Damien Serre

Évaluation des ouvrages hydrauliques de génie civil

This paper reviews Cemagref (Centre national du machinisme agricole, du genie rural, des eaux et des forets) research on assessment of hydraulic works, especially on their performance and safety. A generic functional model has been developed, using reliability methods, to represent the various mecanisms acting on different hydraulic works (gravity and embankment dams, fluvial dikes, etc.). Collecting and analyzing data on the failure of these works allowed us to define structural indicators and the rules for their assessment. Performance indicators for hydraulic works were created through multicriteria aggregation methods; various results were thus obtained. A database of knowledge relating to mechanisms and histories of dam ageing has been produced and constitutes a useful aid for consulting civil engineers. Methods and tools have been developed to assess the performance of fluvial dikes and to assist managers in planning maintenance operations. Similar research is under way on embankment dams and will p...

Improving the Conditions for Urban Resilience through Collaborative Learning of Parisian Urban Services

The concept of urban resilience has taken a leading edge by incorporating the multiscalar interactions within an urban system, revealing the short- and long-term impacts, spatial dependencies, and inequalities. The issue now is to enable local authorities and urban stakeholders to grasp and apply the resilience approach. Technical networks and urban services supporting urban development (drinking water supply, public transportation, etc.) are an interesting case study to apply the resilience concept. The urban resilience approach, tested with the managers of service provision in the City of Paris, demonstrates the effectiveness of integration and collaboration. First, an autodiagnosis realized with each manager identifies the service dependencies and its capacity for continuous operation in case of disturbance. Then workshops raise manager awareness of their interdependencies and feed the discussion toward technical and organizational solutions in an integrated approach. This macroscopic analysis is then completed by a territorial assessment of urban service resilience. In doing so, the spatial and temporal dimensions emphasize gaps but also margins of manoeuver in managing resilient urban services. Our results show that manager strategies can be focused on protection, adaptation, or recovery of their service. However, these are sometimes contradictory and threaten the resilience of the whole system. Indeed, in highlighting the different strategies set up by managers, the region’s resilience can be discussed at different scales: the urban service, the system of urban services, the City of Paris, and the Parisian metropolis. Then we emphasize the difficulties in applying the resilience concept and suggest solutions to improve the conditions for urban resilience and sustainability.

Decision-making method for assessing performance of large levee alignment

Levees are large alignment civil engineering works with a performance that is assessed with great difficulty due to its longitudinal variability. We hereby suggest that a decision-making support procedure should be identified, built and implemented so as to split levee alignments into homogeneous sections and identify them according to their performance level. Our work is focused on defining actions for the purpose of solving the decision-making problem with regard to large alignment works. In order to select a suitable decision-making method, we suggest a formulation and a comparison between two types of multi-criteria methods: the ELECTRE TRI outranking method and a unicriterion method. The relevance of building a unicriterion for the purpose of our study is investigated considering the existing operational interconnections between the levee evaluation criteria. Les digues sont des ouvrages de génie civil à grand linéaire dont la performance est difficile à évauler parce que très variable longitudinalement. Dans cet article, nous proposons l’identification, la construction et la mise en œuvre d’une démarche d’aide à la décision permettant le découpage des linéaires de digues en tronçons homogènes, et leur identification par niveau de performance. Notre travail examine avec attention la question de la définition des actions objets de l’aide à la décision pour des ouvrages à grands linéaires. Pour le choix d’une méthode d’aide à la décision, nous proposons une formulation et une comparaison de deux types de méthodes multicritères : la méthode surclassement ELECTRE TRI et une méthode du critère unique de synthèse. Nous examinons l’intérêt de la construction d’un critère unique de synthèse pour notre recherche du fait des liens fonctionnels existants entre les critères d’évaluation des digues.

A methodology to produce interdependent networks disturbance scenarios .

Quick urban development coupled with technical failures and climate change have increased flood risk and corresponding challenges to urban flood risk management. In this context, there is a need to understand how networked systems are resilient because societal functions are highly dependent on networked systems and the operability of these systems can be vulnerable to disasters. That is why we develop a methodology for producing interdependent networks disturbance scenarios. In order to take advantage of this methodology software is needed.

Assessing Vulnerability to Floods of the Built Environment-Integrating Urban Networks and Buildings

The EU is very concerned by flood risk. The effects of floods on urban areas are substantial in terms of damage and economic loss. It is expected, taking into account climate change and urban growth, that this particular risk will be more frequent and will cause more and more damage; the built environment has become very vulnerable to floods. There is a need to develop methods and tools to assess urban vulnerability to floods. Indeed, some solutions are already available to assess vulnerability of buildings or infrastructure such as networks. But, the city is a complex system and not just a sum of its components. Our purpose is about developing techniques to assess the vulnerability of the city using a systematic approach and integrating existing tools which assess the vulnerability of particular components of the city system.

Assessing quick wins to protect critical urban infrastructure from floods: a case study in Bangkok, Thailand

This paper focuses on the vulnerability and protection of critical urban infrastructure from flooding. It presents a pragmatic and rapid screening procedure, referred to as a “Quick Scan”. The purpose of the Quick Scan is to provide guidance for network operators and decision makers on identifying and rating those critical infrastructure networks and hot spot buildings that may be at risk from flooding and assessing where intervention will be most feasible and cost beneficial – the so-called “quick wins”. This approach will support the development of effective interventions to alleviate direct and indirect flood impacts. Workshops and interviews with stakeholders and experts have been organised in the pilot cities Bangkok, Paris, and Dordrecht to test and further develop the Quick Scan and to obtain feedback and lessons learned for the protection of critical urban infrastructure. This paper presents the findings of the stakeholder workshops carried out in the city of Bangkok.

Levee performance evaluation based on subjective probabilities

Abstract Levees are large alignment works on which only imperfect information are usually available. In this particular context, a probability-based model is suggested for evaluating the levee performance, taking into account imperfect data in a probabilistic format. Such a model will implement subjective probabilities that have been elicited by expert assessment to evaluate all criteria and uncertainties thereof. Based on a deterministic model of multicriteria aggregation and using Monte Carlo simulations, this will ultimately help build probability distributions for the performance indicator and for each levee section. The benefit of this model is to determine how much an evaluation may be trusted and to help decide which technical actions should be taken to improve a levee section performance. Résumé: Les digues sont des ouvrages à grands linéaires pour lesquels on ne dispose généralement que d’informations imparfaites. Dans ce contexte, on propose un modèle probabiliste d’évaluation de la performance des digues permettant la prise en compte des données imparfaites sous format probabiliste. Ce modèle met en œuvre des probabilités subjectives élicitées par jugement expert pour l’évaluation des critères et de leurs incertitudes. Sur la base d’un modèle déterministe d’agrégation multicritère et au moyen de simulations de Monte Carlo, il permet au final de construire des distributions de probabilité pour l’indicateur de performance et pour chaque tronçon de digue. Ce modèle présente les avantages d’apprécier la confiance qui peut être accordée à une évaluation et de guider le choix des actions techniques pour améliorer la performance d’un tronçon de digue.

Urban Flood Mitigation: Sustainable Options

Cities have started to anticipate the effects of global warming dealing with flood management. Indeed, it seems that this last decade, flood risk has increased and cities are facing on the one hand more frequent hazards, and on the other hand different types of flooding: fluvial, coastal, estuarial and pluvial. Most cities have to manage at least two of these flooding types. At the same time, flood risk management practices have changed step-by-step. Indeed, despite efforts made to maintain the flood defense assets well, we often observe failures leading to finally increase flood risk in protected areas during major flood events. Moreover, flood forecasting models, although they benefit from continuous improvements, remain partly inaccurate due to uncertainties populated all along data calculation processes. This means cities cannot continue to manage flood risk only by the use of flood defenses: sustainable options have to be designed to better mitigate the effects of flooding in urban area and in a long term strategy. Several European cities have suffered recent flooding events. It was the case for example in 2007 in United Kingdom. During this period, major events came from extreme rainfall and it appears that pluvial flood risk has become one of the most frequent events. In this context, flood risk can appear on every territory: cities have to develop some methods to take into account this new deal, options to achieve urban flood resilience. Some solutions that cities are using or will be able to set up in the near future will be described.

A Spatial Decision Support System Aiding Levee Managers in their Repair and Maintenance Planning

More and more floods occurred over the last two decades causing important damages. Moreover, levees are often not well maintained, so they hardly resist to major floods and can break easily. At French national scale, the length of levees and the lack of data complicate their management. In this frame, levee managers need approaches and tools to be helped in their maintenance decision. First, we have developed a Levee Geographic Information System. This GIS application allows collecting data necessary for managing a levee portfolio. Secondly, we have developed a SDSS to assist levee managers in their prioritizing maintenance activities. This SDSS is using Operational Safety methods to assess levee performance along their length. The SDSS is aggregating performance indicators with a rule-based multi-criteria assignment method. All these tools and methods are operational and now used by levee managers in their regular infrastructure portfolio maintenance.

Making Urban Territories More Resilient to Flooding by Improving the Resilience of Their Waste Management Network: A Methodology for Analysing Dysfunctions in Waste Management Networks during and after Flooding

In view of all the damage caused by flooding that has affected large numbers of regions throughout the world over the last ten years, urban areas appear to be little prepared for facing up to this type of catastrophe. Today, improving their resilience, i.e. their capacity to recover rapidly after flooding, appears to be a real issue at stake in societies’ sustainable development.