Kees Sloff

Kees Sloff
Deltares · Inland Water Systems Division

PhD, MSc

About

60
Publications
22,336
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936
Citations

Publications

Publications (60)
Conference Paper
Full-text available
Due to sediment accumulation, the dam-cascade system in the Tenryuu River in Japan significantly impacts the downstream habitat of the Ayu, an economically important fish species. To mitigate this detrimental effect and preserve the Ayu's habitat, J-power nourishes the downstream river annually using sediments from upstream reservoirs. These nouris...
Article
Full-text available
Dams have often been constructed for hydropower, water storage and to support socioeconomic development, particularly in areas of water stress. In many places, the water stored in human-made reservoirs is essential to meet the development objectives of water supply, agriculture, industry, energy generation and other sectors. However, in the absence...
Conference Paper
Full-text available
Water Injection Dredging (WID) has been successfully applied for removing sediment deposits in reservoirs, which results in an increase of their storage capacity. This dredging method is based on the fluidization of the top sediment layer by pressurized injection of water by a dredging vessel. The fluidized sediment can be transported towards the d...
Article
Predicting the formation and break-up of immobile layers is of crucial importance for river management, as these processes greatly affect the morphodynamic evolution of the river bed. Two models are currently available for studying these processes: Struiksma's and Hirano's model. In this paper, we show that both models present limitations. This is...
Article
Full-text available
Water Injection Dredging (WID) has been successfully applied for removing sediment deposits in reservoirs, which results in an increase of their storage capacity. This dredging method is based on the fluidization of the top sediment layer by pressurized injection of water by a dredging vessel. The fluidized sediment can be transported towards the d...
Article
River deltas commonly have a heterogeneous substratum of alternating peat, clay and sand deposits. This has important consequences for the river bed development and in particular for scour hole formation. When the substratum consists of an erosion resistant top layer, erosion is retarded. Upon breaking through a resistant top layer and reaching an...
Article
Full-text available
Remarkable 3D flow structures occur at river confluences with small density differences due to differences in sediment concentration or temperature. We explain these by comparing numerical simulations for an idealized confluence with aerial photographs of several river confluences where color differences express the pattern of density differences a...
Conference Paper
Full-text available
Can floodplain excavation help to mitigate bed erosion
Technical Report
Full-text available
De zeespiegel kan mogelijk sneller gaan stijgen dan tot nog toe is aangenomen in het Deltaprogramma. Deze extra versnelling heeft te maken met recente inzichten over het mogelijk versneld afbreken en smelten van het landijs op Antarctica. In Deltaprogramma 2018 is opgenomen dat de mogelijke consequenties van de resulterende extra versnelde zeespieg...
Article
The West African coastal barrier is maintained by significant wave-driven longshore sand transport. This sand originates from rivers and large coastal sand deposits. Today, however, much of the fluvial sand is trapped behind river dams and/or interrupted at several locations by port jetties. As a result, the sandy coastal barrier is eroding almost...
Article
Full-text available
Longitudinal training dams (LTDs) are a promising alternative for river groynes. Here we summarize findings of a recent study focused on the along river transition from a series of river groynes to an LTD, where the flow divides between the fairway and the side channel between the LTD and the river bank. A scale model is setup using lightweight gra...
Conference Paper
Full-text available
Himalayan rivers are known to have very high sediment yield when compared to similar river basins around the world and the same applies to the rivers in Nepal. Therefore, reservoir sedimentation is one of the most serious concerns for all kinds of existing and planned reservoirs in the region. This is particularly important for relatively smaller d...
Conference Paper
Full-text available
The downstream area of hydropower dams suffers from erosion due to lack of sediment passing the dam. We used a calibrated model for investigating the reservoir conditions during the flood season (e.g. sediment inflows, reservoir water level, and reservoir bed level and gate operation modes) as to improve sediment feeding to the downstream of dams....
Article
Full-text available
Sediment deposition is one of the key mechanisms to counteract the impact of sea level rise in tidal freshwater wetlands (TFWs). However, information about sediment deposition rates in TFWs is limited, especially for those located in the transition zone between the fluvially dominated and tidally dominated sections of a river delta where sedimentat...
Conference Paper
Full-text available
In the Bovenrijn (where the Rhine enters the Netherlands), bed level degradation is ongoing at a rate of approximately 2 centimeters per year as the river is still adapting to the river training, which has taken place over the last centuries. To counteract this, two sediment nourishments are foreseen in 2016 and 2019, and possibly more will be perf...
Conference Paper
Full-text available
In the Bovenrijn (where the Rhine enters the Netherlands), bed level degradation is ongoing at a rate of approximately 2 centimeters per year as the river is still adapting to the river training, which has taken place over the last centuries. To counteract this, two sediment nourishments are foreseen in 2016 and 2019, and possibly more will be perf...
Article
Full-text available
We present a 3-D physics-based high-resolution modeling approach to the dynamics of underwater ripples and dunes. The flow is modeled by large eddy simulation on a Cartesian grid with local refinements. The sediment transport is modeled by computing pickup, transport over the bed, transport in the water column, and deposition of rigid spherical par...
Article
Full-text available
The paper describes a numerical model for simulating sediment transport with eddy-resolving 3-D models. This sediment model consists of four submodels: pickup, transport over the bed, transport in the water column and deposition, all based on a turbulent flow model using large-eddy simulation. The sediment is considered as uniform rigid spherical p...
Article
Replacing existing river groynes with longitudinal training dams is considered as a promising flood mitigation measure in the main Dutch rivers, which can also serve to guarantee navigability during low flows and to create conditions favourable for ecological development. Whereas the bed response in the streamwise uniform part of a river trained by...
Article
Full-text available
We present a three-dimensional high-resolution hydrodynamic model for unsteady incompressible flow over an evolving bed topography. This is achieved by using a multilevel Cartesian grid technique that allows the grid to be refined in high-gradient regions and in the vicinity of the river bed. The grid can be locally refined and adapted to the bed g...
Article
The Rhine bifurcation at Pannerden forms the major distribution point for water supply in the Netherlands, distributing not only water and sediment but also flooding risks and navigability. Its morphological stability has been a concern for centuries. We present experiences from more than two decades of numerical morphological modelling of this bif...
Article
With the use of more detailed 3D hydrodynamic flow solvers, their extension to morphodynamic models is hampered by the limited possibilities to include details of turbulence and 3D flowpatterns into sediment entrainment and transport models. In this study we extended a three-dimensional (Delft3D) approach with HLES and k-ε turbulence, with several...
Article
Downstream fining of river bed sediments is well known for gravel-bed rivers, but also occurs in sand-bed rivers. The objective of this study was to determine the effect of selective transport processes, dune sorting, overbank deposition, channel migration and river bifurcations on downstream fining in sandy lowland rivers subject to relative sea l...
Article
Full-text available
In the Rhine-Meuse delta in the south-western part of the Netherlands, the morphology of the river branches is highly dependent on the erodibility of the subsoil. Erosion processes that were initiated after closure of the Haringvliet estuary branch by a dam (in 1970), caused a strong incision of several connecting branches. Due to the geological ev...
Article
Full-text available
Local geometrical perturbations of alluvial channels can generate a pattern of non-migrating bars and pools. This phenomenon is known as “overdeepening”, because the pools locally enhance the scour in river bends. Overdeepening occurs only downstream of a perturbation if the channel is in the subresonant and subcritically damped regime, which corre...
Article
A generic three-dimensional process-based model is presented, aimed at simulation of the construction of turbidite fan stratigraphy by low-density turbidity current events. It combines theoretical formulations on density flow and sediment transport of multiple grain sizes to simulate 2-DH turbidity current flow and sedimentation over arbitrary topo...
Article
Full-text available
At river bifurcations, water and sediment are divided over two branches. The dynamics of the bifurcation determine the long-term evolution (centuries) of the downstream branches, potentially leading to avulsion, but the dynamics are poorly understood. The long-term evolution can only be studied by one-dimensional models because of computational cos...
Chapter
The morphological response of the Dutch Rhine branches to interventions depends sensitively on the morphological development of the bifurcations. Computations in the 1990s revealed that proper modelling of this morphological development requires the inclusion of physical mechanisms for grain sorting. Therefore we apply a two-dimensional (2D) morpho...
Article
For modeling morphology in river with graded-sediment beds, generally methods are used that subdivide the sediment into separate size fractions, and that subdivide the bed into discrete layers. In the past years we have applied and analyzed numerical models using these methods for various river cases, including the full range of time-dependent cond...
Article
We present our experiences with morphological computations using a 2D depth-averaged finite-difference model for river bifurcations. These computations reveal new details of the importance of a proper computational gid and a proper representation of transport processes of graded sediment. The basic structure of the computational grid, irrespective...
Article
A downstream decrease in bed sediment size is well known for gravel-bed rivers, but also occurs in sand-bed rivers. The causes of downstream fining, however, may differ between gravel-bed rivers and sand-bed rivers, due to the fundamental differences between the two river types. In this study a numerical downstream fining model was developed based...
Article
Full-text available
Inland navigation is very important for national and international transport to and from the Netherlands. River management of the main Dutch Rhine branch, the Waal River, aims at improving navigation conditions, at the same time taking into account other, sometimes conflicting interests. Therefore integrated approaches are demanded to implement imp...
Article
By constructing a non-erodible layer in the pool of a river bend, the distribution of flow and sediment discharge can be modified such that the shallow inner bend will degrade to a certain extent. This results in a larger width for navigation. The approach has been successfully applied in two river bends in the Waal River in the Netherlands. We ana...
Article
Full-text available
At river bifurcations, water and sediment are divided over two branches. The dynamics of the division determine the long-term evolution of the downstream branches, which can be studied by ID models. For such models, a relation describing the sediment division is necessary, but this is poorly understood. We study the division of sediment and the mor...
Technical Report
Full-text available
Rijkswaterstaat faces two key issues for sustainable fairway maintenance and improvement in the river Waal: (1) finding sustainable small-scale measures to reduce the required dredging in river bends, with particular reference to the bends in the river Waal at Hulhuizen and Haalderen; (2) finding sustainable measures to arrest the overall bed degra...
Article
Full-text available
Three-dimensional models are not appropriate for the investigation of large-scale and/or long-term river problems, due to limitations in computational capacity. Quasi-3D models, obtained by supplementing 2DH depth-integrated flow models with a closure submodel for 3D effects, provide an interesting alternative. This paper compares simulations of th...

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