Hans Middelkoop

Utrecht University | UU · Department of Physical Geography

Deltas are reliant on upstream fluvial sediment sources for their survival. In the Rhine basin, the suspended sediment transport governs the supply of fines to the delta, a supply that has been dwindling for several decades. We investigate the changes in suspended sediment (SS) fluxes along the main Rhine branch and its tributaries since 1997 and l...

Deltas play a critical role in the ambition to achieve global sustainable development given their relatively large shares in population and productive croplands, as well as their precarious low-lying position between upstream river basin development and rising seas. The large pressures on these systems risk undermining the persistence of delta soci...

Scour holes are common features in deltaic rivers which can destabilise embankments through oversteepening of the river bed. Their development has been studied extensively from the hydraulic perspective, but another important control is the erodibility of the river bed which varies considerably due to thickening of heterogeneous deltaic substrate t...

Dikes often have a long history of reinforcement, with each reinforcement adding new material resulting in a heterogeneous dike. As data on the dike internal heterogeneity is sparse, it is generally overlooked in the stability assessment of dikes. We present an object‐based and process‐based model simulating dike construction history on archeologic...

Dams affect the natural flow regime by altering the magnitude, timing and frequency of high and low flows. Many river ecosystems impaired by dams are currently being restored. Restoration success is difficult to quantify and is often assessed by comparing the restored system to an unimpaired static ‘reference’ system. However, restoring a river to...

Deltas worldwide are at risk of elevation loss and drowning due to relative sea-level rise. Management strategies to restore or enhance sedimentation on delta plains, Sedimentation-Enhancing Strategies (hereafter SES) are now being pursued in many deltas but there has been limited cross-disciplinary and cross-delta review. Here we compare 21 existi...

The Ganges–Brahmaputra–Meghna delta in Bangladesh is one of the largest and most densely populated deltas in the world and is threatened by relative sea level rise (RSLR). Renewed sediment deposition through tidal river management (TRM), a controlled flooding with dike breach, inside the lowest parts of the delta polders (so-called beels) can poten...

With up to 15% of the world’s population being protected by dikes from flooding, climate-change-induced river levels may dramatically increase the flood risk of these societies. Reliable assessments of dike stability will become increasingly important, but groundwater flow through dikes is often oversimplified due to limited understanding of the im...

Shallow coastal ecosystems have high ecological value and contribute to flood protection. Their stability is, however, sensitive to the amount and rate of future sea level rise (SLR), their ability to trap sediment which allows them to grow with rising sea level, and human response to SLR. So far, studies have focused on assessing SLR impacts using...

Dike failure due to piping – concentrated flow of seepage water underneath the dike during periods of high flood water levels – has been recognized as a major component of flood risk. Simulation models to predict piping in risk assessments require detailed information on subsurface characteristics such as sediment grain size and thickness of overbu...

The Ganges-Brahmaputra-Meghna delta in Bangladesh is one of the largest and most populated deltas in the world and threatened by relative sea level rise (RSLR). Renewed sediment deposition through tidal river management (TRM), a controlled flooding with dike breach, inside the lowest parts of the delta polders (so-called “beels”) can potentially co...

The laminated sediment record from Laguna Pallcacocha, Ecuador, is widely used as a sensitive recorder of past variability in the El Niño-Southern Oscillation. However, limited knowledge of local meteorology, hydrogeomorphic processes, and the lateral variability of the lacustrine stratigraphy have resulted in some ambiguity in proxy interpretation...

The Ganges‐Brahmaputra‐Meghna (GBM) delta plain within Bangladesh is one of the most vulnerable to relative sea level rise (RSLR) in the world especially under current anthropogenically modified (i.e., embanked) conditions. Tidal River Management (TRM) as practiced in coastal regions of Bangladesh may provide an opportunity to combat RSLR by raisin...

Palaeoflood hydraulic modelling is essential for quantifying ‘millennial flood’ events not covered in the instrumental record. Palaeoflood modelling research has largely focused on one‐dimensional analysis for geomorphologically stable fluvial settings, because two‐dimensional analysis for dynamic alluvial settings is time‐consuming and requires a...

Reconstruction of past topography in palaeo-DEMs serves various geomorphological analyses. Constructing a palaeo-DEM by stripping young elements from a LiDAR DEM can provide results for large study areas at high resolution. However, such a ‘top-down’ approach is more suited to recent periods and geomorphologically static parts of the landscape than...

Bangladesh, one of the countries most vulnerable to climate change, is threatened by sea level rise (SLR) and land subsidence. The tidal river management (TRM) practised in coastal regions of Bangladesh has the potential to raise the land by sedimentation, to counteract SLR and subsidence. TRM is an indigenous method in which dikes are breached to...

The traditional methods for measuring water quality and suspended sediment concentrations (SSC) are time-consuming and often do not give the spatial and temporal detail needed for assessment of the water quality and sediment transport. The determination of the suspended sediment concentrations using remote sensing through the main channel and tribu...

Suspended sediment is a natural and crucial component and plays a crucial role in the hydrological, ecological and geomorphological functioning of the river system. The main objective of this study was to understand the spatial and temporal variation of SSC in Rhine River. This study used daily data of suspended sediment concentration from 1952 to...

The low-lying and populous Vietnamese Mekong delta is rapidly losing elevation due to accelerating subsidence rates, primarily caused by increasing groundwater extraction. This strongly increases the delta’s vulnerability to flooding, salinization, coastal erosion and, ultimately, threatens its nearly 18 million inhabitants with permanent inundatio...

Deltas are low-relief landforms that are extremely vulnerable to sea-level rise. Impact assessments of relative sea-level rise in deltas primarily depend on elevation data accuracy and how well the vertical datum matches local sea level. Unfortunately, many major deltas are located in data-sparse regions, forcing researchers and policy makers to us...

Uncertain socioeconomic development, biophysical processes and natural disasters in the Ganges delta in Bangladesh continuously transform the state of the socio-ecological system, which challenges local livelihood opportunities to be sustainable. Farmers living in the polders of delta make decisions on their livelihood in response to the changing s...

Understanding of complex sedimentary records formed by transgressive systems is critical for hydrocarbon exploration and exploitation, and carbon capture and storage. This paper discusses the facies proportions and preservation of the Last Interglacial and Holocene transgressive systems tracts in the Netherlands and their applicability as a North S...

Diversion of water and sediment into drowning delta wetlands aims at renewed sediment accumulation for ecosystem regeneration and compensation of sea-level rise and soil subsidence. The success of such measures requires sound understanding of flow pathways and deposition patterns within wetlands and their feeding channels. This study aimed to (1) i...

River morphology and riparian vegetation continuously adapt to changing discharge conditions, which makes it a challenge to distinguish long-term development driven by natural discharge variation from the impacts of flow alteration due to climate change and due to dams. The aim of this study was to investigate how such flow alterations affect bio-g...

The impact of climate change on the development and disintegration of Maya civilisation has long been debated. The lack of agreement among existing palaeoclimatic records from the region has prevented a detailed understanding of regional-scale climatic variability, its climatic forcing mechanisms and its impact on the ancient Maya. We present two n...

The functions of river floodplains often conflict spatially, for example, water conveyance during peak discharge and diverse riparian ecology. Such functions are often associated with floodplain vegetation. Frequent monitoring of floodplain land cover is necessary to capture the dynamics of this vegetation. However, low classification accuracies ar...

Vegetation in river floodplains has important functions for biodiversity, but can also have a negative influence on flood safety. Floodplain vegetation is becoming increasingly heterogeneous in space and time as a result of river restoration projects. To document the spatio-temporal patterns of the floodplain vegetation, the need arises for efficie...

The Vietnamese Mekong delta is subsiding due to a combination of natural and human-induced causes. Over the past several decades, large-scale anthropogenic land-use changes have taken place as a result of increased agricultural production, population growth and urbanization in the delta. Land-use changes can alter the hydrological system or increas...

Human-induced groundwater level lowering in the Holocene coastal-deltaic plain of the Netherlands causes oxidation of peat organic matter, resulting in land subsidence and carbon dioxide (CO2) emissions. Here, a three-dimensional (3D) analysis of the distribution of the remaining peat organic matter is presented, to quantify the potential of this a...

The Volga is the longest river in Europe and 16th longest in the world. The riverine landscape of the Volga is of exceptional scientific and economic importance to Russia; the basin contains approximately 40% of the Russian population and relates to 45% of the country's industrial and agricultural produce. The Volga River drains an area of 1.4 mill...

Many deltas are threatened by accelerated soil subsidence, sea-level rise, increasing river discharge, and sediment starvation. Effective delta restoration and effective river management require a thorough understanding of the mechanisms of sediment deposition, erosion, and their controls. Sediment dynamics has been studied at floodplains and marsh...

The impact of climate change on the development and disintegration of Maya civilization has long been debated. The lack of agreement among existing palaeoclimatic records from the region has prevented a detailed understanding of regional-scale climatic variability, its climatic forcing mechanisms, and its impact on the ancient Maya. We present two...

Utrecht University's "Low Land Genesis" borehole descriptions from 1959-1990 have been digitized since the 1990ies, importantly during a 2017 project (DANS KDP scheme) focusing on corings by staff, next to corings by students. Borehole descriptions of younger years were mostly made digital right after collection. The database contains borehole desc...

Cone Penetration Testing (CPT) was used to determine the void ratio and compressibility of Holocene peat present in the coastal-deltaic plain of the Netherlands, to explore its application for mapping the subsidence potential of this low-lying area. CPT sounds the mechanical behavior of subsurface layers when penetrated with a cone, and is the most...

Purpose A thorough understanding of mechanisms controlling sedimentation and erosion is vital for a proper assessment of the effectiveness of delta restoration. Only few field-based studies have been undertaken in freshwater tidal wetlands. Furthermore, studies that measured sediment deposition in newly created wetlands are also sparse. This paper...

Tidal freshwater wetlands are threatened by climate change, especially by rising sea levels. Until now, research in these wetlands has focused mostly on determining historical and present‐day accretion rates without analysing the influence of climate change on future developments. We study a recently constructed freshwater wetland under influence o...

The beach-ridge sequence of the Usumacinta–Grijalva delta borders a 300 km long section of the southern Gulf of Mexico coast. With around 500 beach ridges formed in the last 6500 years, the sequence is unsurpassed in the world in terms of numbers of individual ridges preserved, continuity of the record, and temporal resolution. We mapped and dated...

Invasive alien plant species negatively impact native plant communities by out-competing species or changing abiotic and biotic conditions in their introduced range. River systems are especially vulnerable to biological invasions, because waterways can function as invasion corridors. Understanding interactions of invasive and native species and the...

The beach-ridge sequence of the Usumacinta-Grijalva delta borders a 300-km-long section of the Southern Mexico Gulf coast. With around 500 beach ridges formed in the last 6500 years, the sequence is unsurpassed in the world in terms of numbers of individual ridges preserved, continuity of the record, and temporal resolution. We mapped and dated the...

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...

Many deltas are threatened by accelerated soil subsidence, sea level rise, increasing river discharge, and sediment starvation. Effective delta restoration and effective river management require a thorough understanding of the mechanisms of aggradation, erosion, and their controls. Sediment dynamics has been studied at floodplains and marshes, but...

Fluvial lowlands have become attractive human settling areas all around the world over the last few millennia. Because rivers kept changing their course and networks due to avulsion, the sedimentary sequences in these areas are archives of both fluvial geomorphological and archaeological development. We integrated geological and archaeological data...

A remarkably long period of Northern Hemispheric cooling in the 6th century CE, which disrupted human societies across large parts of the globe, has been attributed to volcanic forcing of climate. A major tropical eruption in 540 CE is thought to have played a key role, but there is no consensus about the source volcano to date. Here, we present ev...

To evaluate floodplain functioning, monitoring of its vegetation is essential. Although airborne imagery is widely applied for this purpose, classification accuracy (CA) remains low for grassland (< 88%) and herbaceous vegetation (<57%) due to the spectral and structural similarity of these vegetation types. Increased availability of Unmanned Aeria...

River restoration projects, which aim at improved flood safety and increased ecological value, have resulted in more heterogeneous vegetation. However, they also resulted in increasing hydraulic roughness, which leads to higher flood water levels during peak discharges. Due to allowance of vegetation development and succession, both ecological and...

River restoration projects, which aim at improved flood safety and increased ecological value, have resulted in more heterogeneous vegetation. However, they also resulted in increasing hydraulic roughness, which leads to higher flood water levels during peak discharges. Due to allowance of vegetation development and succession, both ecological and...

Coastal plains are amongst the most densely populated areas in the world. Many coastal peatlands are drained to create arable land. This is not without consequences; physical compaction of peat and its degradation by oxidation lead to subsidence, and oxidation also leads to emissions of carbon dioxide (CO2). This study complements existing studies...

Common flood risk analyses often focus on direct impacts corresponding to the maximum depths of flood events. However, this information is not sufficient for risk communication, for the design of flood emergency plans and for the selection of risk management measures. For those issues, not only a static view of the maximum flood intensity is requir...

Climate change is expected to significantly affect flooding regimes of river systems in the future. For Western Europe, flood risk assessments generally assume an increase in extreme events and flood risk, and as a result major investments are planned to reduce their impacts. However, flood risk assessments for the present day and the near future s...

The reach-scale effects of human-induced disturbances on the channel network in large braided rivers are a challenge to understand and to predict. In this study, we simulated different types of disturbances in a large braided river to get insight into the propagation of disturbances through a braided channel network. The results showed that the dis...

Dynamic interaction between river morphodynamics and vegetation affects river channel patterns and populations of riparian species. A range of numerical models exists to investigate the interaction between vegetation and morphodynamics. However, many of these models oversimplify either the morphodynamics or the vegetation dynamics, which hampers th...

This paper describes the sedimentary architecture, chronostratigraphy and palaeogeography of the late Middle and Late Pleistocene (Marine Isotope Stage / MIS 6-2) incised Rhine-valley fill in the central Netherlands based on six geological transects, luminescence dating, biostratigraphical data and a 3D geological model. The incised-valley fill con...

Climate scenarios are used to explore impacts of possible future climates and to assess the robustness of adaptation actions across a range of futures. Time-dependent climate scenarios are commonly used in mitigation studies. However, despite the dynamic nature of adaptation, most scenarios for local or regional decision making on climate adaptatio...

Embanked floodplains are the status-quo where humans are a major component of the environment, especially across Europe and North America. Effective management of embanked rivers requires a comprehensive knowledge of past and present-day geomorphic processes, including sediment transport and channel and floodplain dynamics. Many approaches to manag...

This volume provides a comprehensive perspective on geomorphic approaches to management of lowland alluvial rivers in North America and Europe. Many lowland rivers have been heavily managed for flood control and navigation for decades or centuries, resulting in engineered channels and embanked floodplains with substantially altered sediment loads a...

Recognition of the failure of old perspectives on river management and the need to enhance environmental sustainability has stimulated a new approach to river management over the past couple of decades. The manner that river restoration and integrated management are implemented, however, requires a case study approach that takes into account the in...

The Volga River in the Russian Federation has been regulated by a cascade of reservoir dams since the 1950-1960s. This chapter presents an overview of the main hydrological and morphological responses of the Volga River downstream of the Volgograd reservoir dam. Regulation caused a decrease in magnitude of the spring peak flow, an earlier start and...