contributing a potential peak power that can be regenerated of 15 GWp. The peak electricity demand in Indonesia is approximately 44 GW, typically occurring at 8 p.m. The technical potential of SPHS promises an 11% reduction in carbon emissions from the energy sector, while the economically feasible sites could achieve a 6% reduction in carbon emissions projected in 2030.

The Netherlands has suffered form three successive dry summers resulting in a lowering of the groundwater table, causing water shortage. Also in the area of Water BoardDe Dommel, locatedwithin the province of Brabant, water shortage is a common problem. This results in water abstraction restrictions for farmers in the crop season every year. With climate change the precipitation pattern in the Netherlands will change, resulting in longer dry periods during summertime. Water Board De Dommel is searching for strategies to decrease this water shortage. These strategies need to be tested for future climate scenarios. This research tests different interventions for two specific areas within De Dommel. These areas differ in land-use, location in the catchment, geo(hydro)logy and infrastructure. This research answers the following research question: How does the groundwater of two different areas within Waterschap De Dommel react to different interventions
to prevent water shortage in long-termfuture scenarios?
To find the answer to this research question a stationary groundwater model (iMOD) is used. In this model
the different interventions are tested with four climate scenarios from the KNMI. These interventions take place in the top layers of the subsoil. Next to these interventions also three abstraction scenarios are modeled, to see the effect of changes in deeper aquifer layers. The interventions are tested with three signals from the model: 1) the head of the first aquifer layer, 2) the water balance for both areas for the first aquifer layer as well as the first four aquifer layers combined and 3) the flow paths. Because models include uncertainties and assumptions, expert judgement is included to test the interventions. The expert judgment is based on historical maps and the location of the interventions. At the end of the research a non-stationary model is used to test the "Brook swamp" intervention. This result is compared to the results of the stationary model of this intervention. The results show that changes in the top layers of the subsoil have almost no effect on the groundwater in the deeper layers for De Pielis area. More downstream in the catchment, at the Landschotse Heide area, this effect is bigger, because of changes in the upstream area. In the top soil layers the groundwater reacts positive for most interventions for both areas resulting in more water availability. Also in the top layers the effect is bigger at the Landschotse Heide area than at De Pielis area. With the non-stationary model results the groundwater reacts more positive to the "Brook swamp" intervention than for the stationary model. A non-stationary model is therefore better to see how the groundwater reacts to seasonal dependent interventions. The groundwater reacts differently per areas as well as per intervention. In both areas the groundwater does react positively to most interventions. For the Landschotse Heide area the groundwater reacts more positive than for De Pielis area. For both areas the "higher water level" and "closed ditches" interventions show the most positive reactions of the groundwater. Based on these results the Water Board is advised to research the effect of enriching the top layer of De Pielis, to see if these top layers can then hold more water. For the Landschotse Heide the Water Board is advised to decide if agriculture or nature is more important in that area, because these cannot coincide, and reach all demands, in the way it is set-up now.

This research is aimed at creating a generic design method for infiltration drywells on sandy soils by acquiring knowledge on the functioning of these wells. Infiltration drywells are vertical infiltration pipes that are installed above the groundwater table and through which stormwater is drained to the subsurface. Infiltration drywells can have a prominent place in urban water management since they mimic processes that occur under natural conditions. In urban areas the hydrological cycle is altered due to impermeable surfaces. Utilization of infiltration reduces the effects of the alteration on the hydrological cycle. Hereby, reducing the risk on urban flooding and surface water contamination. Furthermore, urban heat stress is reduced by enabling more drought resilient vegetation through groundwater replenishment. Especially considering that climate change will result in more extreme weather conditions, infiltration facilities can aid in creating more resilient urban areas. Until now, there are no design rules for these wells which hinders the implementation in urban areas that are fit for infiltration facilities. In this research a design method for sandy soils in the Netherlands is created and set forth.

The theoretical and practical performance of infiltration drywells is analysed by conducting experiments with Hydrus 3-dimensional geohydrological model simulations, as well as in the field and laboratory. In the field falling head tests were performed with existing infiltration drywells to determine the functioning while soil samples were analysed in the laboratory to determine the hydraulic conductivity. The model simulations also exist of falling head tests and are compared to the experiments in practice. It was found that the most important parameters on functioning of infiltration drywells are the soil hydraulic conductivity and well dimensions. When comparing the simulated falling head tests to field tests and laboratory tests at the same location, discrepancies were discovered. This can be clarified by simplifications that were made like homogeneity and isotropy of the soil in the model. Furthermore, the absence of wall resistance of the well in the model and the method that was used for the calculation of hydraulic conductivity using in practice falling head test data could be the cause.

To this end the generic design method is based on the Hydrus 3D model. This design method consists of empirical contour plots that give the necessary number of wells based on multiple input parameters, including a design storm of 21 mm in 10 min, which has a statistical return period of 25 years in the Netherlands. Due to discrepancies in the research, the design method is used to test the viability of a plan to implement infiltration drywells. Afterwards, a detailed design procedure is still necessary. Overall, the research resulted in a generic design method and shows the advantages of using infiltration drywells, which could be an essential part of urban water management in the Netherlands in the future.

Human interventions in the White Volta River in Ghana increase the flood risk in living spaces of the local communities, causing great challenges in the area. Burkina Faso has built a hydropower dam near the border with Ghana which has a large impact on the discharge extremes of the White Volta River. As a result of poor water management of this dam, water is spilled during the wet season, causing more floods in northern Ghana. Several communities, living near the White Volta River, depend on the river water for their drinking water demand and use the sand in the river bed as construction material. This puts them in a vulnerable position when changes in the natural flow regime of the river occur.

This thesis studies the impact of constructing multiple small dams in the White Volta river in order to decrease the flood risk in villages located close to the river and create an opportunity for controlled sand mining as a result of sedimentation.

Tamale is, with 672.000 inhabitants, the largest city in this area and struggles with the consequences of the floods as well. The drinking water company has trouble meeting the drinking water demand during both the wet and the dry season. When the area is flooded, the water intake point shuts down, and during low water levels, the pumps can get clogged. This clogging occurs even more often as a result of increased illegal sand mining from the river banks by the local communities. This has broadened the river, resulting in lower water levels and a higher turbidity.

A possible solution to ensure the water intake in Tamale and reduce the flood risk in northern Ghana is the construction of multiple small dams in the river bed to flatten the discharge peaks and slow down the water in the White Volta River. At the same time, these dams can create an additional advantage by causing upstream sedimentation that provides a possibility for controlled sand mining in the river bed. To research the effectiveness of this solution, the impact of the dams on flood risk and sedimentation, near seven villages in northern Ghana, was modelled.

A base case of the flood of 2003 was compared to a scenario in which seven dams were implemented at locations close to villages that are often exposed to floods. This was done by building a hydromorphological model of the White Volta River, using the D-HYDRO 1D2D software.
The results of the morphological simulation show that in total, the sedimentation upstream of the dams can fill 81 trucks with sand per day. However, extracting the sediment at the most upstream dams decreases the possibilities for sedimentation near the downstream dams. The results of the 1D2D hydraulic model show that the proposed dams are not able to reduce the flood extent in villages and can even increase inundation depths, resulting in more flood damage.

It is recommended to increase the 2D grid of the hydraulic model in order to receive more realistic backwater curves.

The Volkerak-Zoommeer is a former estuary located the Rhine Meuse Delta in the southwestern part of the Netherlands. After the completion of the Volkerakdam, Philipsdam and Oesterdam as part of the Delta Works, this estuary was cut of from the Oosterschelde and a fresh water lake was formed in a sea water environment. This new lake became the Volkerak-Zoommeer: a lake that acts as a fresh water supply for the regional water systems of the water boards Hollandse Delta, Scheldestromen and Brabantse Delta as well as providing a tidal free shipping connection between Antwerp and the Rhine. The operational water manager of the lake is Rijkswaterstaat. They manage the water level and water quality by letting fresh water in from the Hollandsch Diep at the Volkeraksluizen and release it at Bath into the Westerschelde. This mechanism enables Rijkswaterstaat to flush the system and adhere to the target levels, as well as managing a maximum chloride concentration of 450 mg Cl/L during the growing season. In 2018, the Netherlands experienced one of the most severe droughts since the beginning of weather measurements started. Low discharges at the Rhine resulted in a decreasing water supply and more salinization in the Rhine Meuse Delta. When the discharge of the Rhine at Lobith reach below 800 m3/s, it is no longer allowed to let in fresh water through the Volkeraksluizen. This could lead to problems in the fresh water supply to the regional system of the water users of the Volkerak-Zoommeer. The question came up whether creating a fresh water buffer by temporarily heightening of the water level could be used to overcome a period with no fresh water supply from the Hollandsch Diep. In autumn 2020, the dynamics of the system were researched during a practical trial. The water level was heightened up to +0.15 m NAP. Next, the inlet was closed and it was measured how long it would take until the water level reached -0.10m NAP with normal flushing operations at Bath. During a second trial, the outlet at Bath was closed too. Based on the insights of these trials, a prototype for a Decision Support System was created. This system is able to give insights in the development of the water level at the Volkerak-Zoommeer according to operational water management decisions. This Decision Support System was used to evaluate the impact of delta and climate scenarios in 2050 and 2085 on the water level of the Volkerak-Zoommeer. The maximum possible duration for a period without a fresh water supply was researched per scenario within the target levels of -0.10 m NAP and + 0.15m NAP. Different flushing regimes at Bath were evaluated. For normal flushing operations, this duration is 5 till 7 days. For flushing every second low tide, this period could be lengthened to 8 to 13 days. When the outlet at Bath is closed, the maximum duration is 20 till 60 days. From the trials, it was found that the chloride concentration will gradually increase in this period. Unfortunately, sufficient insights in the dynamics of the chloride concentration lack at the moment to sufficiently incorporate the chloride concentration in the prototype. From historical data, the maximum duration of a period with discharges lower than 800 m3/s measured at Lobith was 16 days during the growing season and 82 days for all year data. Within the current target levels, this duration cannot be reached. It was therefore researched what initial water level theoretically could be achieved based on historical data. This turned out to be +0.50 m NAP. Here, the Volkerak-Zoommeer was considered as a closed system, neglecting the open connections with the Dintel and the Vliet. With an initial water level of +0.50 m NAP, the duration without fresh water supply could be significantly lengthened. With normal flushing operations, the period can take between 12 and 19 days. For flushing operations every second low tide, this period takes 20 till 34 days. When the outlet at Bath is closed, a period up to 120 days could be bridged.

Drought and subsidence are two out of several water-related urban climate adaptation challenges many cities in the Netherlands currently face. Drought is expected to increase in frequency and extent due to climate change. Therefore, drought is likely to further pressurize (subsiding) urban areas in the coming decades. Although the impact of drought on soft soils and hence subsidence is described in academic literature, in-practice analyzes are limited. Given the expectation of increased drought impacts, as well as the current urge for new housing developments to combat housing scarcity, this research focuses on in-practice drought impacts on subsidence in two soft-soil urban areas in the Netherlands. This research’s objective is to gain insight into drought-induced subsidence in soft-soil urban areas in the Netherlands, in order to better understand drought impacts on subsidence rates in future housing developments on comparable soils. With a better understanding more appropriate site preparation strategies can be applied. The objective is endeavoured by an in-practice analysis of two study areas: a 90s neighbourhood in Diemen and a recently finished urban area in Kampen. Firstly, variations in relative surface levels, observed by InSAR (2015-2019), are compared for dry and wet periods. Afterwards, this subsidence data is separated based upon local characteristics (soil structure, pavement type, vegetation percentage and vicinity of surface water) to analyze their influence on drought-induced subsidence. Lastly, an expert questionnaire is conducted on suggestions for both mitigation and adaptation strategies. Subsidence is not a linear process in time: surface level movements vary due to the soil’s wetting and drying. The extent of soil compaction in dry periods is found to increase with intenser droughts. The extent of soil swell in wet periods is approximately similar for varying wetness extents. This research found that the severe drought of 2018 thereby caused a soil compaction to such extent it could not be balanced with subsequent winter swell, and hence resulted in approximately 1 to 1.5 millimeter of drought-induced subsidence. Drought-induced subsidence is thus a net result of the (change in) seasonal surface level fluctuation. This net result is assumed to be consequence of extensive groundwater level drops, although the exact share of processes and subsidence mechanisms could not be estimated. Moreover, surface level movements are found to be prone to a lag and difference in duration (hysteresis) in comparison to the start and duration of dry and wet periods. Various local characteristics are found to influence drought-induced subsidence. In general more compressible soils show slightly larger surface level movement between dry and wet periods. The (sand) cover thickness is found to be influential on which subsidence mechanisms are triggered during a drought: a cover thickness resulting in groundwater levels to drop to present clay/ peat layers causes shrinkage and/ or peat oxidation additional to clinch. Unpaved surfaces are found to fluctuate more extensively than paved surfaces, but this does not necessarily result in more irreversible subsidence. Furthermore, abundant vegetation might result in extra irreversible subsidence due to its extensive water usage in dense urban areas. Lastly, in the analyzed soft-soil areas the surface waters seem to influence groundwater levels and hence surface level movements only on short distance. Suggestions on feasible enhancing site preparation strategies are given based upon research results and experts’ opinions. The suggested mitigation strategies consist of two approaches in order to hamper the variations in effective stresses and hence minimize the seasonal surface level fluctuation. The first approach focuses on preventing extensive groundwater level variations: increasing storage and infiltration of water, reversed drainage, building crawl-space free and choosing vegetation types based on their water usage. Additionally, it is suggested to apply a sufficient cover thickness (at raises) if soft soil layers are near the surface. This prevents that future extensive groundwater drops within these layers, and thereby limits (seasonal) shrinkage and/ or peat oxidation. The second approach focuses on reducing the top soil’s weight, via lightweight materials or self-carrying constructions. Adapting to drought-induced subsidence starts with measuring/ monitoring surface level movements in order to analyze spatial and temporal trends. Additionally, drought is to be considered to greater extent in subsidence modelling in order to improve subsidence estimations. This can be done by applying variable or lower groundwater levels in estimations of the (change in) effective stresses, at calculations of consolidation or creep. Lastly, urban utility management should focus on long-term costs via e.g. Life Cycle Analysis, and on overlapping maintenance cycles of surface level raising and e.g. sewer pipe replacements. The most important conclusion derived on urban drought-induced subsidence is that despite individual drought impact on subsidence is limited to 1 to 1.5 millimeters, its seasonal occurrence continuously affects surface levels. Moreover, due to climate change drought is expected to increasingly impact surface levels in Dutch soft-soil urban areas in the coming decades. The suggested strategies mainly hamper variations in soil stresses, via fluctuating groundwater levels, and hence drought impacts on soft soils. These strategies help to limit future soil movements and hence result in more climate adaptable soft-soil urban areas. The focus of this research is on qualitative analyses of in-practice data such that significant processes have been disclosed, rather than statistically verifying the results. Consequently, the research initiates further specific studies on statistical verification of drought-induced subsidence, and moreover topics on its mechanisms; its spatial and temporal variation; its measurement and modelling; the influences of local characteristics hereupon; and the effectiveness of the suggested enhanced site preparation strategies.

For hundreds of years, ditch water levels in Dutch agricultural peatlands have been lowered to increase the loading capacity of farming parcels. This lowering results in groundwater levels in the middle of the parcels that fall a few decimeters under the ditch levels. When the groundwater level in a peat soil is lowered, newly uncovered peat is exposed to oxygen and begins to oxidise. This process emits greenhouse gasses (GHG), releases nutrients; like nitrogen and phosphorus that stimulate eutrophication, dries out the top subsurface layer and causes the land to subside. This study focuses on an island polder in Warmond, the Zwanburgerpolder, with a clay - peat subsurface. Half of the Zwanburgerpolder belongs to the Eenzaamheid, a biological cheese farm with the ambition to transition to a regenerative cheese farm. One of the key objectives to achieve this regenerative goal is to limit the GHG emitted from the farm. An analysis of the current (ground)water system of the Zwanburgerpolder was done which focused on limiting land subsidence by raising the groundwater level and thereby reducing the emission of GHG, improving (ground)water quality and stimulating biodiversity. First, four research components were examined through field experiments and literature studies: 1) water quantity, 2) water quality, 3) GHG emissions and 4) land surface displacements. The obtained results were used to understand how the Zwanburgerpolder works and identify the relationships between the four components. Then, two groundwater models were developed to represent the current groundwater level and flows in the Zwanburgerpolder: one in iMOD and one in FlexPDE. The iMOD model was used to get a visual representation of the groundwater level variations across the island and to see the groundwater response to precipitation and evaporation. The FlexPDE model was used to get an overview of the phreatic groundwater level drop between two ditches over the summer. To find the most suitable way to limit land subsidence in the Zwanburgerpolder, the models were adjusted to represent possible future situations. Instead of using the collected climate data of 2021 as input parameter, the projected climate data of 2065 was used. The future models consisted of a base scenario, in which no changes were made to the polder compared to the current situation and adapted scenarios, in which the following five water management measures were tested: 1. Adding ditches, 2. Installing horizontal drains, 3. Temporarily inundating parcels, 4. Installing vertical drains and 5. Raising the summer ditch water level. Temporarily inundating parcels performed the best quantitatively and qualitatively during the comparison of the measures. However, this measure is agriculturally unfavourable because as a consequence, parcels cannot be used for grazing during a significantly long period of time. For the Eenzaamheid, where regenerative practices and agricultural capacity take center stage, the recommendation for limiting land subsidence is to combine and adjust two measures: temporarily inundating parcels and adding ditches. Gutters that currently run down the center of the parcels should be enlarged and inundated during the summer period, by siphoning water from the boezem. Inundation can take place during the whole summer, since grazing is still possible alongside the gutters. It is recommended to start off by only applying the measures in the most critical parcels in order to use it as a testing ground to check the possibly negative effects of the measures besides the desired positive effects of limiting land subsidence, reducing GHG emissions and improving the (ground)water quality. Further, the results discussed in this report provide an interesting addition to peatland subsidence studies. They were obtained through field experiments done on a much smaller budget than other studies done so far with expensive measurement setups. The recommendation towards such peatland subsidence studies is therefore to apply a large network of lower cost measurement setups, instead of a few costly ones, in order to get an extensive representation of the behaviour of different Dutch peatlands. The main limitations in this study are the uncertainties linked to the parameters used to build the iMOD and FlexPDE models and the time constraint on the field experiments. The parameter uncertainties mean that the final model outputs fall within a certain error range. To minimize the error range, a model sensitivity and uncertainty analysis should be done. Without the field work time constraint, it would have been possible to identify the seasonal patterns in the groundwater level fluctuations compared to the other water bodies and in the land surface displacements.

This research focuses on using Sentinel-2 optical imagery to provide a means of high-resolution monitoring and evaluation of changes in Total Suspended Matter (TSM) concentration in the Brantas river basin. In situ spectral measurements as well as laboratory results show an extremely turbid nature of the Brantas River surface water. Current monitoring of the river water quality, is done by point measurements representing point estimations of the water quality in time and pace. Interactions within the system are mostly unknown. Having accurate knowledge of near real time water quality information will greatly enhance the effectiveness of the monitoring organizations, especially if this comes in a high
spatial and temporal resolution. The Sentinel- 2 remote sensing platform delivers information which can be used to derive such data with a 10m resolution and revisit time of 5 days. To estimate TSM concentrations a multi-conditional algorithm is developed. It uses linear regression for low to medium
TSM concentrations based on the green and red band reflectance values and polynomial regression for high to extremely high TSM concentrations based on the red edge NIR band. Testing the multi-conditional algorithm on the WISP-3 in situ spectral data shows the model’s performance is good with r2 = 0.79, RMSE
= 66.5 mg/L and NRMSE = 9.7%. Performance of the multi-conditional algorithm is found to be poor when based on Sentinel-2 (S2) bottom of atmosphere data from bands green, red and red edge NIR. However, when recalibrating the polynomial model on Sentinel-2 atmospherically uncorrected top of atmosphere
data, results are more promising: r2 = 0.75, RMSE = 64.2 mg/L and NRMSE = 11.3% . Also, TSM estimates from remote sensing reflectances atmospherically corrected by different processors are compared, from which ACOLITE (RMSE = 5.0 mg/L, NRMSE = 25.3%) performs significantly better than C2RCC (RMSE =
11.3 mg/L, NRMSE = 57.5%) and Sen2Cor (RMSE = 42.8 mg/L, NRMSE = 217%). This study shows that 1) high-resolution spatial and temporal variation of TSM concentration estimation can be made visible within the Brantas river basin, 2) an overview of TSM concentration estimation of the entire basin at one
moment in time can be achieved and visualised, 3) an extensive historical record of TSM concentration estimations can be accessed, and 4) information is provided to prioritize sampling locations and field surveying times.

Rivers are identified as main sources of plastic litter in oceans. About 65% of the plastic litter is buoyant in fresh waters, meaning it has the capability to float, making transport over rivers relatively easy. A better understanding of how plastic litter is transported via rivers is crucial. Both for quantification and mitigation of the plastic problem. Most research on quantification of the plastic flux is based on surface-measurements only, up till about 50 cm water-depth. Thereby, most cleaning strategies focus on skimming only the surface. This research investigates the distribution of buoyant plastic litter over the water depth in rivers. Given the wide use of marginal buoyant plastics, it is hypothesized that a significant share of the plastic in rivers is transported below the first 50 cm surface-water, due to the mixing ability of turbulent flow. In such case, a great share of the plastic litter is overlooked in both flux estimates and riverine removal strategies. The question arises: How is plastic distributed over the water depth in rivers and how is this distribution related to prevailing flow conditions? The research is based on four pillars: Knowledge on the hydraulic plastic parameters (1), in combination with experimental observations (2), might lead to an explanation of the distribution with a theoretical approximation (3), based on existing literature from neighboring research fields. Lastly, manipulation (4) of this plastic distribution by hydraulic interventions is investigated. With this research, a first insight is created on the vertical behavior of plastic in relation to the flow conditions. This study shows that marginal buoyant plastics can be sensitive to turbulent motions in flow and a significant amount of plastic might be transported below the surface. In order to create a complete picture of the behavior of different kinds of plastic in stream flows, more extensive research is needed.

It is no secret that the climate is changing, however, the severity and speed of this process is under debate. This leads to the question if and when we need to take action to protect the Netherlands against the effects of climate change. In order to deal with the uncertainties in policy- and decision-making, an adaptive approach is desirable. An option is to apply the Dynamic Adaptive Policy Pathways (DAPP) approach.

The DAPP approach has been applied successfully in several large scale projects. However, less attention is given to the application on small scale areas, and no applications on (small-scaled) polder areas are present. The aim of this report is to answer the following research question: "Is the Dynamic Adaptive Policy Pathways approach suited for improving the adaptivity of polder management, given the uncertainty in climate change effects?" The Zuidplaspolder is used as a case area for application of the DAPP approach. This deep-lying polder is interesting due to its diverse land use, the low elevation levels and already present issues in water management.

Through assessing the potential effects of climate change, conducting interviews, creating a hydrological model and following the steps of the DAPP procedure, a pathway map for the Zuidplaspolder is created. This pathway map is evaluated during focus groups with stakeholders from the Zuidplaspolder case area, as well as actors from a different polder area, being the Schermerpolder. Besides evaluating the applicability of the pathway map, the DAPP approach itself was assessed as well.

The pathway map provided several insights, one being the requirement to start considering actions at present in order to timely cope with issues in the future.
Moreover, it was found that the DAPP approach is suited for improving the adaptivity in polder management, given the uncertainty in climate change effects. The pathway map is a helpful tool for authorities and affected stakeholders within polder areas to explicate upcoming issues. However, a cost-benefit analysis is required for actual, well-informed policy- and decision-making based on the pathway map. Nonetheless, it assists in making decisions more strategically and to explain certain choices in decision-making, which helps in creating support and understanding. Even though there are difficulties in translating large-scale actions and their effects to a smaller scale, the scale of the case area proved not to be a major issue. At last, the DAPP approach is found useful for other polder areas as well. However, a general pathway map cannot be created, since each polder has its unique set of characteristics and stakeholders with mindset on urgency.

When the pathway map is utilised for actual policy- and decision making, the use of an extended model is recommended. Here, probabilistic simulations are suggested, as well as the incorporation of several components that were excluded in this research. For identifying an integral pathway map for Dutch polder areas, it is recommended to research the clustering of polder characteristics on their constraints and related measures. By selecting the clusters that fit a designated case polder, a tailored pathway map can be created.

The Meuse river facilitates important socio-economic functions. In the light of Integrated River Management (IRM), the question rises whether these functions can be facilitated in future decades (until 2050) as well. The riverbed is expected to degrade over the coming decades, just like in the past century. On top of that, the discharge regime will alter because of climate change. This research studies the impact of bed degradation and altering discharge regimes on the river functioning regarding navigation and flood safety. This is done by linking hydraulic river conditions to functional performance indicators.

The world’s climate is changing. In the Netherlands one of the consequences is that water boards and municipalities are preparing for an increase in extreme precipitation. To evaluate the consequences in case of extreme precipitation all Dutch municipalities and water boards have to perform a stress test. In these stress tests the response of the water system is evaluated during extreme precipitation events which are much larger than the events used to design the water system. It is analysed which places are vulnerable to flooding and what risk (probability x potential damage) is involved. In the Netherlands the responsibility of different parts of the water system are with different government authorities. The municipality is responsible for the sewer system and the waterboard is responsible the surface water system. As a result both municipalities and waterboards often perform separate climate stress tests. Most of the time the municipality will not take the surface water into account or does it in a very simplified manner, for the waterboards this is vice versa. However, these systems do influence and hinder each other. This may result in an underestimation of the actual flooding, and corresponding damage. The aim of this research is to investigate to what extent the urban drainage system and the rural surface water system influence each other during extreme precipitation. In this research the case study area of Schijndel with the surrounding catchment area of the Schijndelse loop is analysed. The research must clarify if flooding caused by extreme precipitation is underestimated if the urban drainage system and the rural surface water system of Schijndel are analysed separately instead of combined. For this research a hydrodynamic model of the area is constructed in the hydrodynamic software package Infoworks ICM. The hydrodynamic model was used to investigate the difference between a coupled and separate model setup. The results show that the modelled flood locations correspond to known flood reports, but also that the difficult to determine infiltration rate, grid size and surface roughness significantly influence the model response. Nonetheless, the hydrodynamic model can be used to compare the response for short precipitation events between a coupled and separate sewer surface water model. The results show that flooding is underestimated if the sewer system and the surface water system are put to the test separately instead of combined. However, the differences are location and event specific and occur mainly just upstream and downstream of the combined sewer overflow locations in the study area. Here, the results show an increase in flood depth, flood duration, flood extent and the amount of houses flooded when the system is modelled coupled instead of separate. For future stress test studies it is recommended to schematize both the urban sewer system and surface water system together in one model, as this gives a better representation of the flow dynamics which occur in reality.

Flooding is globally one of the most damaging natural hazard. Flood risk will most likely increase in the near future due to increases in flood frequency attributed to climate change and growth in population and wealth in flood prone areas. This growth in wealth and population is increasingly considered as a major driver for the increase in flood losses in the last decades. Floodplains are susceptible to floods, but historically people have always been settling in floodplains. The growth of population in floodplains, which is a substantial cause for increased flood risk, is essential to consider for decision making in floodplain development, as improper development increases flood exposure and aggravates flood risk. The science of socio-hydrology tries to capture the interaction between humans and floods in the floodplain. But, it is necessary to identify these mechanisms on a broader scale. A way of doing this, is to look at the development of floodplain population density over the years, but population data is not available on a long temporal scale. Therefore, Nighttime light data was used to model the gaps in the availability of population data. Nighttime light data data captures the illumination on earth, and is available on a large temporal and spatial scale, and has a high correlation with population data. However, the relationship between Nighttime light data and population data is not straightforward. This study tries to model a population proxy through the use of Nighttime light data data and explains when and why it does or does not work. Validation of the model shows that in some regions the predicted data is relatively precise, but ultimately, due to the lack of data, the accuracy is unknown. This study shows that understanding the behaviour of NTL is valuable, because it has the potential to map Socio-Economic variables in data-scarce areas.

In dit onderzoek zal antwoord worden gegeven op de vraag: Moet het falen van gemalen mee worden genomen in de watersysteemtoets? In de 6-jaarlijkse toetsing van de waterschappen wordt bepaald of het watersysteem voldoet aan de door de provincie opgestelde eisen voor wateroverlast. Op dit moment wordt er in deze toetsing geen rekening gehouden met het feit dat gemalen kunnen falen en dit falen invloed kan hebben op de wateroverlast. In dit onderzoek zijn de onbeschikbaarheid van gemalen en de gevolgen van deze onbeschikbaarheid in kaart gebracht. Met deze gegevens is het risico dat gemalen vormen voor het watersysteem bepaald.

Since coined in 2011, socio-hydrology studies have been dominated with mathematical models developed by mostly hydrologists, which often did not take social aspects into account so seriously. Some people argued that more attention into the social part of socio-hydrology should be given, because often the social aspects were too oversimplified. This thesis research tried to dig deeper into the social aspects of a socio-hydrology system. Keduang sub-basin was chosen to be the case study, as it has a sedimentation problem which has caused a huge operational problem of Gajah Mungkur dam, a multipurpose dam that mainly works as a flood control and hydropower plant in Solo river basin, the largest basin in Java Island of Indonesia.

This research used the case study research approach proposed by Yin (2013). Three different analysis were done to examine the system: stakeholder analysis to identify the relevant actors and their characteristics, historical events analysis to examine what the actors have done that were related to the sedimentation issue, and Socio-cultural, Technological, Economic, Environmental, Political, Legal and Ethical (STEEPLE) analysis, to investigate those each sectors as external factors that might influence the decision making of the related actors. To summarize the analysis, a conceptual model was created to describe the socio-hydrology system of Keduang sub-basin.

There are a total of 10 relevant actors in the system, which come from 3 different groups: government, society and external actors. The government consists of 7 government agencies, the society represents farmers, and the external factors consist of researchers and donators. Between these 3 groups of actors, there is a feedback loop connection between the government and the society, which implies that the government has created some programs based on the society characteristic. Meanwhile, the external actors only interact with the government towards coordination.

The human-water interactions are different between the government and society, the government has a negative feedback loop with the water system, which means the government reduce what occurs in the water system, for example the high sediment in the system influences the government to remove the sediment. Surprisingly, it is not the case for the society, as it has a positive feedback loop especially regarding high sediments. Once the river had high sediments, people started to throw more garbage there thinking it would not be back clean, which would make the river even worse.

The actions done by the government and society are not only influenced by the water system, but also other external factors. For the government, economic, socio-cultural and politic factors are very influential to their actions. On the other hand, economic and socio-cultural factors are very influential to the society actions. These external factors seem to be more influential than the water system itself for their actions towards the water system.

Qualitative socio-hydrology study is clearly different with the quantitative study. Qualitative focuses on the why and how of relations in the system. It can give a good understanding on how such relations occur in the system. Hence, qualitative study can complement the quantitative study so that the model for quantitative study will not be oversimplified and based on valid reasoning.

What are the national and provincial economic potentials of ocean thermal energy conversion in relation to the provincial electricity demand fulfilment in Indonesia? When we are talking about the economic potential of OTEC in Indonesia, we are talking about potential as a result of different possible configurations. On the national level, the economic potentials of both cost assumptions are more than enough to fulfil the total electricity demand of the country. However, Indonesia seizes an immensely broad area of land and sea. A big part of the potential lies outside the provincial boundaries, far away from demand centres. Still, when only the provincial potentials are considered, the total economic potential is higher than the demand. This does not necessarily mean that the available resource is accessible by the demand centres, though. The available resources of OTEC are not distributed evenly throughout the country. Some areas are blessed with remarkably good resources in abundance while the other areas are not so lucky with the resources. Hence, the stations are selected based on the proximity to the demand centres. It turns out that based on the results of the thesis, it is not possible to fully supply the electricity demand on the provincial level in Indonesia solely by OTEC electricity production of the selected stations. It is indeed possible for some areas to do that, but in other areas, there is no economic potential at all. However, it is not likely that a single resource will ever be used to cover 100% of supply. In this sense, there is a huge opportunity for OTEC to enter the energy landscape and become the provider of baseload electricity

Because the earth loses her heat less efficient, the average global temperature rises. As a result, more extreme weather conditions occur. In urban environments, rain during these extreme weather conditions cannot be discharged immediately. A Polder Roof, a combination of a blue and green roof, provides a solution for this problem. This roof stores water under a green layer consisting of soil with vegetation. A Polder Roof is difficult to sell, because the investment of an user is earned back long term and the water storage does not have a direct influence on the user. This study aims to investigate the possibility to add a direct function to this water storage, by harvesting or transfer thermal energy out of or into this water, to heat or cool a building energy-efficiently.
To heat a building, a certain heat input is necessary to keep the building on the same temperature. This heat demand can be determined by standardized yearly values used in the sector. If these are distributed monthly over a year, a mean heat demand per second can be determined. This heat demand is provided by harvesting heat out of the water on the roof by using a heat pump. Therefore the temperature of the water changes. To state that the water may not turn into ice, a maximum daily heat drainage can be calculated. The total amount of thermal energy which can be harvested is determined by the water’s temperature and volume. The temperature of the water is influenced by the temperature of the air in contact with the water, incoming radiation and outgoing heat from the building underneath. The volume rises through precipitation on the roof and lowers by evaporation and the discharge from water of the roof. The influence of the air on the water temperature is modelled with the Cooling Law of Newton.
By modelling the described system, an equilibrium temperature difference between water and air can be found with a given heat demand. When cooling is needed, this difference will also occur because the heat pump transfers heat into the water and is cooled by the air. This method for heating a building can be used from March to November in the Netherlands. By using another isolation layer which can retain more radiation instead of the green layer, the applicability can be increased. Cooling with a heat pump can be applied if the cooling demand is low. A high water temperature is adversely for the efficiency of the heat pump and the vegetation. Because a Polder Roof isolates a building better than a conventional roof, the building has a lower cooling demand, so the temperature of the water will rise less. The use of a heat pump is more energy-efficient than a conventional installation, on the condition that the COP is higher than 1.33.

Plastic debris in water systems form a major problem for our ecosystem because it is extremely persistent in the environment and the global plastic production is still increasing without adequate measures to prevent pollution. Apart from the importance of reducing the amount of plastic entering the ocean, clearing the rivers from debris is important for societal concerns, such as health related issues and flood risks. The interaction between riverine debris and the hydrodynamics of water systems plays an important role in the construction of trash racks that can block water flow in the river. These clogged trash racks lead to an increase in upstream water level and can cause regional flood risks. This study was set up to investigate the amount and accumulation of riverine debris in the Cikapundung River in Indonesia, one of the tributaries of the Citarum River.

The Citarum River is one of the world’s most heavily polluted rivers, predominantly caused by industries and households dumping their waste directly in the river. With a length of 270 kilometers, this is the longest river of West-Java and it is the main source of water for 27 million people. The river flows through three reservoirs and the area upstream of these reservoirs is called the Upper Citarum River Basin. The main contribution of pollution comes from this area, as the city of Bandung is located in this area. The Cikapundung River flows through the city of Bandung and is one of the tributaries of the Citarum River. This river was selected for the field measurements in this study as it allowed measurements to be performed in river parts with rural and urban areas neighboring the river.
Up until now, many studies of riverine debris accumulation are predominantly focused on organic debris accumulations at bridges and gates. This study also investigated plastic debris accumulations, as it forms a significant part of the debris in the Cikapundung River and other Asian rivers.

Field measurements in the Cikapundung River were performed with a single and double trawl, to determine the riverine debris composition and flux. Scaled laboratory tests were carried out, to (1) monitor the blockage growth process for different debris compositions, (2) investigate the influence of different parameters on the upstream water level and (3) determine the impact of a blocked trash rack on regional flood risks.

From the field measurements, an increase in downstream direction was found for the debris flux, but the debris composition varied in both time and space. The plastic debris mass varied between 11\% and 78\% of the total debris mass.
Based on the laboratory tests, the behavior of riverine debris is studied during normal flow conditions and in front of a trash rack. One of the key findings from this study is that plastic debris causes a faster blockage than organic debris, as the plastic blockage contains fewer voids and therefore has a higher blockage density. In the formation of a blockage in front of a trash rack, a mix of organic and plastic debris behaved more similar to plastic debris. The shape of the blockage was also found to be different for plastic and organic debris: a high amount of plastic in the debris lead to an angular blockage shape, whereas mainly organic debris produced a curved blockage shape.
The most important indicators for flood risks related to debris accumulations were found to be the debris load, loss coefficient, initial flow velocity and initial flow depth. By rescaling the results to the case study location in Bandung, it was found that a backwater rise within the hour of O(1 m) is plausible for a blocked trash rack.

This study forms the stepping stone to further quantifying riverine (plastic) debris and investigating its relation to changes in the water system behavior, including its influence on regional flood risks.