Pluvial flooding originating from extreme rainfall is problematic and an increasing issue in Sweden. Higher requirements on adapting cities in urban areas to these challenges have been placed on both municipalities and the county administration. Thus, an increased need for water modelling, both in existing and planned areas have emerged. The Danish Hydrological Institute (DHI) has developed several models and tools to simulate floods and heavy rains, of which MIKE 21 is one. MIKE 21 is a dynamic model consisting of hydrological calculations in each cell, requiring modelling skills and long simulation time, but is proven to be a good and credible model. SCALGO Live, on the other hand, is a static tool simulated by raster-based algorithms and capable of giving fast results directly on the platform. However, compared to MIKE 21, SCALGO Live is not as evaluated nor is its use as widespread for simulating floods and heavy rain events. This study aims to investigate how inundation in twenty urban areas caused by cloudbursts is simulated in both programs to examine how well the result coming from SCALGO Live, is equivalent to the result from the MIKE 21-model. The comparison is made in both depth and spread using three comparative indexes, two statistical equations and one map, showing the extension of the inundation in both models. To make the models comparable, the model in MIKE 21 is made as equivalent as possible with SCALGO Live before simulation and the purpose is to investigate whether there is any type of area where the two different models are equivalent. The result shows that the flooded areas from SCALGO Live are in good agreement in most areas with the MIKE 21-model, but that the depth in the depression zones is somewhat overestimated, compared with the highest value in MIKE 21. The MIKE 21-model has a greater spread upstream, showing flowpaths if compared directly with the flooded areas from SCALGO Live, but if activating the flow accumulation tool in SCALGO Live, the differences are reduced but cannot be quantified in this study. The differences between the models increase with a higher resolution, longer flowpaths and a larger catchment, at least for the confined catchments. To conclude, SCALGO Live is best suited for smaller confined catchments where there are no long or complex flowpaths. SCALGO Live also works well at an early stage in the planning process and as a platform for combining detailed data and results. However, for the more complex areas, MIKE 21 is better suited, since various parameters can be considered.

Översvämningar till följd av skyfall har blivit allt vanligare och förväntas att öka i takt med klimatförändringarna. Översvämningar kan ställa till stora skador för ett samhälle, framförallt när de samhällsviktiga verksamheterna blir drabbade. För att undvika att detta sker bör samhället vara byggt för att tåla stora volymer vatten som faller vid ett skyfall. Ett steg för att nå dit är att göra en skyfallskartering där flödesvägar, vattenvolymer och översvämningens utbredning tas fram genom hydraulisk modellering. Utifrån skyfallskarteringen kan sårbara områden upptäckas och förebyggande åtgärder kan utföras för att minska översvämningens negativa påverkan. Akademiska sjukhuset i Uppsala är en samhällsviktig verksamhet och har tidigare haft problem med översvämningar. I den här studien har en skyfallskartering utförts på Akademiska sjukhusets område för att ta reda på översvämningens utbredning vid ett skyfall och vilka åtgärder som lämpar sig för att förhindra översvämningar. Skyfallskarteringen utfördes i det tvådimensionella (2D) hydrauliska modelleringsprogrammet MIKE 21 Flow Model. Eftersom en skyfallskartering baseras på många generaliseringar finns det vissa osäkerheter kring valet av parametrar. Därför har även en känslighetsanalys utförts kring valet av regntyp (Chicago Design Storm (CDS) jämfört med ett blockregn), regnets varaktighet, grönytornas avrinningskoefficient och markens infiltrationshastighet. Indata till modellen baserades på olika kartdata som bearbetades i GIS-programmet ArcMap. Flera olika regn med varierande återkomsttid simulerades. Resultaten visade att det blir översvämning inne på sjukhusområdet vid ett 100-årsregn som förvärras när återkomsttiden ökar. Åtgärdsanalysen utfördes genom att lägga in förändringar i höjdmodellen för att se hur det påverkar översvämningens utbredning. Analysen visade att åtgärder som jordvallar och höjdsättning av marken kan tillämpas på området för att minska översvämningsrisken. Resultatet från känslighetsanalysen visade att ett CDS-regn ger större översvämningskonsekvenser i modelleringen än om ett blockregn av samma återkomsttid och varaktighet används. Känslighetsanalysen av varaktigheterna visade att en lång varaktighet kan leda till låga flödestoppar som inte representerar ett skyfall väl. En avrinningskoefficient på 0,4 beskriver infiltrationen i området väl och när en större avrinningskoefficient används tenderar översvämningen att bli större på grönytorna. Till sist visade resultatet att infiltrationshastigheten är en känslig parameter som bör väljas efter mer noggrann analys av marken i modelleringsområdet. / Flooding as a cause of cloudbursts have become more common and is expected to increase with climate change. Floods can cause substantial damage to a society, especially when the critical societal functions are affected. To avoid this the city should be built to tolerate large volumes of water from cloudbursts. As a step on the way to accomplish this, a cloudburst mapping could be made where flow paths, water volumes and the extent of the flooding are studied through hydraulic modelling. Through the cloudburst mapping, vulnerable areas can be spotted, and flood prevention measures can be taken to lessen the extent of the floods negative impact. Uppsala University Hospital serves a critical societal function and has previously had problems with flooding. In this project a cloudburst mapping has been made in the two dimensinoal (2D) hydraulic modelling program, MIKE 21. This was done to find out the extent of a flood caused by a cloudburst event and what measures that can be taken to prevent floods. A cloudburst mapping is based off many generalized assumptions and there are some uncertainties when selecting the parameters. Because of this, a sensitivity analysis was performed on the selection of rain-type (Chicago Design Storm (CDS) vs. block-rain), rain duration, the runoff coefficient and the soil's infiltration capacity. The inputs of the model were based off different geographic data and then constructed in the GIS-program ArcMap. Several different rain events with varying duration and return periods were simulated. The results showed that there is considerable flooding in the area after a rain with a 100-year return period and it gets worse when the return period increases. The flood prevention analysis was made by editing the terrain to mimic flood prevention measures and study how the extent of the flood responds to the edits. The analysis showed that measures like soil barriers and changes in elevation were effective in lessening the risk of flooding. The results from the sensitivity analysis showed that a CDS-rain causes a more significant flooding compared to a block-rain of the same return period and duration. The sensitivity analysis of the rain duration proved that a long duration can lead to flat flow curves that doesn't resemble a flow curve from a cloudburst event. A runoff coefficient of 0.4 describes the infiltration in the area well and with a larger coefficient the flooding on greenery tend to grow. Lastly, the infiltration capacity proved to be a sensitive parameter that needs to be selected carefully, preferably after a thorough soil analysis.

Från om med 1 januari 2024 ska alla kommuner ha en vattentjänstplan. En vattentjänstplan ska innehålla varje kommuns långsiktiga plan för att tillgodose allmänna vattentjänster i framtiden samt åtgärder som behöver vidtas vid skyfall för att skydda VA-anläggningar. Lagändringen infördes 1 januari 2023 vilket har gett kommuner en snäv tidsplan att ta fram denna plan. Arbetet har undersökt vad vattentjänstplanen i Västerås kommun behöver innehålla för att uppfylla kravet om åtgärder vid skyfall, identifiera punkter i spill- och dagvattennätet som potentiellt är sårbara för skyfall och ge förslag på skyfallsåtgärder. För att uppfylla syftet har en risk- och sårbarhetsanalys utförts för att identifiera punkter i spill- och dagvattennätet som är sårbara för skyfall. Analysen inkluderade en workshop med nyckelpersoner på Mälarenergi Vatten AB och en riskmatris som användes som bedömningsunderlag. Från riskmatrisen identifierades punkter som var potentiellt sårbara för skyfall och en lågpunktskartering utfördes i SCALGO Live på utvalda punkter. De regnhändelser som utfördes i karteringen var 10-, 20- och 100-årsregn. Lågpunktskarteringen jämfördes även med en skyfallskartering med markavrinning och ledningsnät, vilket är en kartering av hög detaljeringsgrad, för att undersöka ifall lågpunktskartering kan vara lämpligt underlag till en vattentjänstplan. Resultatet av risk- och sårbarhetsanalysen var att sju punkter, som gavs som förslag under workshopen, hade höga riskvärden och var potentiellt sårbara för skyfall. Tre av sju punkter valdes till vidare analys: Branthovda, Skiljebo och Önsta-Gryta, alla belägna i Västerås tätort. Samtliga av dessa tre punkter var i dagvattennätet. Lågpunktskarteringen i SCALGO Live som utfördes över dessa tre punkter visade stora översvämningar vid ett 100-årsregn. Skyfallsåtgärder som föreslogs för platserna var magasinerings ytor och skyfallsled. Vid jämförelse av lågpunktskartering och skyfallskartering med markavrinning och ledningsnät visade skyfallskarteringen en mindre översvämning för Branthovda och Skiljebo. I Önsta-Gryta var skillnaden mellan karteringarna minimal. Detta var då skyfallskarteringens resultat visar på att dagvattenledningarna i området var överbelastade redan vid ett 10-årsregn, vilket liknade villkoret i lågpunktskarteringen att dagvattenledningarna antas vara fulla. Med detta kan endast en lågpunktskartering visa ett områdes potential till att var sårbara för skyfall, men säger inget om hur spill- eller dagvattennätet påverkas. Dock kan en lågpunktskartering hjälpa till att identifiera områden i tätorter som skulle kunna vara sårbara för översvämningar. / As of January 1st, 2024, all municipalities must have a water service plan. A water service plan must contain each municipality's long-term plan to provide public water services in the future and solutions that need to be taken in the event of a cloudburst to protect water and sewage facilities. The change in law was introduced on January 1st, 2023, which has given municipalities a tight timetable to develop this plan. The study has investigated what the water service plan in Västerås municipality needs to contain in order to fulfill the requirement for solutions in the event of cloudbursts, identify points in the waste and stormwater network that are potentially vulnerable to cloudbursts, and provide suggestions for torrential rain measures. In order to fulfill the purpose, a risk and vulnerability analysis has been carried out to identify points in the waste and stormwater network that are potentially vulnerable to cloudbursts. The analysis included a workshop, with key individuals at Mälarenergi Vatten AB, and a risk matrix that was used as an assessment basis. From the risk matrix, points that were potentially vulnerable to cloudbursts were identified and a low-point mapping was performed in SCALGO Live at the selected points. The rain events performed in the mapping were 10-, 20- and 100-year rainfalls. The low-point mapping was compared with a cloudburst mapping with land runoff and conduit network, which is a mapping with a high degree of detail, to investigate whether low-point mapping can be a suitable basis for a water service plan. The result of the risk and vulnerability analysis was that seven points, which were given as suggestions during the workshop, had high-risk values and were potentially vulnerable to cloudbursts. Three out of the seven points were selected for further analysis: Branthovda, Skiljebo, and Önsta-Gryta, all of them located in Västerås city. All of these sensitive points were in the stormwater network. The low-point mapping in SCALGO Live performed over these three points showed major flooding during a 100-year rainfall event. The proposed cloudburst solutions for the sites were storage areas and cloudburst roads. When comparing low-point mapping and cloudburst mapping with ground runoff and conduit networks, the cloudburst mapping showed a minor flood for Branthovda and Skiljebo. In Önsta-Gryta, the difference between the mappings was minimal. This was due to the results of the cloudburst mapping showing that the stormwater pipes in the area were overloaded even with a 10-year rain, which was similar to the condition in the low-point mapping that the stormwater pipes are assumed to be filled. With this, only a low point mapping can show an area's potential for being vulnerable to cloudbursts but does not say anything about how the waste or stormwater network is affected. However, low point mapping can help identify areas in built-up areas that could be vulnerable to flooding.

The study has consisted of creating a place for snow storage with a connecting storm water facility. This is based on findings regarding concentrations of pollutants in Luleå's snow storages in combination with Luleå's standards for design of these storages. For Luleå Municipality, the stormwater issue is relevant as the number of floods will increase as Luleå expands. This results in a greater ratio of hard-made surfaces with increased surface runoff that create risks of flooding and property damage, something that will intensify even further with climate change. Besides this, the runoff concentration of pollutants that are transported out into recipients also increases. The study has been carried out in Luleå, via Luleå Municipality and LTU. The purpose of the study was to answer the following questions:"What concentrations of pollutants are found in Luleå's meltwater?", "What does Luleå' smanagement of snow storage look like, and why?", "Where can a snow storage be placed in Luleå to enable year-round recreation?” and "Which stormwater solution should be chosen to filter pollutants from this snow deposit?". This was answered via seven different means of gathering data: literature studies, field studies/observations, meetings/interviews & E-mail exchanges, selection of a stormwater facility, calculations, simulations, and conceptual design. Through these means, the study concluded that the concentrations of pollutants in meltwater are generally greater than in stormwater, that there are recommendations regarding the size, location and safety of Luleås snow storages, that any snow storage should preferably be located where motor traffic is not present and that its space should be usable year round with regard to recreation, and that a wetland is the most suitable facility for filtering the pollutants in the meltwater from this deposit. Overall, the results conveys that the spaces set aside for snow and meltwater treatment should enable year-round recreation, in addition to their technical functions. However, does the results show nothing in terms of management of extreme cases of rainfall nor any types flooding preventions relating to stormwater management. This paper does not provide any suggestions for a snow storage site nor a stormwater treatment facility for cities with a similar or different climate. The reason that onlyr ecreation and pollution treatment were considered is because these are the most relevant in this context, firstly since toxins are more prevalent in meltwater than in stormwater, and because recreation associated with snow is a given aspect of usage. Thus were a suitable frame of question and suitable means used to generate reasonable and acceptable results.