Sand mining is a growing environmental and socioeconomic concern worldwide. As urbanisation and infrastructure development continue to increase, the demand for sand has skyrocketed. When mined on or near rivers, it alters the river's pathway, eroding riverbanks, damaging housing, infrastructure and livelihoods. This thesis examines the role of sand mining in the river-delta system, by examining the influence of dredging duration, dredging intensity, location and pit size on the river delta system.

A 2-dimensional depth averaged Delft3D model is made. Here a river-delta system is modelled and run for 600 years. Over the last 100 years, different sand mining scenarios have been modelled. With varying duration, intensity, locations, and pit geometry, each of these scenarios is then analysed using various method of analyses. Though changing the dredging scenarios, changes the downstream morphology and hypothe-
sised trends—such as pit migration, increased erosion, and reduced delta growth—were partially
observed. Furthermore, in the five scenarios, dredging influenced the river-delta system in complex, non-linear ways.

Some configurations (e.g., 30-year duration, 5.0x intensity, 200 m width) led to pronounced short-term changes, but long-term outcomes returned toward control-like conditions. In general, the results highlight high internal variability and limited predictability based solely on single dredging parameters. It is recommended to include a cluster of slightly varied control scenarios in future research to distinguish the effect of dredging from the natural variability of the river.

Marine plastic debris has become an established concern as a threat to marine and coastal ecosystems. Despite progress in understanding plastic transport dynamics under deep-water conditions, the characterisation of these processes in the nearshore environment remains incomplete. This poses significant challenges in their parametrisation, essential for the accurate representation of coastal transport dynamics in predictive models.

In this study, experimental measurements of the plastic particles wave-induced transport in intermediate to shallow water depths are presented. The focus is put on the influence of wave steepness as a key parameter affecting the transport of marine plastic debris in the transition from deep water to the shoreline. Its potential as a predictive parameter is investigated through controlled laboratory experiments involving the generation of seven regular breaking wave conditions, characterised by varying offshore steepness, propagating in shallow water depth over a sloped bathymetry.

The results reveal a consistent increase in particle drift speed with increasing offshore wave steepness. While the exact functional nature of the observed positive relationship could not be definitively concluded, the trend appears more likely linear than quadratic, aligning with previous findings for particles deviating from perfect tracers undergoing deep water breaking conditions. Furthermore, wave breaking was observed to play an important role in enhancing particle drift speed. Finally, particle drift speeds were consistently underestimated by the Stokes drift and only partially captured by the wave crest speed estimates, progressively diverging from the former and approaching the latter as offshore steepness increased, though remaining consistently lower than crest speeds. This trend was most recognisable in the breaking zone across all the tested wave conditions.

Overall, the findings suggest offshore wave steepness as a robust predictor for marine plastic debris transport in the nearshore environment, proving its value as a classification parameter for future modelling efforts. By investigating how plastic particles respond to changing wave conditions in the nearshore environment, this study aims to contribute to a better understanding of their dynamics.

Floating marine plastic debris has emerged as a major global environmental threat in recent years due to its persistence, long-distance transport, and harmful impacts on marine ecosystems. Understanding the key processes affecting plastic beaching is essential for accurately modelling plastic transport and predicting accumulation zones in nearshore marine environments. So far, research on plastic transport in shallow, nearshore waters is limited compared to deep ocean studies, resulting in significant uncertainties about wave-driven transport in these zones. While it is established that the impact of plastic density on the movement of floating plastic debris varies across wave zones, the dynamics in shallow water remain poorly understood. This research investigates how the density of finite-sized plastic particles influences the beaching dynamics under controlled, regular wave conditions in a laboratory flume simulating a nearshore environment using a sloped bathymetry. The densities relative to water of idealized spherical particles were systematically varied ranging from 0.09 to 0.93. Particles were released in the shoaling zone and tracked through the wave flume until beaching, allowing drift speeds to be analysed across different wave zones. It is observed that prior to breaking, in the shoaling zone, particles travel onshore with a speed close to the locally estimated Stokes drift regardless of the particles' relative density. In the breaking zone, density significantly affects particle drift speed: low-density particles accelerate strongly, nearing crest and phase speeds, while higher-density particles show only modest acceleration. Extending these findings to real-world coastal environments indicates that low density plastics tend to beach quickly, while denser particles remain suspended longer and thus may be affected more by lateral currents. While further research is needed to fully understand the role of density in plastic transport near the shore, this study clearly demonstrates that density significantly influences beaching dynamics—underscoring its importance in accurately modelling plastic transport in the nearshore environment.

This project explores how landscape design can contribute to rebalancing flood prevention, ecological resilience, and productive land use within the Jing River Flood Storage Area (JRFSA), a key node in China’s middle Yangtze River flood control system. Located in the densely cultivated Jianghan Plain, the area faces a growing mismatch between large-scale flood management strategies and the everyday realities of agricultural production, ecological degradation, and rural development. Through the concept of Cascading Floodspace, the design introduces a multi-layered spatial framework that divides the floodplain into adaptive zones with differentiated flooding frequencies, land use patterns, and ecological functions. These zones support flood-responsive agriculture, habitat diversity, and seasonal tourism, while allowing for long-term landscape transformation without immediate disruption. The project operates across multiple scales—from regional water networks to site-specific interventions—and repositions the role of the landscape architect as both a spatial strategist and a mediator between competing values: risk and livelihood, ecology and economy, permanence and change.

Sand is one of the most extracted natural resources worldwide, and demand continues to rise along with population and infrastructure development. In Argentina, the Lower Paraná Delta has become a key source of sand for both construction and hydraulic fracturing (fracking) activities. While sand mining can generate short-term economic benefits, its environmental and socioeconomic impacts on the delta remain poorly understood. Therefore, this study aims to answer the following research question: ”What are the morphological and socioeconomic effects of sand extraction in the Lower Paraná Delta and how can these be managed to secure a sustainable future?”. Both river and land-based sand mining and their respective effects on the delta were researched.

The research applied a multidisciplinary approach combining hydraulic, geotechnical, and structural engineering perspectives. Quantitative analyses were based on field measurements, sediment sampling, and hydrodynamic modelling with Delft3D. Additionally, stakeholder interviews and data from the Automatic Identification System (AIS) of vessels were used to assess extraction volumes and local perceptions. This combination allowed for a comparative evaluation of river and dry sand mining.

Results show that river sand extraction remains relatively stable across large parts of the study area, while local government intervention has effectively halted dredging activities in the Paraná Ibicuy, in the northern section of the delta. Current extraction volumes are estimated at approximately 588,000 tons
per year. In contrast, dry sand mining has increased sharply, reaching about 2.3 million tons in 2025 in Ibicuy, primarily driven by the growing demand for fracking sand from the Vaca Muerta formation. The established sediment balance of the Paraná Guazú River indicates a negative change in sediment storage of roughly 15,400 tons per day, suggesting a general trend of sediment depletion.

Erosion rates in the study area range between 3 and 7 meters per year, which, although significant, are considerably lower than values reported by some stakeholders. Analyses indicate that natural processes, including river meandering and flood-induced bank instability, are the dominant drivers of bank erosion, while river sand mining does not appear to play a substantial role. Because of their larger scale and intensity, the socioeconomic impacts of dry sand mining are more pronounced, leading to groundwater overuse, road deterioration, and habitat loss. Additionally, low taxation on sand mining activities has enabled these impacts to persist with limited mitigation or compensation. To mitigate erosion, a structural solution in the form of a sheet pile was proposed. Furthermore, Nature-based mitigation strategies have been proposed, the focus lies on floodplains, vegetation and riparian buffer zones.

The accuracy of the study is constrained by the short temporal coverage of field data and the simplified representation of hydrodynamics and sediment transport in the numerical model. To build on these findings, future research should include long-term monitoring, enhanced sediment datasets, and morphodynamic modeling to assess feedbacks between extraction and river response. Integrating Naturebased solutions with targeted structural measures, supported by cost–benefit analyses, would provide a more comprehensive framework for sustainable sand mining management in the Lower Paraná Delta.

Rivers play a crucial role in delivering sediment to the oceans, with deltas acting as key zones for sediment deposition that support ecosystems, human populations, agriculture, and industry. The Vietnamese Mekong Delta, one of the world’s most important and densely populated river deltas, faces increasing stress as human interventions such as dam construction and sand mining disrupt natural sediment supply, intensifying subsidence, sea-level rise, and erosion. These pressures are further amplified by climate change, which contributes to extreme discharge events, saltwater intrusion, and coastal erosion. While considerable research addresses short-term changes, long-term projections remain limited. This study examines how human- and climate-driven factors shape sediment transport and bifurcation behaviour in the Song Hau distributary over 30 years, by evaluating branch flow
partitioning (symmetry) and the system’s ability to remain in equilibrium (stability).

A Delft3D 2D depth-averaged model, simulating both water flow and sediment movement, is used to examine how climatic and human drivers shape sediment transport and bifurcation behaviour in the tidally influenced Song Hau distributary. Scenarios of altered precipitation (AP), sea-level rise (SLR), sand mining (SM), and hydropower-induced discharge flattening (HD) reveal how changes in upstream discharge, downstream water levels, and bed lowering influence the system. The model performs well, with water flow results showing high accuracy (NSE = 0.90–0.94; RMSE = 0.07–0.21 m) and sediment transport reproduced within 10–20% of observed values, indicating good agreement with observed concentrations.

The results show that climate forcing, through altered precipitation and sea-level rise, generally reduces local extremes of sedimentation and erosion, leading to a more uniform distribution of sediment and flow across the bifurcation and faster stabilisation of sediment partitioning. Altered precipitation increases the system’s export capacity, while sea-level rise increases symmetry by reducing the effect of tides on flow partitioning. This helps maintain throughflow, ensuring consistent export of water and sediment to the sea through both branches. In contrast, human interventions such as sand mining and hydropower-induced discharge flattening increase asymmetry between the Dinh An and Tran De branches. Tran De becomes more dominant in exporting water and sediment, while Dinh An is prone to extreme sedimentation near the river mouth, reducing export capacity. Sand mining has nonlinear
effects, with increasing extraction rates indicating a threshold beyond which the system responds differently. Fluctuations in sediment and flow persist over time, preventing the system from reaching an unchanged sediment distribution. Discharge variability, moderated by hydropower dams, plays a key role in maintaining balanced flow and sediment distribution. Overall, climate change tends to stabilise the system, while anthropogenic interventions lead to more unpredictable outcomes, with sediment distribution being more sensitive than water flow.

The impacts of both human and climate drivers extend beyond the study area, influencing sediment export to the ocean. Ecosystems such as mangroves, which are vital for coastal protection, are highly vulnerable to sediment fluctuations. Effective regulation of human activities, including sand mining and discharge management, is crucial to maintain sediment balance and support the resilience of the delta and its ecosystems under increasing environmental pressures.

Understanding morphodynamic processes and structures is essential for effective river management and enhancing our knowledge of river systems. River bars can be investigated through theoretical analyses, field measurements, experimental studies, or numerical modelling. While numerical modelling offers accuracy, it is computationally intensive, making multiple simulations or parameter calibrations both time-consuming and impractical. The numerical simulations follow physical laws and equations which make the runtime significantly high making instantaneous results in times of emergencies unfeasible.
Convolutional neural networks (CNNs), a type of data-driven modelling, have been employed to study the physical parameters defined by linear stability analysis. This study utilizes Delft3D simulations to generate diverse datasets, facilitating easier access and variability. A specific type of riverbar pattern, and alternate bars were chosen for simplicity. The CNN model takes initial bed levels as inputs and provides predictions for the next step of bed level or a time series, with velocity included an additional parameter to assess its influences on the model performance. The model is able to predict the bar behaviour with R2 being 0.99. The model can predict bar suppression or migration solely based on the initial bed levels provided. The model performance did not improve with an additional input parameter although this possibility can be explored with other architectures. However, the model currently lacks accuracy in making one-step-ahead predictions, potentially due to boundary issues within the numerical model or the CNN itself. Further optimization and exploration of additional methods are necessary. The integration of physical parameters into the training process may improve prediction accuracy. Strong conclusions cannot be drawn until additional research is conducted.