Nature-based solutions (NBSs) are often considered to be cure-all remedies for mitigating risks arising from climate change, among others. This study explores the failure modes of NBSs in stormwater management, and analyses challenges across the different stages of their life cycles, including planning, design, and operation. The PRISMA methodology was applied to carry out a systematic literature review to identify the main triggers, consequences and potential mitigation measures for different failure modes and challenges, with a view to enhancing the long-term performance of NBSs. Each identified failure mode was classified along the three typological dimensions of severity, origin and preventability, with sub-dimensions for qualitative and quantitative analysis. Based on 76 reviewed studies, it was concluded that preventable and intrinsic failures dominate the early stages (planning and design), whereas induced and extrinsic failures tend to manifest during operation and maintenance. The application of interdisciplinary and catchment-scale thinking in planning reduces the probability and severity of failure in the design and operation stages. Standardised and data-based approaches are needed to mitigate NBS failures throughout the life cycle.

Der vorliegende Forschungsbericht befasst sich mit den derzeitigen Unsicherheiten bezüglich der technischen Nutzungsdauer und des Alterungsverhaltens der gängigsten Renovierungsmethode in Kanalnetzen, dem Cured in Place Pipe (CIPP) Schlauchlining. Ziel dieser Arbeit ist die Entwicklung einer fundierten Datengrundlage für eine Schlauchliner-Überlebenskurve für die Anwendung in Alterungsmodellen. Das methodische Vorgehen umfasst (i) eine Literaturrecherche, (ii) Interviews mit Kanalsanierungs-Expert:innen sowie (iii) eine Auswertung von Daten der Berliner Wasserbetriebe zur Erstellung einer aktualisierten und geeigneten Datengrundlage für die Überlebenskurven. Dabei zeigen sich in der Auswertung der Literatur und den Interviews mehrheitliche Schätzungen der Nutzungsdauer von Schlauchlinern von über 50 Jahren. Die Untersuchung zeigt jedoch auch, dass diese von vielen Faktoren beeinflusst ist und ein Mangel an belastbaren Daten besteht. Weitere Untersuchungen an langjährig betrieben Schlauchlinern sind daher zwingend notwendig. Der Einbau, insbesondere der Aushärtungsprozess hat sich als Haupteinfluss für Defekte und Mängel an Schlauchlinern gezeigt. Eine Standardisierung der Schadenserfassung und Zustandsbeurteilung von schlauchlinerspezifischen Schäden sowie die Etablierung zerstörungsfreier Inspektionsmethoden sind erforderlich, um das Alterungsverhalten zukünftig besser zu verstehen. Empfehlungen umfassen die Verbesserung der Datenerhebung während des Betriebs, Ein- und Ausbaus von Schlauchlinern, die Erweiterung der Qualitätssicherung beim Einbau, sowie die Untersuchung von Schadenseinflüssen auf die Nutzungsdauer und den Erfahrungsaustausch zwischen Betreibern.

Addressing Europe's current challenges of aging sewer networks, the presented research focuses on the uncertainties in service life and aging behavior of the most used renovation technique, Cured in Place Pipe (CIPP) lining. Examining its aging behavior, common defects and deficiencies were analyzed through literature review and expert interviews. The findings influenced the proposition of a calibration setting for a deterioration model using survival curves. Identified defects stress the need for precise installation and curing processes. The study recommends a thorough review of the initially specified 50-year service life, acknowledging uncertainties during the installation process.

Extending the AI-driven Software SEMAplus with a risk prioritization module.

Selection and analysis of risk criteria as preliminary part of decision making.

Analysis of multicriteria decision approaches and choice of ELECTRE TRI.

During the last decades, municipalities have increasingly invested in new approaches for rehabilitating sewerage networks. With the increasing number of rehabilitation techniques, objectives and constraints, the number of rehabilitation scenarios rises exponentially. This article proposes an asset management approach to create long-term rehabilitation plans where different budget allocations for rehabilitation techniques are considered every year depending on performance and cost indicators. It builds long-term strategies through multiobjective black-box optimization where the impact of the budget allocations over the network life cycle is part of the decision process. It employs a pipe deterioration model based on Markov chains whose transition matrices are estimated by survival curves for different pipe cohorts. The proposed approach seeks to determine the appropriate investment (CAPEX) and operational expenses (OPEX) levels in the coming decades. It was tested with real-world data from a sewerage network in Sofia, Bulgaria, and the results show that it provides efficient long-term rehabilitation plans.

Smart water management is acknowledged as a key component of the solutions to address climate change impact and secure water resources availabilities in the context of Sustainable Development Goals. Over the last decades, digital solutions have become an essential part of water management. Numerous initiatives have been developed to explore hybrid and new AI modeling with concrete approaches such as digital twins. The ambition is to provide water managers with tailored IT solutions that can be implemented in their current management system. These developments raise a wide range of questions in terms of sensors’ approach, interoperable open data models, reference architecture, and cybersecurity that are presented in this chapter. Additionally, IT innovation, as groundbreaking as it may be, requires additional dimensions such as governance, capacity building, and economics to ensure its adoption by water managers. These aspects are also presented in the latest sections of this chapter.