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Urban water infrastructure, i.e., water supply and sewer networks, are underground structures, implying that detailed information on their location and features is not directly accessible, frequently erroneous, or missing. For public use, data is also not made available due to security concerns. This lack of quality data, especially for research purposes, requires substantial effort when such data is sought for both statistical and model-based analyses. An alternative to gathering data from archives and observations is to extract the information from surrogate data sources (e.g., the street network). The key for such an undertaking is to identify the common characteristics of all urban infrastructure network types and to quantify them. In this work, the network correlations of the street, water supply, and sewer networks are systematically analyzed. The results showed a strong correlation between the street networks and urban water infrastructure networks, in general. For the investigated cases, on average, 50% of the street network length correlates with 80%-85% of the total water supply/sewer network. A correlation between street types and water infrastructure properties (e.g., pipe diameter) cannot be found. All analyses are quantified in the form of different geometric-and graph-based indicators. The obtained results improve the understanding of urban network infrastructure from an integrated point of view. Moreover, the method can be fundamental for different research purposes, such as data verification, data completion, or even the entire generation of feasible datasets.

One of the major tasks in urban water management is failure-free operation for at least most of the time. Accordingly, the reliability of the network systems in urban water management has a crucial role. The failure of a component in these systems impacts potable water distribution and urban drainage. Therefore, water distribution and urban drainage systems are categorized as critical infrastructure. Vulnerability is the degree to which a system is likely to experience harm induced by perturbation or stress. However, for risk assessment, we usually assume that events and failures are singular and independent, i.e. several simultaneous events and cascading events are unconsidered. Although failures can be causally linked, a simultaneous consideration in risk analysis is hardly considered. To close this gap, this work introduces the term cascade vulnerability for water infrastructure. Cascade vulnerability accounts for cascading and simultaneous events. Following this definition, cascade risk maps are a merger of hazard and cascade vulnerability maps. In this work cascade vulnerability maps for water distribution systems and urban drainage systems based on the 'Achilles-Approach' are introduced and discussed. It is shown, that neglecting cascading effects results in significant underestimation of risk scenarios.

The dynamics of an actively controlled fluidic diverter with novel actuation method are presented. This bistable fluidic valve is based on the Coanda effect and is able to switch the main flow solely by means of acoustic excitation. The switching is explained through a combination of experiments and large eddy simulations (LES). The switching time and minimum energy required are characterized for a range of pressure ratios, acoustic excitation frequencies, and input powers. It is shown that the switching mechanism depends on the excitation of natural instabilities inside the free shear layer. An enhanced roll-up of vortices at the excitation frequency increases the rate of entrainment and results in a transverse pressure gradient sufficient to counteract the Coanda effect leading to jet detachment and switching.

Sensitivity analysis (SA) evaluates the impact of changes in model parameters on model predictions. Such an analysis is commonly used when developing or applying environmental models to improve the understanding of underlying system behaviours and the impact and interactions of model parameters. The novelty of this paper is a geo-referenced visualization of sensitivity indices for model parameters in a combined sewer model using geographic information system (GIS) software. The result is a collection of maps for each analysis, where sensitivity indices (calculated for model parameters of interest) are illustrated according to a predefined symbology. In this paper, four types of maps (an uncertainty map, calibration map, vulnerability map, and design map) are created for an example case study. This article highlights the advantages and limitations of GIS-based SA of sewer models. The conclusion shows that for all analyzed applications, GIS-based SA is useful for analyzing, discussing and interpreting the model parameter sensitivity and its spatial dimension. The method can lead to a comprehensive view of the sewer system.

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Keywords: street network; water supply network layout algorithms; case unspecific water supply models; water supply network design algorithms; ABSTRACTDeveloping a water distribution infrastructure is a challenging task. Therefore, the presence of layout and design algorithms is crucial. In this work a water supply network layout generation algorithm is investigated, which is able to generate huge sets of case unspecific water supply networks with different characteristics controlled by three parameters. As input as few as possible and easy accessible data sets are used. The algorithm is applied to an Alpine case study with 130,000 inhabitants. The generated water supply models are used as input for systematically testing a water supply network design algorithm. Results show that the investigated water supply network generation algorithm is able to create realistic networks with different characteristics and they can be used as benchmark set for newly developed water supply network design algorithms (e.g. pipe sizing) to identify weak points in the strategy, robustness, runtime of the algorithm.