Abstract
Nature-based solutions (NBS) can protect, manage and restore natural or modified ecosystems. They are a multidisciplinary, integrated approach to address societal challenges and some natural ...hazards effectively and adaptively, simultaneously providing human well-being and biodiversity benefits. NBS applications can be easily noticed in circular cities, establishing an urban system that is regenerative and accessible. This paper aims to offer a review on NBS for urban water management from the literature and some relevant projects running within the COST Action ‘Implementing nature-based solutions for creating a resourceful circular city’. The method used in the study is based on a detailed tracking of specific keywords in the literature using Google Scholar, ResearchGate, Academia.edu, ScienceDirect and Scopus. Based on this review, three main applications were identified: (i) flood and drought protection; (ii) the water-food-energy nexus; and (iii) water purification. The paper shows that NBS provide additional benefits, such as improving water quality, increasing biodiversity, obtaining social co-benefits, improving urban microclimate, and the reduction of energy consumption by improving indoor climate. The paper concludes that a systemic change to NBS should be given a higher priority and be preferred over conventional water infrastructure.
Nature-Based Solutions (NBS) have been proven to effectively mitigate and solve resource depletion and climate-related challenges in urban areas. The COST (Cooperation in Science and Technology) ...Action CA17133 entitled “Implementing nature-based solutions (NBS) for building a resourceful circular city” has established seven urban circularity challenges (UCC) that can be addressed effectively with NBS. This paper presents the outcomes of five elucidation workshops with more than 20 European experts from different backgrounds. These international workshops were used to examine the effectiveness of NBS to address UCC and foster NBS implementation towards circular urban water management. A major outcome was the identification of the two most relevant challenges for water resources in urban areas: ‘Restoring and maintaining the water cycle’ (UCC1) and ‘Water and waste treatment, recovery, and reuse’ (UCC2). s Moreover, significant synergies with ‘Nutrient recovery and reuse’, ‘Material recovery and reuse’, ‘Food and biomass production’, ‘Energy efficiency and recovery’, and ‘Building system recovery’ were identified. Additionally, the paper presents real-life case studies to demonstrate how different NBS and supporting units can contribute to the UCC. Finally, a case-based semi-quantitative assessment of the presented NBS was performed. Most notably, this paper identifies the most typically employed NBS that enable processes for UCC1 and UCC2. While current consensus is well established by experts in individual NBS, we presently highlight the potential to address UCC by combining different NBS and synergize enabling processes. This study presents a new paradigm and aims to enhance awareness on the ability of NBS to solve multiple urban circularity issues.
Blue-green infrastructure (BGI) consists of natural and semi-natural (hence green) decentralized systems for urban stormwater management (hence blue), which, in addition to their primary purpose, ...provide a variety of shared benefits and ecosystem services. With the exception of a few cities that have adopted strategies for systemic BGI implementation, its use is still sporadic, in the form of isolated best practices, and is absent from Slovenian cities. Due to established spatial planning practices, Slovenian cities have a sufficient amount of relatively evenly distributed green areas, but these are not planned according to BGI principles and therefore their potential for managing stormwater is not utilized (i.e., water-wise multifunctionality). Because urban space management and its associated elements are a multidisciplinary field, we explored the link between spatial planning and water management in international strategic documents and in Slovenian national legislation. Based on a literature review, such connections are promoted at the international level; however, they are not sufficiently integrated in national legislation. Thus, a sectoral approach to water management and urban planning still prevails in Slovenian cities. Four examples of systemic BGI implementation (Rotterdam, Copenhagen, Philadelphia, and Chinese cities) are presented here. They link spatial planning and water management in BGI design and implementation. The results of this analysis were used to develop recommendations on integrating spatial planning and water management that go beyond sectoral urban space management, aiming to facilitate BGI implementation in (Slovenian) cities.
Modro-zelena infrastruktura (MZI) so naravni in polnaravni (zato zelena) decentralizirani sistemi, namenjeni upravljanju padavinskih voda (zato modra) v mestih, ki hkrati opravljajo zelo raznovrstne ...ekosistemske storitve. Razen v nekaj tujih mestih, kjer so že sprejeli strategije za njihovo sistematično uvedbo, je uvajanje MZI omejeno na zgolj posamezne osamljene primere. To še posebej velja za Slovenijo, kjer uporaba MZI še ni postala pravilo. Zaradi utečenih prostorskonačrtovalskih praks imamo v slovenskih mestih zadosten delež razmeroma enakomerno razporejenih zelenih površin, ki pa niso načrtovane po načelih MZI, zato njihova večfunkcionalnost z vidika voda ni izkoriščena. Ker upravljanje mestnega prostora in pripadajočih prvin spada pod okrilje več strok, nas je zanimala predvsem povezava med prostorskim načrtovanjem in upravljanjem voda v mednarodnih strateških dokumentih in v slovenski zakonodaji. Na podlagi pregledane literature smo lahko sklenili, da je tovrstna povezava predvsem na mednarodni ravni, na nacionalni ravni pa je že šibkejša in je delovanje predvsem na izvedbeni ravni vezano na posamezne sektorje. V nadaljevanju so predstavljeni štirje primeri sistemskega uvajanja MZI v tujini: v Rotterdamu, Københavnu, v izbranih kitajskih mestih in v Filadelfiji, tem je skupno povezovanje med prostorskim načrtovanjem in upravljanjem voda pri načrtovanju MZI. Rezultati analize stanja so bili izhodišče za oblikovanje priporočil, s katerimi je mogoče preseči sektorsko upravljanje mestnega prostora in doseči celovitejše upravljanje voda v (slovenskih) mestih.
Stormwater control measures (SCMs) are decentralized technical elements, which can prevent the negative effects of uncontrolled stormwater flow while providing co-benefits. Optimal SCMs have to be ...selected and designed to achieve the desired hydrological response of an urban catchment. In this study, automated modeling and domain-specific knowledge in the fields of modeling rainfall-runoff (RR) and SCMs are applied to automate the process of optimal SCM design. A new knowledge library for modeling RR and SCMs, compliant with the equation discovery tool ProBMoT (Process-Based Modeling Tool), was developed. The proposed approach was used to (a) find the optimal RR model that best fits the available pipe flow measurements, and (b) to find the optimal SCMs design that best fits the target catchment outflow. The approach was applied to an urban catchment in the city of Ljubljana, Slovenia. First, nine RR models were created that generally had »very good« performance according to the Nash–Sutcliffe efficiency criteria. Second, six SCM scenarios (i.e., detention pond, storage tank, bio-retention cell, infiltration trench, rain garden, and green roof) were automatically designed and simulated, enabling the assessment of their ability to achieve the target outflow. The proposed approach enables the effective automation of two complex calibration tasks in the field of urban drainage.
Soil hydraulic conductivity has a direct influence on infiltration rate, which is of great importance for modelling and design of surface runoff and stormwater control measures. In this study, three ...measuring techniques for determination of soil hydraulic conductivity were compared in an urban catchment in Ljubljana, Slovenia. Double ring (DRI) and dual head infiltrometer (DHI) were applied to measure saturated hydraulic conductivity (Ks) and mini disk infiltrometer (MDI) was applied to measure unsaturated hydraulic conductivity (K), which was recalculated in Ks in order to compare the results. Results showed significant differences between investigated techniques, namely DHI showed 6.8 times higher values of Ks in comparison to DRI. On the other hand, Ks values obtained by MDI and DRI exhibited the lowest difference. MDI measurements in 12 locations of the small plot pointed to the spatial variability of K ranging between 73%–89% as well as to temporal variability within a single location of 27%–99%. Additionally, a reduction of K caused by the effect of drought-induced water repellency was observed. Moreover, results indicate that hydrological models could be enhanced using different scenarios by employing a range of K values based on soil conditions.
This paper presents a methodology for assessing the selection of stormwater control measures (SCM) within an urban drainage system that combines hydrological-hydraulic modelling and multi-criteria ...analysis (MCA). The methodology's utility is illustrated on urban catchment in the city of Girona, Spain. The SWMM model was applied and calibrated to simulate SCM scenarios. Seven scenarios were evaluated consisting of one grey infrastructure measure using underground storage tank and three nature-based SCM i.e. infiltration basins, infiltration trenches, green roofs, and combinations thereof. These scenarios were evaluated with MCA including combined sewer overflow (CSO) reduction, CAPEX, OPEX, amenity, biodiversity, and feasibility regarding ownership. The results show that the scenario that included only infiltration basins was most favourable, followed by the scenario which combined infiltration basins and trenches. The underground storage tank was the least favourable with the lowest grade, due to high CAPEX and OPEX, and due to single functionality.
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•Methodology for multi-criteria assessment of stormwater control measures.•Nature-based and conventional measures evaluated in real urban catchment.•Scenarios of measures implementation evaluated using MCA.•Infiltration basins proved to be the most favourable measure for given conditions.
Blue and Green Infrastructures (BGIs) are natural or semi-natural systems that are considered an efficient solution to enhance stormwater management. To assess the performance of BGIs in mitigating ...floods and droughts in an urban area, a water balance model was developed in this study to simulate runoff formation and propagation. The developed model features fine spatial and temporal resolutions and flexibly integrates BGIs. Combining the conceptual single reservoir approach and the empirical continuous Soil Conservation Service Curve Number (SCS-CN) method, the model achieves computational efficiency, enabling long-term simulations that capture both short-term extreme events and long-term water balance. Its high transferability allows for easy incorporation of local datasets, making it adaptable to various urban contexts. Applied on a university campus located in Belgium, the model was used to simulate the water balance components of feasible BGIs for the study area, which were green roofs, permeable surfaces and rainwater tanks. Scenario analysis of both single BGI and combined BGI implementations was conducted, and all BGI scenarios were evaluated based on peak flow and runoff volume reduction and water balance analysis. Results demonstrate that the implementation of a combination of several BGIs with different functions is an effective solution for both flood control and drought mitigation, as these solutions can significantly reduce runoff flows, increase infiltration and provide considerable rainwater reuse.
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•A fine-scale water balance model for integrating BGIs was developed.•The long-term water balance analysis of various BGI scenarios was conducted.•For the study area, BGIs effectively mitigate urban flood and drought hazards.•Combined BGIs increased infiltration by 78 % and rainwater reuse by sevenfold.•Combined BGIs reduced overflow volume by over 90 %.
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•A knowledge library for automated urban runoff modelling was developed.•Three alternative infiltration methods were encoded in the knowledge library.•Process Based Modelling Tool was ...used to find the optimal rainfall-runoff model.•Nine models were automatically generated with very good performance.•Models that used a combination of infiltration methods performed best.
Modelling tools are widely used to analyse the urban drainage systems and to simulate the effects of future urban development and stormwater control measures. Usually, these tools use only one mathematical model (predetermined by the modeller) at a time to describe a single hydrological process within the urban catchment. When there are alternative mathematical models for describing the same hydrological process, their suitability needs to be investigated separately, which makes the modelling task even more complex, time consuming and open for human errors. Furthermore, models have to be calibrated to achieve a better fit between measured and simulated runoff. Calibration can be performed either manually, by using a trial-and-error approach, or by employing search techniques and parameter optimization tools. To overcome the drawbacks associated with manual selection and calibration of models, automated modelling based on equation discovery was used in this study to a) find the most suitable mathematical model among multiple alternatives for describing every (environmental) process modelled and b) to calibrate the model parameters against measured data. First, knowledge on urban runoff modelling was formalized into a new library of modelling components, compliant with the equation discovery tool ProBMoT (Process Based Modelling Tool). Next, a conceptual model of the experimental urban sub-catchment within the city of Ljubljana, Slovenia, was defined. ProBMoT was used to find the structure and parameters’ values of alternative rainfall-runoff models, according to the defined conceptual model that provide optimal fit against pipe flow measurements. Three alternative methods were used to describe infiltration: the SCS CN method, the Variable UK runoff equation, and the UK Water Industry Research equation. The proposed automated model discovery approach for finding the optimal rainfall-runoff model proved to be very efficient. Nine rainfall-runoff models were created with very good performance. The best performance was achieved by the models that used a combination of two different infiltration methods, i.e. the SCS CN infiltration method for the pervious area and one of the other two infiltration methods for the impervious area.
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