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Item type:Publication, Access status: with files , Influence of climate change on the wave climate in the Persian Gulf and consequences for port planningThe impact of climate change on wave parameters as well as wave loading on coastal structures in the Persian Gulf is presented in this PhD research by simulating the wave conditions for the past (1979-2020) and future (2021-2100) periods. The study focuses on five major ports along the entire Iranian coast of the Persian Gulf, covering a wide range of input parameters in terms of the geographical characteristics of the study points. The regional climate model RegCM4.7 provides hindcast and forecast wind data with a 3-hour temporal resolution. Additionally, the ERA5 wind model is utilized, providing hindcast data with a 1-hour resolution. A novel downscaling method based on data processing in the frequency domain is proposed to generate future wind data with 1-hour time steps. The trend of change from past to future is obtained from the RegCM model and is then applied to the ERA5 model hindcast data to generate a high-resolution future dataset. The advantage of the proposed downscaling method is that, unlike statistical methods, it does not lose information from the original data and ensures that extreme events are not ignored. Wave conditions at the study sites are simulated using the SWAN model for both historical and future periods. The wave-structure interaction is investigated by calculating the wave load for different return periods. Since the wave-structure interaction depends on the type of coastal structure, we limited our study to the typical structures mainly used at the study points, including rubble mound breakwaters and different types of vertical walls, as well as the drag and inertia forces exerted by waves on cylindrical piles. Our calculations show that an increase in wave loading of up to 50% could be expected, particularly in regions with deep or intermediate water levels.Publicationtype: Thesis63 9 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Integrated modelling of riverine levee breaches and subsequent inundation of protected areasLevees are earthen embankments, often constructed from locally available soil material, used to contain floodwaters in rivers. Levee design standards have improved over time, contributing to their reliability in providing flood protection. However, levees never provide absolute flood protection. The preparation of flood hazard maps for areas behind levees is therefore indispensable. Flood hazard maps can be produced using hydrodynamic numerical models that simulate flood inundation. The modelling of flood inundation due to levee breaching involves the modelling of two processes: i) the breaching of the levee and ii) the propagation of the flood through the resulting opening into the hinterland. This thesis proposes the modelling of flood inundation due to levee breach with a 2D hydrodynamic numerical model with an integrated parametric levee breach model. To model levee breaching, a parametric levee breach model is developed, which is based on analyses of physical levee breaching experiments and of real levee breaches. The breach model is then integrated into the hydrodynamic numerical model Telemac-2D, a publicly available code for modelling flood propagation. The thesis also developed methods for estimating the parameters of the parametric breach model based on historical (available) levee breach data. Regression fitting for the final breach width is performed using multiple linear regression, multiple non-linear regression and artificial neural networks. In addition, an approach is developed to estimate a possible breach location based on flood characteristics (water level and flood duration), geometric and geological characteristics of the levee in question and its foundation, the cause of the breach, and information from historical levee breaches on their breach location. By re-modelling physical laboratory tests simulating levee breaching, this work has demonstrated that the hydrodynamic numerical model, Telemac-2D, is a suitable tool for modelling flood inundation due to levee breaching. The flood inundation caused by the levee breach on the Awash River at Wonji, Ethiopia in August 1996 could be reproduced using the proposed integrated approach. Furthermore, the determination of the breach location for this levee breach case using the approach proposed in this thesis resulted in the same location as the actual breach location, demonstrating the general applicability of the approach. The uncertainties associated with the models used are also discussed. To demonstrate the uncertainty associated with the breach model, the sensitivity of flood inundation depth and breach discharge to variation of the levee breach parameters is systematically analysed using the August 1996 Awash River levee breach flood event at Wonji, Ethiopia.Publicationtype: Doctoral Thesis87 46 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Hydraulische Leistungsfähigkeit von eingestauten und überströmten Brücken über Fließgewässer mit mildem Gefälle und kompaktem Querschnitt(2025); There is a lack of physically based hydraulic computation methods for submerged and overtopped bridges during extreme floods with lateral constriction. In this work, the momentum equation is used uniformly across different hydraulic situations utilizing non-linear distributions of measurable quantities at control volume boundaries. Polynomial approximations for distributions determined in the laboratory and CFD model allow a simple treatment of the boundary integrated forces in the practical calculation without structure individual coefficients.Publicationtype: Doctoral Thesis69 93 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Klimawandelbedingte Veränderungen des örtlichen Seegangs und Auswirkungen auf die Belastungen von KüstenschutzbauwerkenFor the further development and optimization of concepts and methods for climate change adaptation in coastal protection, information on possible changes of hydrodynamic input variables, in particular local water levels and local waves, is needed, since these are among the most important input variables for the planning and design of coastal protection structures. The work contributes to this by developing and applying a methodology, based on different ensembles of regional climate projections, for the spatial and temporal quantification of possible long-term climate change-induced changes of local wave conditions along the German Baltic Sea coast for average conditions and extreme events, as well as for the estimation of the ensemble bandwidth (uncertainty) of selected climate scenarios in combination with analyses of the statistical significance of the changes. In addition, the effects of sea level rise and changes in local wave conditions due to climate change on the resulting structural loads were analyzed and evaluated using scenarios and typical coastal protection structures. The work is based on innovative methods such as (i) the use of ensembles of regional climate projections with high spatial and temporal resolution for the extended analysis and assessment of climate change induced changes of local wave conditions and (ii) the development and application of a hybrid method for sea state calculation, which is currently the only one that allows long-term calculations and the uncertainty assessment based on climate projection ensembles. The developed methodology has been used to calculate the local sea state in the area of the southwestern Baltic Sea as an application case, but can in principle also be applied to other semi-enclosed regional inland seas, where the sea state is mainly influenced by the local wind field and only to a small extent by swell effects and not by strong currents. For example, for the climate projection ensembles and mean conditions considered, statistically significant increases in wind speed, significant wave height and mean wave period, as well as changes in mean wind and wave directions toward more westerly directions, were observed predominantly at sites exposed to westerly winds. In contrast, no clear (consistent) signal or uniform trend was found for extreme events. Overall, the changes are characterized by high spatial, interannual and seasonal variability, and represent a subset of the full range of possible future changes in local sea state. It was also shown that without adaptation of the structures and in the case of unfavorable morphological development due to sea level rise and climate change induced changes in the wave boundary conditions, both the local wave conditions and the wave induced loads on the structures as well as possible damage will increase and the functional effectiveness and structural safety will decrease.Publicationtype: Doctoral Thesis72 76 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Zur Beschreibung der vertikalen Bodenaustauschprozesse von kohäsiven Sedimenten am Beispiel des Weserästuars(2025); This thesis deals with the processes of erosion, deposition and consolidation that determine the accumulation of cohesive sediments in the navigational channel within the estuarine turbidity maximum in estuaries. The overall objective is to better understand the vertical sediment exchange processes and the properties of sediments based on experimental investigations in the field and in the laboratory using cohesive sediments from the turbidity zone of the Weser estuary as an example, and to describe them using mathematical formulations. In order to achieve the set objectives, the first step was to develop new methods and equipment that enable the transport properties of cohesive sediments to be recorded in both the field and the laboratory in a repeatable and systematic manner. This includes the development of a gravity core sampler for sediment sampling, the development of a methodology for recording density depth profiles, the development of a methodology for determining concentration-dependent effective settling velocities, and the development of the C-GEMS, a mobile erosion test rig based on the Gust microcosm. In a second step, the developed methods and equipment have been applied in systematic test series in the field and in the laboratory, using natural sediments from the turbidity zone of the Weser estuary as the object of investigation. Within the scope of the experimental investigations carried out, at least one adequate model approach could be identified, parameterised and developed for each of the processes erosion, deposition and consolidation. The present work thus enables a consistent description of the vertical soil exchange of cohesive Weser sediments based on measurements of the total density and water density.Publicationtype: Doctoral Thesis84 57 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Nature-based Solutions for sandy coasts as sustainable adaptation measures to climate change - a contribution to the broadened conceptual understanding of NbS from an engineering as well as a societal perspectiveFor centuries, coastal protection was characterized by the fight against nature. Nowadays it enables a safe life and economic activity along the coast, but climate change poses new challenges to the existing coastal protection and requires substantial adaptations. In combination with a paradigm shift in society's view of the coastal landscape and nature in general, a discourse on future technically possible, sustainable and sensible coastal protection is stimulated. Nature-based Solutions (NbS) represent promising adaptations for sandy coasts, providing ecological and societal benefits in addition to protection. In order for these to find their way into future common practice and to fully exploit their potential for Water, Nature and People, a broadened understanding of NbS from both engineering and societal perspectives is needed to facilitate cooperation at all levels. The present thesis starts off at this point. Adopting an inter- and transdisciplinary approach allows the issues to be considered and analysed from different scientific disciplines as well as actors’ perspectives. By combining a broad spectrum of analytical tools, insights can be generated that go beyond the spectrum of the disciplines involved. Exemplary for sandy coasts, the North Frisian Islands of Amrum and Föhr are selected as investigation area. An insight into the evolution of coastal protection and its characterising rationale is obtained through a systematic literature review. How this rationale is anchored in the minds of people is investigated with an analysis of the assessment of protective measures based on conducted semi-structured interviews. In combination, both analyses reveal a dynamic evolution characterised by experimenting and tinkering with various types of coastal protection. Well-established measures like diking or stalk plantings in dunes, are prevailingly assessed as useful, adequate and trustworthy for the time being. Supposedly new concepts like NbS are initially often met with scepticism as they cannot be readily placed in the existing category system of coastal protection. The conducted review of coastal ecosystems as NbS discloses that they offer a chance to close this gap. Thanks to their inherent resilience, in addition to the existing coastal protection, NbS represent a sustainable adaptation option to climate change. To broaden the understanding of NbS from an engineering perspective, a conceptual analysis of the underlying processes within coastal ecosystems reveals and analyses the properties of NbS which can be fine-tuned and their role and interrelationships with regard to service, resistance and resilience. To broaden the understanding of NbS from a societal perspective, a socio-scientific analysis identifies the coastal dwellers’ key requests towards coastal protection. The Key Societal Requests can help coastal dwellers to contextualise NbS in their established category system of coastal protection and highlight the importance and the potential of societal aspects to coastal engineers. Both perspectives add to a broadened conceptual understanding of NbS, so that NbS can find way into common practice as sustainable adaptation measures to climate change and, thus, ultimately contribute to the re-diversification of coastal protection for an increased coastal resilience.Publicationtype: Doctoral Thesis148 202 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , A contribution to understanding the recently enhanced coastal siltation in the German Wadden SeaThe Wadden Sea on the Northwestern European Shelf is world's largest channel-shoal system that comprises broad coherent intertidal flats, islands, shoals, and several estuaries. Coastal management has shaped the Wadden Sea's coastline and its estuaries for centuries which is why navigational channel dredging and coastline maintenance have become routine coastal engineering tasks. Since the 2010s, German coastal stakeholders reported further enhanced coastal siltation. My research objectives were (1) to identify whether there was quantifiable evidence of enhanced coastal siltation and (2) to find the driving processes behind this development. An analysis of bathymetry data confirmed that intertidal flats accreted and that lateral expansion and subtidal deepening occurred. Balanced subtidal and intertidal sediment budgets suggested a redistribution of local subtidal sediments to intertidal flats. In addition, surface sediment data indicated a gradually increasing mudflat coverage over time. Based on this information, numerical modeling and observational data were used to quantify changes in tidal and non-tidal forcing: I found near-constant wind-wave and storm surge conditions which indicated that event-driven phenomena were an unlikely driver. Spatial tidal analysis and observational data revealed amplitude and phase shifts of principle and shallow water tidal constituents which reflected in increased tidal amplitude, and reduced flood dominance. Furthermore, diminishing flood flow velocity and increased slack duration were noted. These phenomena were related to increased relative intertidal storage and to subtidal deepening from bathymetry evolution. Hence, the reduction in channel volume and the intertidal accretion likely decreased tidal and wave energy on the tidal flats and enabled the deposition of more fines. Longer flood and ebb slack duration should add to this effect. The import of sand into the coastal zone was likely reduced as flood dominance diminished at the entire study site.Publicationtype: Doctoral Thesis432 180 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Dynamic draft of extraordinary large vessels on the Lower Elbe waterway(2020-12); Vessels on the Lower Elbe Estuary experience draft increasing impacts from confined waters like squat as well as influences due to density and maneuvering motions. Recent ship size developments towards vessel units with 22000 TEU stresses out the gap between existing design approaches and present fleet sizes. With the central method of extensive field-investigations on the Lower Elbe sea-waterway, this dissertation analyses and assesses generally accepted dynamic draft determination approaches. The work discovers that with increasing ship sizes, safety margins within the squat determination approaches decrease to a critical extend. On the other hand, the dissertation discovers unutilized safety margins within the draft determination process.Publicationtype: Doctoral Thesis458 1752 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Zur Modellierung des Transports kohäsiver Sedimente am Beispiel des Weserästuars(2020-05-27); Cohesive Sediments show in comparison to other sediment fractions a differing hydrodynamic transport behaviour. This leads in combination with occurring residual flow and mixing processes in estuaries to the formation of the so-called estuarine turbidity zone. A new process-based model approach is presented, which enables the applied modelling of the dynamics of cohesive sediments for the estuarine environment with numeric methods. The approach was tested for the Weser estuary. The modelled turbidity zone is establishing in the model like in nature as a dynamic equilibrium due to the sediment accumulation.Publicationtype: Doctoral Thesis941 1425 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Integrating local scale drainage measures in meso scale hydrological modelling of backwater affected catchments(2020-02-25); This work presents the development, implementation and evaluation of methods to overcome limitations in the hydrological numerical modelling of local scale drainage measures in backwater affected meso scale catchments. The demand arises, among others, by the need to analyse the performance of local adaptation measures to mitigate the magnitude of flooding on a regional scale. In current hydrological numerical models, resolved limitations include (1) a required flexible spatio-temporal resolution in the methods, (2) a physical-based parametrisation to model processes in local scale measures, (3) hydrological methods to model backwater effects and (4) approaches to generate hydrological networks.Publicationtype: Doctoral Thesis862 547