This study gained insight into riverbank development in the presence of ship traffic. Understanding the processes that govern shoreline stability is of importance because it leads to adequate strategies to prevent severe erosion. This is especially relevant in the context of future climate scenarios. In this study, bank lines along Bird-Long Island were observed. This is an island located in the Savannah River, on the border of Georgia with South Carolina, USA. Bird-Long Island is an important wetland mitigation bank for the Georgia Department of Transportation and houses an archaeological site with Civil War artillery. The site is exposed to the primary wave generated by vessels. Egg Island serves as a control site and is located in the Altahama River (without vessel traffic).

Riverbanks are delineated on satellite imagery using the CoastSat toolkit. Two indicators of the riverbank are used: the boundary between sand and water (shoreline), and vegetation and sand (vegetation line). Delineation of the latter involved adaptation of CoastSat. Yearly and 30-year migration rates are determined through linear regression of all shoreline positions along a defined cross-shore transect.

Riverbanks erode when exposed to hydraulic loading by ships. This is supported by the finding that the whole bank along Bird-Long Island is eroding, while the site without vessel traffic displays both erosion and accretion. At Bird-Long Island, the erosion rates range between -0.90 m/year (m/yr) to -6 m/yr (vegetation line) and -1.0 m/yr to -4.6 m/yr (shoreline). The strongest erosion occurs at a headland and an embayment, where local bathymetry likely enhances wave focusing and deformation. These spatial patterns demonstrate that the impact of vessel waves is dependent on local conditions and shoreline features, such as shallow banks, perturbations, and channel orientation.

The vegetation line and shoreline behave differently at Bird-Long Island. The vegetation line, marking the scarp, develops more uniformly and erodes at a larger rate than the shoreline. Hydraulic loading by ship waves leads to the strongest attack at the top of the bank.

Yearly fluctuations in erosion rates of Bird-Long Island are related to yearly developments in ship traffic. Ship size, sailing speed, and intensity are assessed. Ship size and speed of vessel passages are accessed through AIS data and transformed into yearly distributions. Intensity is assessed through the handled cargo (throughput in TEU) at the Port of Savannah. From 1994 to 2025, the throughput increased tenfold. The AIS data is restricted to the period 2011 to 2025 and shows that the extreme vessel size increased over time. Spearman's correlation coefficient and linear regression lines express the strength of the relationship between vessel traffic and erosion rates.

The vegetation line erosion rates are correlated to the median vessel length, draft, and blockage ratio. The linear regression line indicates that a year with a higher median length and draft results in stronger erosive behavior in that year. Riverbank erosion is driven by the cumulative effect of vessel load. The riverbank erodes faster when repeatedly exposed to high shear stresses during multiple ship wave events.

These relationships are found only for the median values, and not for extreme vessel sizes. The banks do not show larger erosion rates when the largest vessels increase in size. This is likely because of a stabilizing mechanism by the banks. As the top bank erodes, the sediment is redistributed over the cross-section, causing the primary wave to break and dissipate energy before reaching the top bank.

The thesis shows that ship traffic is associated with sustained riverbank erosion at Bird-Long Island, and that the response depends strongly on local morphology and cumulative hydraulic loading by vessels passing Bird-Long Island. ... Read more

The vector based, freeform shoreline development model ShorelineS can efficiently simulate the development of a shoreline through the use of relatively simple bulk longshore transport formulas. This allows it to be multiple orders of magnitude more efficient compared to complex two-dimensional horizontal process-based models. The model does make some assumptions in order to be this efficient. One of these assumptions is the constant profile angle along the shoreline. This means the model does not account for bathymetry. The version of the ShorelineS model used is from 03/08/2023.

This study analyses the applicability of ShorelineS for simulation of a shoreline with a river mouth. To this extent a synthetic case of a shoreline with a river mouth is set up to analyse the model behaviour of ShorelineS in a simplified environment. The effect of many input parameters on the shoreline development is analysed. These parameters include wave parameters, channel parameters, transport parameters, model parameters, and relative sea level rise. The applicability is further tested in a more complex environment with a real-world case. For this, a hindcast is set up. The location of the hindcast is the shoreline of the Rhône delta. This is a wave dominated, sandy coast with a negligible tidal range. Data on the shoreline, the wave climate, the sediment budget, and the shoreline profile were required to get a successful hindcast.

The implementation of a river mouth in ShorelineS is done through specifying the river flow path as well as to what extent the channel should be kept. The sediment discharge is then approximated by a nourishment in the flow path that is pushed out to the shore. This approach was found to work well in a simplified environment through analysis of results from the synthetic case. The different simulations resulted in the expected model behaviour and the simulations were stable.

The results of the hindcast are mostly positive. The hindcast gets a good skill score and the simulations are mostly stable. The biggest differences between the simulated shoreline and the actual shoreline of the Rhône delta can be explained by the existence of relict sediment lobes along the shoreline. These lobes are the result of the combination of progradation and avulsion in the Rhône delta. They make the shoreline profile variable and provide time limited sediment sources.

ShorelineS cannot account for these naturally occurring lobes because of the assumption of the constant profile angle along the shoreline. Combining this with the fact that ShorelineS is incapable of simulating processes related to river dynamics such as avulsion and the forming of mouth bars limits the applicability of ShorelineS in environments governed by natural processes, such as the Rhône delta.

However, there is enough applicability for ShorelineS outside of these environments. When the shoreline is not governed by natural processes but is instead regulated by humans, a canal for instance, the results of the ShorelineS simulations will only get better. The big difference in time and cost efficiency compared to other models makes ShorelineS uniquely suited for applicability where the demand for accuracy of the simulation is lower. For instance, in data limited environments or on a global scale. ... Read more

This research examined the influence of low- to mid-latitude mountain deglaciation on the channel pattern of proglacial rivers and evaluated the suitability of the Badlands Landscape Evolution Model to simulate glacial thinning, retreat, and runoff. Glacier types and scenarios were constructed based on size, mass turnover, and climate projections. Seasonal precipitation maps were derived from runoff projections to represent meltwater production and rainfall and inputted into Badlands. Glacier thinning was modelled using a modified stream power law, enforcing a linear dependence of erosion on precipitation. Modelled proglacial discharge was used to determine the dominant channel pattern. The results show that annual glacial runoff will slightly increase in the short term, leading to a minor and largely insignificant increase in river braiding. Over time, runoff will decline to slightly below initial levels, resulting in a similarly insignificant reduction in braiding. Seasonal patterns will shift, with runoff decreasing in summer and autumn and increasing in winter and spring due to rainfall replacing snowfall. Runoff was found to be strongly dependent on glacier size, moderately dependent on mass
turnover, and only marginally affected by climate scenario. The fluvial pattern was found to be braided in almost all cases. Only low mass turnover glaciers in arid climates may experience minor downstream changes in channel pattern, depending on the extent of current glaciation. At present, Badlands is unable to model glacier dynamics efficiently due to computational limitations and the lack of mass balance, glacial erosion, and sliding laws. Furthermore, it only models glacial thinning and does not directly convert ice mass loss into runoff. Nevertheless, the model provides a strong foundation for implementing glacial features such as elevation-dependent melting and ice-to-runoff conversion.
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In rapidly growing urban areas, river dynamics have become major hazards, endangering vulnerable populations and their environments. The Msimbazi River Basin in Dar es Salaam, Tanzania, demonstrates these challenges, where unplanned urban expansion, deforestation, and infrastructure development have influenced river morphodynamics. Although prior studies have addressed flood risks, sedimentation, and bank erosion, an understanding of the river’s migration patterns, widening trends, and key drivers at the full catchment scale has been lacking. This research applies a descriptive approach combining manual riverbank tracking from satellite imagery, identification of potential morphological change drivers, and hotspot mapping based on hazard severity and exposure susceptibility. From 2007 to 2024, the Msimbazi River experienced significant lateral migration and localized widening, with notable episodes of instability after 2017. These changes are primarily driven by land cover transformations, such as urbanization and deforestation, which have led to gradual shifts in river morphology, rather than being the result of changing precipitation patterns. In contrast, abrupt and localized changes, particularly after 2017, appear to be associated with infrastructural developments like the Standard Gauge Railway, as well as the coincidence of the El Niño phase with the cyclone season, which contributed to elongating the wet seasons. Findings reveal that river migration rates and widening trends fluctuate considerably, often doubling or tripling during periods of rapid change, with the highest vulnerability observed in the upper catchment. By identifying zones where hazard severity and exposure intersect, this study provides a framework for prioritizing mitigation in the Msimbazi Basin and other urban rivers in rapidly eveloping regions.
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Tsunamis, flood waves and dam-break waves are highly destructive waves where a better description of these waves will contribute to a safer design of hydraulic structures. These waves are characterized by a sudden increase in water elevation with a breaking roller, which is a recirculating flow mixture of air and water, at the front of the wave. This study aims to get a better understanding of the fluctuating behaviour of dam-break waves over a wet bed across scales, focusing on the roller toe, which marks the transition from the downstream water level to the incoming bore.

Dam-break wave experiments, generated by the use of a lift gate system, were conducted on two scales for Froude numbers in a range of 2.44- 7.05, resulting in a range of varying Reynolds numbers between 0.22e5- 3.49e5. A High-Speed video camera recorded the waves from the top which enabled the wave profiles of the roller toe to be distinctly extracted. Due to the high level of unsteadiness in the flow, ensemble statistics are used, leveraging statistical properties to compare wave characteristics across different flow conditions.

The bore front celerity, roller toe fluctuations, instantaneous celerity (fluctuations) and indentation coefficient give in-depth insight in the hydrodynamic behaviour of the roller toe. Comparison with the dam-break wave theory showed good agreement with the bore’s celerity based on the experimental results. The fluctuating behavior of the roller toe increased for an increasing Froude number, indicating that gravity is the dominant force driving these variations. The magnitude of fluctuations in relation to the Reynolds number showed a slightly decreasing trend, indicating the presence of scale effects and emphasizing the importance of investigating these highly turbulent flow motions. The indentation coefficient underscored the presence of turbulence as highlighting different results between wave types. Overall, this study contributes to a better understanding of highly unsteady flows. ... Read more

This report documents the impact of floods in the Tapanahony region as a step to start developing the region in a sustainable manner. The Tapanahony region of the Okanisi people harbours descendants of enslaved people that freed themselves during the 1700s. Currently the development of the region is stagnating and the Okanisi experience problems when trying to build a living for themselves and their families. By conducting interviews in the 28 villages along the river an impression is obtained of the role that the river plays in this area. These results are then combined with a flood vulnerability model for which depth and velocity measurements of the river have been conducted. This study shows how the lives of the inhabitants are intertwined with the river. It also stresses the severity of the issues at play here. A lack of clean drinking water in the dry season in combination with heavy floods in the wet season make it difficult for people to progress and drives them to turn to goldmining as a source of income. This report also shows that there are solutions to the situation, as long as there is strong collaboration between developers, researchers and especially the villages themselves. ... Read more

High-altitude páramo ecosystems in the Ecuadorian Andes, which serve a vital function in controlling the local water cycle, conserving biodiversity and securing the livelihoods of the inhabitants, are increasingly threatened. Climate variability, natural disasters and the growing pressure on natural resources due to extractive land use are the main driers. This study assesses the future environmental and social risks in the South Ecuadorian páramo surrounding Cuenca using a multidisciplinary approach. It focuses on hydrological change, slope instability, water quality and stakeholder conflict. Long-term in-situ observations made at the Zhurucay and Quinuas ecohydrological observatories are complemented by satellite and reanalysis data. We analyse multi-year trends in temperature, precipitation, soil moisture and solar radiation. Remote sensing data are calibrated and validated against ground measurements in order to make them applicable to data-scarce areas. This work also uses trend analysis and forecasting of time-series to identify the emerging hydro-meteorological patterns and the synthetic rainfall scenarios and spatial data sets to assess the slope instability under changed conditions. Additionally, water-quality risks related to changed runoff dynamics and potential mining activities are assessed. The study also includes an analysis of stakeholders of the mining Loma Larga project in order to examine how the differences in power, interests and perceived risks contribute to social tensions around water security and land use. The results show an increasing hydro-meteorological variability which may worsen the landslide risk and challenge the buffer capacities of páramo soils, while mining-related disturbances pose an additional threat to the water quality downstream and to the governance. This work integrates the physical science, remote sensing and social analysis in order to provide a comprehensive framework for understanding the coupled human-environment risks in the páramo systems. The finding may help policymakers navigate these trade-offs to support informed decision-making and ecosystem-based approaches to hazard mitigation in fragile high-mountain landscapes.
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The current flood risk assessment framework in the Netherlands aims at ensuring a nation-wide protection level with a long-term vision. It assumes that future river bed level changes will not pose negative effects on flood safety and it adopts a fixed-bed assumption. However, the river bed level shows a strong spatial and temporal variability, where bed aggradation trends could lead to higher water levels in the future. Recent measurements in the Dutch Rhine have shown both bed degradation and aggradation in different river sections along the lower river domain. This raises questions to what implications does future river bed level changes have on flood safety in the Netherlands and whether the current fixed-bed assumption has adverse connotations to it.

The objective of this MSc thesis is to study the impact of river bed level changes on flood safety in the Netherlands. To achieve this, a framework for incorporating large-scale bed level changes into flood risk assessments is developed and applied under the current Dutch context. The implications on the long-term and short-term flood safety are analyzed separately, as fundamentally different approaches and uncertainties relate to the flood safety standards derivation and for the periodic safety assessment in the Netherlands.

In the long-term, I propose to incorporate morphodynamic modelling scenarios into the flood safety standards derivation process to account for future bed level changes and their long-term uncertainties. Modelling scenarios should include future river discharge, sea level rise, river maintenance and the evolution of river bifurcations, as they represent main drivers in the long-term river bed response in the Netherlands. Based on existing long-term morphodynamic modelling studies of the Rhine River, it is estimated that the extreme water levels decrease over the upper Waal, but increase over the lower Waal by 0.15 m and 0.30 m in 2050 and 2100, respectively. These scenarios consider that river dredging is not maintained after 2025.

In the short term, I propose to incorporate the analysis of the recent river bed level behaviour into the safety assessment process to account for its uncertainty in the near future. Based on yearly bed level measurements in the Waal from 2005 to 2020, decreasing and increasing water level trends have been identified in the upper and lower Waal, respectively, with increments in the order of 0.05 m. This is small in absolute terms, but significant compared to the accuracy level of the hydraulic loads used in the safety assessment process. As a consequence, these increments can have important economical implications on dike reinforcement programs.

In summary, this thesis provides a framework incorporating large-scale river bed level changes into the current flood risk assessment framework in the Netherlands. Furthermore, it quantifies the impacts of bed level variability on flood safety in the Waal River. In general, the fixed-bed assumption in the current flood safety framework is a conservative, or safe, assumption for the hydraulic loads’ calculation in the upper Waal. However, it may underestimate the future hydraulic loads in the lower Waal and impose adverse conditions on flood safety. ... Read more

Predicting and modelling meandering river migration is necessary for river engineering, land development, and risk assessment. One chaotic process that makes predicting the migration more difficult is the cutoff of a river bend, which is the subject of this report. This report describes the research process and results of a study on overbank flood effects on chute and neck cutoffs in single-thread meandering alluvial rivers. The following research question is addressed in this report: “What is the relationship between the duration of overbank flooding and the formation of chute versus neck cutoffs?”. The relationships between the overbank flood shear stress and the frequency of chute versus neck cutoffs, and between the soil type of the floodplain and the frequency of chute versus neck cutoffs are evaluated.

An overbank flood exceeds the bankfull limit of a river, flowing over the floodplain. When a river bend is cut off, two cutoff types are visually distinguished: neck cutoffs and chute cutoffs. Cutoffs of both types were analysed in four rivers in the United States of America: Cheyenne River in North Dakota, Powder River in Wyoming and Montana, Pearl River in Mississippi, and Trinity River in Texas. These rivers have a chute cutoff regime, a mixed cutoff regime, and two neck cutoff regimes, respectively.

For these four rivers satellite imagery on Google Earth Pro was combined with measurements from USGS measurement stations and soil data from SoilWeb. The bankfull river discharge was converted to bankfull river depth to calculate the overbank flood heights and the overbank flood shear stresses acting on the floodplain during floods. Subtraction of the critical shear stresses of the soils resulted in residual shear stresses. These were combined with the corresponding flood durations to calculate the flood impulses of each flood.

The floods associated with chute cutoffs showed larger overbank flood shear stresses than those for neck cutoffs. Rivers with steeper slopes seem to be more prone to a chute cutoff regime than rivers with gentler slopes. The soils in which chute cutoffs were formed contained high sand percentages, while the neck cutoffs occurred in a wider range of soil types. The overbank floods creating chute cutoffs exerted larger residual shear stresses for shorter durations, as opposed to smaller residual shear stresses for longer durations of floods associated with neck cutoffs. The overbank flood impulses associated with chute cutoffs show a larger range and higher values, but are on average not significantly different to those of neck cutoffs.

The processes related to river bend cutoffs are very complex and not entirely understood yet and more research is needed on a local and a greater scale. The formulation of general relationships for chaotic events such as cutoffs will improve the prediction and modelling of meandering rivers. This will be increasingly useful, especially now with more extreme weather events and river floods all over the world. ... Read more

Sediments play a crucial role in civil engineering branches like delta and river flood risk management and in maintaining natural ecosystems. Changes in the availability of sediment can have a major impact on all of these. It is therefore crucial to understand how sediment load in a source-to-sink system behaves in changing environments. Studies quantifying these behaviors often do not span further than a few decades to a hundred years. Carbon emissions will likely have an effect on our climate on the much larger scale of millennia. Humans have begun to plan and adapt their behavior to mitigate climate change by way of greenification of urban areas and replacing traditional agricultural practices by more sustainable alternatives. This study looks at the influence of climate change and different anthropogenic land use changes on the sediment load of the river Rhine by integrating tectonics, sea-level and precipitation change, and land use change for the coming 10,000 years using Badlands. This is done by utilizing a scenario-based approach. The essential role of topsoil dynamics, and a lack thereof in traditional landscape evolution models, such as Badlands, was identified. Using a general scale of topsoil and bedrock erodibilities calibrated to produce realistic sediment load in the Rhine, we found that any implementation of more sustainable land use like agroforestry is predicted to decrease the sediment load of the Rhine in most climate change scenarios, agreeing with similar studies that focused on short-term modeling. Implementing non-uniform precipitation change resulted in significantly different outcomes than using a uniform approximation, so it is advised to implement region-based precipitation change. Furthermore, Badlands has shown impressive versatility and adaptability, and shows potential to be used for the growing demand of studies that focus on predicting future influences of different processes in light of climate change using a holistic process-based approach. ... Read more