The Age and Origin of the Gelderse IJssel

Historic trading cities are located on the Gelderse IJssel and flourished in the late Middle Ages. Little is known about this river in the early Middle Ages and before, and there is considerable debate on the age and origin of the Gelderse IJssel as a Rhine distributary. A small river draining the surrounding Pleistocene uplands must have been present in the IJssel valley during most of the Holocene, but very diverse opinions exist as to when this local river became connected to the Rhine system (and thereby to a vast hinterland), and whether this was human induced or a natural process. We collected new AMS radiocarbon evidence on the timing of beginning overbank sedimentation along the lower reach of the Gelderse IJssel. Our data indicate onset of overbank sedimentation at about 950 AD in this reach. We attribute this environmental change to the establishment of a connection between the precursor of the IJssel and the Rhine system by avulsion. Analysis of previous conventional radiocarbon dates from the upper IJssel floodplain yields that this avulsion may have started ~600 AD. Our results contradict earlier suppositions, based on interpretation of archaeological data and historical accounts, that the Gelderse IJssel is much older and originated as a canal, dug under supervision of the Roman general DrususThe Gelderse IJssel is the third major distributary of the Rhine in the Netherlands and diverts on average similar to 15% of the Rhine discharge northward. Historic trading cities are located on the Gelderse IJssel and flourished in the late Middle Ages. Little is known about this river in the early Middle Ages and before, and there is considerable debate on the age and origin of the Gelderse IJssel as a Rhine distributary. A small river draining the surrounding Pleistocene uplands must have been present in the IJssel valley during most of the Holocene, but very diverse opinions exist as to when this local river became connected to the Rhine system (and thereby to a vast hinterland), and whether this was human induced or a natural process. We collected new AMS radiocarbon evidence on the timing of beginning overbank sedimentation along the lower reach of the Gelderse IJssel. Our data indicate onset of overbank sedimentation at about 950 AD in this reach. We attribute this environmental change to the establishment of a connection between the precursor of the IJssel and the Rhine system by avulsion. Analysis of previous conventional radiocarbon dates from the upper IJssel floodplain yields that this avulsion may have started similar to 600 AD. Our results contradict earlier suppositions, based on interpretation of archaeological data and historical accounts, that the Gelderse IJssel is much older and originated as a canal, dug under supervision of the Roman general Drusus

Highway Procurement : Performance-based Contractor Selection

No abstract

Bouwsteen riviermorfologie en -dynamiek Rijntakken t.b.v. het koepelbeheerplan natura2000 rivierengebied

Voor de Natura2000 gebieden Rijntakken wordt een koepelbeheerplan opgesteld. Dit koepelbeheerplan betreft de habitat- en vogelrichtlijngebieden in het rivierengebied. Specifieke kenmerken van het rivierengebied, zoals de relatie tussen rivierdynamiek, morfologie en de Natura2000 doelen worden uitgewerkt in het koepelplan. Dit document is één van de bouwstenen daarvoor. De volgende onderdelen komen in deze bouwsteen achtereenvolgens aan de orde: * Een indeling van de Rijntakken in riviertrajecten met een korte beschrijving van de belangrijkste morfologische en hydraulische kenmerken; * de kansrijke gebieden voor morfodynamische processen (sedimentatie-erosie); * betekenis van deze specifieke kenmerken (rivierdynamiek) voor de realisatie van de natura2000doelen (abiotische randvoorwaarden); * vanuit de specifieke kenmerken van de riviertakken het aangeven van de potenties voor de belangrijkste N2000-doelstellingen: hardhoutooibos, zachthoutooibos, stroomdalgraslanden, moeras en moerasruigten, pioniervegetaties op slikoever

Boomkwekerij en aardkunde in Nederland

In opdracht van het Planbureau voor de Leefomgeving (PBL) is een verkennend onderzoek uitgevoerd naar het effect van de sector boomkwekerij op de kwaliteiten van het landschap die samenhangen met het reliëf en de bodem. De vraag in dit onderzoek is of er teeltmethoden in de boomkwekerij worden gehanteerd die een grotere impact hebben op bodem en reliëf dan algemeen landbouwkundig gebruik en die leiden tot het beschadigen of verdwijnen van aardkundige kwaliteiten, met name het reliëf

Managing performance design of smart homes

Smart homes are considered a vital technology in an aging society as they compensate for a shortage in care workers. However, often smart homes do not perform well. Performance management is well known in the manufacturing industry but not common in the building industry. The performance approach is the practice of thinking and working in terms of ends rather than means. It is concerned with what a building or a building product is required to do, and not with prescribing how it is to be constructed. Performance based building (PBB) includes amongst others functional briefing and performance assessments. However, an overview of tasks in PBB is lacking and the principle has not yet been applied to smart homes. Aim of this research is to contribute to performance management in the construction of health smart homes by identifying tasks and proposing a task assignment. Tasks are identified by studying the extended reporting of the Performance Based Building Network (PeBBu). In conclusion we may say that PBB of health smart homes primarily differs from traditional building in the way tasks are performed. PBB demands that the client does not design (specify how to build) but restricts himself to specifying why he wants and why he wants it. PBB also demands that the designers and contractors are selected on both price and capabilities. Besides these alterations in how tasks are performed merely two tasks are added. These are the verification of the realized design and the monitoring of performance of the building in use

The best criteria for the selection of contractors in the Dutch construction industry!

Selecting contractors in the Netherlands is often done by the criterion of lowest price. This leads to a lack of innovation and a loss of quality in the construction industry. From the field of Purchasing and Procurement, we learn that there are several theories and processes for finding the best contractor for the execution of a work. One of the steps in those processes is the assessment of the contractors on the basis of specific criteria. Which criteria have to be used depends on the wishes of the client. But what are, in general, the best criteria to use? Assessment on the basis of which criterion or combination of criteria really says something on the quality of the cooperation and the final product? In this research, a comparison is made between the criteria that were found in literature with the criteria that were found during a research in the Dutch construction industry. The aim of this research is to find the best criteria for the selection of contractors in the Dutch construction industry

Partner Selection Criteria for Participation-based Cooperation

The Dutch construction industry is under pressure. In order to answer the expectations set by society, innovations are necessary. The industry stands in need of clients and contractors who find common objectives and work in participation-based cooperation (such as partnering or alliance) in order to stimulate innovation development. On paper, public clients strive for innovative cooperation with their contractors. Yet, many clients and contractors still try to realise their conflicting objectives, which leads to difficulties in the relationship and counteract innovation. Underlying this lack of support for participation-based cooperation is the inadequate knowledge on the criteria public clients must and may set in order to select a suitable partner. This study describes and analyses the selection of a partner for participation based cooperation by a public client. Criteria for partner selection were assessed with a literature review in relation to participation-based cooperation. A hierarchical case study on five project alliances verified these criteria. The study shows that public clients have to reconsider the specification phase in the tendering process. The research indicates that certain additional criteria must be set if the selection of a partner is to succeed. In particular, criteria concerning the potential employees in the participation-based relationship are necessary. It is recognized by the Regieraad Bouw that public clients need wise applications in order to make clear decisions in the tendering process. The result of this study is a practical set of criteria, which can simplify the selection of a suitable partner and which can contribute to the support of participation-based cooperation in the Dutch construction industry

Transaction Costs for Design-Build-Finance-Maintain Contracts

This paper gives insight in how transaction costs arise and how in theory transaction costs can be reduced. A comparison between theory and practice has been made. A study of a case in the Netherlands, the Second Coentunnel showed how transaction costs in practice appear, in which stage of the purchasing process these cost arise and also how transaction costs can be reduced. Cost specifications, handed by the public and private parties, make clear that in every phase of the process the client makes expenses. The client spends the most money during the initiative phase. The private parties start making costs in the first phase of the tender (prequalification). For contractors the most expensive phase is the dialogue phase. Taking all the costs in overview, noticeable is that all of the costs are related to the duration of the different phases of the process and required capacity of personnel. Success factors from theory and practice have been identified in the process in which transaction costs arise. Theory and practice have been compared and resulted in a list of twelve success factors. By implementing these success factors in future projects the expectation is that transaction costs will not be unnecessary high

Risk Allocation in Joint Ventures

The method of risk allocation within joint-ventures differs from project to project. In a jointventure the division of responsibilities and risks is not always clear for the participating parties. At this moment there is no model which can lead the risk allocation to good results within a joint-venture. This study has been developed by conducting a literature study and a case study in order to find a suitable model for risk allocation in joint ventures. Using this model, the parties are more aware of risk allocation and it can serve as a guideline the process of risk allocation, as a result of which the participating actors will be able to get a handle on the process