Frédéric Cherqui

Assessing urban potential flooding risk and identifying effective risk-reduction measures.

Flood protection is one of the traditional functions of any drainage system, and it remains a major issue in many cities because of economic and health impact. Heavy rain flooding has been well studied and existing simulation software can be used to predict and improve level of protection. However, simulating minor flooding remains highly complex, due to the numerous possible causes related to operational deficiencies or negligent behaviour. According to the literature, causes of blockages vary widely from one case to another: it is impossible to provide utility managers with effective recommendations on how to improve the level of protection. It is therefore vital to analyse each context in order to define an appropriate strategy. Here we propose a method to represent and assess the flooding risk, using GIS and data gathered during operation and maintenance. Our method also identifies potential management responses. The approach proposed aims to provide decision makers with clear and comprehensible information. Our method has been successfully applied to the Urban Community of Bordeaux (France) on 4895 interventions related to flooding recorded during the 2009-2011 period. Results have shown the relative importance of different issues, such as human behaviour (grease, etc.) or operational deficiencies (roots, etc.), and lead to identify corrective and proactive. This study also confirms that blockages are not always directly due to the network itself and its deterioration. Many causes depend on environmental and operating conditions on the network and often require collaboration between municipal departments in charge of roads, green spaces, etc.

Decision support for sustainable urban drainage system management: A case study of Jijel, Algeria

This paper aims to develop a methodology to support the sustainable management of Urban Drainage Systems (UDSs) in Algeria. This research is motivated by the various difficulties that the National Sanitation Office (ONA) has in managing this complex infrastructure. The method mainly consists of two approaches: the top-down approach and the bottom-up approach. The former facilitates the identification of factors related to a sustainable UDS, the development priorities and the criteria available to managers. The latter assesses UDS performance using the weighted sum method to aggregate indicators or criteria weighted using the Analytical Hierarchy Process (AHP). The method is demonstrated through its application to the UDS in the city of Jijel, Algeria.

Benefits of using basic, imprecise or uncertain data for elaborating sewer inspection programmes

One key goal of sewer inspection programmes is to target segments in the worst condition. Despite the development of deterioration models, the influence of available data on models’ predictive power has not been studied in depth yet. In this article, numerical experiments have been conducted to answer three main questions: (1) How can the data most probably available within a utility be used to define an effective inspection programme? (2) Can we use an auxiliary variable in order to compensate effects of missing data on inspection programmes? (3) Is it worth to accept a degree of uncertainty within data instead of not having them? In other words, is it preferable to have uncertainty instead of incompleteness within utility database? In order to respond to these questions, we considered an asset stock and then degraded the information by introducing uncertainty, imprecision and incompleteness within, to form a utilitys database. The results show that significant improvement of inspection programmes could be achieved by using the most probably available data within utilities. We also show that using the notion of ‘district’ can provide efficient results when the most informative factor ‘age’ is not available. Finally, it is shown that having uncertain data is preferable to having incompleteness.

Condition grading for dysfunction indicators in sewer asset management

Asset management is an increasing concern for the water and wastewater industry. Condition assessment of sewer segments is an important component of sewer asset management and relies mostly on visual inspection. Observed defects are translated into a score for each segment. Although most protocols give a segment a condition grade by comparing its score with a subjective scale of numerical values, we propose a protocol to calibrate thresholds for each asset stock. Thresholds are calculated according to two sets of parameters: overall condition of the asset stock in question (estimated by a representative sample or provided by the utility manager) and assignment-error weighting (determined by the utility manager) linked to either over-estimation or under-estimation of condition grade. This method is applied to 150 km of sewers from the Greater Lyon asset stock. Sensitivity analyses of these parameters are then implemented. Three hypotheses about overall condition of the asset stock are combined with three matrices of assignment-error weights. Both parameters influence thresholds and change the assessment of the studied segments. The synthesis of such sensitivity analyses can be used to prioritise complementary investigations.

Transitioning to sustainable urban water management systems: how to define expected service functions?

Sustainable water management is a worldwide challenge for the twenty-first century. It involves replacing traditional management approaches with a new concept, often referred to as sustainable urban water management (SUWM). This paradigm shift means that SUWM systems must include new services, some of which have already emerged. However, no publications have presented the expected SUWM system in terms of the full range of services it would need to include, and no publications have proposed a method for identifying the services the system must provide. This paper proposes a method for identifying these services and presents a generic petal diagram to represent the service functions of the SUWM system. Moreover, this paper presents a new method for defining these services in a specific territory. This method is based on the confrontation between a general representation and the objectives of the stakeholders in a given system in a given territory. The method is illustrated with a full-scale case study on the Doua eco-campus (Lyon University). This method is intended to aid practitioners to manage its system and to transition to SUWM. It is designed to improve the transparency of decision formulation and to involve stakeholders in the process.

Sewer asset management: impact of sample size and its characteristics on the calibration outcomes of a decision-making multivariate model

Utilities are faced with the challenge of how to manage their assets cost-effectively while providing safe and reliable services to their customers (Marlow et al., 2007). A small number of utilities have completely inspected their sewer networks. Therefore, the use of an asset stocks sample to calibrate deterioration models and to study scenarios about the future seems mandatory. This sample should reflect the asset stocks characteristics in the best manner. However, authors have calibrated deterioration models without paying attention to the impact of used samples on their outcomes. The main scopes of this article are then to: 1) draw a representative sample of an asset stock, 2) provide a reliable estimation of a specific property of the asset stock from this sample and 3) study the impact of calibration sample on the outcomes of a multivariate model. We show that the calibration of deterioration models depends heavily on the characteristics of the used sample.

Eco-EAR: A method for the economic analysis of urban water systems providing services

In the context of new challenges and emerging needs for transparency regarding users, urban water management is obliged to forge links between different technical fields. This implies managing interfaces between multiple stakeholders on the one hand, and ensuring the adaptability and sustainability of technical infrastructures on the other hand. In a period dominated by public spending cuts, the optimisation and efficiency of the systems infrastructures and the organisation of the stakeholders involved has become important for guaranteeing the continuity of the services provided. From the economic viewpoint, this challenge is related to tracking and reducing costs. Moreover, it also concerns the need to communicate arguments related to service costs to both users and stakeholders. Consequently, the “Eco-EAR” method was developed by adapting Functional Analysis (FA), Activity Based Costing (ABC) and Whole Life Costing (WLC) approaches in view to describing how the direct costs of the sewerage service provided by wastewater utilities are structured. The cost structure is analysed according to the activities and physical flows comprising the primary and secondary functions of an urban water management system. Three goals are targeted: i) to explain the costs of the system to the local authority (owners) and users; ii) to identify the activities that have the greatest impact on costs in order to plan cost reduction actions; and iii) to assess the apportionment of costs per activity and per physical flow, in order to better understand the system by combining both its economic and technical dimensions. The performance indicators proposed by the “Eco-EAR” method could also be used for benchmarking. The method is implemented in a real case study: the sub-system territory around the city of Mulhouse (northeast France) under the responsibility of a water management authority.

From sewer inspection programmes to rehabilitation needs: research and results related to data quality and availability with the support of numerical experiment

The purpose of this paper is to discuss the influence of data availability and quality within a utility to prioritise inspection and rehabilitation needs. Data are required in order to predict the structural condition of assets. Lack of data and budget limitation do not encourage utilities to evolve from reactive to proactive management. Methods and tools exist; however, improving operational practices will require the demonstration of data collection benefits. In this article, asset management approaches are presented and discussed regarding influence of data; from closed-circuit television reports elaboration to prioritisation of rehabilitation needs. Bottlenecks related to uncertainty, imprecision and incompleteness of data are identified, and the authors propose approaches to study these questions. This article also highlights the use of numerical experiment to simulate asset management scenarios, to experiment methods or to demonstrate the interest of new practices. Numerical experiment allows construction and use of virtual degraded databases derived from a completely known asset stock.

Assessment of district projects : Quality of the physical environment in the Espaces Gare (project in La Rochelle)

ABSTRACT The fast and uncontrolled emergence of a will to promote sustainable development in the field of building construction generates new requirements for urban development. Besides technical solutions, project managers or urban planners must take into consideration the overall impact of their project on the local and global environment as well as social trends, economic development, health and safety for users. Integration of a huge number of evaluation criteria makes the assessment of such strategy very hard to carry out without a real methodological work. This paper proposes a first methodological approach in order to evaluate sustainability at the district scale and is based on 8 objectives. It is also a contribution to the French research project ADEQUA. This article presents a comparison between two district projects through the objective “quality of the physical environment”. This objective is defined and applied to a case study: the project “Espaces Gare” which concerns the planning of districts near La Rochelle train station (France).