A.J.M. Smits

Classification of floodplain vegetation by data fusion of spectral (CASI) and LiDAR data

To safeguard the goals of flood protection and nature development, a river manager requires detailed and up‐to‐date information on vegetation structures in floodplains. In this study, remote‐sensing data on the vegetation of a semi‐natural floodplain along the river Waal in the Netherlands were gathered by means of a Compact Airborne Spectrographic Imager (CASI; spectral information) and LiDAR (structural information). These data were used to classify the floodplain vegetation into eight and five different vegetation classes, respectively. The main objective was to fuse the CASI and LiDAR‐derived datasets on a pixel level and to compare the classification results of the fused dataset with those of the non‐fused datasets. The performance of the classification results was evaluated against vegetation data recorded in the field. The LiDAR data alone provided insufficient information for accurate classification. The overall accuracy amounted to 41% in the five‐class set. Using CASI data only, the overall accuracy was 74% (five‐class set). The combination produced the best results, raising the overall accuracy to 81% (five‐class set). It is concluded that fusion of CASI and LiDAR data can improve the classification of floodplain vegetation, especially for those vegetation classes which are important to predict hydraulic roughness, i.e. bush and forest. A novel measure, the balance index, is introduced to assess the accuracy of error matrices describing an ordered sequence of classes such as vegetation structure classes that range from bare soil to forest.

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

The soil of several floodplain areas along large European rivers shows increased levels of heavy metals as a relict from past sedimentation of contaminants. These levels may pose risks of accumulation in food webs and toxicologic effects on flora and fauna. However, for floodplains, data on heavy-metal concentrations in vertebrates are scarce. Moreover, these environments are characterised by periodical flooding cycles influencing ecologic processes and patterns. To investigate whether the suggested differences in accumulation risks for insectivores and carnivores, omnivores, and herbivores are reflected in the actual heavy-metal concentrations in the species, we measured the current levels of Zn, Cu, Pb, and Cd in 199 specimens of 7 small mammal species (voles, mice, and shrews) and in their habitats in a diffusely polluted floodplain. The highest metal concentrations were found in the insectivorous and carnivorous shrew, Sorex araneus. Significant differences between the other shrew species, Crocidura russula, and the vole and mouse species was only found for Cd. The Cu concentration in Clethrionomys glareolus, however, was significantly higher than in several other vole and mouse species. To explain the metal concentrations found in the specimens, we related them to environmental variables at the trapping locations and to certain characteristics of the mammals. Variables taken into account were soil total and CaCl2-extractable metal concentrations at the trapping locations; whether locations were flooded or nonflooded; the trapping season; and the life stage; sex; and fresh weight of the specimens. Correlations between body and soil concentrations and location or specimen characteristics were weak. Therefore; we assumed that exposure of small mammals to heavy-metal contamination in floodplains is significantly influenced by exposure time, which is age related, as well as by dispersal and changes in foraging and feeding patterns under influence of periodic flooding.

Changing Estuaries, Changing Views

During the design and the execution of the Delta project, carried out after the storm flood of 1953 in the SW Netherlands, the importance of the long-term effects of morphological and ecological developments driven by tides and currents, have been underestimated. Due to these processes the height of the dams will have to be increased for centuries to come, because the land behind the levees cannot grow in elevation anymore with the rising of the sea. Maintenance of the civil-engineering structures, and mitigating their unpredictable impacts on ecosystems, involve very high recurrent costs. The chance of flooding is reduced, but the potential damage after a storm flood is enlarged: seawalls and dykes provide a false sense of safety against flooding. Changes in the role of agricultural use in the European context, offer an opportunity to abandon arable fields and to retrocede them to the sea in order to absorb tidal energy and to allow the land to rise concomitant with the sea. A cost-benefit analysis of this approach should assess the direct and indirect economic values, as well as the non-use (intrinsic) values, whereby public engagement in management questions, facilitates decision-making processes. Reversible and resilient economic measures within the limits of the natural processes are preferable. A future, speculative perspective is an urbanised landscape, where people and investments are located in safe places, e.g. on floating, or sea-encircled artificial dwelling-mounds, surrounded by a landscape that is ruled by the forces of nature. New approaches such as developed in the Westerschelde offer flexible solutions to flooding problems, and are worth a broader evaluation. A worldwide platform of experts should be organised to study the future management of estuaries and deltas, and to develop and exchange new ideas and techniques.

Partial root drying effects on biomass production in Brassica napus and the significance of root responses

Partial root drying (PRD) has been shown to stimulate stomatal-closure response and improve water-use efficiency and thus biomass production and grain yield under water deficiency. While most studies focus on above-ground responses to PRD, we examined how root responses contributed to effects of partial root drying. In particular, in two experiments with oilseed rape (Brassica napus L.) we investigated whether roots were able to forage for patchily distributed water, and how this affected plant growth compared with uniform watering and alternate watering (in which different parts of the roots receive water alternately). The first pot experiment was carried out in the greenhouse and the second outside under a rain-shelter in which also the watering amount was varied. The results indicate that B. napus roots were able to forage for fixed water patches by selective root placement. In the first experiment with small plants, root foraging was equally effective as enhanced water-use efficiency under alternate watering. Both treatments resulted in about 10% higher shoot biomass compared with uniform watering. Alternate watering generally outperformed uniform watering in the second experiment, but the success depended on the time of harvest and the water supply level. Measurements indicated that only the alternate watering regime effectively reduced stomatal conductance, but lead to a higher shoot biomass only under more severe (50%) rather than under milder water deficiency (70% of a well watered control). Water deficiency strongly reduced leaf initiation rates and leaf sizes in B. napus, but for a given level of water supply the supply pattern (uniform control, fixed patchy or alternate watering) hardly influenced these growth parameters. Although also in the second experiment, the plants selectively placed their roots in the wet parts of the pot, root foraging was not as effective as in the first experiment. Possible reasons for these discrepancies are discussed as well as their implications for the application of PRD effects for crop growth.

Analyzing Collaborative Governance Through Social Network Analysis: A Case Study of River Management Along the Waal River in The Netherlands

Abstract Until recently, governmental organizations played a dominant and decisive role in natural resource management. However, an increasing number of studies indicate that this dominant role is developing towards a more facilitating role as equal partner to improve efficiency and create a leaner state. This approach is characterized by complex collaborative relationships between various actors and sectors on multiple levels. To understand this complexity in the field of environmental management, we conducted a social network analysis of floodplain management in the Dutch Rhine delta. We charted the current interorganizational relationships between 43 organizations involved in flood protection (blue network) and nature management (green network) and explored the consequences of abolishing the central actor in these networks. The discontinuation of this actor will decrease the connectedness of actors within the blue and green network and may therefore have a large impact on the exchange of ideas and decision-making processes. Furthermore, our research shows the dependence of non-governmental actors on the main governmental organizations. It seems that the Dutch governmental organizations still have a dominant and controlling role in floodplain management. This challenges the alleged shift from a dominant government towards collaborative governance and calls for detailed analysis of actual governance.

Combined effects of partial root drying and patchy fertilizer placement on nutrient acquisition and growth of oilseed rape

Partial rootzone drying (PRD) is widely investigated as an effective irrigation technique, resulting in higher water use efficiency and yield for plants growing under mild water deficit. Nutrition is another important factor affecting plant yield, but nutrient acquisition has only rarely been considered in conjunction with PRD. Here we investigate the interaction between water and fertilizer supply in a pot experiment with oilseed rape (Brassica napus L.). Eight treatments were set up for the experiment, a factorial combination of four watering regimes (100% control watering at both sides of the plants; 50% control watering at both sides of the plants; 50% fixed watering applied only to one side of the plants; 50% alternate watering applied alternately to both sides of the plant) and two fertilizer placement levels (uniform over the entire pot, and patchy supplied to one side). For the 50% watering treatments, the total amount of water supplied to the plants was the same, only the pattern of application differed between treatments. Also the total fertilizer applied was the same for all treatments. Oilseed rape roots foraged effectively for water and nutrients resulting in relatively small differences in nutrient uptake and above-ground growth among the water-deficit treatments. Placing fertilizer at one side of the plants increased nutrient uptake, but there were differences between the water treatments and interactions with water uptake. Alternate watering resulted in the highest growth, as a result of the largest nitrogen and phosphorus uptake with the smallest root investment among the three water deficit treatments. Fixed watering resulted in poorest performance when fertilizer was uniformly spread throughout the pot, because the plants were unable to acquire the nutrients on the dry side. Our results show that PRD can be well combined with patchy fertilizer supply, but that reduced nutrient uptake may be expected when nutrients are supplied in parts of the soil volume that remain too dry.

Root foraging and yield components underlying limited effects of Partial Root-zone Drying on oilseed rape, a crop with an indeterminate growth habit

We report on two experiments with oilseed rape (Brassica napus L.) to test if partial root-zone drying techniques improve yield in a crop in which vegetative and reproductive growth overlap (indeterminate growth habit), and to investigate what plant morphological responses contribute to the yield that is realized. Deficit irrigation resulted in smaller plants with smaller yields but larger seeds compared to treatments with shallow groundwater (first experiment) and with fully watered conditions (second experiment). Different partial root-zone drying treatments (water supply patterns) under deficit irrigation, however, had little effect on plant growth and yield components (number of branches, branch lengths, number of pods, etc.). Our results suggest that partial root-zone drying doesn’t work well with oilseed rape. Detailed measurements of soil water contents and root distribution indicate that roots were extremely plastic, effectively foraging for water, and these root responses may have overwhelmed physiological effects of partial root drying on the shoot. Furthermore, in crops with indeterminate growth with a short vegetative growth phase, partial root-zone drying may be ineffective in enhancing the major yield components. Further reasons for the lack of success are discussed.

Coping with poor water supply in peri-urban Bandung, Indonesia: towards a framework for understanding risks and aversion behaviours

This paper explores the daily risks of households with respect to dimensions of inadequate water access and supply (quality, quantity, continuity and affordability). We describe how perceptions of risk are shaped and how households seek to reduce possible health impacts and potential economic losses through aversion behaviours. To this end, households’ activities relating to water storage, treatment and usage, together with water source preference, were analysed using a qualitative approach. We developed a framework that describes actual risk, risk perceptions and aversion behaviours. Risk perceptions and the adoption of aversion behaviours of varying frequency and intensity are based on a complex interaction between personal and shared experiences that relate to water supply dimensions, socioeconomic characteristics, and social networking. Moreover, we discuss household risk management strategies and provide some recommendations aimed at improving future approaches to the study of aversion behaviours.

Towards a Joint Maintenance Approach for floodplain management in the Netherlands: tensions and possibilities

While multi-functional river rehabilitation has taken the limelight in todays water management, its follow-up phase, maintenance, has done so to a far lesser extent. A key challenge for today´s environmental management is the number and diversity of actors and sectors involved, each with their own perceptions, interests and resources. This chapter seeks to apply the gains made in the Joint Planning Approach (JPA), developed earlier at Radboud University, the Netherlands, to the maintenance stage of river planning. The application of that approach in the densely populated Netherlands is contrasted with an example of top-down, mono-functional maintenance in a floodplain area in the southwest. It is found that the approach brings considerable opportunities to integrate a fragmented field but that considerable challenges remain related to fragmented policies, building collaborative entities, and organizational constraints.

Implementing integrated river basin management in China

This paper examines the role of the World Wildlife Fund for Nature China as policy entrepreneur in China. It illustrates the ways in which the World Wildlife Fund for Nature is active in promoting integrated river basin management in the Yangtze River basin and how the efforts at basin level are matched with the advice of the China Council for International Cooperation on Environment and Development task force on integrated river basin management to the national government of China. This article demonstrates that the World Wildlife Fund for Nature uses various strategies of different types to support a transition process towards integrated river basin management. Successful deployment of these strategies for change in environmental policy requires special skills, actions, and attitudes on the part of the policy entrepreneur, especially in China, where the government has a dominant role regarding water management and the position of policy entrepeneurs is delicate.