The sheer volume as well as the schema complexity of today’s graph databases impede the users in formulating queries against these databases and often cause queries to “fail” by delivering empty answers. To support users in such situations, the concept of differential queries can be used to bridge the gap between an unexpected result (e.g. an empty result set) and the query intention of users. These queries deliver missing parts of a query graph and, therefore, work with such scenarios that require users to specify a query graph. Based on the discovered information about a missing query subgraph, users may understand which vertices and edges are the reasons for queries that unexpectedly return empty answers, and thus can reformulate the queries if needed. A study showed that the result sets of differential queries are often too large to be manually introspected by users and thus a reduction of the number of results and their ranking is required. To address these issues, we extend the concept of differential queries and introduce top-k differential queries that calculate the ranking based on users’ preferences and therefore significantly support the users’ understanding of query database management systems. The idea consists of assigning relevance weights to vertices or edges of a query graph by users that steer the graph search and are used in the scoring function for top-k differential results. Along with the novel concept of the top-k differential queries, we further propose a strategy for propagating relevance weights and we model the search along the most relevant paths.

Climate change is predicted to cause an increase in cloudbursts and heavy precipitation, which makes urban flooding an issue that needs to be dealt with. The term Sponge city is a theory that intends to deal with urban flooding and worsening water quality in urban areas with absorption. The study area Hemlingby is an area that has been prone to flooding before, for instance on the 17–18 of August 2021. The area is located about 3 km from the city center Gävle with Hemlingbybäcken running north through the study area. The study was performed in several parts, the first was to use the GIS tool ArcMap 10.8 and hydraulic software CAESAR-lisflood 1.8 to investigate which areas are considered sensitive. In ArcMap 10.8, a bluespot map was created to estimate how much water is needed to fill different areas of Hemlingby, and in CAESAR-lisflood 1.8, the flood inundation area was mapped based on different water flow scenarios. Subsequently, two site visits were made to the study area to photograph and validate the results from the GIS analyses. Based on the GIS analyses, an interview with the municipality of Gävle and an extensive literature analysis, measures were identified that suited both the concept and the study area. The results show what affects the drainage in Hemlingby and how it could be improved through the use of Sponge city. Hemlingbybäcken, which is easily flooded by large water flows, and the topography of the area are factors that have been identified as particularly problematic for the study area's drainage. To show how the area could be planned after the Sponge city concept, proposals for both types of measure and location have been presented, also restrictions and how similar concepts can be applied in other areas are presented. Given that the frequency and intensity of future cloud bursts are not known, there is no answer as to whether the measures presented in the study would stop the study area from being flooded in the future. Especially when data and statistics from previous rainfall were missing, the area's exact reaction to a cloud burst could not be analyzed. On the other hand, it is possible to determine from the analyzes in the method that the study area was not adapted to the type of downpour it was affected by. Therefore, measures aimed at Hemlingbybäcken become significant as the topography or soil type of the area is much more difficult to influence. In order to investigate exactly what impact the proposed measures would have on Hemlingby, further studies need to be carried out to map both the collection capacity and the impact on Hemlingbybäcken the proposal has. / Klimatförändringar förutspås i framtiden leda till en ökning av antalet skyfall och kraftig nederbörd generellt, vilket gör översvämningsproblematiken i urbana områden till ett allt större problem som måste hanteras. Konceptet Sponge city syftar på en teori vars huvuduppgift är att hantera urbana översvämningar och försämrad vattenkvalitet i städer med hjälp av absorberande ytor. Studieområdet Hemlingby i Gävle är ett område som tidigare drabbats av kostsamma översvämningar vid skyfall, bland annat 17–18 augusti 2021. Studieområdet ligger cirka 3 kilometer från Gävle stadskärna och har Hemlingbybäcken rinnandes norrut genom området. Studien utfördes i flera delar, där den första var att med hjälp av GIS-verktyget ArcMap 10.8 och den hydrologiska programvaran CAESAR-lisflood 1.8 utreda vilka områden som bedöms känsliga för översvämning. I ArcMap 10.8 skapades en bluespot-karta för att uppskatta hur mycket vatten som krävs för att fylla olika områden av Hemlingby och i CAESAR-lisflood 1.8 karterades översvämningsutbredningen utifrån olika vattenföringsscenarion. Därefter utfördes ett platsbesök i studieområdet för att fotografera och validera resultatet från GIS-analyserna. Utifrån GIS-analyserna, intervju med Gävle kommun samt omfattande litteraturanalys identifierades åtgärder som både passade konceptet och studieområdet. Resultatet visade vad som påverkar dräneringen i Hemlingby och hur den skulle kunna förbättras genom implementering av konceptet Sponge city. Hemlingbybäcken, som lätt översvämmas vid stora vattenflöden, samt områdets topografi är egenskaper som identifierats som särskilt problematiska för studieområdets dränering. För att visa hur området skulle kunna planeras efter Sponge city har förslag på både åtgärdstyp och placering presenterats, men även begränsningar och hur liknande koncept kan appliceras i andra områden presenteras. Med tanke på att frekvensen och intensiteten på framtida skyfall inte går att veta exakt, finns inget svar på om åtgärderna presenterade i studien skulle stoppa studieområdet från att översvämmas i framtiden. Eftersom data och statistik från tidigare skyfall till viss del saknats har områdets exakta reaktion på ett skyfall inte kunnat analyseras. Däremot går det att utifrån analyserna i metoden fastställa att studieområdet inte var anpassat för den typen av skyfall det drabbats av. Därför blir åtgärder riktade mot Hemlingbybäcken av mycket stor vikt, eftersom områdets topografi eller jordarter är betydligt svårare att förändra. För att undersöka exakt vilken påverkan föreslagna åtgärder skulle ha på Hemlingby behöver ytterligare studier genomföras för att kartlägga både uppsamlingsförmågan och påverkan på Hemlingbybäcken förslaget har.

This thesis uses flooding driven by Hurricane Harvey in 2017 and a history of inundation in Houston, Texas to critique the systems of floodplain mapping through the National Flood Insurance Program (NFIP). The role of Geographic Information Systems becomes a subject of interest in the context of U.S governance and the role of property as a driving force in urban development. The shortcomings of existing systems of mitigation are examined through mappings that bring measures of risk, damage, and recovery into contrast with each other. Racial and economic inequality are integrated into the analysis through a deeper consideration of the NFIP as the main form of federal protection against losses. Seeing that the NFIP has not protected the true status quo of urban life, it is argued that public perceptions of risk are formed contrary to the logic of home insurance, leading to observable inequalities in preparation and recovery

Extrema skyfall till följd av klimatförändringar blir att vanligare och när de inträffar riskerar de att leda till urbana översvämningar. Den ökade frekvensen av skyfall är anledningen till att urbana översvämningar har lyfts som ett problem i svensk lagstiftning. Enansvarsproblematik har identifierats i relation till detta, då fastighetsägare inte är medvetna om sitt eget ansvar och därför inte anpassar sina bostäder. En kunskapsbrist bland fastighetsägare samt uppfattningen om deras exponering och utsatthet har identifierats som grunden bakom denna problematik. Sommaren 2021 inträffade ett skyfall i Gävle vilket ledde till omfattande översvämningar. Många fastighetsägare drabbades, däribland bostadsrättsföreningar. Hur bostadsrättsföreningar påverkas och resonerar kring översvämningar är ett relativt outforskat forskningsområde i svensk kontext. Av den anledningen blev därför syftet med denna studie att undersöka föreningarnas uppfattning om risk och anpassning. Detta genom att studera ordföranden inom föreningarnas uppfattning om utsatthet, sårbarhet samt möjlighet till hantering i relation till översvämningen. För att ta reda på detta genomfördes semistrukturerade intervjuer. Resultaten visar på att föreningarna har fått en något högre riskuppfattning kopplat till översvämning. I kontrast till tidigare studier kan respondenterna även identifiera ett samband till klimatförändringar. Den faktor som främst påverkade föreningarnas anpassningsförmåga negativt var att det rådde en utbredd kunskapsbrist inom föreningarna. Det finns därmed ett fortsatt stort behov av en ökad kunskap och vägledning från externa aktörer. / Extreme cloudbursts due to climate change are increasing and when these events occur urban flooding is a potential consequence. This is the reason urban flooding has been addressed in the Swedish legislation, at a national level. However, liability issues have been identified, as property owners are not fully aware of their responsibility and therefore neglect adaptation. A lack of knowledge has been identified as the main reason, as well as perception of risk. In the summer of 2021, cloud bursts struck Gävle and caused substantial urban flooding. Many housing co-operatives were affected. Housing co-operatives and how they are affected by flooding is a relatively unexplored research area in a Swedish context and therefore the purpose of this study became to: analyze how experiences of flooding has affected housing co-operatives' perception of risk and adaptation by exploring chairmans perceptions of exposure, vulnerability and flood risk management. Semi structured interviews were performed with chairmans within the boards of the housing co-operatives. The results proved there had been a slight increase in flood risk awareness. The respondents were also able to connect the flood with climate change. However, a large lack of knowledge negatively affects the adaptive capacity of the housing co-operatives. The need for further knowledge and guidance from external actors is therefore large. / Stöd för aktörssamverkan och mångfunktionell anpassning av bostadsområden

Climate change effects are getting more evident year by year. Athens is specially affected by climate change related shocks, especially by poor air quality, flooding and heat waves. Every year climate shocks threatens and worsens the situation in the city. The municipality of Athens, together with the European Investment Bank and EQO-NIXUS (consulting company) have undertaken a project in order to increase the resilience and the mitigation and adaptation measures of the city, taking as case study 5 public buildings located in different areas of the centre of the city. This project is in line with the Athens Resilience Strategy drawn by the Municipality of Athens in order to integrate new ways to prepare and protect the city from future shocks and stresses. This study aims to investigate and propose mitigation and adaptation measures that could be potentially applied into the 5 selected public buildings in order to improve the energy efficiency and the resilience towards heat waves, flooding and pollution of the air. A literature review study has been performed in order to look for good practices worldwide in terms of energy efficiency and climate mitigation and adaptation in order to find the best measures that could be applied in the 5 selected buildings. Finally, a multi-criteria decision analysis has been executed to prioritise which measures result to be more relevant for each specific building. The study shows that, in overall, energy efficiency and raise of public awareness are the most relevant measures that can be potentially applied in the buildings in order to tackle the climate shocks that threatens Athens. Finally, if the measures are applied into the buildings and the resilience and energy efficiency measures are improved, this study could be replicated to other buildings of Athens in order to achieve the 2030 strategy plan set by the municipality of Athens. / Effekterna av klimatförändringen blir alltmer tydliga. Greklands huvudstad Aten påverkas exempelvis av försämrad luftkvalitet, översvämningar och värmeböljor och extrema klimatrelaterade händelser förvärrar situationen i staden. Atens kommun har tillsammans med Europeiska investeringsbanken och EQO-NIXUS (ett privat konsultföretag) genomfört ett projekt för att öka motståndskraften mot klimatförändringens effekter, genom anpassningsåtgärder, där fem offentliga byggnader i olika delar av Atens centrum studeras. Projektet är relaterat till Atens resiliensstrategi som handlar om hur staden ska integrera nya sätt förbereda och skydda staden och dess invånare från framtida extrema händelser och påfrestningar. Denna studie syftar till att undersöka och föreslå anpassningsåtgärder som potentiellt kan tillämpas i de fem olika offentliga byggnaderna för att förbättra energieffektiviteten och resiliensen mot värmeböljor, översvämningar och luftföroreningar. En litteraturstudie har genomförts för att identifiera globala, goda exempel när det gäller energieffektivitet och anpassning till ett förändrat klimat som potentiellt kan tillämpas i de fem byggnaderna. Slutligen har en multikriterieanalys med flera kriterier genomförts för att prioritera vilka åtgärder som är mest relevanta för varje specifik byggnad. Studien visar att energieffektivitet och ökning av allmänhetens medvetenhet totalt sett är de mest relevanta åtgärderna som potentiellt kan tillämpas i byggnaderna för att hantera klimatförändringar. Slutligen, om dessa åtgärder tillämpas och resiliensen och energieffektivitetsåtgärderna förbättras, skulle denna studie kunna vara relevant även för andra byggnader i Aten och därmed bidra till uppfyllelsen av stadens 2030-strategi.

Floods are becoming more frequent and the magnitude of direct consequences, relating to destruction of critical infrastructure and loss of life, has highlighted the importance of flood management. This thesis proposes a new methodology to quantify the impact of predicted and historic flooding events on emergency services. The approach moves beyond simple flood inundation mapping by accounting for the relationship between flood depth and vehicular speed. A case study was presented for Calgary Alberta, where the depths of a predicted 100-year flood and an historic 2013 flood event were modelled. The methodology applied geographic information systems (GIS) to flood depth mapping, utilizing digital elevation models (DEMs), flood extents, and hydrological data. Flood depths were then assigned to links comprising the road network, where the maximum vehicle speed was calculated as a function of the standing depth of water on a link. The flooded network was used to derive service areas for several types of emergency services (emergency medical services (EMS), fire, and police), following targeted response times. The results quantified and located the residential and work populations that no longer meet the targeted response times. During both flood scenarios, EMS were found to have the greatest reduction in accessibility, with 23% to 47% of residents and workers, respectively, not served. Fire services were seen to be more resilient with only 3% to 9% of residents and workers, respectively, not served. The results for police services were similar to fire services. However, the former have a greater range of response times, meaning these areas represent those that are completely isolated during both flood events. Overall, the proposed methodology quantified vulnerable populations on a partially degraded network, which can be used to develop evacuation plans and emergency response strategies, minimizing disturbances in the network and the number of people affected. / Thesis / Master of Science (MSc)

Flooding has always been and is still today a disastrous event with agricultural, infrastructural, economical and not least humanitarian ramifications. Understanding the behaviour of floods is crucial to be able to prevent or mitigate future catastrophes, a task which can be accomplished by modelling the water flow. In this thesis the finite element method is employed to solve the shallow water equations, which govern water flow in shallow environments such as rivers, lakes and dams, a methodology that has been widely used for flooding simulations. Alternative approaches to model floods are however also briefly discussed. Since the finite element method suffers from numerical instabilities when solving nonlinear conservation laws, the shallow water equations are stabilised by introducing a high-order nonlinear artificial viscosity, constructed using a multi-mesh strategy. The accuracy, robustness and well-balancedness of the solution are examined through a variety of benchmark tests. Finally, the equations are extended to include a friction term, after which the effectiveness of the method in a real-life scenario is verified by a prolonged simulation of the Malpasset dam break.

Nuclear power is a foundational part of our electrical grid in the present and through our transition towards more sustainable and renewable alternatives. However, given the serious consequences of reckless and/or dangerous operation of nuclear power plants, they are subject to strict regulation and supervision by the Swedish radiation protection authority (SSM) and other regulating bodies (e.g. IAEA). In order to prove that a nuclear power plant is operating in a safe and accident preventative manner, the “Safety Analysis Report” (SAR) is created and submitted. The SAR categorizes and ranks all possible incidents and operation affecting events in terms of risk and available countermeasures to ensure that the radioactive release from the power plant and impact on a third party from any event is at acceptable levels. This projects limits its analysis to flooding of the reactor building or “internal flooding events” as described in the SAR. To determine the affected areas and impacted systems of any flooding event, deterministic safety analyses (DSA) are employed. The goal of this project is to develop a comprehensive thermohydraulic model of the Forsmark 2 reactor building and evaluate its performance with respect to the previously used MATLAB model. The model  should allow for a detailed nodalisation of the reactor building as well as realistic modelling of structural components such as doors, hatches, stairwells and drainage systems. The resulting thermohydraulic model  can be used to evaluate different flooding incidents dynamically and follow the spread of water and/or steam throughout the reactor building. Furthermore, the resulting pressure changes and heat generation in the reactor building can also be evaluated. The model allows for the possibility to couple the thermohydraulic reactor building model with the existing power plant systems model to holistically evaluate the power plant response to flooding related incidents. / Kärnkraft är en grundläggande del av vårt elnät i nuläget och under vår övergång mot mer hållbara och förnybara alternativ. Men med tanke på de allvarliga konsekvenserna av vårdslös och/eller farlig drift av kärnkraftverk, är de föremål för strikt reglering och tillsyn av Strålsäkerhetsmyndigheten (SSM) och andra reglerande organ (t.ex. IAEA). För att bevisa att ett kärnkraftverk drivs på ett säkert och olycksförebyggande sätt, upprättas och inlämnas "Strålsäkerhetsanalysrapport" (SAR). SAR kategoriserar och rangordnar alla möjliga incidenter och händelser som påverkar driften i termer av risk och tillgängliga motåtgärder för att säkerställa att radioaktiva utsläpp från kraftverket och påverkan på tredje person från någon händelse är på acceptabla nivåer. Detta projekt begränsar sin analys till översvämning av reaktorbyggnaden eller "interna översvämningshändelser" enligt beskrivningen i SAR. För att fastställa de påverkade områdena och drabbade systemen vid en översvämningshändelse, används deterministiska säkerhetsanalyser (DSA). Målet med detta projekt är att utveckla en omfattande termohydraulisk modell av Forsmark 2 reaktorbyggnad och utvärdera dess prestanda i förhållande till den tidigare använda MATLAB-modellen. Modellen ska möjliggöra en detaljerad nodalisering av reaktorbyggnaden samt realistisk modellering av strukturella komponenter som dörrar, luckor, trapphus och dräneringssystem. Den resulterande termohydrauliska modellen kan användas för att dynamiskt utvärdera olika översvämningsincidenter och följa spridningen av vatten och/eller ånga genom reaktorbyggnaden. Dessutom kan de resulterande tryckförändringarna och värmegenereringen i reaktorbyggnaden också utvärderas. Modellen möjliggör koppling av den termohydrauliska reaktorbyggnadsmodellen med den befintliga kraftverkssystemmodellen för att holistiskt utvärdera kraftverkets respons på översvämningsrelaterade händelser.

Soybean and wheat are important crop species due to their significance for human consumption, animal feed, and industrial use. However, increasing global population and worsening climate change have put a major strain on the production system of these crops. Natural disasters such as flooding and drought can severely impact growth and productivity of these crops. In addition, increased application of synthetic nitrogenous fertilizers to meet the global food demand has led to environment related issues. Therefore, with a goal of understanding mechanisms of flooding and drought tolerance in soybean and nitrogen-use-efficiency in wheat, we explored their physiological and transcriptomic regulation. We characterized the fundamental acclimation responses of soybean to flooding and drought and compared the metabolic and transcriptomic regulation during the stresses in a tissue-specific manner. We demonstrated the dynamic reconfiguration of gene expression and metabolism during flooding, drought, and recovery from these stresses. Our study displayed that flooding triggers more dramatic adjustments than drought at the transcriptional level. We also identified that the soybean genome encodes nine members of group VII ERF genes and characterized their responses in leaves and roots under flooding and drought. Based on the expression patterns, it is estimated that two of the nine genes are promising candidate genes regulating tolerance to submergence and drought. In addition, our genome-scale expression analysis discovered commonly induced ERFs and MAPKs across both stresses (flooding and drought) and tissues (leaves and roots), which might play key roles in soybean survival of flooding and drought. In wheat, we evaluated the effect of three different nitrogen rates on yield and its components across four diverse soft red winter wheat genotypes. The cultivar Sisson displayed superior performance in grain yield and nitrogen use efficiency at low nitrogen levels. Our results suggested that improvement of nitrogen use efficiency in low nitrogen environments can be achieved through the selection of three components: grain number/spike, 1000-seed weight, and harvest index. Overall, this study has advanced our understanding of how plants respond to abiotic stresses such as flooding, drought, and nutrient limitation conditions. / Ph. D. / Soybean and wheat are commercially important crop throughout the world. Soybean is a major source of protein and oil for humans, livestock and industrial products including biofuel production. Similarly, wheat is a major source of food products such as bread, pasta, and cookies. However, increasing global population and worsening climate change have put a major strain on the production system of these crops. Natural disasters such as flooding and drought are on the rise, which have severely impacted soybean growth and productivity. In addition, increased application of synthetic nitrogenous fertilizers in wheat production to meet the global food demand has led to environment related issues. Therefore, a mechanistic understanding of flooding and drought tolerance in soybean and nitrogen use efficiency in wheat is of utmost importance. The knowledge obtained from these studies can aid in the development of new varieties in these crops. Here, we carried out our study on soybean by imposing either complete submergence or restricting water supply to characterize the responses to these stresses in shoot and root systems. We found several compounds and genes that were altered distinctly under these two water-related stresses. In addition, we identified some promising genes that can significantly regulate tolerance in soybean to flooding and drought in soybean. To study wheat nitrogen use efficiency, we selected four diverse soft red winter wheat varieties and grew them under three nitrogen levels. We found that the cultivar Sisson has the lowest yield penalty among the four varieties resulting from low nitrogen conditions. In addition, we also demonstrated that three yield traits (grain number per spike, 1000-seed weight, and harvest index) are important selection targets to develop high nitrogen use efficiency varieties.

Utbyggnation av städer och allt större andel hårdgjorda ytor leder till problem med dagvattenhanteringen. Flödena blir snabbare samtidigt som större mängder än tidigare bildar avrinning och då är det viktigt att de befintliga systemen klarar av att hantera dem. Dagvatten från tak och hårdgjorda ytor och dräneringsvatten från källarfastigheter kan vara kopplat till spillvattennätet och leda till att vattenflödena i ledningarna vid stora regn kan bli betydligt större än de är dimensionerade för, med kapacitetsproblem som följd. En lösning som många VA-huvudmän har implementerat är att använda öppna dagvattenlösningar istället för att välja det mer kostnadskrävande alternativet att bygga ut ledningssystemet. Att koppla om stuprör, brunnar och dräneringsledningar och gräva diken för att leda om vattnet är både kostnads- och resurskrävande. Syftet var därför att undersöka om multikriterieanalys kan fungera som ett lämpligt verktyg för att allokera resurserna till de områden som ger mest nytta per satsad krona. Detta genom att ta fram en metodik för detta syfte och testa dess robusthet för att avgöra om den är lämplig att applicera eller om osäkerheterna i parametervärdena blir för stora för att några slutsatser ska kunna dras. Metodiken som togs fram testades på Bjursås, ett litet samhälle två mil utanför Falun, eftersom omfattande utredningar gjorts i området tidigare, vilket innebar att mycket data fanns att tillgå. Undersökningar gjordes av var mängderna kunde förväntas bli stora, var det fanns stor risk för källaröversvämningar och vilka områden som bidrog mest till bräddningar. Detta utvärderades tillsammans med förväntade åtgärdskostnader och en samlad bedömning gjordes av var nyttan per satsad krona bör bli störst. Stora osäkerheter återfanns i bedömningen. Slutsatsen blev att metoden kan fungera som stöd vid beslutsunderlag, men att den inte är tillräckligt robust för att kunna användas uteslutande utan att efterföljande utvärderingar och kritisk granskning av resultaten måste göras. Detta kan lämpligtvis ske genom en känslighetsanalys. För att resultaten ska utgöra ett användbart verktyg för VA-huvudmannen måste också kostnaderna utvärderas noggrannare än de har gjorts i den här studien. / Urbanization along with a greater amount of hardened surfaces affects the storm water management. When the flows get faster and larger amounts create runoff, it is crucial that the available systems are able to handle the water. Storm water from roofs and asphalt surfaces and drainage water can be connected to the sewage water pipelines and make the flows in the conduits at rainfall much greater than they are designed for, leading to capacity issues. Many municipalities have implemented open storm water solutions instead of choosing the more cost-ineffective way of expanding the conduit system. Reconnecting downspouts, wells and drainage pipelines and digging trenches to lead the water is both cost and resource demanding. Therefore the aim of this study was to investigate whether multi criteria analysis can be used as an appropriate tool in order to allocate the resources to the most beneficial areas. This was done by developing a method for this aim and testing its robustness in order to determine if it is suitable to use in this context or if the uncertainties make the method too unreliable. The robustness in the method developed can be questioned since the uncertainties can be substantial. To be able to use this method, a lot of data is needed and the method needs to be updated relatively often in order to contain relevant information. It is recommended that a sensitivity analysis is performed along with the method, since the use of only one set of parameters can make the result relatively arbitrary. Using a Monte Carlo procedure with the uncertainties defined can reduce the time needed to measure and identify the values. The sensitivity analysis showed that the parameters that have the largest impact on the results are the number of residents living in every real estate with a basement, the catchment areas, the roughness parameters of the pipelines and the use of energy and chemicals in the system. In the future, the urbanization is expected to increase as well as the amount of rainfall and problems related to inflow and infiltration are expected to become more common. The hope is that the method used and its results will be useful for the municipalities’ future planning and to inspire to more studies on this topic.