Meshness of sewer networks and its implications for flooding occurrence

Reyes-Silva, Julian D.; Helm, Björn; Krebs, Peter

doi:10.2166/wst.2020.070

Cited by 14 publications

(19 citation statements)

References 24 publications

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“…As mentioned before, the general implication with respect to the flooded volume generation indicates that the more branched the network is, the greater the flood volume is produced. This overall finding is in agreement with the relevant studies conducted in the literature [23,24]. However, the variation and fluctuation of the surface flood behavior within all the networks (Figure 3) is attributed to the interplay between total storage volume and flow distribution resulting from the (additional) pipe arrangements.…”

Section: Hydraulic and Design Costs Performance Assessmentsupporting

confidence: 92%

“…However, the variation and fluctuation of the surface flood behavior within all the networks (Figure 3) is attributed to the interplay between total storage volume and flow distribution resulting from the (additional) pipe arrangements. Although this interaction has been indicated in [24] for eight subnetworks of the city of Dresden, systematically analyzing the contribution of system capacity as well as alternative flow path in a single specific network (under hydraulic design) was missing. Thus, the outcome of this section provided a more vivid insight towards the role of achieved capacity and flow direction in one single network, which ultimately extends the previous relevant researches.…”

Section: Hydraulic and Design Costs Performance Assessmentmentioning

confidence: 99%

“…Likewise, the impact of structures of different stormwater networks on the relationship between peak rainfall and runoff (regression model) and their drainage density was studied [23]. Reyes-Silva et al evaluated the functional failures of eight subnetworks of the city of Dresden that have different characteristics in terms of capacity as well as structure [24]. They inferred that networks with more meshed structural characteristics are associated with less flooding volumes and flooding nodes compared to branched ones.…”

Section: Introductionmentioning

confidence: 99%

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Assessing Redundancy in Stormwater Structures Under Hydraulic Design

Hesarkazzazi

Hajibabaei

Reyes-Silva

et al. 2020

Water

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As environmental change is happening at an unprecedented pace, a reliable and proper urban drainage design is required to alleviate the negative effects of unexpected extreme rainfall events occurring due to the natural and anthropogenic variations such as climate change and urbanization. Since structure/configuration of a stormwater network plays an imperative role in the design and hydraulic behavior of the system, the goal of this paper is to elaborate upon the significance of possessing redundancy (e.g., alternative flow paths as in loops) under simultaneous hydraulic design in stormwater pipe networks. In this work, an innovative approach based on complex network properties is introduced to systematically and successively reduce the number of loops and, therefore, the level of redundancy, from a given grid-like (street) network. A methodology based on hydrodynamic modelling is utilized to find the optimal design costs for all created structures while satisfying a number of hydraulic design constraints. As a general implication, when structures are subject to extreme precipitation events, the overall capability of looped configurations for discharging runoff more efficiently is higher compared to more branched ones. The reason is due to prevailing (additional) storage volume in the system and existing more alternative water flow paths in looped structures, as opposed to the branched ones in which only unique pathways for discharging peak runoff exist. However, the question arises where to best introduce extra paths in the network? By systematically addressing this question with complex network analysis, the influence of downstream loops was identified to be more significant than that of upstream loops. Findings, additionally, indicated that possessing loop and introducing extra capacity without determining appropriate additional pipes positions in the system (flow direction) can even exacerbate the efficiency of water discharge. Considering a reasonable and cost-effective budget, it would, therefore, be worthwhile to install loop-tree-integrated stormwater collection systems with additional pipes at specific locations, especially downstream, to boost the hydraulic reliability and minimize the damage imposed by the surface flooding upon the metropolitan area.

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Section: Hydraulic and Design Costs Performance Assessmentsupporting

confidence: 92%

Section: Hydraulic and Design Costs Performance Assessmentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Assessing Redundancy in Stormwater Structures Under Hydraulic Design

Hesarkazzazi

Hajibabaei

Reyes-Silva

et al. 2020

Water

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“…a measure to quantify how close an UDN structure resembles a tree-graph layout (0%) or a grid-like pattern (100%). The values are derived based on the methodology proposed by Reyes-Silva et al (2019.). For example, the networks N3 and N5 have a layout more similar to a branching system, i.e.…”

Section: Case Studiesmentioning

confidence: 99%

Centrality and shortest path length measures for the functional analysis of urban drainage networks

et al. 2020

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The objective of this research is to evaluate whether complex dynamics of urban drainage networks (UDNs) can be expressed in terms of their structure, i.e. topological characteristics. The present study focuses on the application of topological measures for describing the transport and collection functions of UDNs, using eight subnetworks of the Dresden sewer network as study cases. All UDNs are considered as weighted directed graphs, where edge weights correspond to structural and hydraulic pipe characteristics which affect flow. Transport functions are evaluated in terms of travel time distributions (TTDs), under the hypothesis that frequency distributions of Single Destination Shortest Paths (SDSP) of nodes to the outlet had similar shapes than TTDs. Assessment of this hypothesis is done based on two-sample Kolmogorov-Smirnov tests and comparisons of statistical moments. Collection analysis, i.e. determination of flow paths, is done based on two approaches: (1) using Edge Betweenness Centrality (EBC), and (2) based on the number of SDSP going through an edge connecting a node to the outlet, referred as Paths. Hydrodynamic simulation results are used to validate the outcomes of graph analysis with actual flow behaviors. Results indicate that given an appropriate edge weighting factor, in this case Residence Time, SDSP has the potential to be used as an indicator for flow transport in UDNs. Moreover, both EBC and Paths values were highly correlated to average flows. The first approach, however, proved to be inadequate for estimating flows near the outlet but appropriate for identifying different paths in meshed systems, while the second approach lead to better results in branched networks. Further studies regarding the influence of UDNs layout are needed.

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“…In this context, the present research evaluates the variation of urban drainage system structure on the occurrence of CSO events, using a subnetwork of the city of Dresden, Germany as study case. The structure of a network is determined based on the meshness coefficient proposed by Reyes-Silva et al [24]. In this approach, urban drainage networks are interpreted as graphs (G = (E,V)), where the edges (E) correspond to pipe sections, while the nodes (V) are the junctions between them, usually representing manholes.…”

Section: Introductionmentioning

confidence: 99%

The Role of Sewer Network Structure on the Occurrence and Magnitude of Combined Sewer Overflows (CSOs)

Reyes-Silva

Bangura

Helm

et al. 2020

Water

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Combined sewer overflows (CSOs) prevent surges in sewer networks by releasing untreated wastewater into nearby water bodies during intense storm events. CSOs can have acute and detrimental impacts on the environment and thus need to be managed. Although several gray, green and hybrid CSO mitigation measures have been studied, the influence of network structure on CSO occurrence is not yet systematically evaluated. This study focuses on evaluating how the variation of urban drainage network structure affects the frequency and magnitude of CSO events. As a study case, a sewer subnetwork in Dresden, Germany, where 11 CSOs are present, was selected. Scenarios corresponding to the structures with the lowest and with the highest number of possible connected pipes, are developed and evaluated using long-term hydrodynamic simulation. Results indicate that more meshed structures are associated to a decrease on the occurrence and magnitude of CSO. Event frequency reductions vary between 0% and 68%, while reduction of annual mean volumes and annual mean loads ranged between 0% and 87% and 0% and 92%. These rates were mainly related to the additional sewer storage capacity provided in the more meshed scenarios, following a sigmoidal behavior. However, increasing network connections causes investment costs, therefore optimization strategies for selecting intervention areas are needed. Furthermore, the present approach of reducing CSO frequency may provide a new gray solution that can be integrated in the development of hybrid mitigation strategies for the CSO management.

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Meshness of sewer networks and its implications for flooding occurrence

Cited by 14 publications

References 24 publications

Assessing Redundancy in Stormwater Structures Under Hydraulic Design

Assessing Redundancy in Stormwater Structures Under Hydraulic Design

Centrality and shortest path length measures for the functional analysis of urban drainage networks

The Role of Sewer Network Structure on the Occurrence and Magnitude of Combined Sewer Overflows (CSOs)

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