The responsibility for mitigation of the ecological effects of urban stormwater runoff has been delegated to local government authorities through the Clean Water Act's National Pollutant Discharge Elimination Systems' Stormwater (NPDES SW), and Total Maximum Daily Load (TMDL) programs. These programs require that regulated entities reduce the discharge of pollutants from their storm drain systems to the "maximum extent practicable" (MEP), using a combination of structural and non-structural stormwater treatment — known as stormwater control measures (SCMs). The MEP regulatory paradigm acknowledges that there is empirical uncertainty regarding SCM pollutant reduction capacity, but that by monitoring, evaluation, and learning, this uncertainty can be reduced with time. The objective of this dissertation is to demonstrate the existing sources and magnitude of variability and uncertainty associated with the use of structural and non-structural SCMs towards the MEP goal, and to examine the extent to which the MEP paradigm of iterative implementation, monitoring, and learning is manifest in the current outcomes of the paradigm in Virginia. To do this, three research objectives were fulfilled. First, the non-structural SCMs employed in Virginia in response to the second phase of the NPDES SW program were catalogued, and the variability in what is considered a "compliant" stormwater program was evaluated. Next, the uncertainty of several commonly used stormwater flow measurement devices were quantified in the laboratory and field, and the importance of this uncertainty for regulatory compliance was discussed. Finally, the third research objective quantified the uncertainty associated with structural SCMs, as a result of measurement error and environmental stochasticity. The impacts of this uncertainty are discussed in the context of the large number of structural SCMs prescribed in TMDL Implementation Plans. The outcomes of this dissertation emphasize the challenge that empirical uncertainty creates for cost-effective spending of local resources on flood control and water quality improvements, while successfully complying with regulatory requirements. The MEP paradigm acknowledged this challenge, and while the findings of this dissertation confirm the flexibility of the MEP paradigm, they suggest that the resulting magnitude of SCM implementation has outpaced the ability to measure and functionally define SCM pollutant removal performance. This gap between implementation, monitoring, and improvement is discussed, and several potential paths forward are suggested. / Ph. D.

Protection of downstream channels and reduction in flooding can potentially be improved by evaluating alternative site stormwater management (SWM) strategies at a watershed scale and selecting the optimal strategy for a subject watershed. Tailoring a management strategy for a specific watershed may be worthwhile to minimize development costs and maximize downstream benefit. A hydrologic/hydraulic model for a watershed in Blacksburg, Virginia, is used to evaluate downstream results based on implementation of several alternative SWM strategies currently practiced within the United States. Results show none of the strategies meet the goal of maintaining the baseline goal at the watershed POI for the full range of design storms. Modification to the strategy that performs best at the watershed scale did meet the watershed goal for all design storms except the 1-year. For smaller storm events, it appears that increasing the volume of an initial capture and the drawdown time to release that volume does not increase performance downstream. This is potentially significant as extra dollars spent on site would not provide extra benefit downstream. When post-development peak runoff rates are detained to the predevelopment rate for larger storm events, whether based on a site or watershed focused strategy, the watershed goal can be met. A volume reduction strategy performs well, but implementation is hindered by soils with poor infiltration and the presence of karst. Other insight to watershed based management strategies, the role of regional facilities and predevelopment condition assumptions at the site scale to maintain a baseline condition downstream are discussed. / Master of Science

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: In the context of rapidly expanding cities, it is imperative that urban planning in South Africa has sufficient guidance regarding stormwater and river corridor management, in order to provide solutions that address issues of flood risk and the environmental health of river systems. Attenuation of stormwater runoff, the focus of this study, is one of the most important structural mechanisms used for the mitigation of many of the negative impacts caused by uncontrolled urban runoff. Typically, it involves the use of attenuation ponds or wetlands, which temporarily store runoff during a storm and release flow downstream at a reduced rate so as to mimic natural flow patterns. The focus of urban stormwater management and flood control has historically been on the protection of human life and property. However, in recent decades, through growing environmental awareness and the advancement of the concept of sustainable development, urban stormwater management has become a growing field of research worldwide, with a broader focus which considers not only flood control, but also water quality, aquatic biodiversity and the amenity value of urban drainage systems. Flood attenuation controls are becoming more widely used within South African urban areas, primarily due to policies or legislation brought into effect by local authorities. However, there is often little understanding regarding the positive and perhaps negative effects that these attenuation controls are having on receiving watercourses downstream. Three case studies were assessed by means of stormwater modelling simulations to evaluate various flood attenuation practices which are currently in use in South Africa. Two of the study areas, the Mosselbank River Catchment and the Bayside Canal Catchment, were selected in areas of Cape Town where future development has been proposed by spatial planners. The third study area, the Upper Kuils River Catchment, was evaluated in terms of the performance of existing attenuation facilities in an area which is already almost completely developed. The study found that attenuation facilities constructed with a single culvert-type outlet structure, designed to reduce flows during large storm events, do not mitigate the impact of post-development runoff occurring during lower recurrence interval storm events. Attenuation facilities with multi-stage outlet structures were found to be much more effective at mimicking pre-development flow during a range of storm events. It was also found that because attenuation does not reduce post-development runoff volumes to pre-development levels, but merely reduces peak flow rates, the cumulative runoff from multiple attenuation controls across a large (>30 km2) urban catchment resulted in higher runoff peaks in downstream watercourses. The study concluded that more widespread use of stormwater Best Management Practices (BMPs) and Sustainable Drainage System (SuDS) controls allows a greater portion of runoff to infiltrate, resulting in less runoff volume and therefore reduced peak flows downstream, especially during low recurrence interval storm events. In addition, the study recommended the use of detailed catchment-wide stormwater modelling to understand specific catchment dynamics holistically, thus increasing the potential for designing effective attenuation controls in urban stormwater systems. / AFRIKAANSE OPSOMMING: In die konteks van die vinnige tempo van stedelike uitbreiding, is dit noodsaaklik dat stedelike beplanning in Suid-Afrika plaasvind met in aggenome van voldoende riglyne vir die bestuur van stormwater en rivierkorridors, ten einde oplossings te vind vir die kwessies van vloedrisiko en die omgewingsgesondheid van rivierstelsels. Vloedvertraging, wat die fokus van hierdie studie is, is een van die belangrikste strukturele meganismes wat gebruik word vir die verligting van talle negatiewe impakte wat veroorsaak word deur onbeheerde stormwaterafloop in stedelike gebiede. Tipies behels dit die gebruik van vloedvertragingsdamme of vleilande, wat afloop vertraag tydens 'n storm en dus vloei stroom-af teen 'n verlaagde tempo uitlaat met die doel om natuurlike vloeipatrone na te boots. Die fokus van stedelike stormwaterbestuur en vloedbeheer was in die verlede hoofsaaklik op die beskerming van lewe en eiendom gefokus, maar het egter die afgelope dekades verskuif na water gehalte, die biodiversiteit van waterekosisteme en die geriefswaarde van stedelike dreineringstelsels. Hierdie verskuiwing van fokus is weens die groeiende omgewingsbewustheid en die bevordering van die konsep van volhoubare ontwikkeling wat wêreldwyd 'n groter navorsingsgebied geraak het. Vloedvertraging beheermeganismes word al hoe meer algemeen gebruik in Suid-Afrikaanse stedelike gebiede, hoofsaaklik as gevolg van die beleide of wetgewing wat deur plaaslike owerhede in werking gestel is. Daar is egter dikwels min begrip vir die positiewe en moontlike negatiewe gevolge wat hierdie vertragingsmeganismes op stroom-af sisteme het. Drie gevallestudies is geëvalueer deur middel van numeriese modelstudies wat verskeie benaderings van vloed beheer, wat tans in Suid-Afrika gebruik is, in ag neem. Twee van die studie areas, naamlik die Mosselbank en die Bayside-kanaal opvanggebiede in die Kaapse metropool, is gekies in areas waar toekomstige ontwikkeling in die vooruitsig gestel is deur stadsbeplanners. Die derde studie area, die opvangsgebied van die bolope van die Kuilsrivier, is in terme van die prestasie van bestaande stormwater infrastruktuur in 'n gebied wat reeds byna heeltemal ontwikkel is, geëvalueer. Die studie het bevind dat vloedvertragingsfasiliteite met 'n enkele duiker uitlaatstruktuur, wat ontwerp is met die doel om die vloeispitse tydens groot storms te demp, nie die impak van die na-ontwikkeling afloop, wat gedurende storms met laer herhalingsinterval voorkom, verminder nie. In terme van vloedvertragingsfasiliteite met 'n veelvuldige uitlaatstruktuur, is dit bevind dat voorontwikkelingsafloop tydens 'n reeks van groot en kleiner storms veel meer effektief nageboots word. Daar is egter ook bevind dat die demping van die vloedspitse nie die naontwikkeling afloopvolumes verminder tot voorontwikkelingsvlakke nie, maar slegs tot die vermindering van maksimum snelhede lei. Die gevolg is dat die totale afloop van ‘n kombinasie van ‘n aantal vertragingsdamme oor 'n groot (> 30 km2) stedelike opvanggebied ‘n hoër spitsvloei in die stroom-af riviere tot gevolg het. Die studie het bevind dat die wydverspreide gebruik van bestebestuurspraktyke (BMPs) en volhoubare stedelike dreineringstelsels (SuDS) tot die infiltrasie van ‘n groter gedeelte van die afloop lei, wat laer afloopvolume en dus verminderde spitsvloei stroomaf tot gevolg het, veral gedurende storms met ‘n lae herhalingsinterval. Daarbenewens word die aanwending van gedetailleerde modellering van stormwatersisteme binne die groter opvangsgebied aanbeveel ten einde ‘n meer holistiese begrip van spesifieke aspekte van die opvangegebied dinamika, om sodoende die potensiaal vir die ontwerp van effektiewe vloedvertragingskontroles in stedelike stormwaterstelsels te verbeter.

Purpose: Climate change and increased proportion of hard surfaces due to urbanization is causing problems with flooding. Although it has been known for a long time that traditional stormwater management needs to be complemented, progress towards Sustainable Drainage Systems, SuDS, is slow. Techniques to locally handle storm water are available for most situations, but there is a lack of knowledge and experience. The aim of this thesis is to present a proposal on how implementation of SuDS can be promoted in urban development projects in Jönköping municipality. Method: Using literature review, interviews, document analysis and observation a qualitative study was conducted in two urban development projects; Ekostaden Augustenborg in Malmö and Munksjöstaden in Jönköping. Findings: The majority of the stormwater management techniques available in Augustenborg have also been discussed in Munksjöstaden by Jönköping municipality. Only one third of the techniques which has been discussed will be realized. Jönköping municipality lacks clear goals and a vision that is integrated into the planning process, which can explain this. During the interviews the site conditions were presented as arguments to why SuDS is difficult to implement. However the analysis showed that it is the other conditions that are decisive, something that also the scientific studies indicated. In order to promote the implementation of SuDS general and project-specific actions were elaborated. Implications: The local plan is the municipality’s sharpest tool for control of the physical development and demands must be submitted in the local plan in order to promote SuDS. The municipality needs to reprocess a practice level and equate SuDS with traditional stormwater management in order to make relevant demands on developers. To promote the implementation of SuDS, the authors suggests that Jönköping municipality carry out a pilot project focusing on sustainable stormwater management in an upcoming urban development project. Limitations: Since the thesis only includes two projects, there is a limitation of the conditions treated. Since the other conditions and the recommended actions are based on the factors identified in a national survey, the applicability is considered to be good. Although the project-specific actions are based on Jönköping municipality, it is possible for other municipalities to apply the PDSA-wheel to the extent that is suitable for the municipality. / Syfte: Klimatförändring och urbanisering med ökad andel hårdgjorda ytor orsakar problem med översvämningar. Trots att det sedan länge är känt att den traditionella dagvattenhanteringen behöver kompletteras går utvecklingen mot Sustainable Drainage Systems, SuDS, långsamt. Tekniker för att ta hand om dagvattnet lokalt finns för de flesta situationer men det saknas kunskap och erfarenhet. Målet med arbetet är därför att presentera ett förslag på hur implementering av SuDS kan främjas i stadsbyggnads-projekt i Jönköpings kommun. Metod: Med hjälp av litteraturstudie, intervjuer, dokumentanalys och observation har en kvalitativ studie genomförts på två stadsbyggnadsprojekt; Ekostaden Augustenborg i Malmö och Munksjöstaden i Jönköping. Resultat: Majoriteten av de tekniker för dagvattenhantering som finns i Augustenborg har diskuterats även i Munksjöstaden från Jönköpings kommuns sida. Det visade sig dock att endast en tredjedel av det som diskuterats kommer att förverkligas. Detta kan bland annat förklaras av att Jönköpings kommun saknar tydliga mål och en vision som är integrerad i planeringsprocessen. Vid intervjuerna lyftes platsen förutsättningar fram som argument till varför SuDS är svårt att tillämpa. Analysen visade dock att det är de övriga förutsättningarna som är avgörande, något som även de vetenskapliga studierna pekat på. För att främja implementeringen av SuDS har därför generella och projektspecifika åtgärder riktade mot de övriga förutsättningarna utarbetats. Konsekvenser: Detaljplanen är kommunens skarpaste verktyg för att styra den fysiska bebyggelsen och för att främja SuDS är det därför viktigt att det finns krav i detaljplanen. Kommunen behöver upparbeta en praxisnivå och likställa SuDS med traditionell dagvattenhantering för att kunna ställa relevanta krav på exploatörer. För att främja implementeringen är författarnas förslag att Jönköpings kommun genomför ett pilotprojekt med fokus på hållbara dagvattenlösningar i ett kommande stadsbyggnadsprojekt. Begränsningar: Eftersom arbetet endast innefattar två projekt finns det en begränsning i vilka förutsättningar som behandlats. Eftersom de övriga förutsättningarna och de rekommenderade åtgärderna utgår från faktorer som identifierats i en nationell enkät-undersökning bedöms ändå tillämpligheten vara god. Även om de projektspecifika åtgärderna utgår från Jönköpings kommun, är det möjligt för andra kommuner att tillämpa PGSA-hjulet i den omfattning som passar den aktuella kommunen.

[EN] Under the well-known slogan 'think global, act local', cities in the 21st century face the enor-mous challenge of catalyzing, intensifying and accelerating sustainable urban transformations. Without losing a holistic view, the methodology presented in this thesis places the focus on 're-source management and climate mitigation and adaptation', in particular in urban stormwater management, proposing processes that can bring about the required change, shaped by the place-based approach of the regenerative sustainability paradigm. Building upon literature and practice that supports a flexible approach to stormwater manage-ment in urban environments that mimic natural processes and predevelopment hydrology (Sus-tainable Drainage Systems, SuDS) as one way to, amongst others, help to prevent and adapt to climate change, the thesis highlights the relevance of the connection to the place for adoption of best practices that conduct towards a regenerative system. Hence, it incorporates this con-nection to the place to the SuDS representation, naming it the SuDS 'landed rocket'. The proposed methodology includes a conceptual framework, specific method and tools, that allows for the understanding and the characterization of the current situation of a urban stormwater system in a process that guides future actions to move towards the desired regen-erative urban built environment concept, with a place-based holistic view. This methodology has been applied to Benaguasil, a Mediterranean city, where stormwater management is the local authority's responsibility and has been historically guided by main-stream conventional drainage practices. The thesis shows how, by taking a multi-dimensional and trans-disciplinary approach to solve environmental problems, future actions can be proper-ly addressed. Working with academia has been essential to develop wider evidence base. In this case, a sequence of research projects has advanced the innovative approach to stormwater management in Benaguasil, but it is contended that this methodology could be applied to any urban context. The thesis aims to enhance smart governance by providing information about the successful implementation and monitoring of SuDS showcase sites in Mediterranean Spain. These show-case sites are catalysts in the transition towards regenerative urban built environments in the region. In addition, it provides international examples that add further credence for improved urban ecological infrastructure by demonstrating what success can look like. / [ES] Bajo el conocido eslogan 'piensa global, actúa local', las ciudades del siglo XXI se enfrentan al gran reto de catalizar, intensificar y acelerar las transformaciones hacia un urbanismo sostenible. Desde una perspectiva holística, la metodología presentada en esta tesis se centra en 'la gestión de los recursos y la adaptación y mitigación al cambio climático', en particular en la gestión de las escorrentías urbanas, proponiendo los procesos que pueden ayudar al cambio requerido, bajo el enfoque del paradigma de la sostenibilidad regenerativa local. A partir de las referencias bibliográficas y experiencias que avalan a los Sistemas de Drenaje Sostenible (SuDS) como enfoque flexible a la gestión de las escorrentías urbanas, tratando de mimetizar los procesos hidrológicos previos al desarrollo urbano (que entre otros, contribuyen a la prevención y adaptación frente al cambio climático de las ciudades), la tesis subraya la relevancia de la conexión con el lugar para la selección de las mejores soluciones que lo conduzcan hacia un sistema regenerativo. Así, se incorpora esta conexión con el lugar a la representación de los SuDS, dándole el nombre de 'SuDS landed rocket'. La metodología propuesta incluye un marco conceptual, un método y herramientas específicas que permiten el entendimiento y caracterización de la situación actual de un sistema de drenaje urbano en un proceso que guíe acciones futuras para progresar hacia el concepto del medioambiente urbano regenerativo deseado, con una perspectiva holística local. La metodología se ha aplicado en Benaguasil, una ciudad mediterránea, donde la gestión del agua de lluvia es responsabilidad local y que ha estado influenciada históricamente por prácticas convencionales de drenaje. La tesis muestra cómo adoptando un enfoque multidimensional y multidisciplinar para resolver problemas medioambientales, las acciones futuras se pueden plantear correctamente. El trabajo con las instituciones académicas se ha demostrado esencial para desarrollar evidencias de base más amplias. En este caso, una serie de proyectos de investigación ha permitido el avance de Benaguasil hacia una gestión del agua de lluvia más innovadora. La experiencia demuestra que la metodología podría ser aplicada a cualquier otro contexto urbano. La tesis pretende mejorar la gobernanza inteligente proveyendo información respecto de la implementación y monitorización exitosas de SuDS en experiencias piloto en la España mediterránea. Estas demostraciones son catalizadoras de la transición hacia un medio ambiente urbano regenerativo en la región. Además, presenta ejemplos que se añaden al catálogo internacional de experiencias, mostrando el camino del éxito hacia un entorno urbano más saludable y habitable. / [CAT] Sota el conegut lema 'pensa global, actua local', les ciutats del segle XXI s'enfronten al gran repte de catalitzar, intensificar i accelerar les transformacions cap a un urbanisme sostenible. Des d'una perspectiva holística, la metodologia presentada en esta tesis es centra en 'la gestió dels recursos i la adaptació i mitigació al canvi climàtic', en particular en la gestió de les escorrenties urbanes, proposant processos que poden ajudar al canvi requés, des d'una òptica del paradigma de la sostenibilitat regenerativa local. A partir de les referències bibliogràfiques i experiències que avalen els Sistemes de Drenatge Sostenible (SuDS) com una aproximació flexible a la gestió de les escorrenties urbanes, tractant de mimetitzar els processos hidrològics previs al desenvolupament urbà (que entre altres, contribueixen a la prevenció i adaptació al canvi climàtic de les ciutats), la tesis subratlla la rellevància de la connexió al lloc per a la selecció de les millors solucions que el puguen conduir cap a un sistema regeneratiu. D'esta manera, s'incorpora esta connexió al lloc en la representació dels SuDS, donant-li el nom de 'SuDS landed rocket'. La metodologia proposta inclou un marc conceptual, un mètode i unes eines especifiques que permeten l'enteniment i caracterització de la situació actual d'un sistema de drenatge urbà en un procés que guie accions futures per a progressar cap al concepte de medi ambient urbà regeneratiu desitjat, amb una perspectiva holística local. La metodologia s'ha aplicat a Benaguasil, una ciutat mediterrània, on la gestió de l'aigua de pluja és responsabilitat local, i que ha estat influenciada històricament per pràctiques convencionals de drenatge. La tesis mostra com adoptant un punt de mira multidimensional i multidisciplinari per a resoldre problemes medi ambientals, les accions futures es poden plantejar correctament. El treball amb les institucions acadèmiques s'ha demostrat essencial per a crear evidències de base més amples. En este cas, una sèrie de projectes europeus d'investigació ha permès l'avanç de Benaguasil cap a una gestió de l'aigua de pluja més innovadora. L'experiència demostra que la metodologia podria ser aplicada a qualsevol altre context urbà. La tesis pretén millorar la governança intel¿ligent aportant informació respecte de la implementació i monitorització exitoses de SuDS en experiències pilot en la Espanya mediterrània. Estes demostracions son catalitzadores de la transició cap a un medi ambient urbà regeneratiu en la regió. A més a més, presenta exemples que s'afegeixen al catàleg internacional d'experiències, mostrant el camí del èxit cap a un entorn urbà més saludable i habitable. / Perales Momparler, CS. (2015). A regenerative urban stormwater management methodology. The role of SuDS construction and monitoring in the transition of a Mediterranean city [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/59063 / TESIS

Low Impact Development (LID) is a sustainable stormwater management approach that aims to control runoff close to its source, mimicking the natural hydrological processes such as infiltration and storage. It is being adopted by many cities, where its implementation is rapidly evolving. The LID practices are small-scale measures; therefore, they need to be widely implemented to impact significantly. The selection of LIDs depends on the land use and characteristics of the area of interest. This study focuses on residential LIDs. First, a systematic and bibliometric literature review is conducted on the residential LIDs articles published up to the year 2020; a total of 94 papers were found in the Web of Science. This review resulted that LID implementation in residential areas still needs to be investigated. To assist the City, engineers, and policy-makers in implementing the suitable LIDs for detached houses, a multi-criteria decision analysis framework incorporating a hydrological model is developed in this study. The commonly used LIDs were identified, which are rain gardens, permeable pavement, rain barrels, soakaways. Seven criteria were selected – runoff depth reduction rate, peak runoff reduction rate, installation cost, maintenance cost, retrofit cost, life cycle, and aesthetical view. For the properties of the single-detached house and LIDs, the standards of Credit Valley Conservation (CVC) and Toronto and Region Conservation Authority (TRCA) were followed. The proposed decision-making framework also was applied to a case study. This framework is still in the preliminary stage, thus holds the potential to convert into a tool that will be handy enough for the homeowners and consume less time. / Thesis / Master of Applied Science (MASc)

Förekomsten av vattenrelaterade problem som extrem nederbörd, översvämningar, torka och vattenbrist kommer att öka i urbana områden till följd av de globala klimatförändringarna. Sponge city-konceptet är ett urbant dagvattenhanteringssystem som lanserades i Kina och syftar till att förbättra vattenhanteringen i städer genom att återställa stadens kapacitet att absorbera, infiltrera, lagra och rena vatten. Den här studien syftade till att undersöka om sponge city-konceptet hade kunnat implementeras i Malmö genom att besvara frågeställningen ” Vilka möjligheter respektive hinder finns det för Malmö att implementera sponge city-konceptet?”. Genom en systematisk litteraturstudie och innehållsanalys i kombination med det teoretiska ramverket som baserades på konceptet sårbarhet för klimatförändringar visade resultatet på att det både finns en del möjligheter men också hinder. Det huvudsakliga hindret som identifierades är att en stor del av marken i Malmö består av täta moränleror vilket utgör ett hinder för de infiltrationsåtgärder som ingår i sponge city-konceptet. Några möjligheter som identifierades är att sponge city-konceptet kan minska känsligheten för skada som uppstår i förhållande till exponeringsnivån, samt att Malmös anpassningskapacitet är relativt hög. På grund av att den här studien enbart undersökte specifika fysiska/miljömässiga aspekter inom sponge city-konceptet krävs däremot fler studier som tar hänsyn till fler aspekter om en implementering av konceptet skulle bli aktuell. / The occurrence of water related problems such as extreme precipitation, floods, drought and water scarcity will increase in urban areas as a result of global climate change. The sponge city-concept is an urban stormwater system launched in China and aims to improve the water management in cities by restoring the city’s capacity to absorb, infiltrate, store and purify water. This study aimed to investigate if the sponge city-concept could be implemented in Malmö by answering the question “What possibilities and obstacles exist for Malmö to implement the sponge city-concept?”. Through a systematic literature review and content analysis in combination with the theoretical framework, which was based on the concept climate change vulnerability, the results showed that there are some possibilities but also obstacles. The main obstacle that was identified is that the ground in Malmö largely consists of dense moraines which forms an obstacle for the infiltration measures that are included in the sponge city-concept. Some possibilities that were identified is that the sponge city-concept can decrease the sensitivity to harm that occurs in relation to the exposure level but also that Malmö’s adaptation capacity is relatively high. However, because this study only investigated specific physical/environmental aspects within the sponge city-concept, more studies that consider more aspects are required if an implementation of the concept would become prevailing.