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  • 1.
    Berggren, Karolina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Indicators for urban drainage system: assessment of climate change impacts2008Ingår i: Conference Proceedings : 11th International Conference on Urban Drainage: Edinburgh International Conference Centre, Scotland : 11 ICUD: 31st August - 5th September 2008, Munich: Oldenbourg Industrieverlag , 2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    Changes of the climatic conditions will affect urban drainage systems, as they are closely related to the weather phenomenon and are built as to cope with the weather occurring. The aim of this paper is to investigate indicators that can be used to describe and compare impacts and adaptation measures in existing urban drainage systems. Problems in the system due to climate change can be summarised as problems with flooding of surfaces and basements, increased amount of combined sewer overflows (CSO), increase of the inflow to waste water treatment plants (WWTP) and increase in pollutants spreading from urban areas to the environment. The impacts needs to be described with indicators taking into account the system behaviour both before, during and after an event (e.g. urban flooding) has occurred, and can be divided into (A) description of the system performance, (B) capacity exceeding in the system, and (C) description of consequences as a result of capacity exceeding. The consequences can be divided into sustainable aspects as: technical, economical, socio-cultural, environmental, and health. The research is performed within a project which will also include model simulations of urban drainage systems in four Swedish municipalities as to assess impacts and evaluate the use of indicators.

  • 2.
    Berggren, Karolina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Urban drainage and climate change: impact assessment2007Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    According to the Intergovernmental Panel on Climate Change (IPCC, 2007), the global mean temperature has increased by 0,7 °C during the last 100 years and, as a consequence, the hydrological cycle has intensified with, for example, more intense rainfall events. As urban drainage systems have been developed over a long period of time and design criteria are based upon climatic characteristics, these changes will affect the systems and the city accordingly.The overall objective of this thesis is to increase the knowledge about urban drainage in a changing climate. In more detail, the objective is to investigate how climate change may affect urban drainage systems, and also to suggest methods for these investigations.The thesis consists of four papers. The first paper concentrates on the Delta change method for adaptation of rainfall data from climate models for urban hydrology use. The second paper is an impact assessment with urban drainage model simulation of a study area in the south of Sweden. The third paper is also an impact study, from a cause and effect approach, where the whole urban water is included. Finally, the fourth paper contains a strategy and suggestions about tools to use for assessing impacts on urban drainage systems due to climate change. The suggested tools are urban drainage model simulations, Geographical Information Systems (GIS), and risk analysis methods.The Delta change approach is feasible for handling the differences in spatial and temporal resolution between climate model data and the needs for urban drainage model simulations, as the method is relatively simple and the temporal resolution of observed rainfall series is preserved. In the study area with separated storm water system, the model simulations show that the number of surface floods as well as the geographical distribution of the floods increases in the future time periods (2011-2040, 2041-2070, and 2071-2100). Future precipitation will also increase both the flooding frequency and the duration of floods; therefore, the need to handle future situations in urban drainage systems and to have a well-planned strategy to cope with future conditions is evident. The overall impacts on urban drainage systems due to increased precipitation may, for example, be an increased number of basement floods, surface floods, problems with property and road drainage, and also increased amount of infiltration into pipes and combined sewer overflows (CSOs). The knowledge gained from this thesis, and the strategy suggested, can be used as a starting point for impact studies on urban drainage systems. Since most impacts concern several different disciplines and a multifunctional understanding, the studies should also be performed in cooperation with parties concerned.

  • 3.
    Berggren, Karolina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Urban stormwater systems in future climates: assessment and management of hydraulic overloading2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Increasing global temperatures and tendencies of more frequent extreme weather events have been observed over the recent decades, and the continuation of this trend is predicted by future climate models. Such climatic changes impact on many human activities and hence the interest in, and focus on, climate change has increased rapidly in recent years. One of the fields strongly affected by ongoing climate change is urban water management and, in particular, the provision of urban drainage services. Modern urban drainage systems (UDSs) are designed to manage stormwater and convey residual runoff from urban areas to receiving waters, in order to fulfill such UDS primary functions as e.g., preserving local water balance; mitigating increases in runoff and the associated flood risks; and protecting water quality. There are also other drivers that influence the future urban runoff regime and the UDS performance, including urban planning, land-use changes (progressing urbanization), and implementation of sustainable stormwater management systems by such approaches as e.g., Best management practices (BMPs), Low impact development (LID), Water sensitive urban design (WSUD), and Green Infrastructure (GI). This doctoral thesis focuses on urban rainfall and runoff processes, and runoff conveyance by separate storm sewer systems, and the changes in these processes caused by climate change, with the overall objective of investigating urban stormwater systems response and performance related to future climate changes, and particularly the future rainfall regime, by means of urban rainfall/runoff modelling. Furthermore, future influences on the runoff regime of urban green/pervious areas have also been studied. Specifically, the thesis has focused on future rainfall changes and hydraulic performance of the stormwater system, and the influential response parameters needed for evaluating the simulated impacts, with the overall aim of contributing new knowledge to this field. The results included in the thesis are based on three published journal papers, one manuscript, and three conference papers. The research project started by addressing the needs for relevant UDS hydraulic response parameters (or indicators), which reflect both the capacity exceedance (when the UDS design fails) and indicate the safety margins in the system (e.g., locations with low or high capacities). The pipe flow rate and maximum water levels in the system exceeding a critical level, are examples of such parameters. Another issue addressed in this thesis is the difference in resolution (temporal and spatial) of the original climate model data (even if downscaled) compared to the requirements on rainfall input data in urban drainage modelling. Therefore, an existing statistical downscaling method (the delta change method, DCM) was refined by focusing on changes in rainfall intensities and seasonal rainfalls, and the refined DCM was recommended for use in UDS modelling. The UDS performance in future climates, studied by modelling these systems, showed that a future change in rainfall poses significant impacts on the existing UDSs. Important aspects in addressing such impacts are, for example, the input rainfall data types (e.g. design storms, or observed rainfall), as well as the climate factors, and the methods used to produce such factors. Green/permeable areas within the urban catchments may, however, provide opportunities for adaptation of urban catchments and UDS, by potentially increasing the infiltration of rainwater, instead of converting it into rapid runoff contributing high flows and flow volumes to the urban drainage systems. Influential factors in these processes include soil types, soil moisture content, groundwater levels and the rainfall input. While climate change with uplifted rainfalls tends to increase runoff contributions from all urban surfaces (impervious and green/pervious), strategic application of runoff controls in the form green infrastructure may counterbalance such increases, and even lead to reduced runoff inflows into the UDS.

  • 4.
    Berggren, Karolina
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Lans, Axel
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Ashley, Richard
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Future changes affecting hydraulic capacity of urban storm water systems2012Ingår i: Urban Drainage Modelling: Proceedings of the Ninth International Conference on Urban Drainage Modeling, Belgrade, Serbia, 4-6 September 2012, Belgrade: Faculty of Civil Engineering, University of Belgrade , 2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Urban areas may develop and change its character over time, but the urban drainage system is often 12 more constant in character – as the technical design life can be up to 100 years. The hydraulic capacity 13 of an existing urban storm water system is affected by future changes, e.g. rate of imperviousness 14 (urbanization), changes in the rainfall characteristics (e.g. by climate change) and system deterioration 15 (pipes and other facilities). Recently the urban planning process in Sweden and elsewhere has become 16 more appreciative of urban drainage issues, and the need to include these earlier in development 17 processes. In this paper a small urban catchment is used to study how future factors affect the 18 hydraulic capacity and the potential development of the area. Factors tested are scenarios of: (1) 19 Urbanization; (2) Climate change and (3) Pipe system deterioration. The results show that each of 20 these factors impact on the hydraulic capacity and that any sensitivity analysis should include all of 21 them to understand future development potential for the area. This type of investigation can increase 22 the understanding of the needs of the infrastructure provision in the area in a planning process context, 23 and provide information about appropriate areas of development within the catchment.

  • 5.
    Berggren, Karolina
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Moghadas, Shahab
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Gustafsson, Anna-Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Ashley, Richard
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Sensitivity of urban stormwater systems to runoff from green/pervious areas in a changing climate2013Konferensbidrag (Refereegranskat)
  • 6.
    Berggren, Karolina
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Olofsson, Mats
    Viklander, Maria
    Svensson, Gilbert
    Tools for measuring climate change impacts on urban drainage systems2007Ingår i: Techniques et stratégies durables pour la gestion des eaux urbaines par temps de pluie: NOVATECH 2007 ; 6e conférence internationale, juin 2007, Lyon, France, Villeurbanne: Graie , 2007, Vol. 1, s. 239-246Konferensbidrag (Refereegranskat)
  • 7.
    Berggren, Karolina
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Olofsson, Mats
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Svensson, Gilbert
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Gustafsson, Anna-Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Hydraulic impacts on urban drainage systems due to changes in rainfall, caused by climatic change2012Ingår i: Journal of hydrologic engineering, ISSN 1084-0699, E-ISSN 1943-5584, Vol. 17, nr 1, s. 92-98Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The changes in climate were of a growing concern in the last decade, and will be even more so in the coming years. When investigating impacts on urban drainage systems due to changes in the climate, two challenges are (1) what type of input rainfall data to use, and (2) what parameters to measure the impacts. The overall objective of this study is to investigate the hydraulic performances ofurban drainage systems related to changes in rainfall, and through these hydraulic parameters describe impacts of climate change. Input rainfall data represents today's climate, as well as three future time periods (2011-2040, 2041-2070, and 2071-2100). The hydraulic parameters used were water levels in nodes (e.g. as the number of floods, frequency and duration of floods), and pipe flow ratio. For the study area, the number of flooded nodes and the geographical distribution of floods will increase in the future, as will both the flooding frequency and the duration of floods.

  • 8.
    Berggren, Karolina
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Packman, John
    Centre for Ecology and Hydrology, Wallingford, Oxon.
    Ashley, Richard
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Climate changed rainfalls for urban drainage capacity assessment2014Ingår i: Urban Water Journal, ISSN 1573-062X, Vol. 11, nr 7, s. 543-556Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Guidance on what type of rainfall to use when assessing hydraulic capacity of urban drainage systems under climate change is unclear; focus is mainly on what climate factors to use. Based on a case study in Kalmar, Sweden, this paper compares system performance using two design rainfalls, Block rainfalls and Chicago Design Storm (CDS), and selected observed rainfalls, with two methods of addressing future climate: a constant factor and Delta Change (DC) factors that depend on rainfall intensity. The use of CDS rainfalls presents the maximum hydraulic response, whereas Block rainfalls give lower responses but identify critical durations in the system, which may be useful addressing adaptation actions. Observed rainfalls of target return periods gave similar responses to CDS rainfalls, and can be applied with DC factors to address future changes in both intensity and volume. Differences between the two methods indicate a high dependence related to the maximum factors applied on the rainfalls

  • 9. Berggren, Karolina
    et al.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Will the existing urban drainage systems cope with future climate?: a Swedish study2006Konferensbidrag (Övrigt vetenskapligt)
  • 10.
    Moghadas, Shahab
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Berggren, Karolina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Gustafsson, Anna-Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Regional and seasonal variation in future climate: is green roof one solution?2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this study, regional climate data was used to investigate the trend of changes for some climatic parameters, i.e. temperature, precipitation and maximum hourly precipitation in four different regions in Sweden. The general trend shows that Sweden will have warmer and wetter climatic conditions by 2100; however, the seasonal changes will affect the system differently, which makes them one of the main factors to be considered. The climatic data was used to determine the probable magnitude of changes by 2100 and to investigate the climate change impacts on urban drainage systems. The problems arising due to such changes were discussed regionally and seasonally and finally BMP methods, as an alternative way, to mitigate the climate change impacts were considered. As an example, green roof was applied to different urbanized conditions to estimate the approximate reduction of the extra water into the drainage system. As well as to investigate how much each of the BMP methods (green roof as an example for opening the further studies) could be useful for city planners towards more secure and sustainable cities in the future against the climate change.

  • 11.
    Olofsson, Mats
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Olsson, Jonas
    SMHI.
    Berggren, Karolina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Adaptation of RCA3 climate model data for the specific needs of urban hydrology simulations2006Ingår i: Extreme Precipitation, Multisource Data Measurement and Uncertainty: Proceedings of the 7th International workshop on precipitation in urban areas / [ed] Peter Molnar, Zürich: Institute of Environmental Engineering, ETH, Zürich , 2006, s. 144-148Konferensbidrag (Refereegranskat)
    Abstract [en]

    Adapting climate model data to urban drainage applications can be done in several ways but a popular way is the so-called ‘delta change' method. In this method, relative changes in rainfall characteristics estimated from climate model output are transferred to an observed rainfall time series, generally by multiplicative factors. In this paper, a version of the method is proposed in which these ‘delta factors' are related to the rainfall intensity level. This is achieved by calculating changes in the probability distribution of rainfall intensities and modelling the delta factors as a function of percentile. The model is applied to 30-min output from the RCA3 regional atmospheric climate model, in a grid box covering Kalmar City, Sweden. The climate model results indicate an increase of the highest intensities by up to ~20% and a decrease of lower intensities by up to almost 40%. This result is valid for a 30-min time scale, and to evaluate whether urban drainage impact assessment can be meaningfully performed on this time scale, a MOUSE model was applied in Kalmar using different time steps. The results indicate that a 30-min time step may be meaningful, but that ways to transfer the rainfall changes also to data of a higher time resolution needs to be considered. This will be done in future studies, as well as further testing and evaluation for other Swedish cities.

  • 12.
    Olsson, J.
    et al.
    Research and Development (hydrology), Swedish Meteorological and Hydrological Institute, Norrköping.
    Berggren, Karolina
    Olofsson, Mats
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Applying climate model precipitation scenarios for urban hydrological assessment: a case study in Kalmar City, Sweden2009Ingår i: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895, Vol. 62, nr 3, s. 364-375Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is growing interest in the impact of climate change on urban hydrological processes. Such assessment may be based on the precipitation output from climate models. To date, the model resolution in both time and space has been too low for proper assessment, but at least in time the resolution of available model output is approaching urban scales. In this paper, 30-min precipitation from a model grid box covering Kalmar City, Sweden, is compared with high-resolution (tipping-bucket) observations from a gauge in Kalmar. The model is found to overestimate the frequency of low rainfall intensities, and therefore the total volume, but reasonably well reproduce the highest intensities. Adapting climate model data to urban drainage applications can be done in several ways but a popular way is the so-called Delta Change (DC) method. In this method, relative changes in rainfall characteristics estimated from climate model output are transferred to an observed rainfall time series, generally by multiplicative factors. In this paper, a version of the method is proposed in which these DC factors (DCFs) are related to the rainfall intensity level. This is achieved by calculating changes in the probability distribution of rainfall intensities and modelling the DCFs as a function of percentile. Applying this method in Kalmar indicated that in summer and autumn, high intensities will increase by 20-60% by year 2100, whereas low intensities remain stable or decrease. In winter and spring, generally all intensity levels increase similarly. The results were transferred to the observed time series by varying the volume of the tipping bucket to reflect the estimated intensity changes on a 30-min time scale. In an evaluation of the transformed data at a higher 5-min resolution, effects on the intensity distribution as well as single precipitation events were demonstrated. In particular, qualitatively different changes in peak intensity and total volume are attainable, which is required in light of expected future changes of the precipitation process and a step forward as compared with simpler DC approaches. Using the DC transformed data as input in urban drainage simulations for a catchment in Kalmar indicated an increase of the number of surface floods by 20-45% during this century.

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