Climate adaptation of deltas is a hot topic given their high population density in many countries. We quantified trade-offs between hydraulics, potential biodiversity, implementation costs, and the number of land owners involved, using a newly developed tool called RiverScape. With our approach, we move towards finding integrated solutions at the scale of a large river in a delta to support the negotiations among stakeholders in the decision-making process.

The challenge to measure three-dimensional bank irregularities in a mid-sized river reach can be quickly solved in the field flying a drone with ground-control points and later applying structure from motion photogrammetry. We tested a simple approach that achieved sufficient resolution and accuracy to identify the full bank erosion cycle, including undermining. This is an easy-to-use and quickly deployed survey alternative to measure bank erosion processes along extended distances.

In estuaries, mud sedimentation enhances salt marsh accretion. Here we explore system-scale effects of plants and mud on planform shape and size of estuaries. We coupled Delft3D for hydromorphodynamics with our vegetation model and ran controls for comparison. Effects are greatest at the fluvial–tidal transition, where for the first time in a model, a bedload convergence zone formed. Regardless of local vegetation effects, mud and vegetation cause gradual filling of estuaries over time.

This paper reports the along-channel variability in occurring bed levels as described by hypsometry in natural estuaries. We found a novel relation between the estuary planform shape and the hypsometric function shape, which implies that it is possible to characterise and predict subwater estuarine morphology and bed levels in data-poor environments.

In this study we show how the Overijsselse Vecht river changed from a laterally stable to a meandering river ca. 500 years ago. We developed a methodology to reconstruct the historical discharge and found that the change in river style was caused by an increase in peak discharges. This increase was likely caused by the Little Ice Age and land use changes in the catchment (peat reclamation and exploitation). This study shows how river style changes as a result of discharge regime changes.

Creating estuaries in the laboratory has been challenging. When the ebb and flood currents are driven by ebb and flood in the sea, they are too weak to move sand. Here we describe how the periodic tilting of an entire experimental set-up leads to ebb and flood currents with similar behaviour as in nature and with enough strength to move sand. This means that this novel set-up now allows for the creation of estuarine landscapes in experiments.

Mud raises concern in the short-term management of estuaries, but it is not known whether cohesive mud affects the long-term development of estuaries. We discovered that a small supply of mud from the river confines the estuary by forming stable mudflats on the sides in centuries, whereas estuaries with only sand continue to grow. Mudflats also reduce the shifting of channels and bars. This implies that changes in mud supply in estuaries may have led to changes in shape and dynamics in the past.

We studied the propagation of natural and human-induced perturbations in large braided sand-bed rivers using a physics-based 3-D model. The results show that the perturbations not only affect the local morphology but their effects amplify while propagating through the braided network. This occurs by destabilization of bifurcations in combination with reshaping of bars and branches. These results could have a major impact on the assessment of engineering measures in large braided sand-bed rivers.

Groundwater seepage creates valleys with typical theater-shaped valley heads, which are found on Earth and on Mars. For a better interpretation of these systems, we conducted scale experiments on the formation such valleys. We find that entire landscapes, instead of just the shape of the valleys, provide insights into the source of groundwater. Landscapes filled with valleys indicate a local groundwater source in contrast to sparsely dissected landscapes formed by a distal source of groundwater.