R.S.E.W. Leuven

Exploring field vegetation reflectance as an indicator of soil contamination in river floodplains

This study investigated the relation between vegetation reflectance and elevated concentrations of the metals Ni, Cd, Cu, Zn and Pb in river floodplain soils. High-resolution vegetation reflectance spectra in the visible to near-infrared (400-1350 nm) were obtained using a field radiometer. The relations were evaluated using simple linear regression in combination with two spectral vegetation indices: the Difference Vegetation Index (DVI) and the Red-Edge Position (REP). In addition, a multivariate regression approach using partial least squares (PLS) regression was adopted. The three methods achieved comparable results. The best R(2) values for the relation between metals concentrations and vegetation reflectance were obtained for grass vegetation and ranged from 0.50 to 0.73. Herbaceous species displayed a larger deviation from the established relationships, resulting in lower R(2) values and larger cross-validation errors. The results corroborate the potential of hyperspectral remote sensing to contribute to the survey of elevated metal concentrations in floodplain soils under grassland using the spectral response of the vegetation as an indicator. Additional constraints will, however, have to be taken into account, as results are resolution- and location-dependent.

The potential of field spectroscopy for the assessment of sediment properties in river floodplains

Investigations have shown that visible-near-infrared (VNIR) spectroscopy can accurately determine soil properties under laboratory conditions. In situ assessment of soil properties is of great benefit for several applications, as spectra can be acquired fast and almost continuously. The present study used partial least squares (PLS) regression to establish a relationship between soil reflectance spectra measured under field conditions and the organic matter and clay content of the soil. Spectra were acquired with a fieldspectrometer in a recently reconstructed floodplain along the river Rhine in The Netherlands. Several spectral pre-processing methods were employed to improve the performance and robustness of the models. Results indicate that, under varying surface conditions, field spectroscopy in combination with multivariate calibration does result in a qualitative relation for organic matter (R2=0.45) and clay content (R2=0.43) while under laboratory conditions more accurate results are obtained (R2=0.69 and 0.92, respectively). Soil moisture and vegetation cover had a negative influence on the prediction capabilities for both soil properties. Although the performance of the spectra measured in situ is not as accurate as physical analysis, the accuracy obtained is useful for rapid soil characterisation and remote sensing applications.

Flood Defense in The Netherlands: A New Era, a New Approach

Intensive land use and far-reaching alterations to the fluvial hydrosystem, made feasible by technological developments in the past century, have reduced the hydromorphological resilience of the Rhine and Meuse river basins. Because the hydromorphodynamic processes could be controlled to a greater extent, residents of the riverine areas lost their sense of the natural dynamics of river systems, and further urbanization of areas prone to flooding took place without the potential dangers being recognized. It was particularly in the low-lying polders of The Netherlands that the potential damage from flooding increased tremendously over time. The Dutch Ministry of Transport, Public Works and Water Management is currently trying to achieve sustainable water and river management by developing and implementing a new approach to flood defense. In addition to the implementation of technological measures, the government aims to create more space for the rivers, combined with objectives from other policy areas, including the reconstruction of rural areas, development of the ecological infrastructure, surface mineral extraction, land use and other area-specific projects such as housing schemes. This approach is not confined to The Netherlands: similar concepts have recently been introduced at various other locations in the Rhine and Meuse river basins. The new approach requires land-use changes and introduces new scientific research issues relating to land and water use, hydromorphology, river management and socio-economics. This paper discusses this new approach and related scientific developments.Abstract Intensive land use and far-reaching regulation of the fluvial hydrosystem in the past century have reduced the hydromorphological resilience of the Rhine and Meuse river basins. Because the hydromorphodynamic processes could be controlled to a greater extent, residents of the riverine areas lost their sense of the natural dynamics of river systems, and further urbanization of areas prone to flooding took place without the potential dangers being recognized. It was particularly in the low-lying polders of the Netherlands that the potential damage from flooding increased tremendously over time. The high water discharges of the rivers Rhine and Meuse in 1993, 1995, and 1998 caused a considerable change in governmental policy, public awareness, and international cooperation in terms of flood protection and inland water management. The Dutch government is currently trying to achieve sustainable water and river management by developing and implementing a new approach to flood defense. In addition to the implementation of technological measures, the government aims to create more space for the rivers, combined with objectives from other policy areas, including the restructuring of rural areas, development of the ecological infrastructure, surface mineral extraction, land use and other area-specific projects such as housing schemes. This approach is not confined to the Netherlands: similar concepts have recently been introduced at various other locations in the Rhine and Meuse river basins. The new approach requires land-use changes and introduces new scientific research issues relating to land and water use, hydromorphology, river management, and socio-economics. This paper discusses this new approach and related scientific developments.

River restoration and flood protection: controversy or synergism?

This is a series of contributions, expressing explicit opinions with regard to contemporary topics in limnology.These texts can be based on new book with a large impact, but can also refer to other currently debated topics.Documented reactions to these contributions should be sent to the editor-in-chief; they will be considered forpublication in subsequent issues.

Effects of water acidification on the distribution pattern and the reproductive success of amphibians

Nine amphibian species were encountered in poorly buffered waters of The Netherlands (alkalinity ≦1 meq·l−1). These soft water systems are highly sensitive to acidifying precipitation. The number of species as well as the percentage of waters which harbour amphibian populations are strongly reduced in the extremely acid pH-class

Ecological rehabilitation of the lowland basin of the river Rhine (NW Europe)

(\bar pH< 4.0)

Heavy-metal concentrations in small mammals from a diffusely polluted floodplain : Importance of species-and location-specific characteristics

. The reproductive success of amphibians is negatively affected by low pH. The eggs become heavily infested with fungi (Saprolegniaceae). In acidifying systems many physico-chemical parameters are significantly correlated with the pH of the water. Strongly acidified waters are characterized by low alkalinity, conductivity and ionic content but high acidity and high concentrations of (heavy) metals and ammonium and a high relative sulphate concentration. Culture experiments with eggs and larvae ofRana arvalis. Rana ‘esculenta’, Rana temporaria andBufo bufo show that apart from the pH, elevated aluminium, cadmium and ammonium contents may also affect the reproductive success of amphibians.

Characterization Factors for Water Consumption and Greenhouse Gas Emissions Based on Freshwater Fish Species Extinction

The effect of preservation methods on dry weight (DW) and ash-free dry weight (AFDW) of Radix peregra (Gastropoda), Asellus aquaticus (Isopoda), Erpobdella octoculata (Hirudinea) and Glyptotendipes sp. (Chironomidae) was studied. Ethanol, formaldehyde, and Bouin were used as preservative. In case of preservation of macro-invertebrates in ethanol substancial changes in DW and AFDW biomass were observed. In the four different taxa the loss in DW varied between 7.2–21.9% after a 3 month preservation period in 70% ethanol. A comparatively small range in AFDW loss (16.2–19.7%) was found. Changes in DW and AFDW biomass during preservation were significantly affected by the duration of the preservation, by temperature, light conditions and the volume of the preservative. The changes in AFDW were also significantly affected by the concentration of the preservatives. Preservation in 10% formaldehyde did not cause significant changes in DW and AFDW biomass.