Analyse territorialisée du risque de débordements de réseau d'assainissement liés aux eaux pluviales : application au Grand Lyon : Analyse spatio-temporelle du risque de débordements au Grand Lyon

Abstract : An increase in impermeable surfaces and hence runoff, has lead to a greater risk of flooding in urban areas. Sewer networks experience excessive water volumes which exceed their absorption capability, notably during exceptional rainfall events, consequently leading to overflowing and flooding. The Water Direction Agency of Greater Lyon has created a database so that these overflowing events can be analysed and vulnerable infrastructure identified and protected. This database consists of historical data from 1932-2005 obtained from bibliographical work. Since 2005 it has been updated live by digital writing tablets utilised by Water Direction ground teams. The date and precise location of the flooding event; the nature of the sewer network and of the infrastructure; and the nature and cause of overflowing are recorded on the database. A sample of rainfall events has been selected from the database based on physical criteria as well as disturbance caused. Exceptional rainfalls in terms of average maximum intensity in 18 minutes, average water precipitated and of the duration of rainfall have been related to the overflowing events. This sample of exceptional rainfall events has been completed by a sample of ordinary rainfall events without extraordinary physical criteria, which have nevertheless been the cause of flooding in the city. A study focussing on the rainfall event and another centred on the vulnerability of the sewer network have been carried out, quantitatively and spatially to the scale of the urban area of Greater Lyon. Density surface maps of overflowing have been created and a cross spatial analysis of different sewer system devices with the types of rainfall events has been completed. It has been shown that the urban centre and west Greater Lyon have a higher vulnerability to overflowing during exceptional intense rainfall, whereas abundant and enduring precipitation affects in main only the West area, and more precisely the Yzeron catchment. In contrast, ordinary rainfall events which have led to overflowing have been shown to affect the East part of Greater Lyon. To conclude, this study shows that with relatively low rainfall levels, the risk of flooding could be increased if vulnerability of the sewer system is high. Subsequently, even with low precipitation, if the sewer system is classed as vulnerable, the risk of flooding and overflowing is high.
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https://hal-univ-lyon3.archives-ouvertes.fr/hal-00959929
Contributor : Florent Renard <>
Submitted on : Monday, March 17, 2014 - 11:35:07 AM
Last modification on : Wednesday, April 10, 2019 - 1:34:17 AM

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Florent Renard, Jérémie Riquier. Analyse territorialisée du risque de débordements de réseau d'assainissement liés aux eaux pluviales : application au Grand Lyon : Analyse spatio-temporelle du risque de débordements au Grand Lyon. Norois, Presses universitaires de Rennes, 2008, 208 (3), pp.45 - 60. ⟨10.4000/norois.2181⟩. ⟨hal-00959929⟩

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