02 Fakultät Bau- und Umweltingenieurwissenschaften

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    Managed retreat as adaptation option : investigating different resettlement approaches and their impacts : lessons from metro Manila
    (2021) Lauer, Hannes; Delos Reyes, Mario; Birkmann, Joern
    Managed retreat has become a recommended adaptation strategy for hazard-prone coastal cities. The study aimed to improve considerations for the contextual factors that influence the success of managed retreat and resettlement projects in Metro Manila. Data were collected through a mixed-method approach consisting of a screening of relevant literature, a qualitative case analysis of resettlement projects, and a workshop series with Philippine stakeholders. It turned out that the resettlement of informal settlers is a central element of urban development. Though in-city resettlement is preferred, the majority of existing and planned projects are developed in off-city locations. The findings present a nuanced view of different retreat approaches. Not all in-city resettlements are successful, and the unpopular off-city projects have a potentially important role for urban and regional development. A strategic planning thread to develop concepts for qualitative off-city settlements that counteract uncontrolled urban sprawl with monofunctional residential areas for urban poor people was deduced. The other thread asks for pathways for inner-city development with innovative, vertical, in-city projects. A final observation was that climate change and the COVID-19 pandemic are worsening the situation in informal settlements, thus strengthening the argument for the planned decentralization of Metro Manila’s congested urban areas.
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    New methods for local vulnerability scenarios to heat stress to inform urban planning : case study City of Ludwigsburg/Germany
    (2021) Birkmann, Jörn; Sauter, Holger; Garschagen, Matthias; Fleischhauer, Mark; Puntub, Wiriya; Klose, Charlotte; Burkhardt, Albrecht; Göttsche, Franziska; Laranjeira, Kevin; Müller, Julia; Büter, Björn
    Adaptation strategies to climate change need information about present and future climatic conditions. However, next to scenarios about the future climate, scenarios about future vulnerability are essential, since also changing societal conditions fundamentally determine adaptation needs. At the international and national level, first initiatives for developing vulnerability scenarios and so-called shared socioeconomic pathways (SSPs) have been undertaken. Most of these scenarios, however, do not provide sufficient information for local scenarios and local climate risk management. There is an urgent need to develop scenarios for vulnerability at the local scale in order to complement climate change scenarios. Heat stress is seen as a key challenge in cities in the context of climate change and further urban growth. Based on the research project ZURES (ZURES 2020 website), the paper presents a new method for human vulnerability scenarios to heat stress at the very local scale for growing medium-sized cities. In contrast to global models that outline future scenarios mostly with a country-level resolution, we show a new method on how to develop spatially specific scenario information for different districts within cities, starting from the planned urban development and expansion. The method provides a new opportunity to explore how different urban development strategies and housing policies influence future human exposure and vulnerability. Opportunities and constraints of the approach are revealed. Finally, we discuss how these scenarios can inform future urban development and risk management strategies and how these could complement more global or national approaches.
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    Adaptation after extreme flooding events : moving or staying? The case of the Ahr Valley in Germany
    (2023) Truedinger, Alessa Jasmin; Jamshed, Ali; Sauter, Holger; Birkmann, Joern
    More than 130 lives were lost in the 2021 heavy precipitation and flood event in the Ahr Valley, Germany, where large parts of the valley were destroyed. Afterwards, public funding of about 15 billion Euros has been made available for reconstruction. However, with people and settlements being in highly exposed zones, the core question that is not sufficiently addressed is whether affected people want to rebuild in the same place, or rather opt to move out. The paper explores this question and assesses motivations and reasons for moving or staying in the Ahr Valley. For this purpose, a household survey was conducted focusing on 516 flood-affected households. The collected data was analyzed using descriptive and inferential statistics. The results revealed that the ownership of the house or flat significantly influenced the decision of whether to stay or to leave. In addition, an attachment to the place and the belief that such extreme events occur very rarely influenced the decision to stay and rebuild. Age, gender and household income barely influenced the decision to stay or to move to a new place. Interestingly, results demonstrated that many respondents view settlement retreat and the relocation of critical infrastructures as important options to reduce risk, however, many still rebuild in the same place. These insights enable local policy and practice to better address the needs of the population in terms of whether to stay or move after such an extreme disaster.
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    Heat vulnerability and adaptive capacities : findings of a household survey in Ludwigsburg, BW, Germany
    (2021) Laranjeira, Kevin; Göttsche, Franziska; Birkmann, Joern; Garschagen, Matthias
    In 2019, record-setting temperatures in Europe adversely affected human health and wellbeing (WMO 2020) and cities - thus, people in urban areas suffered particularly under heat stress. However, not only heat stress but also the differential vulnerability of people exposed is key when defining adaptation priorities. Up to now, local data on vulnerability and particularly adaptive capacities is rather rare. Various aspects of human vulnerability to heat and capacities to adapt to heat stress in urban areas still have to be explored and assessed, for example in terms of the adaptation at home, during work or while commuting to work. The paper presents new findings of a household survey on how and where different groups experience heat stress and how they assess their susceptibility and capacities to cope and adapt. The findings are based on a survey conducted in the medium-sized city of Ludwigsburg, Germany. Findings show significant linkages and correlations between socio-economic factors and heat vulnerability and capacities to respond. The analysis gives special emphasis to relationships between willingness to implement adaptive measures to reduce heat stress risks and risk perception and adaptive capacities. Particularly, the analysis of future adaptation options and the ability and willingness of different households to implement these provides new insights on the differential capacities to adapt and the need for tailor-made transformation programs.
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    Planning for climate change: an assessment of vulnerability in the city of São Paulo
    (2022) Batista Resende, Nayara Caroline
    The evidence on climate change and its implications to the future generations have motivated an increasing discussion on adaptation agendas and the necessity to plan more resilient urban spaces. However, implementing effective approaches for climate change adaptation are particularly challenging in countries like Brazil, where the planning of an adequate infrastructure system was not able to accompany the accelerated urbanisation process. Particularly in the city of São Paulo, such rapid urban population growth contributed to an urbanisation that is territorially extensive and characterised by socio-spatial inequalities and severe environmental issues. As the existent inequalities are predicted to aggravate the effects of climate change in the livelihoods of the population, it becomes of utmost importance to identify and address current vulnerabilities in order to strengthen the resilience of cities. Therefore, the aim of the thesis is to identify areas within the municipality of São Paulo that are subjected to a greater risk when faced with extreme events and climate change, so that vulnerable regions, sectors or population groups can be prioritised when planning adaptation strategies. Thus, a vulnerability assessment was elaborated through the construction of a social vulnerability index and the geospatial analysis of data using GIS tools. The results of the assessment were then combined to data regarding the susceptibility to flood events in order to produce a map of risk posed by flooding, so that “territories of risk” - where social and environmental vulnerabilities overlap - could be identified for intervention.
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    Nitrous oxide emission fluxes in coffee plantations during fertilization : a case study in Costa Rica
    (2021) San Martin Ruiz, Macarena; Reiser, Martin; Kranert, Martin
    The main source of N2O emissions is agriculture, and coffee monocultures have become an important part of these emissions. The demand for coffee has increased in the last five decades. Thus, its production in agricultural fields and the excess of fertilizers have increased. This study quantified N2O emissions from different dose applications and types of nitrogen fertilizer in a region of major coffee production in Costa Rica. A specific methodology to measure N2O fluxes from coffee plants was developed using Fourier-transform infrared spectroscopy (FTIR). Measurements were performed in a botanical garden in Germany and plots in Costa Rica, analyzing the behavior of a fertilizer in two varieties of coffee (Catuai and Geisha), and in a field experiment, testing two types of fertilizers (chemical (F1) and physical mixture (F2)) and compost (SA). As a result, the additions of synthetic fertilizer increased the N2O fluxes. F2 showed higher emissions than F1 by up to 90% in the field experiment, and an increase in general emissions occurred after a rain event in the coffee plantation. The weak levels of N2O emissions were caused by a rainfall deficit, maintaining low water content in the soil. Robust research is suggested for the inventories.
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    Combining crop modeling with remote sensing data using a particle filtering technique to produce real-time forecasts of winter wheat yields under uncertain boundary conditions
    (2022) Zare, Hossein; Weber, Tobias K. D.; Ingwersen, Joachim; Nowak, Wolfgang; Gayler, Sebastian; Streck, Thilo
    Within-season crop yield forecasting at national and regional levels is crucial to ensure food security. Yet, forecasting is a challenge because of incomplete knowledge about the heterogeneity of factors determining crop growth, above all management and cultivars. This motivates us to propose a method for early forecasting of winter wheat yields in low-information systems regarding crop management and cultivars, and uncertain weather condition. The study was performed in two contrasting regions in southwest Germany, Kraichgau and Swabian Jura. We used in-season green leaf area index (LAI) as a proxy for end-of-season grain yield. We applied PILOTE, a simple and computationally inexpensive semi-empirical radiative transfer model to produce yield forecasts and assimilated LAI data measured in-situ and sensed by satellites (Landsat and Sentinel-2). To assimilate the LAI data into the PILOTE model, we used the particle filtering method. Both weather and sowing data were treated as random variables, acknowledging principal sources of uncertainties to yield forecasting. As such, we used the stochastic weather generator MarkSim® GCM to produce an ensemble of uncertain meteorological boundary conditions until the end of the season. Sowing dates were assumed normally distributed. To evaluate the performance of the data assimilation scheme, we set up the PILOTE model without data assimilation, treating weather data and sowing dates as random variables (baseline Monte Carlo simulation). Data assimilation increased the accuracy and precision of LAI simulation. Increasing the number of assimilation times decreased the mean absolute error (MAE) of LAI prediction from satellite data by ~1 to 0.2 m2/m2. Yield prediction was improved by data assimilation as compared to the baseline Monte Carlo simulation in both regions. Yield prediction by assimilating satellite-derived LAI showed similar statistics as assimilating the LAI data measured in-situ. The error in yield prediction by assimilating satellite-derived LAI was 7% in Kraichgau and 4% in Swabian Jura, whereas the yield prediction error by Monte Carlo simulation was 10 percent in both regions. Overall, we conclude that assimilating even noisy LAI data before anthesis substantially improves forecasting of winter wheat grain yield by reducing prediction errors caused by uncertainties in weather data, incomplete knowledge about management, and model calibration uncertainty.
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    Spatial planning and systems thinking tools for climate risk reduction : a case study of the Andaman Coast, Thailand
    (2022) McMillan, Joanna M.; Birkmann, Joern; Tangwanichagapong, Siwaporn; Jamshed, Ali
    The impact of climate change and related hazards such as floods, heatwaves, and sea level rise on human lives, cities, and their hinterlands depends not only on the nature of the hazard, but also on urban development, adaptation, and other socioeconomic processes that determine vulnerability and exposure. Spatial planning can reduce climate risk not just by influencing the exposure, but also by addressing social vulnerability. This requires that relevant information is available to planners and that plans are implemented and coordinated between sectors. This article is based on a research project in Thailand, particularly on the results of multi-sectoral workshops in the case study region of the Andaman Coast in southern Thailand, and draws upon climate risk, spatial planning, and systems thinking discourses. The article formulates recommendations for planning in the context of Thailand that are relevant for other rapidly growing and urbanizing regions. Among other conclusions, it suggests that systems thinking approaches and cross-sectoral strategies are ways to grasp the interdependencies between and within climate risk and spatial development challenges.
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    Infrastructure cost implications of urban forms in developing countries : an analysis of development patterns in Ghana
    (2012) Adaku, Ebenezer; Siedentop, Stefan (Prof. Dr.-Ing.)
    The interdependency or relationship between infrastructure costs and urban form has been an important issue in town and regional planning over the years. Debates have generated among practitioners and theorists for over three decades now as to which development is the most cost efficient. However, the conclusions are still fuzzy and not clear, partly, because both practitioners and theorists often deliberately or unintentionally gloss over the realistic impacts of alternative development patterns in their submissions. Interestingly, most planning authorities rarely know and consider the costs of alternative development patterns in their decision making process. Besides, studies on infrastructure costs efficiency of alternative developments have constantly focused on developed countries without any attention to developing countries. This study then sought to contribute to the debate from developing countries’ perspective – using Ghana as the reference point – by analysing the effects of urban forms on infrastructure costs from both developing and developed countries’ points of view; determining the urban form that is infrastructure costs efficient as well as recommending to planners and policy makers in developing countries, possible areas in the development process, where infrastructure costs could be reduced. In approaching the study, both qualitative and quantitative methods were employed. The qualitative approach deals with the literature review of urban sprawl, particularly its general impacts and influence on the costs of infrastructure. Again, the phenomenon of urban sprawl is situated in the context of both developing and developed countries with differences and similarities of attributes in the different economic regions of the world ascertained. The literature review, further, focuses on how infrastructure costs relate to urban forms as well as analysing how the urban structures (with respect to social and spatial distributions) in both developing and developed countries affect infrastructure costs and financing. The conclusions of the literature review form the bedrock of the investigation and further reinforce the isolation of the effect of urban configuration on infrastructure costs. A graph theoretic tool, by means of AutoCAD, was employed for further isolation of the effect of urban configuration on infrastructure costs. Pattern classification – to delineate the primary urban patterns – coupled with agreement in literature on historical and current urban patterns gave rise to four hypothetical residential neighbourhood patterns – tributary, radial, grid and hybrid patterns. The four hypothetical patterns held all other factors constant and isolated the effect of street patterns and density on the capital costs of roads, water and electricity distribution networks. The study found out that, generally, the major factors that drive the current urban development patterns – urban sprawl – in developed countries have reached, relatively, higher levels of development in comparison with developing countries. Therefore, developed countries have higher urban dispersion potential and hence higher infrastructure costs vis-à-vis developing countries. The phenomenon also occasions a shift from intra-city to inter-city infrastructure costs concerns in the case of developed countries while in developing countries, emphasis is on intra-city infrastructure costs concerns with respect to urban forms. Again, the phenomenon of urban sprawl is perceived to be occasioned by market distortions and failures. The market distortions and failures leading to urban sprawl are deemed to be anchored in the cost-sharing scheme of infrastructure financing. Hence, the externalities and market failures associated with the cost-sharing scheme (which induces urban sprawl) could be dealt with so as to ensure more efficient urban forms through marginal costs pricing of infrastructure. The phenomenon of urban sprawl albeit evident in developing counties (particularly Ghana), does not fit exactly into the developed countries’ scheme of urban sprawl – both in causes and impacts. Besides, the urban structures of both developing and developed countries are different and have different implications on the costs of infrastructure development and financing. The study also found out that there is a relationship between urban forms and infrastructure costs. However, the relationship is not a single relationship but rather a multiple one. The intrinsic purpose of these relationships, as claimed by studies in developed countries, is independent of the socio-economic situation of any particular region. Hence, this relationship is presumably applicable in developing countries as well. It has also been shown in this study that apart from density, lot size, lot shape, location and dispersion of developments, street pattern or configuration relates to and has influence on infrastructure costs, particularly network infrastructure. In isolating the effect of street patterns on urban forms, the total capital costs of three infrastructure (roads, water and electricity distribution networks) revealed the tributary pattern as the most economical pattern in terms of the capital costs of linear infrastructure while the grid pattern is the least economical. The tributary pattern showed a 27% costs savings per dwelling over the costs of the grid pattern. The radial and hybrid patterns also indicated 9% and 3% savings per dwelling, respectively, in comparison with the grid pattern. Clearly, the savings in capital costs of linear infrastructure by the tributary, radial and hybrid patterns in comparison with the grid pattern, largely, resulted from savings in water distribution and road networks. The study showed that – it appears – other factors such as demand, density and type of distribution system other than the configuration of the street pattern influence the costs of electricity distribution network significantly. The capital costs per dwelling showed a gradual rise in infrastructure cost as one moved from the pure tributary pattern towards the pure grid pattern. Besides, in isolating the effect of density on linear infrastructure costs, it was revealed that the capital costs per dwelling of linear infrastructure reduce sharply, initially, with increasing density and later reduce, marginally, with further increments in density. Again, a density from 13 DPH to 53 DPH means approximately a 300% increment in density. However, the corresponding decrease in capital costs per dwelling for linear infrastructure was about 68% across the alternative hypothetical residential patterns. The general street pattern in Ghana is the cellular or grid type which is expensive in terms of linear infrastructure. Thus, since most developing countries (including Ghana) have fiscal challenges, urban configurations which reduce infrastructure costs and enhance revenues would be more appropriate. Thus, as shown by this study, the tributary pattern appears to fulfil this goal. However, the shortfall in accessibility – a key planning goal – could be augmented by a carefully designed network of footpaths. This measure fits well into Ghana or developing countries’ scheme of transportation – slow mode or walking. Again, geometry seems to provide a tool to optimise the values of infrastructure costs minimisation and accessibility enhancement. The fused grid, a new residential neighbourhood layout, is a good example. See Grammenos et al. (2008) for more discussions on the fused grid model. Besides, the price of infrastructure comprises costs and profits. Hence, an approach like urban configuration which seeks to reduce the costs is not enough. Other factors or areas which also influence the price of infrastructure to the user should also be considered and their effects – preferably – minimised. Such areas are developer or client’s costs, risks and contingencies related to the infrastructure development and profit margin of the construction contractor or developer.