We project climate-driven changes in flow and sediment partitioning across the Rhine delta using a hybrid one-dimensional model informed by two-dimensional sediment-partitioning data. Simulations spanning 150 years and 540 km show a continued shift of discharge toward the Waal branch, while the effects of historical interventions gradually diminish. Climate impacts on flow division emerge around 2050 and intensify thereafter: by 2150, the IJssel is projected to convey approximately up to 17% less discharge under low-flow conditions, whereas the Waal may receive up to 6% more. Although hydrograph changes have limited influence on flow partitioning, they markedly increase channel-bed erosion by coarsening the sediment flux delivered to the bifurcation region and enhanced sensitivity to shear-stress gradients across the bifurcation. Consequently, climate forcing, particularly sea-level rise, overtakes past interventions as the dominant driver of future flow partitioning and bed level adjustment. These results have direct implications for long-term water management, navigation, and ecological resilience in the Rhine delta.

Tsunamis, impulse waves, and extreme floods are catastrophic events that can result in significant loss of life and cause extensive damage. Understanding the effects of these extreme events on infrastructure is crucial for designing resilient buildings in hazard-prone regions. While most previous studies focused on idealized (frontal) impacts, this study experimentally investigated the combined effect of building orientation and openings on the hydrodynamic loading. Visual observations revealed that rotating the building altered the dynamics of the impact, improving the streamlines and lowering upstream water levels. In terms of loading, building rotation primarily influenced the initial impact phase, delaying and often reducing the peak forces compared to frontal impacts, in line with literature. Openings (e.g. windows, doors) allowed water to flow through the buildings, significantly reducing loads in the streamwise direction. However, for oriented structures, loads in non-streamwise directions become considerable and should be considered in the design process. To address this, simple empirical equations are introduced to predict forces and moments, providing engineers with practical tools to design safer and more resilient coastal infrastructure.

Engineered rivers are often prone to channel bed incision. This decreases the channel-floodplain connection, hampers navigation where nonerodible reaches increasingly protrude from the bed, and can destabilize structures. Here we inventorize causes and characteristics of channel incision measures. We elaborate on how channel bed incision is a transient channel response toward a new equilibrium channel state. Causes of incision comprise base level fall, channel narrowing (e.g., due to river training), channel shortening (bend cut-offs), an increased channel-forming discharge (e.g. due to climate change), and a decrease (or fining or coarsening) of the sediment flux from the upstream part of the basin. Finally, we discuss two measures that may mitigate channel bed incision: sediment nourishments and longitudinal training walls.

Erosion-control measures in rivers aim to provide sufficient navigation width, reduce local erosion, or to protect neighboring communities from flooding. These measures are typically devised to solve a local problem. However, local channel modifications trigger a large-scale channel response in the form of migrating bed level and sediment sorting waves. Our objective is to investigate the large-scale channel response to such measures. We consider the lower Rhine River from Bonn (Germany) to Gorinchem (the Netherlands), where numerous erosion-control measures have been implemented since the 1980s. We analyze measured bed level data (1999–2020) around four erosion-control measures, comprising scour filling, bendway weirs, and two fixed beds. To get further insight on the physics behind the observed behavior, we set up an idealized one-dimensional numerical model. Finally, we study how the geometry and spacing of the measures affect channel response. We show that erosion-control measures reduce the sediment flux due to (a) lack of erosion over the measure and (b) sediment trapping upstream of the measure, resulting in downstream-migrating incision waves that travel tens of kilometers at decadal timescales. When the measures are in close proximity, their downstream effects may be amplified. We conclude that, despite fulfilling erosion-control goals at the local scale, erosion-control measures may worsen large-scale channel-bed incision.

Tipping occurs when a critical point is reached, beyond which a perturbation leads to persistent system change. Here, we present observational indications demonstrating presently ongoing noise-tipping of a real-world system. Noise in a river system is associated with the changing flow rate. In particular, we consider the upper Rhine River delta, where flow and sediment fluxes are partitioned over the two downstream branches (bifurcates) of an important river bifurcation. Field observations show that a sequence of peak flows in the 1990s resulted in sudden sediment deposition in one bifurcate, triggering a persistent and ongoing change in the flow partitioning. This has caused the system to move toward an alternative equilibrium state or attractor. An idealized model confirms that a river bifurcation system under such conditions is prone to tipping, and provides insight on the onset of tipping.

Human intervention makes river channels adjust their slope and bed surface grain size as they transition to a new equilibrium state in response to engineering measures. Climate change alters the river controls through hydrograph changes and sea level rise. We assess how channel response to climate change compares to channel response to human intervention over this century (2000–2100), focusing on a 300-km reach of the Rhine River. We set up a schematized numerical model representative of the current (1990–2020), non-graded state of the river, and subject it to scenarios for the hydrograph, sediment flux, and sea level rise. We conclude that the lower Rhine River will continue to adjust to past channelization measures in 2100 through channel bed incision. This response slows down as the river approaches its new equilibrium state. Channel response to climate change is dominated by hydrograph changes, which increasingly enhance incision, rather than sea level rise.

While most of the world's large rivers are heavily engineered, channel response to engineering measures on decadal to century and several 100 km scales is scarcely documented. We investigate the response of the Lower Rhine River (Germany-Netherlands) to engineering measures, in terms of channel slope and bed surface grain size. Field data show domain-wide incision, primarily associated with extensive channel narrowing. Remarkably, the channel slope has increased in the upstream end, which is uncommon under degradational conditions. We attribute the observed response to two competing mechanisms: bedrock at the upstream boundary increases the channel slope over the upstream part of the alluvial reach to compensate for the reduction of net annual sediment mobility, and extensive channel narrowing reduces the equilibrium slope. Another striking feature is the advance and flattening of the gravel-sand transition, suggesting its gradual fading due to an increasingly reduced slope difference between the gravel and sand reaches.