| Partenaires |
| Contenu |
| Livrables |
Partenaires:
Veolia-Eau Agence Drôme Ardèche (J. Malandain, responsable); ARIA ; CNRM-GAME ; City of Romans-sur-Isère (“Direction de l’eau et de l’assainissement”) ; INSA Lyon ; IPSL.
Contenu:
The development of the urbanization and consequently the progressive proofing of the grounds, the climatic modifications especially in rainfall modes, the ecological state of the receiving mediums, lead sewer systems to solve three problems :
- risks of urban flooding related to the hydraulic capacity of pipes
- network collect of pollutant loads produced rainfall runoff on the urban surfaces
- the requirements in water treatment and the control of combined sewer overflows.
These quantitative and qualitative specificities of rainwater management contribute to design the current sewer systems and provide the future needs for their adaptation to climatic changes. Currently, reference values used to design sewer systems are prescribed and regulated by the decree of June 22nd, 2007. These values have been calculated considering that flow regulation and treatment plants have to guaranty the optimal transport and treatment of pollutant loads for some extreme water flow. This threshold flow is associated to a rainfall event with specified return period. In practice the modelling approaches used for the transformation rainfall/runoff are most usually based on rainfall records and a statistical analysis of their characteristics (intensity, duration and frequency). However the rainfall records present several limits. They are sometimes not representative of the local features (farther rain gauge), they are not distributed (one single rain gauge) and not representative of future conditions (design of the sewer systems according to the past events recorded at the nearest rain gauge). This space and time ignorance of rainfall modes leads to strong uncertainties in the conception and the adaptation of infrastructures dedicated to the sustainable management of rainwater flow and the associated pollution. The consequences of those uncertainties are currently observed and will be more in the future. Within the framework of this project, we propose to analyse the vulnerability of sewer system at the level of a mean size agglomeration in France, the city of Romans sur Isère where Veolia Eau met already difficulties. The study will rely on
- knowledge of rain modes and projections at special time and space resolution:
- Observation in real time based on a network of rain gauges coupled to radar technology
- Confrontation to medium (10-20 years) and long-term projections (50 years) at different horizontal resolution.
- Transformation rainfall/runoff with detailed hydraulic model (CANOE)
- Production, transport, treatment and discharges of pollution generated by domestic,industrial and rainfall activities (vulnerability assessment).
Needed climate information for this study is hourly precipitation projections at local scale. They will be developed in task 3.3 and/or using the work of Arnaud, 2007 or Flecher, 2009. We will also use the results obtained in the CYPRIM project for extreme precipitation events on the Mediterranean region (Boudevillain B. et al, 2009; Ricard et al; 2009). This integrated approach presents relevant scientific and operational interests. The confrontation of existing rain/flow and pollutants production models to observations taking into account time and space variability of rainfall will help to adapt existing models or recommend new modelling practices for sewer systems conception. This study will also offer a first guide for the designing of sewer systems relying on a stronger adaptability to the change.
Livrables :
Milestone 1: feedback of implementation of a measure network for the management and adaptation of combined sewer systems. It will be a synthesis elaborate during the task group “Rhône Alpes autosurveillance des reseaux” with the GRAIE organisation (http://www.graie.org) and the “Rhône Méditerranée et Corse” Water Agency.
Milestone 2: Organisation of a local thematic conference about “impact of climate change on sewer system” with authorities from Valence-Romans cities, Drôme administrative area and Water policies service.
D2.2.1 : Synthesis about the vulnerability and adaptation to climate change of a sewer system based on the Romans-sur-Isère study.
