Modelling the physical dynamics of estuaries for management purposes.

Doctoral Degree. University of KwaZulu-Natal, Durban.South African estuaries are characterised by highly variable inflows owing to the semi-arid nature of the land mass which they drain. The interaction of this variability with that of the marine environment (seasonality, high wave events, synoptic effects) gives rise to the distinctive character of South African estuaries. In general, they are small, micro-tidal, bar-built systems with strong flood tidal dominance. Approximately half of the 273 systems along the coast exhibit intermittent closure of the mouth, while a number can become hypersaline during dry periods. In view of the increasing development pressures on the rivers and estuaries of South Africa and their strong dependence on freshwater flow for the maintenance of their character and functioning, and the need for justifiable, scientifically-based decision making regarding the freshwater requirements of estuaries is evident. This study was initiated to address this issue by first developing a model to simulate the physical dynamics of South African estuaries over time scales from months to years, so enabling prediction of the medium to long term consequences of alterations in the freshwater inflow on the abiotic components of an estuary. Thereafter, the efficacy of management policies involving water releases and mouth breachings could be evaluated in terms of their success in maintaining the character and functioning of an estuary. A semi-empirical estuarine systems model incorporating seven state variables, namely water volume, salt content, stratification, circulation, tidal flushing, freshwater flushing and the height of the sill at the mouth, was formulated and implemented on two case studies. Estuarine physics concepts were incorporated dynamically in the model in a novel manner. For instance, the bulk densimetric Froude number and the Estuarine Richardson number are used in the simulation of the stratification-circulation states, while the Ackers and White sediment transport formula was modified to yield results which agreed with field observations of the closure and breaching of the mouth of the Great Brak Estuary. Additionally, tidal exchange through the mouth was modelled phenomenologically and successfully calibrated against observations for both case studies. Model results were found to be fairly robust to uncertainties in parameter values. However, most encouraging of all is that behaviour known to occur in shallow estuaries, such as modulation of the n11.:.m water level by low frequency forcing and the generation of overtides, was reproduced by the estuarine systems model although it was not specifically included in the model formulation. The model is thus considered to reliably predict the physical dynamics of South African estuaries over time scales of months to years. A number of management policies involving freshwater allocations, water releases and breachings of the mouth (where appropriate) were tested on the two case studies, namely the Great Brak Estuary, a small, temporarily open system, and the permanently open Kromme Estuary. The results indicate an increase in marine dominance as freshwater flow to the estuaries decreases. The variability in the estuarine environment declines and the systems become more inert to freshwater flooding and more sensitive to marine forcing. By applying the estuarine systems modelling approach, the performance of different management policies could be evaluated in comparison with reference policies. Accordingly, for both case studies, preferred management policies which utilize the present total annual allocations to the estuaries more beneficially could be indicated. Further management applications included the use of the estuarine systems model in a linked system of abiotic and biotic models to facilitate more comprehensive prediction of the consequences of freshwater abstraction and so more informed assessment of estuarine freshwater requirements. The estuarine systems model results were critical in enabling the prediction of the faunal and floral responses in the intermittently closed Great Brak Estuary as it is presently the only abiotic model capable of simulating the closure and breaching of the estuary mouth over a number of years. It is anticipated that further developments will occur in biological prediction in the near future and that this could require developments or adaptations to the estuarine systems model, particularly when details of the type of information required for biological prediction becomes known. Additionally, the use of the estuarine systems model in a strategic management sense is suggested. It could play a role as a screening tool for regional water resource planning, while the preliminary quantification of the extent of anthropogenic influence in expediting the movement of estuaries towards the later successionary stage of a coastal lagoon is a powerful indication of the level of prediction which could become possible in the future. Thus enhanced management decision making is now possible on a site specific basis and at a more strategic water resources planning level

Engineering roles in Building with Nature interdisciplinary design: Educational experiences

Building with Nature (BwN) infrastructure designs are characterised by disciplinary integration, non-linearity, diverse and fluid design requirements, and long-term time frames that balance the limitations of earth’s natural systems and the socio-technical systems created by humans. Differentiating roles in the engineering design process may offer strategies for better solutions. Four complementary engineering design roles were distinguished, namely: Specialists, System Integrators, Front-end Innovators, and Contextual Engineers. The key research question addressed in this paper asks, how can the introduction of engineering roles enhance interdisciplinary processes for BwN design? Three Building with Nature design workshops with international groups of students from multiple disciplines and various education levels provided the ideal context for investigating whether engineering roles enhance such interdisciplinary ways of working. Results indicate that the application of engineering roles in each of the three workshops indeed supported interdisciplinary design. A number of conditions for successful implementation within an authentic learning environment could be identified. The engineering roles sustain an early, divergent way of looking at the design problem and support the search for common ground across the diverse perspectives of the team members, each bringing different disciplinary backgrounds to the design table. The chapter closes with a discussion on the value of engineering design roles and their significance for the Building with Nature approach

Narrative and Frame Analysis: Disentangling and Refining Two Close Relatives by Means of a Large Infrastructural Technology Case

Social science literature frequently conflates the concepts "narrative" and "frame." We argue not only that using the terms interchangeably is conceptually imprecise but also that analyses based on them actually produce different kinds of knowledge. A systematic disentanglement, contrast and refinement of both concepts benefits from a comparative framework applied to the same case. We provide both. The illustrative case is a large infrastructural coastal management project. The key difference between narratives and frames turns out to be on the respective scale level: frames are actors' perspectives, whereas narratives are the expressed products of those perspectives. Being the mode of expression of one's perspective, we pinpoint "storytelling" as the link between narratives and framing and the origin of the conceptual confusion. Our framework clarifies the terminological usage and enables an informed method choice based on the desired kind of knowledge. With this clearer terminological understanding in mind, we encourage researchers to let the requirements and idiosyncrasies of their specific research interest and context inform their methods choice and to view the comparative framework as a heuristic rather than a deductive scheme.In der sozialwissenschaftlichen Literatur werden die Konzepte Narrative und Frame zumeist nicht trennscharf verwendet. Für uns ist es jedoch nicht nur konzeptuell unpräzise, beide Begriffe auswechselbar zu nutzen, sondern wir gehen auch davon aus, dass die jeweiligen Analysen unterschiedliche Wissensarten produzieren. Eine systematische Trennung sowie ein Vergleich und eine Verfeinerung beider Begriffe benötigt einen Rahmen, der auf denselben Fall angewandt wird. Wir illustrieren dies am Fall eines großen, infrastrukturellen Küstenschutzprojekts. Im Ergebnis besteht ein zentraler Unterschied zwischen Narrative und Frame in der Situiertheit auf unterschiedlichen Ebenen: Frames verweisen auf Akteur*innenperspektiven, Narratives auf deren Produkte. Als Ausdrucksmittel der eigenen Perspektive lokalisieren wir Storytelling als die konzeptuelle Verbindung zwischen Narrative und Frame. Gleichzeitig ist das Konzept des Storytelling der Ursprung der konzeptuellen Verwirrung. Mittels des von uns vorgestellten Vergleichsrahmens verdeutlichen wir den terminologischen Gebrauch und eine informierte Methodenwahl je nach gewünschter Wissensart. Mithilfe dieses klareren terminologischen Verständnisses regen wir Forscher*innen an, ihre Methodenwahl von den Anforderungen und Eigenarten des spezifischen Forschungsinteresses und des Forschungskontexts abhängig zu machen. In diesem Sinne sollte unser Vergleichsrahmen als Heuristik gesehen werden und nicht als ein deduktiver Verfahrensvorschlag

Coastal engineers embrace nature: characterizing the metamorphosis in hydraulic engineering in terms of Four Continua

Hydraulic engineering infrastructures, such as reservoirs, dikes, breakwaters, and inlet closures, have significantly impacted ecosystem functioning over the last two centuries. Currently, nature-based solutions are receiving increasing attention in hydraulic engineering projects and research programs. However, there is a lack of reflection on the concomitant, fundamental changes occurring in the field of hydraulic engineering, and coastal engineering in particular, and what this could mean for sustainability. In this article, we signal the shift from conventional to ecosystem-based hydraulic engineering design and characterize this in terms of four continua: (i) the degree of inclusion of ecological knowledge, (ii) the extent to which the full infrastructural lifecycle is addressed, (iii) the complexity of the actor arena taken into account, and (iv) the resulting form of the infrastructural artefact. We support our arguments with two carefully selected, iconic examples from the Netherlands and indicate how the stretching ideals of ecosystem-based engineering could engender further shifts towards sustainability

Assessing the IUCN global standard as a framework for nature-based solutions in river flood management applications

Nature-based Solutions (NbS) are actions that harness nature to help address major societal challenges. The assessment frameworks for NbS proposed in the literature differ in scope and intended use. In 2020, the International Union for Conservation of Nature (IUCN) introduced their Global Standard for NbS as a framework that can be used by anyone working on different types of NbS. Since research on the applicability of the IUCN Standard remains limited, the aim of this paper is to analyse whether the IUCN Standard may be used as an overarching assessment framework for NbS in river flood management applications and to identify the main differences in content with other NbS-frameworks. This was achieved through a comparison with 29 assessment frameworks for NbS, that are applicable to physical interventions for riverine flood risk reduction. The comparisons showed that the IUCN Standard has the largest breadth in scope of application and may therefore be used as an overarching framework. In addition, we identified a distinction between frameworks for the assessment of project processes (process-oriented) and project results (results-oriented), where the IUCN Standard can be characterized as process-oriented. This implies that the IUCN Standard may be used to assess the processes (e.g. stakeholder engagement and adaptive management) of planned, ongoing or completed NbS projects for a wide variety of environmental contexts and societal challenges. This will help persuade policy makers to consider NbS as one of the solutions in flood management issues, next to or in combination with e.g. engineering solutions or changing land use. We also identified that, while the IUCN Standard is straightforward to use and incorporates stakeholder input, the environmental context specificity as well as guidance depth on resources for assessment can be improved.</p

‘Mind the Gap’ between ecosystem services classification and strategic decision making

Ecosystem services (ES) are increasingly embedded in policy agendas, but if and how policy actors are considering them is not often reported. This study assesses the extent to which ES were considered by key policy actors involved in the strategic decision-making process leading to an innovative large-scale Dutch coastal management project. We analysed retrospective interviews to ascertain which ES were considered and how they were described by policy actors. Over half of the quotes (118/228) and 16 out of the 17 interviewees referred to three broad ES categories, with high degrees of adoption: coastal safety, recreation and cognitive development (learning by doing). The broad terms ‘nature’ and ‘spatial quality’ were also referenced often (36 times). Our findings suggest that broad, unspecified ecosystem services were adopted highly by the policy actors, while specific ecosystem service categories were rarely considered. Relatable and comprehensible cultural ecosystem services also constituted critical arguments for policy actors in their strategic decision making. We reflect that ambiguous, broad terms can help to garner support and unite efforts across disciplinary and institutional boundaries. For ES to align with relevant aspects of decision making, a ‘translation step’ between ES research and decision making might be required and ambiguity should be acknowledged.</p

The Influence of Scale Preferences on the Design of a Water Innovation: A Case in Dutch River Management

The debate on scale use in river management focuses primarily on the (lack of) fit between the bio-geophysical and institutional systems. However, in this article we focus on the ‘subjective’ aspect of scale preferences in water governance. We apply an adapted version of the Integrated Scale Hierarchy for Rivers to determine the degree of fit between the scale preferences of the actors involved in a Dutch case study and the scale requirements of the innovative river management concept. This allows us to understand which riverine processes and characteristics are regarded as important by the different actors and to identify mismatches in scale perspectives as they manifest themselves in water management practice. We discover that inflexibility in scale use on the part of the involved actors places bounds on the design and quality of interventions and demonstrate that a more flexible use of scales in the design phase of a river management intervention has the potential to lead to more effective solutions

Engineering: Building with Nature 101x video #04 - Engineering design process

This is video #04 :Engineering design process in the series of 11 videos. Video material forming a component of a Massive Open Online Course Engineering: Building with Nature 101x on the EDx platform about ecosystem-based, integrated design of hydraulic infrastructures. 11 videos in total, introducing Building with Nature and why it is important, and dealing with Building with Nature as a worldwide trend, the engineering design process, designing storm surge barriers, designing dikes, distilling engineering design principles, distilling ecological design principles, the Building with Nature design process, the Building with Nature design assignment and the peer review process

Building with nature video #02 - Introduction to Building with Nature @ TU Delft 2015

Introducing the Building with Nature course @ TU Delft 2015. A brief introduction to the concept of Building with Nature is given. Study goals are described, and the structure of the course in 5 design assignments is explained. Video 2 in the series of 13 videos