This paper discusses a model which simulates dune development resulting from aeolian saltation tr... more This paper discusses a model which simulates dune development resulting from aeolian saltation transport. The model was developed for application to coastal foredunes, but is also applicable to sandy deserts with transverse dunes. Sediment transport is calculated using published deterministic and empirical relationships, describing the influence of meteorological conditions, topography, sediment characteristics and vegetation. A so-called adaptation length is incorporated to calculate the development of transport equilibrium along the profile. Changes in topography are derived from the predicted transport, using the continuity equation. Vegetation height is incorporated in the model as a dynamic variable. Vegetation can be buried during transport events, which results in important changes in the sediment transport rates. The sediment transport model is dynamically linked to a second-order closure air flow model, which predicts friction velocities over the profile, influenced by topography and surface roughness.
Wiederholte grenzüberschreitende Bestandsaufnahmen der Grundwasserbeschaffenheit im Oberrheingrab... more Wiederholte grenzüberschreitende Bestandsaufnahmen der Grundwasserbeschaffenheit im Oberrheingraben (ORG) haben bestätigt, dass die Belastung durch Nitrat am weitesten verbreitet ist [9], [10]. In Präventions-und Sanierungsmaßnahmen ist bereits viel Geld investiert worden, die Erfolge scheinen demgegenüber gering. Insofern wird von verschiedenen Seiten die Effizienz und sogar die Wirksamkeit der getroffenen Maßnahmen kritisch hinterfragt. In einem trinationalen Projekt [7], mit dem die lange, erfolgreiche Zusammenarbeit im ORG fortgesetzt wurde, sollte darum untersucht werden, ob die Nitratbelastung des Grundwassers für den gesamten ORG ausreichend genau simuliert werden kann, um die bisherige Entwicklung zu interpretieren, Prognosen zu erstellen und ein Werkzeug zur vergleichenden Bewertung der Wirksamkeit verschiedener Maßnahmen zu erhalten. Das Projektgebiet umfasst den mittleren und südlichen ORG zwischen Basel und Lauterburg mit einer Fläche von 4 293 km 2 und die angrenzenden Randgebirge bis zur Wasserscheide. Der Grundwasserleiter im ORG besteht aus Lockergesteinen mit Mächtigkeiten bis zu 260 m. Er bildet einen intensiv genutzten Grundwasserkörper mit einem Volumen von ca. 80 Mrd. m 3 . Das Grundwasser ist jedoch wegen unzureichend schützender Deckschichten durch die intensive landwirtschaftliche Nutzung (Anteil der landwirtschaftlich genutzten Fläche (LF) im ORG: 60 %), die dichte Be-siedlung und zahlreiche Verkehrswege besonders gefährdet. Für die Projektbearbeitung wurde nach Abwägung verschiedener Modellkonzepte ein Verbund bewährter Sektormodelle statt eines integrierten hydrologischen Modells verwendet (Bild 1) [2]. Die Koppelung erfolgte über gemeinsame Datenformate. Damit war es möglich, lokal vorhandenes Expertenwissen optimal einzubinden und auch die landwirtschaftliche Seite umfassend zu beteiligen. Jedes der Sektormodelle wurde soweit möglich an die Bedingungen im ORG adaptiert und validiert.
In the framework of a climate change research project, an approach and preliminary results are pr... more In the framework of a climate change research project, an approach and preliminary results are presented of modelling the suspended sediment supply to the drainage network of the River Rhine. Concepts of the GAMES model are used as a basis. In the model, the amount of mobilized sediment that actually reaches the stream network depends on the proximity of the sediment source to the stream, the occurrence of overland flow and on the character of the terrain along the route towards the channel (including surface roughness and slope angle). Attention is paid to problems that are specific to the large size of the studied basin and the spatial resolution of the available data set. Preliminary results show that estimates of sediment supply from hillslope to streams are reasonable. Calculated sediment supply was compared with measured sediment yields at several sampling stations in the Rhine basin. It appeared that suspended sediment supplied in lower parts of the basin is transported more ...
Soil erosion rates depend in many ways on soil and soil surface characteristics which vary in spa... more Soil erosion rates depend in many ways on soil and soil surface characteristics which vary in space and in time. To account for spatial variations of soil features, most distributed soil erosion models require data input derived from soil maps. Ideally, the level of spatial detail contained in the applied soil map should correspond to the objective of the modelling
ABSTRACT Over a two-year period, rainfall, runoff and sediment output were measured in six small ... more ABSTRACT Over a two-year period, rainfall, runoff and sediment output were measured in six small agricultural catchments (3-10 ha) in south Limburg (the Netherlands). In this paper, results of the measurements are presented and processes that determine surface runoff and sediment yield during winter and summer rainfall are identified. The measurement results discussed in this paper show that in some catchments much runoff occurred in winter and that soil moisture storage capacity may be just as important for runoff generation as infiltration capacity.
The objective of this study was to estimate the potential effects of changes in climate and land ... more The objective of this study was to estimate the potential effects of changes in climate and land use on the mobilization of fine sediment and the net transport of wash load from the upstream basin to the lower Rhine delta. For this purpose, a suite of geographical information system-embedded models was developed that simulates the production, and transport of wash load through the drainage network and deposition on floodplains along the lower river reaches. The model results indicate that if climate changes in accordance with the UKHI climate-change scenario, in combination with land use changes, erosion rates will increase in the Alps and decrease in the German part of the basin. Averaged over the entire basin, erosion will increase by about 12%. However, due to inefficient sediment delivery, increasing erosion in the Alps will have little effect on the sediment load further downstream. In the delta area, sediment loads are expected to decrease by 13%. When changes in river discharge are accounted for, it appears that, although very high discharges are expected to occur more frequently, sedimentation on floodplains tends to decrease. This is caused mainly by reduced sediment loads at discharges during which the floodplains are just inundated and trapping efficiencies are high.
Surface runoff may be generated when the rainfall intensity exceeds the infiltration capacity, or... more Surface runoff may be generated when the rainfall intensity exceeds the infiltration capacity, or when the soil profile is saturated with water. Indications exist that both types of overland flow may occur in hilly agricultural loess regions. Here, for a loessial hillslope under maize in the southern part of The Netherlands, it was shown, with pressure head and runoff measurements, that Hortonian overland flow occurs during typical summer rain events. Surface runoff was initiated after saturation of the top 5-10cm of the soil. Deeper in the soil, unsaturated conditions prevailed while runoff took place. Peak runoff discharges at the outlet of the subcatchment occurred a few minutes after peak rainfall intensities were measured. It appeared that SWMS_2D, a two-dimensional water flow model, was capable in simulating observed pressure head changes and runoff. Simulated potential runoff for the transect studied was higher by a magnitude of three than the measured areal average. This indicates effects of surface ponding, and the probable location of this particular transect in a region with high runoff production.
ABSTRACT For the development of the Limburg Soil Erosion Model (LISEM) a validated hillslope hydr... more ABSTRACT For the development of the Limburg Soil Erosion Model (LISEM) a validated hillslope hydrology module was needed. Therefore, hydraulic heads were monitored on four hillslopes in the southern part of the Netherlands in 1992 and 1993. The hydraulic headswere recorded automatically, using standalone measuring devices. Rainfall amounts and run-off were recorderd simultaneously. Observed changes in hydraulic head and run-off were simulated using the SWMS_2D computer program. Measured and simulated results proved to correlate well.
This paper discusses a model which simulates dune development resulting from aeolian saltation tr... more This paper discusses a model which simulates dune development resulting from aeolian saltation transport. The model was developed for application to coastal foredunes, but is also applicable to sandy deserts with transverse dunes. Sediment transport is calculated using published deterministic and empirical relationships, describing the influence of meteorological conditions, topography, sediment characteristics and vegetation. A so-called adaptation length is incorporated to calculate the development of transport equilibrium along the profile. Changes in topography are derived from the predicted transport, using the continuity equation. Vegetation height is incorporated in the model as a dynamic variable. Vegetation can be buried during transport events, which results in important changes in the sediment transport rates. The sediment transport model is dynamically linked to a second-order closure air flow model, which predicts friction velocities over the profile, influenced by topography and surface roughness.
Wiederholte grenzüberschreitende Bestandsaufnahmen der Grundwasserbeschaffenheit im Oberrheingrab... more Wiederholte grenzüberschreitende Bestandsaufnahmen der Grundwasserbeschaffenheit im Oberrheingraben (ORG) haben bestätigt, dass die Belastung durch Nitrat am weitesten verbreitet ist [9], [10]. In Präventions-und Sanierungsmaßnahmen ist bereits viel Geld investiert worden, die Erfolge scheinen demgegenüber gering. Insofern wird von verschiedenen Seiten die Effizienz und sogar die Wirksamkeit der getroffenen Maßnahmen kritisch hinterfragt. In einem trinationalen Projekt [7], mit dem die lange, erfolgreiche Zusammenarbeit im ORG fortgesetzt wurde, sollte darum untersucht werden, ob die Nitratbelastung des Grundwassers für den gesamten ORG ausreichend genau simuliert werden kann, um die bisherige Entwicklung zu interpretieren, Prognosen zu erstellen und ein Werkzeug zur vergleichenden Bewertung der Wirksamkeit verschiedener Maßnahmen zu erhalten. Das Projektgebiet umfasst den mittleren und südlichen ORG zwischen Basel und Lauterburg mit einer Fläche von 4 293 km 2 und die angrenzenden Randgebirge bis zur Wasserscheide. Der Grundwasserleiter im ORG besteht aus Lockergesteinen mit Mächtigkeiten bis zu 260 m. Er bildet einen intensiv genutzten Grundwasserkörper mit einem Volumen von ca. 80 Mrd. m 3 . Das Grundwasser ist jedoch wegen unzureichend schützender Deckschichten durch die intensive landwirtschaftliche Nutzung (Anteil der landwirtschaftlich genutzten Fläche (LF) im ORG: 60 %), die dichte Be-siedlung und zahlreiche Verkehrswege besonders gefährdet. Für die Projektbearbeitung wurde nach Abwägung verschiedener Modellkonzepte ein Verbund bewährter Sektormodelle statt eines integrierten hydrologischen Modells verwendet (Bild 1) [2]. Die Koppelung erfolgte über gemeinsame Datenformate. Damit war es möglich, lokal vorhandenes Expertenwissen optimal einzubinden und auch die landwirtschaftliche Seite umfassend zu beteiligen. Jedes der Sektormodelle wurde soweit möglich an die Bedingungen im ORG adaptiert und validiert.
In the framework of a climate change research project, an approach and preliminary results are pr... more In the framework of a climate change research project, an approach and preliminary results are presented of modelling the suspended sediment supply to the drainage network of the River Rhine. Concepts of the GAMES model are used as a basis. In the model, the amount of mobilized sediment that actually reaches the stream network depends on the proximity of the sediment source to the stream, the occurrence of overland flow and on the character of the terrain along the route towards the channel (including surface roughness and slope angle). Attention is paid to problems that are specific to the large size of the studied basin and the spatial resolution of the available data set. Preliminary results show that estimates of sediment supply from hillslope to streams are reasonable. Calculated sediment supply was compared with measured sediment yields at several sampling stations in the Rhine basin. It appeared that suspended sediment supplied in lower parts of the basin is transported more ...
Soil erosion rates depend in many ways on soil and soil surface characteristics which vary in spa... more Soil erosion rates depend in many ways on soil and soil surface characteristics which vary in space and in time. To account for spatial variations of soil features, most distributed soil erosion models require data input derived from soil maps. Ideally, the level of spatial detail contained in the applied soil map should correspond to the objective of the modelling
ABSTRACT Over a two-year period, rainfall, runoff and sediment output were measured in six small ... more ABSTRACT Over a two-year period, rainfall, runoff and sediment output were measured in six small agricultural catchments (3-10 ha) in south Limburg (the Netherlands). In this paper, results of the measurements are presented and processes that determine surface runoff and sediment yield during winter and summer rainfall are identified. The measurement results discussed in this paper show that in some catchments much runoff occurred in winter and that soil moisture storage capacity may be just as important for runoff generation as infiltration capacity.
The objective of this study was to estimate the potential effects of changes in climate and land ... more The objective of this study was to estimate the potential effects of changes in climate and land use on the mobilization of fine sediment and the net transport of wash load from the upstream basin to the lower Rhine delta. For this purpose, a suite of geographical information system-embedded models was developed that simulates the production, and transport of wash load through the drainage network and deposition on floodplains along the lower river reaches. The model results indicate that if climate changes in accordance with the UKHI climate-change scenario, in combination with land use changes, erosion rates will increase in the Alps and decrease in the German part of the basin. Averaged over the entire basin, erosion will increase by about 12%. However, due to inefficient sediment delivery, increasing erosion in the Alps will have little effect on the sediment load further downstream. In the delta area, sediment loads are expected to decrease by 13%. When changes in river discharge are accounted for, it appears that, although very high discharges are expected to occur more frequently, sedimentation on floodplains tends to decrease. This is caused mainly by reduced sediment loads at discharges during which the floodplains are just inundated and trapping efficiencies are high.
Surface runoff may be generated when the rainfall intensity exceeds the infiltration capacity, or... more Surface runoff may be generated when the rainfall intensity exceeds the infiltration capacity, or when the soil profile is saturated with water. Indications exist that both types of overland flow may occur in hilly agricultural loess regions. Here, for a loessial hillslope under maize in the southern part of The Netherlands, it was shown, with pressure head and runoff measurements, that Hortonian overland flow occurs during typical summer rain events. Surface runoff was initiated after saturation of the top 5-10cm of the soil. Deeper in the soil, unsaturated conditions prevailed while runoff took place. Peak runoff discharges at the outlet of the subcatchment occurred a few minutes after peak rainfall intensities were measured. It appeared that SWMS_2D, a two-dimensional water flow model, was capable in simulating observed pressure head changes and runoff. Simulated potential runoff for the transect studied was higher by a magnitude of three than the measured areal average. This indicates effects of surface ponding, and the probable location of this particular transect in a region with high runoff production.
ABSTRACT For the development of the Limburg Soil Erosion Model (LISEM) a validated hillslope hydr... more ABSTRACT For the development of the Limburg Soil Erosion Model (LISEM) a validated hillslope hydrology module was needed. Therefore, hydraulic heads were monitored on four hillslopes in the southern part of the Netherlands in 1992 and 1993. The hydraulic headswere recorded automatically, using standalone measuring devices. Rainfall amounts and run-off were recorderd simultaneously. Observed changes in hydraulic head and run-off were simulated using the SWMS_2D computer program. Measured and simulated results proved to correlate well.
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Papers by Paul van Dijk