Modeling the Effects of Introducing Low Impact Development in a Tropical City: a Case Study from Joinville, Brazil

In tropical countries like Brazil, fast and uncontrolled urbanization, together with high rainfall intensities, makes flooding a frequent event. The implementation of decentralized stormwater controls is a promising strategy aiming to reduce surface runoff and pollution through retention, infiltration, filtration, and evapotranspiration of stormwater. Although the application of such controls has increased in the past years in developed countries, they are still not a common approach in developing countries, such as Brazil. In this paper we evaluate to what extend different low impact development (LID) techniques are able to reduce the flood risk in an area of high rainfall intensities in a coastal region of South Brazil. Feasible scenarios of placing LID units throughout the catchment were developed, analyzed with a hydrodynamic solver, and compared against the baseline scenario to evaluate the potential of flood mitigation. Results show that the performance improvements of different LID scenarios are highly dependent on the rainfall events. On average, a total flood volume reduction between 30% and 75% could be achieved for seven LID scenarios. For this case study the best results were obtained when using a combination of central and decentral LID units, namely detention ponds, infiltration trenches, and rain gardens.(VLID)2512613Version of recor

Morphogenesis of Urban Water Distribution Networks: A Spatiotemporal Planning Approach for Cost-Efficient and Reliable Supply

Cities and their infrastructure networks are always in motion and permanently changing in structure and function. This paper presents a methodology for automatically creating future water distribution networks (WDNs) that are stressed step-by-step by disconnection and connection of WDN parts. The associated effects of demand shifting and flow rearrangements are simulated and assessed with hydraulic performances. With the methodology, it is possible to test various planning and adaptation options of the future WDN, where the unknown (future) network is approximated via the co-located and known (future) road network, and hence different topological characteristics (branched vs. strongly looped layout) can be investigated. The reliability of the planning options is evaluated with the flow entropy, a measure based on Shannon’s informational entropy. Uncertainties regarding future water consumption and water loss management are included in a scenario analysis. To avoid insufficient water supply to customers during the transition process from an initial to a final WDN state, an adaptation concept is proposed where critical WDN components are replaced over time. Finally, the method is applied to the drastic urban transition of Kiruna, Sweden. Results show that without adaptation measures severe performance drops will occur after the WDN state 2023, mainly caused by the disconnection of WDN parts. However, with low adaptation efforts that consider 2–3% pipe replacement, sufficient pressure performances are achieved. Furthermore, by using an entropy-cost comparison, the best planning options are determined

Enabling Efficient and Sustainable Transitions of Water Distribution Systems under Network Structure Uncertainty

This paper focuses on the performance of water distribution systems (WDSs) during long-term city transitions. A transition describes the pathway from an initial to a final planning stage including the structural and functional changes on the infrastructure over time. A methodology is presented where consecutive WDSs under changing conditions are automatically created, simulated and then analyzed at specific points in time during a transition process of several decades. Consequential WDS analyses include (a) uncertain network structure, (b) temporal and spatial demand variation and (c) network displacement. With the proposed approach, it is possible to identify robust WDS structures and critical points in time for which sufficient hydraulic and water quality requirements cannot be ensured to the customers. The approach is applied to a case study, where a WDS transition of epic dimensions is currently taking place due to a city relocation. The resulting necessity of its WDS transition is modelled with automatically created planning options for consecutive years of the transition process. For the investigated case study, we tested a traditional “doing-all-at-the-end” approach, where necessary pipe upgrades are performed at the last stages of the transition process. Results show that the sole design of the desired final-stage WDS is insufficient. Owing to the drastic network deconstruction and the stepwise “loss of capacity”, critical pipes must be redesigned at earlier stages to maintain acceptable service levels for most of the investigated future scenarios

Impact of hybridwater supply on the centralised water system

Traditional (technical) concepts to ensure a reliable water supply, a safe handling of wastewater and flood protection are increasingly criticised as outdated and unsustainable. These so-called centralised urban water systems are further maladapted to upcoming challenges because of their long lifespan in combination with their short-sighted planning and design. A combination of (existing) centralised and decentralised infrastructure is expected to be more reliable and sustainable. However, the impact of increasing implementation of decentralised technologies on the local technical performance in sewer or water supply networks and the interaction with the urban form has rarely been addressed in the literature. In this work, an approach which couples the UrbanBEATS model for the planning of decentralised strategies together with a water supply modelling approach is developed and applied to a demonstration case. With this novel approach, critical but also favourable areas for such implementations can be identified. For example, low density areas, which have high potential for rainwater harvesting, can result in local water quality problems in the supply network when further reducing usually low pipe velocities in these areas. On the contrary, in high demand areas (e.g., high density urban forms) there is less effect of rainwater harvesting due to the limited available space. In these high density areas, water efficiency measures result in the highest savings in water volume, but do not cause significant problems in the technical performance of the potable water supply network. For a more generalised and case-independent conclusion, further analyses are performed for semi-virtual benchmark networks to answer the question of an appropriate representation of the water distribution system in a computational model for such an analysis. Inappropriate hydraulic model assumptions and characteristics were identified for the stated problem, which have more impact on the assessments than the decentralised measures

A Century of Topological Coevolution of Complex Infrastructure Networks in an Alpine City

In this paper, we used complex network analysis approaches to investigate topological coevolution over a century for three different urban infrastructure networks. We applied network analyses to a unique time-stamped network data set of an Alpine case study, representing the historical development of the town and its infrastructure over the past 108 years. The analyzed infrastructure includes the water distribution network (WDN), the urban drainage network (UDN), and the road network (RN). We use the dual representation of the network by using the Hierarchical Intersection Continuity Negotiation (HICN) approach, with pipes or roads as nodes and their intersections as edges. The functional topologies of the networks are analyzed based on the dual graphs, providing insights beyond a conventional graph (primal mapping) analysis. We observe that the RN, WDN, and UDN all exhibit heavy tailed node degree distributions [P(k)] with high dispersion around the mean. In 50 percent of the investigated networks, P(k) can be approximated with truncated [Pareto] power-law functions, as they are known for scale-free networks. Structural differences between the three evolving network types resulting from different functionalities and system states are reflected in the P(k) and other complex network metrics. Small-world tendencies are identified by comparing the networks with their random and regular lattice network equivalents. Furthermore, we show the remapping of the dual network characteristics to the spatial map and the identification of criticalities among different network types through co-location analysis and discuss possibilities for further applications

Transformation der Stadtentwässerung unter Berücksichtigung von „grüner“ und „blauer“ Infrastruktur

Neue Bestrebungen in der Siedlungswasserwirtschaft zielen darauf ab, leitungsgebundene („graue“) Wasserinfrastruktur und die damit verbundene rasche Ableitung von Niederschlagswasser zu vermeiden. Neben einer Annäherung an den natürlichen Wasserkreislauf besteht die Erwartung, dass „grün-blaue“ Konzepte flexibler und robuster hinsichtlich zukünftiger Veränderungen, wie Klimawandel oder Urbanisierung, sind. In dieser Arbeit wird ein möglicher Übergang von grauer (traditioneller) zu grün-blauer Infrastruktur anhand der Stadt Kiruna (Schweden) untersucht, in der in den nächsten Jahrzehnten eine große Stadtumwandlung bevorsteht und die Implementierung von dezentralen (grün-blauen) Entwässerungsanlagen angestrebt wird. Dabei wird die hydraulische Leistungsfähigkeit des städtischen Entwässerungssystems über die Zeit anhand von unterschiedlichen Implementierungsmaßstäben grün-blauer Infrastruktur sowie unter Berücksichtigung von zukünftigen Unsicherheiten (zufolge Klimawandel und Urbanisierung) untersucht. Im Zuge der Umwandlung werden die Systeme mit den verfolgten Strategien über die Zeit bewertet und ermöglichen dem Planer einen Vergleich der Systemvarianten und die Identifizierung von kritischen Zuständen. Zudem soll eine robuste Systemvariante ermittelt werden, welche unter einer großen Bandbreite möglicher zukünftiger Entwicklungen ihre Funktionsfähigkeit beibehält. Der entwickelte generische Ansatz stellt eine Methodik zur Beurteilung jeglicher Stadttransformationsprozesse und deren Auswirkungen auf die Wasserinfrastruktur dar (bspw. Stadtwachstum, Absiedlung, Umsiedlung etc.).New urban water resources management approaches aim to move away from pipeline-based (gray) water infrastructures and the associated rapid drainage of stormwater runoff. As well as coming closer to the natural water cycle, the “green-blue” concept is expected to be more flexible and robust in the context of future developments such as climate change and urbanization. This study investigates a possible transition from a gray (conventional) to a green-blue infrastructure, based on the example of Kiruna Municipality (Sweden), which will undergo a major transition to a decentralized (green-blue) drainage system over the next few decades. It examines the hydraulic capacity of the urban drainage system over time and in connection with various measures for implementing green-blue infrastructures, taking into account future uncertainties (as a result of climate change and urbanization). In the course of the transition, the systems are evaluated for different strategies, allowing planners to compare planning alternatives and to identify critical situations. In addition, a robust system is identified that will retain its functionality in a wide range of possible future scenarios. The generic approach developed here offers a new method for evaluating these urban transition processes and their impact on the water infrastructure (e.g. urban growth, resettlement, relocation etc.).(VLID)456930