To manage sewer networks, reliable data is needed, which is often challenging. This study proposes a novel methodology to reconstruct the sewer network topology using graph theory. Two core procedures—flow adjustment and edge addition—re-establish hydraulically consistent flow paths and restore connectivity in disconnected portions of the network by reversing and adding links. The proposed approach operates at the pipe level, repairing directional reachability. It leverages only the existing network topology to reconstruct connectivity, guided by the principle that every node must have a downstream path to an outlet. The methodology is first applied to reconstruct the sewer network of Montpellier Metropolis in the South of France. Then it is validated by deliberately removing and reversing edges and applying the algorithms to test the methodology’s capability in recovering the correct topology. Both methods performed well individually, especially at lower percentages of reversal (1%) and removal (1%), with a correctness of 0.99 for flow adjustment and 0.8 for edge addition. Although the results were poorer when combining the methods and increasing data degradation—particularly at 10% reversal and 10% removal (correctness of 0.64)—the methodology continued to produce a functionally consistent and logically coherent network, highlighting its robustness given the absence of supporting attribute data.

Wastewater network management is being digitised and integrated across municipalities. A shared understanding and terminology of the systems is important both for modern urban water management and modelling climate-induced stressors on the network. Ontologies are a well-known mechanism to record the shared understanding. While several ontologies exist that focus on the water, and several exist on service infrastructure, there is a gap in the ontology landscape about wastewater services infrastructure. We are currently developing an ontology about wastewater networks and a first version is publicly available at http://sewernet.hsm.umontpellier.fr/. Key aims for the use of the ontology in our project are data integration, ontology-based query answering the detect incoherent data in wastewater network databases, and document annotation, but, it being a domain ontology, SewerNet is usable also for other types of ontology-mediated information systems. In this talk, we focus on interesting discrepancies and lack of clarity in non-ontological resources we used for the development, such as the INSPIRE EU directive and the RAEPA geostandard, that needed to be harmonised in the ontology. Examples include pipe versus conduit, disambiguation between maintenance plans and individual repair actions, precision/uncertainty in the measurements, circulation mode. The use of a foundational ontology (DOLCE) to assist structuring content was perceived beneficial, as well as the ontological questions to align to the DOLCE entities, which helped probing the nature of the entity and elucidate assumptions about terms.

In sewer networks, adding a new element involves multiple phases, including planning, installation, and ongoing maintenance. At each stage of the element's lifecycle—whether it is a pipe, a structure, or an apparatus—different stakeholders and experts are involved. Due to variations in data practices, maintaining accurate and standardized data becomes a significant challenge. However, managing these networks requires consistent and reliable data to ensure effective decision-making and operational efficiency.These imperfections can stem from various reasons, including discrepancies in data collection methods, outdated or incomplete documentation, and human errors during data entry. Additionally, the integration of data from diverse sources, such as GIS systems, maintenance reports, and sensor networks, often lead to inconsistencies and redundancies, complicating data processing and analysis.For large datasets, which are common in sewer networks, it becomes increasingly difficult to identify and address inconsistencies. To address this, we built an Ontology-Based Data Access (OBDA) system which provides a unified semantic view of the data facilitating data access and integration. The system consists of a conceptual layer that provides the controlled vocabulary of sewer networks, a data layer where Montpellier Metropole open data is stored in relational databases, and a mapping layer between the two. Through this framework, common inconsistencies were identified such as missing node connections, duplicate entries, and conflicting attribute values for a specific dataset.

Urban sewer networks are critical infrastructures that support residents' everyday life and ensure the collection and transportation of wastewater and stormwater. Yet operational datasets describing these networks are frequently imperfect: pipes may be missing, connectivity may be fragmented, and flow direction may be inconsistent due to incomplete attributes (e.g., invert levels, slope) or digitizing errors. We present a topology-focused study that transforms sewer data into a directed network by combining (i) graph-based representation and (ii) geometry-based consistency checks and rules. Starting from a directed (multi)graph built from available pipe and node geometries, which represent the edges and nodes in the graph, we detect topological anomalies including disconnected components, missing connections, dead ends, and closed loops.When two pipes converge at a manhole with no outgoing pipe, it forms a non-outlet sink. To resolve this, we apply a two-stage methodology: edge orientation to reduce flow inconsistencies and resolve any sink nodes, followed by targeted edge addition to reconnect remaining disconnected components when reversals alone are insufficient. We test feasibility of the approach on a large open-access urban sewer dataset. The results illustrate how topology-oriented methods can still be applied to establish a well-connected network when data attributes are missing or unreliable.

1. Climate change and urbanisation are placing increasing stress on the infrastructure, posing a challenge for upholding the services (Fontecha et al. 2020, Hughes et al. 2021). Among these assets,...