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Admissible post-wave overtopping flow for persons on a horizontal surface
Get PDFAdmissible wave overtopping is a key parameter in design specifications and also in safety assessments of the crest level of many coastal structures. This paper considers the hazard to people/pedestrians by post-wave overtopping flow over a horizontal surface, like a dike or breakwater crest, or a boulevard. Such flow is given by a flow velocity and a flow thickness. The most recent guideline is given in EurOtop (2018), where a maximum overtopping wave volume of 600 l/m is seen as the admissible or tolerable maximum. But no flow velocities or flow thicknesses are given.
Previous work has been summarised by Sandoval and Bruce (2017) who brought existing fluvial tests on people or human subjects together with data derived from videos of actual overtopping hazard events available from the internet. A graph was developed with stable and unstable combinations of flow velocity and flow depth or thickness.
The paper describes first tests in the Delta Flume of Deltares with a volunteer exposed to wave overtopping hazard on the crest of a dike with wave heights up to 1.8 m. Analysis determines flow velocities and flow thicknesses for stable and unstable situations. Additional tests with the wave overtopping simulator on the crest of a dike are described. In these tests, flow velocities and flow thicknesses were accurately recorded as well as the reaction of a volunteer, guarded by a safety line, on the crest of the dike as well as on the landward slope. These tests gave also stable and unstable situations with known flow velocities and flow thicknesses.
The new data were added to the work of Sandoval and Bruce (2017) and a physically based as well as a simple guideline has been proposed for the transition between stable and unstable situations for people/pedestrians. In general overtopping velocities are allowed of 4 m/s with a flow thickness of 0.2 m, but also a large velocity of 7 m/s with only a flow thickness of 0.1 m. Flow thicknesses are always given without air entrainment
EDITORIAL : Relaunching International Journal of Water Governance (IJWG 2.0)
Get PDFWe proudly relaunch the International Journal of Water Governance. Free to read, free to publish in and peer reviewed as ever, it is now also open to practitioner contributions and commentaries. We (non-exhaustively) lay out some of our key water governance concerns and interests in the interrelationships between nature, society and technology that produce water governance, such as emerging ideas and imaginaries, ‘institutional spaghetti’, representation, recognition and (re)distribution as well as sociotechnical systems. We invite a range of potential approaches but would encourage power-sensitivity in the analysis. Your contributions are most welcome, whether insightful overviews or groundbreaking ideas, no matter how contrarian, as long as they are well argued and based in fact
Virtues of Proximity: The Coordinated Spatial Action of Community Land Trusts
Get PDFWhereas real estate-driven development tends to invest in singular and concentrated sites, resident-led development thrives in scattered patterns. The properties of community land trusts (CLTs) — one of the foremost models of resident-led development whereby land is claimed and used by a community without landlords — are almost always dispersed in a context where every property line is a potential obstacle to development. What these populist landholdings lack in terms of economy of scale is compensated for by virtues of proximity. This article examines the historic phenomena of property scattering and spatial patterns of CLTs across the US, articulating the possibility of designing patterns of scattered landholdings that support the values of resident-led development
The Evolution of Ancient Urban Defense Spaces in Northwest China During the Song–Ming Period
Get PDFBased on the historical geographic database of the cities subordinated to the Ming Great Wall defense system and the Northern Song fortress defense system built by the research team, the history of military settlements in northwest China and their urban defense structure were traced. A comparative analysis of the spatial characteristics of urban defense planning during the Song and Ming Dynasties using settlement morphology data revealed significant differences in urban defense planning in the two eras. Focusing on typical urban settlements that span two historical periods and have continued into the present time, we analyzed continuous space-time slices of ancient urban defense spaces and explored their historical causes using ancient urban maps, local chronicles, and aerial photographs. Finally, the historical evolution sequence of ancient urban defense spaces was determined
Transformation and Stability: The Impact of Women on the Built Environment
Get PDFIn late 19th century, a new form of colonies was established in Ottoman Palestine by Jewish immigrants, mostly from Eastern Europe. This paper will explore the initial four decades of these colonies, from the founding of the first one in 1878 to the beginning of the British Mandate in Palestine in 1918. During these years, the colonies experienced processes of reformation, enlightenment, modernization, and secularization, including advances in women\u27s rights. The new colonies offered architects and entrepreneurs a rare opportunity to plan and implement a host of innovative ideas. Baron Edmond de Rothschild, a key figure in the colonies\u27 development, hired architects and other professionals and promoted the education of young women. Public space in the colonies became a significant place where women were able to negotiate social change. This paper will present a few case studies of public spaces in the colonies -- streets, gardens, bathhouses, and synagogues: the ways they were planned and how they were transformed over time. Based on new archival materials, I will discuss topics such as work and education, water and hygiene, body and beauty, and the way women impelled changes in public space
Habiter l’Habitat: Towards an ecological urban lexicon
No full textThe paper is focused on the interdisciplinary and cross-cultural paradigm of “habitat” - as anthropological and ecological interdependency between domestic space and its environment.
Since the mid 20th Century, our built environment has faced a long totalising-planetary urbanisation process, which urges us to review the old conventional urban-architectural categories we use to describe and understand our cities and countryside. In front of the urgency of a more inclusive understanding of our built environment, this paper sheds more light on the paradigm of Habitat as an interdisciplinary urban lexicon, as it gained momentum in post-war urban thinking and has influenced urban design ever since.
The paper holds that the post-war discussion on Habitat represented a unique moment in which interdisciplinary thinking on the built environment became central. The paper shows alliances and resonances between the post-war CIAM’s discourse on Habitat and other coeval sociological and philosophical studies to delineate a complex theoretical framework. Beyond the parameters and boundaries that have been considered and presumed conventionally within ordinary urban design and social science, the paper focuses on the complex interdisciplinary meanings, interpretations, and translations regarding the paradigm of post-war Habitat as a complex social and spatial notion which encompasses the human settlement as a whole
Building latent segments of goods to improve shipment size modelling: Confirmatory evidence from France
Get PDFFreight transport demand models are generally based on administrative commodity type segmentation which are usually not tailored to behavioral freight transport demand modelling. Recent literature has explored new approaches to segment freight transport demand, notably based on latent class analysis, with promising results. In particular, empirical evidence from road freight transport modelling in Germany hints at the importance of conditioning and handling constraints as a sound basis for segmentation. However, this literature is currently sparse and based on small samples. Before it can be accepted that conditioning should be integrated in the state-of-the-art doctrine of freight data collection and model specification, more evidence is required. The objective of this article is to contribute to the issue. Using detailed data on shipments transported in France, a model of choice of shipment size with latent classes is estimated. The choice of shipment size is modelled as a process of total logistic cost minimization. Latent class analysis leverages the wide range of variables available in the dataset, to provide five categories of shipments which are both contrasted, internally homogenous, and directly usable to update freight collection protocols. The groups are: "‘standard temperature-controlled food products"’, "‘special transports"’, "‘bulk cargo"’, "‘miscellaneous standard cargo in bags"’, "‘palletised standard cargo"’. This segmentation is highly consistent with the empirical evidence from Germany and also leads to better estimates of shipment size choices than administrative segmentation. As a conclusion, the finding that conditioning and handling information is essential to understanding and modelling freight transport can be regarded as more robust
Flight Delays in Germany: a Model for Evaluation of Future Cost Risk
Get PDFAir traffic has been increasing in Germany over the last decades reaching in 2018 an all-time high with more than 3 million flights. This increase has led to a rise in delays, which generate different costs to airlines, passengers, and Air Navigation Service Providers. This paper focuses on understanding and predicting these costs. For this purpose, a stochastic modelling method is proposed to estimate future air traffic, delays and the cost of future delays. The model allows to better understand what the full distribution of the delay costs may look like. To that end, the paper analyses 1,826 daily items (from 1/1/2014 to 12/31/2018) with information of air traffic and delays for German airspace. Findings suggest that overall mean delay costs for 2019 may be up to 280 million €, while in the 5% worst cases this value could go up to an average of 319 million €
Airport classification in Chinese multi-airport regions: An interaction network perspective between aviation and high-speed rail
Get PDFThe agglomeration of airports into multi-airport regions (MARs) has become one of the salient features of the worldwide air transport system in the last decades. Meanwhile, in China, the development of HSR is growing quickly, and is both competitive to and cooperative with the aviation network. To date some research has focused on the airport classification with aviation network properties within the specific MARs. However, little research comprehensively integrates complementary transport systems (such as civil aviation versus high-speed rail (HSR)) into the analytical framework for airport classification. The purpose of this paper is to identify the unique nature of component airports and their distribution in MARs in China from multiple perspectives by accounting for the influence of the HSR system. Airports are classified along multiple dimensions including competitive concentrations, the interaction between air transport and HSR, and airport community structure, among others. The results produce distinct partitions of the component airports in Chinese MARs, and provide insights into Chinese airport functionality and impacts of the HSR network on the distribution of different types of airports. The conclusions provide a more comprehensive assessment of airports’ spatial arrangement in the unique Chinese MAR context. Although this paper did not derive the market share allocation and co-opetition relationship between a specific airport and HSR, it proposed a basic framework for future research