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4. Vegetation and peat accumulation steer Holocene tidal–fluvial basin filling and overbank sedimentation along the Old Rhine River, The Netherlands

Author

Dep Fysische Geografie, Biogeomorphology of Rivers and Estuaries, Coastal dynamics, Fluvial systems and Global change, Geomorfologie, Landdegradatie en aardobservatie, Landscape functioning, Geocomputation and Hydrology, Pierik, Harm Jan, Moree, Jelle I.M., van der Werf, Karianne M., Roelofs, Lonneke, Albernaz, Marcio Boechat, Wilbers, Antoine, van der Valk, Bert, van Dinter, Marieke, Hoek, Wim Z., de Haas, Tjalling, Kleinhans, Maarten G., Dep Fysische Geografie, Biogeomorphology of Rivers and Estuaries, Coastal dynamics, Fluvial systems and Global change, Geomorfologie, Landdegradatie en aardobservatie, Landscape functioning, Geocomputation and Hydrology, Pierik, Harm Jan, Moree, Jelle I.M., van der Werf, Karianne M., Roelofs, Lonneke, Albernaz, Marcio Boechat, Wilbers, Antoine, van der Valk, Bert, van Dinter, Marieke, Hoek, Wim Z., de Haas, Tjalling, and Kleinhans, Maarten G.

Published
2023

5. Depth-limiting resistant layers restrict dimensions and positions of estuarine channels and bars

Author

Biogeomorphology of Rivers and Estuaries, Sub FG Externen, Coastal dynamics, Fluvial systems and Global change, Pierik, Harm Jan, Leuven, Jasper R.F.W., Busschers, Freek S., Hijma, Marc P, Kleinhans, Maarten G., Biogeomorphology of Rivers and Estuaries, Sub FG Externen, Coastal dynamics, Fluvial systems and Global change, Pierik, Harm Jan, Leuven, Jasper R.F.W., Busschers, Freek S., Hijma, Marc P, and Kleinhans, Maarten G.

Published
2023

6. Observed and modelled tidal bar sedimentology reveals preservation bias against mud in estuarine stratigraphy

Author

Coastal dynamics, Fluvial systems and Global change, Biogeomorphology of Rivers and Estuaries, Geomorfologie, Braat, Lisanne, Pierik, Harm Jan, van Dijk, Wout M., van de Lageweg, Wietse I., Brückner, Muriel Z.M., van der Meulen, Bas, Kleinhans, Maarten G., Coastal dynamics, Fluvial systems and Global change, Biogeomorphology of Rivers and Estuaries, Geomorfologie, Braat, Lisanne, Pierik, Harm Jan, van Dijk, Wout M., van de Lageweg, Wietse I., Brückner, Muriel Z.M., van der Meulen, Bas, and Kleinhans, Maarten G.

Published
2023

7. Vegetation and peat accumulation steer Holocene tidal–fluvial basin filling and overbank sedimentation along the Old Rhine River, The Netherlands

Author

Pierik, Harm Jan, Moree, Jelle I.M., van der Werf, Karianne M., Roelofs, Lonneke, Albernaz, Marcio Boechat, Wilbers, Antoine, van der Valk, Bert, van Dinter, Marieke, Hoek, Wim Z., de Haas, Tjalling, Kleinhans, Maarten G., Pierik, Harm Jan, Moree, Jelle I.M., van der Werf, Karianne M., Roelofs, Lonneke, Albernaz, Marcio Boechat, Wilbers, Antoine, van der Valk, Bert, van Dinter, Marieke, Hoek, Wim Z., de Haas, Tjalling, and Kleinhans, Maarten G.

Abstract

In the transformation from tidal systems to freshwater coastal landscapes, plants act as eco-engineering species that reduce hydrodynamics and trap sediment, but nature and timing of the mechanisms of land creation along estuaries remains unclear. This article focuses on the Old Rhine estuary (The Netherlands) to show the importance of vegetation in coastal landscape evolution, predominantly regarding tidal basin filling and overbank morphology. This estuary hosted the main outflow channel of the river Rhine between ca 6500 to 2000 cal bp, and was constrained by peat during most of its existence. This study reconstructs its geological evolution, by correlating newly integrated geological data and new field records to varying conditions. Numerical modelling was performed to test the inferred mechanisms. It was found that floodbasin vegetation and resulting organic accumulation strongly accelerated back-barrier infill, by minimizing tidal influence. After tidal and wave transport had already sufficiently filled the back-barrier basin, reed rapidly expanded from its edges under brackish conditions, as shown by diatom analysis and datings. Reed growth provided a positive infilling feedback by reducing tidal flow and tidal prism, accelerating basin infilling. New radiocarbon dates show that large-scale crevassing along the Old Rhine River – driven by tidal backwater effect – only started as nutrient-rich river water transformed the floodbasin into an Alder carr in a next phase of estuary evolution. Such less dense vegetation promotes crevassing as sediments are more easily transported into the floodbasin. As river discharge increased and estuary mouth infilling progressed, crevasse activity diminished around 3800 to 3000 cal bp, likely due to a reduced tidal backwater effect. The insights from this data-rich Holocene study showcase the dominant role that vegetation may have in the long-term evolution of coastal wetlands. It provides clues for effective use of vegetation

Published
2023

8. Depth-limiting resistant layers restrict dimensions and positions of estuarine channels and bars

Author

Pierik, Harm Jan, Leuven, Jasper R.F.W., Busschers, Freek S., Hijma, Marc P., Kleinhans, Maarten G., Pierik, Harm Jan, Leuven, Jasper R.F.W., Busschers, Freek S., Hijma, Marc P., and Kleinhans, Maarten G.

Abstract

Estuaries comprise channels vital for economic activity and bars as valuable habitats. They are increasingly under human-induced pressures (e.g. sea-level rise and dredging), resulting in morphological changes that affect navigability, flood safety and ecology. Antecedent geology may strongly steer how estuary channels will adapt to these pressures, but is surprisingly absent in most models. Here geological data and a unique bathymetry dataset covering 200 years from the Ems-Dollard estuary (Netherlands/Germany) were used to demonstrate how local resistant layers force the position and dimensions of confluences and bars on the scale of an entire estuary. These layers limit channel depth and consequently cause widening, resulting in mid-channel bar formation and increased channel curvature. This could lead to unexpected estuary widening and may cause land loss in densely populated areas. With increasing channel volume (as may happen again under future sea-level rise), resistant layers in the estuary's substrate become more exposed, which enhances their effects. Many systems around the world contain shallow resistant layers that potentially constrain estuary channel dimensions and steer bank erosion. This highlights that resistant layer effects are important to consider as part of mixed depositional processes in coastal environments. It is therefore necessary to globally account for the effects of inherited resistant layers in the possible response of estuaries to sea-level rise and increased tidal penetration.

Published
2023

9. Vegetation and peat accumulation steer Holocene tidal–fluvial basin filling and overbank sedimentation along the Old Rhine River, The Netherlands

Author

Pierik, Harm Jan, primary, Moree, Jelle I. M., additional, van der Werf, Karianne M., additional, Roelofs, Lonneke, additional, Albernaz, Marcio Boechat, additional, Wilbers, Antoine, additional, van der Valk, Bert, additional, van Dinter, Marieke, additional, Hoek, Wim Z., additional, de Haas, Tjalling, additional, and Kleinhans, Maarten G., additional

Published
2022
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11. Building and raising land: mud and vegetation effects in infilling estuaries

Author

Biogeomorphology of Rivers and Estuaries, Coastal dynamics, Fluvial systems and Global change, Weisscher, Steven Alexander Hubertus, Van den Hoven, Kim, Pierik, Harm Jan, Kleinhans, Maarten, Biogeomorphology of Rivers and Estuaries, Coastal dynamics, Fluvial systems and Global change, Weisscher, Steven Alexander Hubertus, Van den Hoven, Kim, Pierik, Harm Jan, and Kleinhans, Maarten

Published
2022

12. Observed and modelled tidal bar sedimentology reveals preservation bias against mud in estuarine stratigraphy.

Author

Braat, Lisanne, Pierik, Harm Jan, van Dijk, Wout M., van de Lageweg, Wietse I., Brückner, Muriel Z. M., van der Meulen, Bas, and Kleinhans, Maarten G.

Subjects
SEDIMENTOLOGY, ESTUARINE ecology, TIDAL flats, INTERTIDAL zonation, FLOW velocity, MUD, ESTUARIES
Abstract

Mud plays a pivotal role in estuarine ecology and morphology. However, field data on the lateral and vertical depositional record of mud are rare. Furthermore, numerical morphodynamic models often ignore mud due to long computational times and simplifications of mixed depositional processes. This study aims to understand the spatial distribution, formative conditions and preservation of mud deposits in the intertidal zone of bars in high‐energy sand‐dominated estuaries, and to elucidate the effects of mud on morphology, ecology and stratigraphic architecture. To meet these objectives, field data (historic bathymetry, bio‐morphological maps and sediment cores of the shoal of Walsoorden, Western Scheldt estuary, the Netherlands) were combined with complementary hydro‐morphodynamic numerical modelling (Delft3D). Based on the field observations, two types of mud deposits were distinguished: (1) mudflat deposits, which are thick (>10 cm) mud beds at the surface associated with high elevations and low accumulation rates; and (2) mud drapes, which are thin (millimetre to centimetre) buried laminae that form and preserve at a wide range of elevations and energy conditions. Model results show that deposition on mudflats occurs just after high‐tide slack water in areas shielded from high flood velocities, suggesting that mud accumulation is mostly controlled by elevation, flow velocity and flow direction. Mud accumulation increases shoal elevation, sometimes to supratidal levels. This reduces flow over the shoal, which in turn reduces chute channel formation, stabilises bar morphology and decreases local tidal prism. These effects further promote mud deposition and vegetation settling. Although observations show that mud cover at the surface is relatively high (20%–40% of the intertidal area), mud constitutes only a small percentage of the total estuary volume (ca 5%) revealing that only a small fraction is preserved in the stratigraphy. Due to this mismatch between surface and subsurface expression of mud, interpretations of estuarine stratigraphy risk underestimating the influence of mud at the surface on morphodynamics and habitats. [ABSTRACT FROM AUTHOR]

Published
2023
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15. Building and Raising Land: Mud and Vegetation Effects in Infilling Estuaries

Author

Weisscher, Steven Alexander Hubertus, Van den Hoven, Kim, Pierik, Harm Jan, Kleinhans, Maarten, Biogeomorphology of Rivers and Estuaries, Coastal dynamics, Fluvial systems and Global change, Biogeomorphology of Rivers and Estuaries, and Coastal dynamics, Fluvial systems and Global change

Subjects
salt marsh, flume experiments, Geophysics, steady state, mudflat, estuaries, Earth-Surface Processes
Abstract

Many Holocene estuaries were infilled to form convergent, single-channel systems, while others remained partially or wholly unfilled. This difference in the degree of infilling depends partly on the balance between fluvial and coastal sediment input and the hydrodynamics that can export sediment. However, it remains unclear to what degree this balance is tipped by mud supply and eco-engineering vegetation, and by what planform patterns the infilling proceeds. This study aims to explore experimentally how mud and vegetation change the degree and process of infilling, elevate and merge bars above intertidal levels and affect the planform of estuaries. To this end, three experiments were conducted in the Metronome, a flume that tilts periodically to create tidal currents, wherein forced tidal asymmetry resulted in net importing estuaries. In the second and third experiments, mud was supplied and in the third experiment seedlings were released of three vegetation species with eco-engineering traits at a laboratory scale. With only sand, the estuary fills sufficiently to form a multi-channel pattern with intertidal bars. Both mud and vegetation settle on intertidal bars and on the fluvial bay-head delta, thereby contributing to bar stabilization and further estuary infilling, pointing at effective strategies to keep up with future sea-level rise. This reduces channel mobility and effectively narrows the summed subtidal channel width toward an ideally converging funnel shape. This seems especially effective where vegetation stabilizes the mud. The experiments suggest that a range of steady states exists between the end-members of an unfilled and a completely infilled, ideal estuary.

Published
2022

17. Natural levee evolution in vegetated fluvial-tidal environments

Author

Boechat Albernaz, Marcio, Roelofs, Lonneke, Pierik, Harm Jan, Kleinhans, Maarten G., Biogeomorphology of Rivers and Estuaries, Coastal dynamics, Fluvial systems and Global change, Hydrologie, and Geomorfologie

Subjects
vegetation, levees, Geography, Planning and Development, Earth and Planetary Sciences (miscellaneous), crevasses, eco-morphodynamic, deltas, geomorphology, estuary, Earth-Surface Processes
Abstract

Natural levees are common features in river, delta and tidal landscapes. They are elevated near-channel morphological features that determine the connection between channel and floodbasin, and consequently affect long-term evolution up to delta-scales. Despite their relevance in shaping fluvial-tidal systems, research on levees is sparse and often limited to fluvial or non-tidal case studies. There is also a general lack of understanding of the role of vegetation in shaping these geomorphic units, and how levee morphology and dimensions vary in the transition from fluvial to coastal environments, where tides are increasingly important. Our goal is to unravel the effects of fluvial-tidal boundary conditions, sediment supply and vegetation on levee characteristics and floodbasin evolution. These conditions were systematically explored by 60 large-scale idealized morphodynamic simulations in Delft3D which self-developed levees over the course of one century. We compared our results to a global levee dataset compilation of natural levee dimensions. We found that levee height is determined by the maximum water level, provided sufficient levee building sediments are available. Discharge fluctuations increased levee width and triggered more levee breaches, i.e. crevasses, that effectively filled the fluvio-tidal floodbasin. The presence of wood-type (sparse) vegetation further increased the number of crevasses in comparison with the non-vegetated scenarios. Conversely, reed-type (dense) vegetation strongly dampened tidal amplitude and reduced the accommodation space and sedimentation further into the floodbasin, resulting in narrower levees, no crevasses and limited floodbasin accretion. However, dense vegetation reduced tidal forces which allowed levee growth further downstream. Ultimately, the levees merged with the coastal barrier, eliminating the floodbasin tides entirely. Our results elucidate the mechanisms by which levee and crevasse formation, and vegetation may fill fluvio-tidal wetlands and affect estuary evolution. This brings new insights for geological reconstructions as well as for the future management of deltas and estuaries under sea-level rise.

Published
2020

19. Natural levee evolution in vegetated fluvial-tidal environments

Author

Biogeomorphology of Rivers and Estuaries, Coastal dynamics, Fluvial systems and Global change, Hydrologie, Geomorfologie, Boechat Albernaz, Marcio, Roelofs, Lonneke, Pierik, Harm Jan, Kleinhans, Maarten G., Biogeomorphology of Rivers and Estuaries, Coastal dynamics, Fluvial systems and Global change, Hydrologie, Geomorfologie, Boechat Albernaz, Marcio, Roelofs, Lonneke, Pierik, Harm Jan, and Kleinhans, Maarten G.

Published
2020

24. Calculating connectivity patterns in delta landscapes: Modelling Roman and early-medieval route networks and their stability in dynamic lowlands

Author

van Lanen, R.J., Pierik, Harm Jan, Geomorfologie, Biogeomorphology of Rivers and Estuaries, and Coastal dynamics, Fluvial systems and Global change

Subjects
Past route networks, Landscape archaeology, Early Middle Ages, Network friction, Route-network persistence, Roman period, Earth-Surface Processes
Abstract

River landscapes can be regarded as amongst the most densely populated regions in the world. Despite their dynamic nature and their susceptibility to natural hazards, pull factors such as fertile soils and trade connections always have attracted people to these regions. During the Roman (12 BCE - 450 CE) and early-medieval periods (450 CE-1050) the Rhine-Meuse delta in the Netherlands underwent significant simultaneous cultural and environmental changes such as changing settlement patterns, the collapse of the Roman limes, changing flooding regimes and river avulsions. Past route networks are influenced by both cultural and natural dynamics and are therefore a useful tool to better understand the complex interaction between these dynamics. By applying and enhancing recently-developed methods of modelling route networks in dynamic lowlands, this study reconstructs connectivity patterns in the Rhine-Meuse delta. Based on newly-available high-resolution geoscientific and archaeological data, network-friction maps and route networks were calculated for three time slices: 100 CE, 500 and 900. These modelled networks were validated using archaeologically-excavated infrastructural and isolated finds. Additionally the amount of network stability between these networks was calculated. Results show that for each of the route zones a clear correlation exist between the modelled network and the occurrence of infrastructural and isolated finds. Although clear periodic differences between these correlations percentages are visible. Despite the dynamic nature of the research area the routes show clear signs of network stability, with 80% of the 500 CE network being persistent with their 100 CE counterparts. Between 500 CE and 900 CE the persistence percentage slightly rises to 81% indicating a similar level of network stability. This shows that large parts of the Rhine-Meuse delta were persistently used during the Roman period and Early Middle Ages despite local settlement dynamics and changing natural settings.

Published
2019

28. Travelling through a river delta: a landscape-archaeological reconstruction of river development and long-distance connections in the Netherlands during the first millennium AD

Author

Jansma, E, Van Lanen, Rowin J, and Pierik, Harm Jan

Abstract

Medieval Settlement Research, 32, 35-39, A landscape-archaeological reconstruction of long-distance riverine communication routes in the Low Countries, presenting initial results of the Dark Age of the Lowlands in an Interdisciplinary Light project

Published
2017
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35. A global analysis of the future morphology of estuaries under sea-level rise.

Author

Leuven, Jasper, Pierik, Harm Jan, van der Vegt, Maarten, Bouma, Tjeerd, and Kleinhans, Maarten

Subjects
*ESTUARIES, *TSUNAMIS, *SAND bars, *SALT marshes, *SEA level, *GLOBAL analysis (Mathematics), *MORPHOLOGY
Abstract

Sea level will rise 1-2 m in the next century, while sediment supply to estuaries is decreasing globally. The effect of rising sea level on the morphology of estuaries is unknown. If sediment supply is sufficient, estuaries may adapt through sedimentation in channels, on sand bars and saltmarsh formation. However, if sea-level rise outpaces formation of new land, the present-day intertidal area and habitat may drown because of sediment starvation. We developed a model based on theory and data for equilibrium morphology and hydrodynamic conditions along estuaries, depending only on the tidal amplitude at the estuary mouth and the estuary outline taken from imagery. This allowed us to calculate the sensitivity of 30 estuaries from all around the world to rising sea level. We varied estuary planform size and tidal amplitude in our model to test effects of sea-level rise using the following scenario sets: (1) widening of the estuary planform shape when salt marshes inundate, (2) a range of increases and decreases in tidal amplitude at the mouth, either of which can occur due to shifting amphidromic points offshore and reduced friction for the tidal wave inside the estuary, (3) a combination of the previous two scenarios. Results were validated with geological data on past planform sizes of systems that evolved under early to mid-Holocene sea-level rise, which is in the same order of the future expected sea-level rise. The results show that the breakdown and reworking of salt-marshes on sandy substrates would deliver part of the sediment required for adaptation to sea-level rise, but at the cost of intertidal and supratidal habitat loss. An increased tidal amplitude typically reduces the required sediment for adaptation because it will increase the equilibrium channel volume. Moreover, we found a novel relation between sensitivity to future change in tidal amplitude and the characteristic channel convergence length and depth of the estuary. Estuaries with relatively deep channels and with a weak channel convergence are most sensitive: their channel volume increases more with tidal amplitude increase and decreases more with tidal amplitude decrease than for other systems. The results are promising for further exploration of the vulnerabity to sea-level rise caused by changing estuary shape and changing tidal regimes. [ABSTRACT FROM AUTHOR]

Published
2019

36. Long-term evolution of the Old Rhine estuary: Unravelling effects of changing boundary conditions and inherited landscape.

Author

de Haas T, van der Valk L, Cohen KM, Pierik HJ, Weisscher SAH, Hijma MP, van der Spek AJF, and Kleinhans MG

Abstract

The long-term morphodynamic evolution of estuaries depends on a combination of antecedent topography and boundary conditions, including fluvial input, sea-level change and regional-landscape interactions. Identifying effects of such boundary conditions on estuary evolution is important to anticipate future changes in specific boundary conditions and for hindcasting with numerical and physical models. A comprehensive synthesis of the evolution of the former Old Rhine estuary is presented here, together with its boundary conditions over its full lifespan from 6,500 to 1,000 cal. yr bp. This system formed during a period of sea-level high stand, during which the estuary served as the main River Rhine outlet. The estuary went through three stages of evolution: a maturation phase in a wide infilling back-barrier basin, a stable mature phase and an abandoning phase, both in a laterally confined setting. The Old Rhine River formed by a river avulsion around 6,500 cal. yr bp that connected to a tidal channel within a large back-barrier basin. Decelerating sea-level rise caused the back-barrier basin to silt up around 5,700 cal. yr bp, resulting in shoreline progradation by beach-barrier formation until ∼ 2,000 cal. yr bp. Beach-barrier formation along the coast and natural levee formation along the river triggered peat formation in the coastal plain, laterally constraining the estuary and limiting overbank deposition, which caused most sediment to accumulate offshore. The abandoning phase started around 2,200 cal. yr bp when a series of upstream avulsions led to a substantial reduction in fluvial input. This induced a period of enhanced estuarine overbank clay deposition that continued into near-complete silting up and estuary closure around 1200 ad. These findings exemplify how tidal systems, formed in wide coastal plains during sea-level high stand, depend on antecedent conditions, and how they respond to connection and disconnection of a large river over long, millennial timescales., Competing Interests: The authors declare no conflicts of interest.

Published
2019
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