In the context of climate change and urbanization, sustainable urban drainage systems (SUDS) are widely adopted measures to manage stormwater in the city on-site. However, their performance in practice often differs from modelled and laboratory-scale predictions due to the variability in properties of real sediments (in terms of size, shape, density and coagulation) compared to the silicate standard Millisil®W4. Clogging is a common source of failure. 
The SediSubstrator L is a decentralized stormwater treatment device installed as a pre-treatment step to mitigate clogging in a storage and infiltration system on the Rooseveltlaan in Amsterdam. It consists of a sedimentation pipe with a flow-separating grate, the SediPipe, and a filter-adsorbent, the SediSorp+. It is purported to remove 80 % of TSS by DiBT (the technical authority in the German construction sector) test principles that use Millisil®W4 to simulate real sediments. The full-scale unit was monitored in the city throughout May-September 2022 to assess its performance. 
The stormwater runoff discharged from the catchment had high concentrations of lead (54 μg/L) and zinc (790 μg/L), likely due to contact with gutters and old roofing material, amplified by the relative contribution of these roofs to the total catchment discharge (accounting for 50 % of the area contributing to runoff). The sediment (TSS) concentration was low, equivalent to 20 mg/L on average. The sediments were also light and fine—with an organic fraction of 66 % and with 78 % of diameter smaller than 63 μm.
In the SediSubstrator L, the TSS removal efficiency was 34 % on average. This corresponds to an estimated caught load of 2.7 kg for this period. The removal efficiency was shown to increase with an increasing stormwater TSS concentration, with longer antecedent dry periods and with lower TSS organic fractions. Turbidity dynamics in the system suggest that while a net sequestration of solids occurs in the SediPipe, there is a resuspension of fine solids. This was observed in a camera inspection to occur from solids which settle on or near the grate. In an extreme rainfall event on September 28th 2022, water collected on the section of the street connected to the SediSubstrator, the cause of which is still subject to speculation. The observed SediSorp+ filter resistance across the summer was not indicative of gradual clogging, but an inspection showed signs of decayed organic matter throughout the full length of the filter bedas well as traces of cement in two of the four cartridges. It is possible that these two effects together with turbulent inflows prompted the acute clogging behavior.

There is interest in using the SediSubstrator beyond the city of Amsterdam to reduce phosphorus loadings in the road runoff discharged to sensitive nature areas. On the Rooseveltlaan, the average total phosphorus removal efficiency was 18 % (50 % for dissolved, readily bioavailable ortho-phosphate). Interactions with settled sediments generated ortho-phosphate in the SediPipe, and fine particulate and colloidal organic phosphorus was shown remobilized in both the SediPipe and SediSorp+. The removal of ortho-phosphate in theSediSorp+ in natural rainfall was good (on average 50 %) and was shown to be consistent at different contact times (approximately 10-30 minutes). 
The installed unit should be monitored over a longer time period of two years for statistical significance and to capture seasonal variation in loads. Nevertheless, the removal efficiency observed on site is consistent with the results of a sedimentation model developed according to Ferguson & Church (2004), using a stormwater sediment particle density as measured at another location in the city. Design adaptations are recommended to improve the SediSubstrator L to the conditions observed in Amsterdam: namely, better site selection, a longer SediPipe section (24 m) and a second filter stage to better capture the fine suspended solids.

To reduce the Urban Heat Island (UHI) effect Green Infrastructure (GI) is seen as a key measure. Though, often the need for water to evaporate is neglected. This study focuses on showing the effects of irrigation and increased soil moisture contents on GI within urban areas to reduce the UHI-effect. ENVI-met, a micro-climate model, is used to model various scenarios for a tropical day and a heatwave in the Netherlands. For two Dutch urban areas, with different building typology and subsoil, the current situation, a greener scenario and various soil moisture profiles have been modelled to show the effects of increased soil moisture content on thermal comfort and the UHI-effect.

Research towards aquathermal energy solutions is still in a pioneering phase. Especially in urban environments, these solutions could potentially form the missing connection between heating supply and demand. This study focuses on the application of these solutions in the city canal waters in the largest city of the Netherlands, Amsterdam . Currently, these so-called Surface Water Heat (SWH) systems have not been implemented at all in the inner city canals of Amsterdam. One of the reasons for this can be found in a lack of knowledge about natural water temperature variations in these types of waters and the unknown thermal effects related to SWH systems. This study is an answer to this knowledge gap and an attempt is made to provide insight in the thermal effects of SWH on a city canal. The Amsterdam city canals form a unique water system in open connection with larger waterways and they are part of a hydrodynamically complex interaction between sea and the river Rhine. Until date, such a study towards SWH system effects, not being restricted to the boundaries of the respective water body, is scarce or even non-existent.\\ The case study location is situated at the Jacob van Lennepkanaal in Amsterdam, where a collective of civilians has recently started the exploratory phase for installation of the first SWH city canal system for heating of their own district. To respond to this societal development, this specific case study location was chosen. To be able to model the SWH system for this neighborhood, the first part of this thesis focuses on system layout and related system characteristics. It was found that open-loop SWH systems are often applied at district level. Secondly, a reference surface water temperature model without SWH systems was built and validated upon meteorological forcing with local water temperature measurements. The third part of the followed method was to apply the modelled SWH system to this validated three-dimensional thermodynamic model. For this purpose, the Delft3D model was chosen, which computes the RANS equations under the hydrostatic assumption. Several scenarios were calculated with varying temperature difference through the SWH heat exchanger and varying distance between system intake and outfall. The modelling results for the Jacob van Lennepkanaal case show that SWH systems used for heating purposes, thereby cooling the surface water, produce a negatively buoyant flow, causing the discharged cold water plume to sink to the bottom. Existing thermal stratification in the city canals is enhanced and hydrodynamic mixing processes are not strong enough to disturb this stratification built-up. Further away along the plume, in the far-field, a combination of buoyant spreading and the process of passive diffusion mix the water column and the temperature decrease, induced by the SWH system, becomes uniformly spread over the entire water column. Currently, steady state one-dimensional models are often used for assessment of SWH thermal effects. It was demonstrated that these models are useful and accurate, provided that the right heat exchange coefficient is used and near-field mixing at the outfall is represented correctly. These models can be used to study for example the time-averaged extent of the cold water plume, but fail to provide insight in time-varying and spatial characteristics of the canal. Local changes in bed level height, attraction of ambient water by the intake and intersections with lateral canals also influence the thermal profile. For a study towards these effects in greater detail, three-dimensional modelling or 2DV-modelling are preferred. Also, in case of a study towards application of multiple systems, these are the models of choice.

The goal of this study was to get a better understanding of the current groundwater drainage in New Orleans, Louisiana. An analysis was conducted on the interactions between groundwater drainage and different water infrastructure systems like: the sanitary sewer system, the storm water drainage system, and the drinking water system. Due to the age of these networks, damage caused during natural disasters like Hurricane Katrina, the ground movement sensitivity of the region and the existing land subsidence, these networks are in poor shape. To quantify the groundwater drainage component of each system, an existing QGIS wastewater model was used along with different time series, including hourly and daily data for precipitation and sewer station influents, and a storm drainage analysis based on pumping station data. The following notable conclusions per water system were made: 1) 50% of the total water treated in the wastewater treatment plant is groundwater, adding a large amount of unnecessary stress to the treatment process, 2) the storm water drainage system is the largest groundwater drainage component contributing to 58% of the total groundwater drainage and 3) 55% of the produced drinking water is lost during distribution, meaning the drinking water losses are a larger groundwater recharge than the annual precipitation surplus. A large part of this lost drinking water is then drained by the adjacent sewer and storm water drainage pipes.

Urban climate adaptation is generally attained --- in a hydrological perspective -- by implementing stormwater management techniques, such as grey, blue and green adaptation measures. Implementing such multi-functional adaptation measures touches on the interests of many stakeholders who need to work together to find resilient and suiting solutions in urban climate adaptation. To facilitate this cooperation, Deltares developed the Adaptation Support Tool. The AST defines eight different performance indicators to compare the effectiveness of urban runoff reduction measures, among which the runoff volume reduction factor. This factor is defined as the rate at which a specific adaptation measure increases the return time of the extreme runoff event. This factor is determined by the underlying model of the AST, the Urban Water Balance Model (UWBM).
The UWBM has the benefit of using long times series instead of single precipitation events (design storms) as input to determine the effectiveness of measures; antecedent conditions for every extreme event are therefore known. Currently, the UWBM is only determining the runoff volume reduction factor. At the same time, the literature shows the importance of analysing the effectiveness of measures using both flow peak reduction and storage peak reduction. Exploration of the possibility to implement these two reduction factors into the UWBM forms the challenge of this study.
This research aims to define a flow peak- and storage peak reduction factor based on modelling systems in the UWBM using long time series. Because the model describes these factors over the measure area, the second goal of this study is to investigate the possibility of converting this measure factor to a whole project area factor and combining this factor for a combination of measures. Main conclusions of this research are as follows: A flow peak reduction factor can be empirically determined based on the proposed method in this study. A storage peak reduction factor can not be empirically determined based on the proposed method in this study. It is recommended to do more research into the analysis of the storage peaks using time series, since it can give an extra insight into the effectiveness of measures. Converting the found flow peak reduction factor for the measure area to the project area with multiple interventions is substantiated with a proposed equation. However, it is recommended to do more research into the conversion equation to be used in the Adaptation Support Tool. By determining the flow peak reduction factor together with the runoff volume reduction factor, the effectiveness of urban runoff reduction measures in a project area can be quantified and used to compare alternative solutions for their effectiveness in flood risk reduction. The added flow peak reduction factor gives a more thorough insight into this effectiveness of measures.

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.

In collaboration with the University of the Bahamas, we used the Charette model, the Three-point Approach and the conceptual framework: Build Back Better to propose a solution that involves several aspects: Reduced risk overall, increased social cohesion on the island, improved life quality and reduced costs during reconstruction in the aftermath of a hurricane event. Based on the analysis of the island, the hurricane and the important physical processes, a division between protection method is proposed based on the location on the island: collective and
individual protection.

Water challenges the livelihood of all living beings through its scarcity and its abundance. Due to climate change these extremes will intensify in the future. As mankind continues to cluster in economic centre points, housing areas as well as infrastructure increases. This situation forces the water to run off rather than infiltrate. Inundated areas place a threat to health and mankind will be forced to increase the resilience in urban areas. Adaptation to more extreme weather situation on private terrain is necessary as private space contributes 50% of the area. In order to stimulate inhabitants to adapt different measures it is essential to get an idea of their receptivity. The receptivity model of Jeffrey and Seaton (2009) offers a framework to understand with which of the 4 A’s (Awareness, Association, Acquisition and Application) residents are struggling most. A sequential mixed method of combining questionnaires and focus groups was used to collect data on residents’ receptivity and perceived effectiveness of potential rainproof measures. Additionally, the hydrologic expected effectiveness of selected rainproof measures was analysed with help of the Adaptation Support Tool and compared to the perceived effectiveness. Although residents are developing all 4 A’s simultaneously to different extend and speed, it appears that residents are struggling with Awareness. Their experience with flooding and water damage reveals awareness of the issue itself; however, hesitation to implement countermeasures was noticed. The awareness of solutions is missing for more than half of the respondents. The association with their own agenda and recognising the benefits is not yet widespread among residents. The acquisition requirement of receptivity – the knowledge about implementation, operation and maintenance – is missing. It is evident that the application requirement cannot be accomplished as acquisition is absent. Residents demand additional information. The development of the 4 A’s, specifically Association and Acquisition, require more attention. Residents recognise their own responsibility for the private lot, but also shared responsibility and thus community actions are expected. Residents insist that the municipality and Waternet fulfil their tasks within their responsibilities. Transparency and communication with residents are important features, whereby provision of tailor-made advice has high importance. Recognising responsibilities and also dependencies between different stakeholders as well as knowledge requests reveal lacking receptivity and further encouragement is required. Frontrunners can hereby play an important role. The effectiveness of countermeasures is an important consideration for increasing resilience. Evidently respondents indicated rainwater barrels as possible measure to temporarily store water. Green roofs were also well known. The perceived effectiveness scored relatively high for all temporary water storage measures. The Adaptation Support Tool (AST ) calculated effectiveness between 2% and 42%, where this is a percentage of a 60mm precipitation storage target. The highest effectiveness of 42% is achieved by intensive green roofs, whereas the costs are relatively high. A rainwater pond on the other hand has low investment and maintenance costs and scored an effectiveness of 22%. Green gardens reveal higher costs, but also greater effectiveness. It is expected that all gardens already have some green spaces and a simple intervention as reducing tiles could contribute up to 30% of the target. The calculations demonstrate that none of the measures could achieve the target alone. A combination is required, whereby the order of implementation can be guided by their effectiveness and costs. For improving receptivity of residents, several points should be considered. First of all connect residents with similar issues, they possibly motivate each other and develop an urge to action. Tailor-made information improves information distribution. Residents are reluctant due to unfamiliarity with alternatives for their specific situation. It is also important that residents are aware of the effectiveness and the costs of measures for when they need to chose. The AST calculations give insight in the effectiveness and costs of measures. Transparency of tasks, responsibilities and choices of the municipality, Waternet and Amsterdam Rainproof could provide a positive mindset towards the implementation of rainproof measures. Communication about (possible) barriers might be helpful in order to prepare residents. It is important that the municipality promotes climate adaptation throughout the entire legal and organisational levels.

Water is cherished as treasure in traditional Chinese culture and expected to stay in harmony with human. However, the disharmony between water and urban life is looming especially after over thirty-year rapid urbanization in China with notable global climate change. Faced with water-related issues, e.g. flooding, water pollution, water shortage, etc., Government of China initiated a so-called Sponge City Program (SCP) in 2014 for constructing ‘sponge-like’ water-resilient cities. Nevertheless, challenges and gaps lie in practice of SCP, one of which is that an operationalizable design approach of a sponge city to realise its multiple objectives is neither available in current guidelines, nor thoroughly studied or proposed in recent literatures.
The aim of this master thesis was to formulate an improved approach, as well as to improve planning & design framework for supporting integrated sponge design process and enhancing the involvement of various stakeholders. Literature study, the study of current guidelines and sponge plans of Nanjing, and interviews with sponge city practitioners were performed to evaluate current Sponge City (SC) concept and assess SC planning & design practice. Analysis of SC concept development showed that SC has been evolving from a term mainly describing measures with ecological benefits towards a more inclusive urban development paradigm, considering not only water ecology, but also water safety, water environment and water resource. Analysis on SC practice identified the gaps in current SC water management contents, including a lack of design method for calculating storage capacity against pluvial flooding, ignorance of extreme drought assessment, missing groundwater management, etc. Challenges that might impede comprehensive sponge city planning & design process were also enumerated, including data availability and accessibility, the bond between SC and other sector plans, etc. 
Based on the identified challenges and gaps, improvements on current planning & design practices were given and a new design approach was proposed, including changing collaboration method, introducing a co-design workshop and using a sponge design toolbox to facilitate planning & design process. The approach provided a method to calculate the required sponge capacity for not only preventing flood damage but also mitigating water shortage in dry spells, as well as quantifying other co-benefits. The improved design approach was tested by a case study in Nanjing, in the Qinhuai District sponge city planning project. Case study results showed that most steps in the proposed design process were successfully taken in Qinhuai project, and the toolbox was able to facilitate planning and design of sponge measures to have functions not only for pluvial flooding prevention and control, but also for water shortage mitigation, ecological benefits and other day-to-day values. The design process also demonstrated the collaborative contribution to a sponge city plan from water managers, water engineers and landscape architects. Therefore, the new design approach can contribute to a more integrated SC planning and design.

Chennai, one of the largest cities in India, has been suffering from ‘’too little, too much and too polluted’’ water. As a response, in 2002, the local government took a step forward at the policy level by mandating the provision of rainwater water harvesting structure for every building. This system contributes to take advantage of the excess water during monsoon and palliating the situation during the dry season, while preventing it from being discharged into the polluted waterways. However, the widespread uptake of rooftop rainwater harvesting systems has been slow partly due to the lack of accurate and reliable information on the benefits of rooftop rainwater harvesting to make more informed decision. This research seeks to bring forward the potential of leveraging decentralized rooftop rainwater harvesting (RRWH) systems to mitigate Chennai’s water challenges by quantifying the hydrological effect of RRWH using a multi-purpose approach. To do so, a RRWH model was developed using daily continuous simulation method with ‘Yield Before Spill’’ as the operational rule to determine the optimum design capacity required to meet the domestic water demand and to provide its associated hydrological benefits on water supply, groundwater recharge and urban flooding. In this research, a closed system of RRWH designed to maximize water supply is applied for the analysis. Two areas of Chennai were investigated : urban area and peri-urban area. The Mambalam area, located in the historical center of Chennai, was selected as the urban area case study. Assuming 380,000 inhabitants are living in an estimated area of 11,690,000m2, approx. four million cubic meters of water can be harvested annually from the existing building’s roofs. From this, 50% of the buildings in the Mambalam is assumed to be residential which can provide 51d/yr/p of the domestic water demand. Thus, other sources of water supply are required to supplement the water demand. Maximizing water supply reduces groundwater recharge to nearly 0m3/yr in the Mambalam area. There is clearly a trade-off between water supply and groundwater recharge. However, when considering the adoption of RRWH for groundwater recharge (also refer as open system of RRWH) for the remaining 50% of the non-residential buildings in the Mambalam, approx. two million m3/aof rainwater can be recharged into the aquifer, balancing out the urban water system. This volume of recharged groundwater can also be considered as available groundwater for water supply because in urban area, groundwater is also used for domestic water supply. Together, the potential of decentralized water supply is increased up to 30% of the annual water demand (equivalent to 105d/yr/p) . Finally, the combined systems of RRWH for water supply and RRWH for groundwater recharge can contribute to reduce a volume of approx. four million m3/yr going into the stormwater drainage network and the polluted waterways in Chennai. According to the results, RRWH can reduce up to 60% of the stormwater runoff during a heavy rain event in the Mambalam. The results show that scaling up RRWH at the macro-scale level can have a significant impact in terms of drought and flood resilience for the Mambalam area. These numbers can serve as inputs for stakeholders’ dialogues to make informed decisions and raise awareness on the benefits of multi-purpose RRWH to transition Chennai toward a water resilient city. In practice, retrofitting existing building with RRWH for water supply in urban areas may become challenging mainly due to political, legal, physical and socio-economic factors. The adoption of a close system for RRWH is found to be more relevant for the periurban areas of Chennai. Indeed, buildings are developed on top of marshland with a high-water table level and saline water. This is the case of many residential apartment complexes located along the IT Corridor in the southern part of Chennai. Groundwater recharge and groundwater abstraction for water supply are not possible. As a
consequence, people need to rely solely on water tankers which is around 20 times more expensive than the cost of water per kiloliters in urban areas. The case of Sabari Terrace residential apartment complex showed that the adoption of RRWH for water supply contributes to 15% of the annual water demand and it saves up to $6/yr/p.

As climate change takes hold, extreme weather events increasingly pressure the performance of the railway infrastructure. A first insight has been obtained into the impacts of climate change for the train system and the railway network, but there are almost no studies on the impact of our changing climate on railway stations. This study therefore aims to provide insight into the risks of climate change-induced hazards for railway stations in The Netherlands and the associated effects on the functionality of the station for passengers. Scenarios of climate change show that the Netherlands will experience increasingly intense rainfall, dryer, hotter summers and warmer, wetter winters. This poses a number of risks to the operation, reliability, availability and safety of train stations in a country with the busiest and densest rail network of the European Union. In this study, a method was created to study the risks of climate extremes for train stations on the basis of thirteen identified threats, and risk matrices were developed to support ProRail in defining their attitude towards climate risks. Results show that Dutch railway stations are vulnerable to climate change and demonstrate that there are many aspects of climate change at stations that require attention. The most important nodes in the station network, and stations that have a relatively high number of boarding and disembarking passengers per day, are at a higher risk than the national average. The results of this study show that this could have implications for a relatively high number of travellers in terms of their safety and contentment, and it could have socio-economic consequences for both ProRail and NS, as well as for the accessibility of The Netherlands. The local applicability of the risk assessment methodology was tested in five case studies on stations with very different characteristics, sizes and locations. The case studies have demonstrated that many of the identified risks appear to be relevant and appropriate on a local scale as well, but that risk is situation-specific. Furthermore, the case studies provide strategic long-term quantitative insights on adaptation strategies for all stations in the Netherlands, projecting the cases onto comparative situations.

With urbanization and climate change, the reliable water supply by centralized system is facing challenges. Research on the (re)use of the outflow from an urban area as an alternative water resource is increasing in recent years. This research requires spatial and temporal information on the status of components of urban water cycle. Several hydrological models exist for the purpose of urban water management. However, none of them considers modeling the total urban water cycle by a water balance approach in a spatial explicit manner. Distributed Urban Water Cycle Model (DUWCM) is developed in this thesis to investigate the benefit of a scalable and efficient water balance model that simulates the rainfall-runoff system and water supply-wastewater system in urban areas. Two case studies were carried out to verify the model and demonstrate the capability of modeling a large hydrological catchment respectively. DUWCM is developed as adaptable to a planning-support tool UrbanBEATS. Spatial representation of the second case study will be provided by it in squared and hexagonal tessellation. Hexagons have been applied in many spatial modeling fields, while rare applications can be found in water balance modeling. A comparison of model results from squared and hexagonal grids is done in this study. The comparison demonstrates that the difference in flow direction and sampling of the land cover ratio between square and hexagon blocks results in obvious differences in the location and the magnitude of peak flows. Since hexagonal grids perform better in flow path simulation (de Sousa et al.,2006), it is expected to be preferred over squared grids in distributed hydrological models. Thus, DUWCM, being scalable in the number of blocks and shapes, has the potential to be widely applied in sustainable water management.

Due to climate change, extreme phenomena like droughts are going to be intensified. Even though droughts in agriculture have been studied, regarding urban environment their consequences are rather unexplored. Cities are susceptible to droughts and the estimation of their vulnerability is the first step for their protection. The objective of this thesis is to determine vulnerability of cities to groundwater and soil moisture droughts. Since drought is a complex phenomenon which is difficult to define, its analysis is not straightforward especially in cities. For that reason, an urban drought categorization framework is created. In the current research, two of the four drought categories were studied (groundwater and soil moisture droughts). A case study for the vulnerability calculation was chosen for Leiden, the Netherlands. Before determining its vulnerability, different techniques to identify drought exposure characteristics were investigated. More specifically, regarding deficit and duration, the following methods were used: (i) fixed, (ii) variable, (iii) moving window method, and (iv) median groundwater level as threshold for the case of groundwater droughts. Spatial analysis was performed to estimate the areal extent of droughts whereas frequency distribution analysis is assessed of the minima of monthly blocks. A similar approach was applied for soil moisture droughts. Soil moisture is modeled via the lumped Urban Water Balance Model. Vulnerability was estimated as the aggregation of exposure and sensitivity (physical and social). For both components of vulnerability, their indicators were normalized. Out of the four drought characteristics (deficit, duration, spatial extent, and frequency), only the two first were included as exposure indicators for the vulnerability estimation. The indicators' weights were computed using the Analytical Hierarchy Process (AHP). Vulnerability estimation was applied for both groundwater and soil moisture droughts separately. One of the main results is that variable threshold performance is higher than fixed threshold and moving window for deficit and duration estimation regarding groundwater droughts. However, a combination of fixed and variable threshold can provide a profound insight into drought exposure. That applies to soil moisture droughts too. To increase performance of deficit and duration identification, pooling can be applied. An inter-event time of around 10 days for the case of variable threshold and 30th percentile is suggested regarding groundwater droughts. The analysis on soil moisture droughts was not sufficient to draw conclusions regarding inter-event time. Vulnerability follows sensitivity patterns - rather than exposure pattern - for both groundwater and soil moisture droughts at both fine and coarse space resolution. Besides, out of all indicators used, those which contribute to vulnerability variation the most were determined for both studied types of droughts. Those indicators are: `land use' and `percentage of households belonging to the lowest 40% income nationwide' for groundwater droughts whereas for soil moisture ones, it is `green areas'. Another result is that the differences in vulnerability vary marginally using different techniques to identify drought events for both studied types of droughts. Therefore, even applying a sophisticated technique to identify drought events, will not lead to significant improvement regarding vulnerability estimation. All aforementioned conclusions regarding vulnerability are highly uncertain since drought experts assigned different indicators' weights; the convergence of opinions was low. Based on the proposed methodology, water managers would be able to determine vulnerability of cities to droughts and policy makers would be able to protect the regions which are highly vulnerable. Consequently, the adverse impacts of droughts on cities could be mitigated, reducing residents' hardship.

The purpose of this thesis is to conduct research on increasing flood resilience and, albeit to a lesser extent, drought resilience of New Orleans, Louisiana, United States of America. Focusing on the Orleans Lakeside sub-basin, this project builds on previous work through a joint design-engineering approach. This project seeks to address two shortcomings of existing proposals such as the Greater New Orleans Urban Water Plan: consideration for extreme weather events in the design framework as well as focusing on the integration of technical adaptation measures with the built environment. Hence, the main research question answered in this report is “How can Orleans Lakeside be made more flood and drought resilient by integrating multi-layered resilience capacities of the built environment, whilst safeguarding consistent design of technical adaptation measures within the urban space?”. The development of a design framework and detailed design interventions follows from a synthesis of earlier proposals, supplemented with a vulnerability analysis that focuses on the different capacities of the built environment in dealing with weather events of various magnitudes. For this analysis, the threshold (preventing damage), coping (mitigating damage), recovery (recovering from damage) and adaptive (flexibility to change) capacities of the built environment are investigated. The multidisciplinary approach taken in this project culminates in an urban water management design for Orleans Lakeside which is focused on introducing open water in the urban environment. This design proposal offers a high potential of meeting the required water storage capacity, with the intention to reintroduce the lost identity of wetlands to the suburbs of New Orleans. Typological and urban design across scales aim to integrate water system elements into the urban fabric, and to merge a new water-based urban environment with traditional desired American neighborhood qualities.

In the face of climate change, urban stormwater management practices are subject to an uncertain context. More frequent and extreme rainfall events are expected in many urban areas. The extent how climate change will affect weather patterns is however uncertain. This challenges contemporary stormwater management practices. A post-disaster reconstruction of an urban area would potentially be an opportunity to anticipate climate change uncertainties from the initial design phase of new urban development. This would allow for taking advantage of the disaster recovery by rebuilding a more resilient stormwater system than was present before, in which the uncertainties are anticipated. A resilient stormwater system would thus be able to cope a wide range of plausible futures, rather than the average. As academic literature lacks insight on re-establishing resilient urban stormwater management in a post-disaster reconstruction, this thesis aims to gain more insights into what extent resilient urban stormwater management has been established in a Tsunami reconstruction, with regard to uncertainties on climate change and urban development. A case study is conducted in which is focused on a) the conducted design approach, b) the realm of conditions for which the implemented stormwater system would be vulnerable and c) which solutions could be implemented to reduce the vulnerability, and reflected upon opportunities of an interdisciplinary approach from a stormwater management perspective. The selected study area is a town called Ötsuchi Town, in Northern Japan, Iwate Prefecture, which was severely hit during the 2011 Tsunami. The disaster necessitated a comprehensive reconstruction. To gain more insight into what extent a resilient urban stormwater system has been implemented, an exploratory modelling and analysis approach has been applied, which is also known as Scenario Discovery. Prime drivers of Scenario Discovery are exploring the system's performance for wide-ranging plausible futures by sampling the system myriad times with aid of computational modelling, and, the use of regional sensitivity mapping algorithms to understand the dominant factors that lead to insufficient system performance. The latter can be used as input for seeking vulnerability-reducing strategies. In this research, the Patient Rule Induction Method (PRIM) algorithm is used to understand the conditions for which the stormwater drainage system capacity would be exceeded, for an acceptable flooding level of 0.2 meter. Two open-source tools were combined: the conceptual stormwater flow model EPA-SWMM, and, python library EMA-workbench which provides the tools needed for applying Scenario Discovery and supportive analysis. After the 2011 Tsunami a separate half-open sewer system was established in the reclamation area of Ötsuchi Town. No natural-based solutions, or Blue-Green infrastructure were implemented, even though the residential is adjacent to steep mountain slopes. The uncertainty parameters over which is sampled, include rainfall intensity, rainfall duration, external runoff coefficient, imperviousness, the hydraulic conductivity, Manning's roughness coefficient and depression storage. The Scenario Discovery results show that the system has been built robust. For almost all locations no flooding occurrence arise from the sampling, even for very extreme rainfall events (>100 mm/hr, for a duration of 60 min). However, when the runoff coefficient of the external runoff from the mountain would be above 0.58, a small area in the northern part would be vulnerable. The dominant factors, are found with PRIM and the relative weights are with very high precision and recall found by pre-processing the sampling data with Principal Component Analysis. It showed that for the vulnerable area, the hydraulic conductivity of the soil and the proportion of paved area are decisive in whether or not flooding occurs. Paying attention to certain thresholds, would significantly reduce the vulnerability of flooding occurrence. Given the high volumes for which flooding would occur, a preliminary feasibility study has been done for both a vegetative swale and infiltration trenches, in combination with a storage retention area in the lower lying area, such that the pressure on the stormwater drainage system can be released. The vegetative swale reduce the vulnerability significantly. The infiltration trenches seem to be effective for the lower rainfall duration and rainfall intensity. PCA-PRIM outcome showed that when implementing infiltration trenches in the vulnerable area, the impervious rate becomes relatively less sensitive in comparison with outcomes of PRIM with the reference situation. More information on mountain runoff, soil properties and land use would enhance the accuracy of the results. In addition, since, no information is known yet on initial losses of mountain runoff, more information on runoff flow processes from the mountains would enable to perform joint probability analysis with the results of this research, to better assess whether or not the time is now to implement additional measures. From the results of this research it seems that the urban stormwater drainage of Ötsuchi Town has been rebuilt very robust, however when the system would fail, no additional measures outside the grey infrastructure are taken. An interdisciplinary approach could have encouraged a more resilient stormwater management. As this research shows that multiple commutative reconstruction measures could be found from a stormwater management perspective, the obtained information with applying Scenario Discovery, would have been useful to encourage an interdisciplinary approach during the reconstruction process. It is therefore suggested to explore the usage of Scenario Discovery on urban stormwater management even further, such that it enables to take advantage of the disaster reconstruction to establish a resilient urban stormwater management. An example would be to investigate whether the relative sensitivity of the uncertainty parameters would change when a less robust system would be examined. For example, for an urban drainage system for which the threshold would already be exceeded for lower rainfall intensity and duration than 100 mm/hr, and 60 minutes respectively. In addition, a coarse representation of rainfall events are considered in this research. Therefore it would be suggested to examine the applicability of region-specific storm profiles in combination with an exploratory modelling and analysis approach, to better assess the implication of the PRIM outcomes for implementing resilient urban stormwater management strategies.

Bioswales contribute to climate resilience, as they positively impact the urban water infrastructure by improving the water balance and water quality. However, current bioretention design ignores the facts that different designs in different soils and climatic locations produce different performance results.
The effect of polder conditions on the hydraulic performance, as well as the effect of different storm-types and initial conditions will be researched in this report. To this end, 5 bioswales located in Rotterdam, The Netherlands are monitored on their hydraulic behaviour. The discharge of the drain, groundwater levels in and at the edge of the bioswale and the water level in the bioswale are monitored for 4 of the bioswales. One bioswale only has groundwater and surface water measurements. The polder conditions resulted in a low volume reduction and faster and stronger reacting drain. However, the peak reduction and peak delay were still quite good due to the low permeability of the top-soil. For smaller storms, even the goal for volume reduction could be met. It was found that the structural porosity governed the infiltration, but large plants can increase the permeability too much. In addition, the textural porosity should start high enough to allow for vegetation development.

With rapid urbanization, Low Impact Development (LID) is promoted as an alternative to Conventional Drainage (CD), seeking a natural solution for current urban water problems. The positive effects of LID were the main theme of recent LID researches, but this project aims to deeply explore the hidden troubles about the extreme peak runoffs influenced by LID city on catchment scale.
In this research, the SUPERFLEX conceptual model was adapted to a rural-urban semi-distributed model to simulate the current rainfall-runoff relationship of the catchment where San Antonio city is located in. Besides, the model expressions of 4 representative LID practices (bioretention cells, vegetated swales, green roofs, and permeable pavements) were devised under SUPERFLEX framework. To deal with the prediction uncertainty, three urban development scenarios in 2040 and five LID implementation scenarios were designed for San Antonio city. And their influences on the basin peak runoffs will be quantitively studied.
Research result shows that, the urban runoff tended to swing between extreme flood and extreme drought in the reference situation; And next, the infill urban development strategy, which means developing the vacant or undeveloped land within an existing community, was more helpful on peak runoff and total runoff volume control than sprawl urban development strategy with the same population growth; Thirdly, the bioretention cells, vegetated swales, and permeable pavements had similar good performance on peak runoff reduction, which can be mainly ascribe to the stormwater infiltration process. As for the retention of total runoff volume, the bioretention cells, permeable pavements, and green roofs perform better than vegetated swales since the rapid water transportation character of vegetated swales decrease the water residence time for infiltration;
The runoff reduction function of LID practices performs effective on the large peaks in dry and normal seasons, but it will be restrained significantly in flood season. According to model result, the rural peak runoffs happened 6.5 to 15.5 hours after the urban peaks. And for 4 LID implementation scenarios in which 15% of urban grey areas is covered by LID practices, the urban peaks are delayed between 0.5 and 2.5 hours. And for the scenario with the LID cover areas as 50% of the urban grey areas, the time lag of urban peaks varies from 0.5 to 6.5 hours. For this scenario, since the obvious time delay of urban peaks, more stack of urban and rural peaks is caused by the time approaching of urban and rural peaks, which causes the increases of two total basin peaks in flood season from 3.57 to 3.65 mm/d and from 6.35 to 6.47 mm/d respectively.
In conclusion we may say that the stacking effect of LID implementation on total basin runoff is limited in the case of San Antonio basin, partly due to the fact that only a small part of this basin is urbanized.

Gouda deals with land subsidence and groundwater problems. A solution to these challenges is the application of Drainage-Infiltration-Transport (DIT) sewers, on which research is lacking. This thesis provides provides infiltration and drainage capacity values on DIT sewers and helps to understand the governing processes.

Identify the barriers within Arcadis by evaluating internal approaches, knowledge and differences in domains to increase the action perspective in the approach of climate-proof cities. The data was collected by performing 24 interviews and this was analysed and structured using the PRIMO-chain model.

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.