ISL Ingenierie

Paris, France

ISL Ingenierie

Paris, France
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Louati D.M.H.,Ministere de lAgriculture et des Ressources Hydrauliques DGBGTH | Deroo L.,ISL Ingenierie | Abbas D.,SIAA
Houille Blanche | Year: 2012

Mejerda is the most important river ("wadi") of Tunisia; it has the largest catchment (23,500 km2) and provides half of the country surface water resources. The river is also feared for its large floods, which have recently inundated cities and roads during weeks. The Ministry of Agriculture has decided to implement a protection program dedicated to reduce the intensity and conse-quences of Mejerda's floods. This program aims at reducing flood discharge, improving the river hydraulic capacity and providing protection levees. This paper presents a first appraisal of this protection program. Both hydrological and hydraulic models have been implemented so as to ascertain the actual situation and to propose mitigation measures. These models have made it possible to derive a pro-gram: flood flows reduction by dams implementation and increasing of the existing dams efficiency, river hydraulic capacity en-hancement by dredging and excavation works and through vegetation control, implementation of local levee schemes, and various measures aiming at restoring the river erosion capacity to counterbalance its tendancy at clogging. © 2012 Société Hydrotechnique de France.

Savatier J.,ISL Ingenierie | Salembier M.,ISL Ingenierie | Monnier L.,Cap Ingelec | Gillot P.,Service Immobilier du Palais de Justice Cour dAppel
Houille Blanche | Year: 2011

The flood risk assessment of Paris'courthouse, located on 'la Cité' island, highlights that the underground and ground floor are undergoing flood hazard by groundwater seeping for floods equal or greater than the one of 1982 (10 years return period) and especially for 1955-like floods (50 years return period, generalized flood of the underground floor) and 1910-like floods (100 years return period, flood over most of the ground floor). The flood durations may be important, with for instance about 10 days on the ground floor for the 1910's flood. Paris'courthouse vulnerability is high but fairly recent since almost all the technical equipment has been displaced to the underground floor since 1962 and above all after 1995. The courthouse has therefore not known any major flood in its current configuration. For a flood like the ones of 1955 or 1910, all the technical equipment would be severely affected and the courthouse would be out of service during the flood and until the equipment is repaired or replaced (probable duration of several weeks). The costs of the technical damages are estimated at 11,5 M€ (except the costs due to the long-lasting interruption of the courthouse service and the loss of the archives, that could not be estimated). Vulnerability reduction by transfer of all the technical equipment to unflooded areas or by constructing waterproof casing around the equipment is not possible due to the lack of available space in the unflooded areas and to the narrowness of the technical premises. The courthouse has therefore chosen to reduce vulnerability by adapting the technical equipment in order to be able to maintain deteriorated service during the flood, to facilitate the return to normal state and to reduce the damages. The adaptations include the transfer of essential equipment to available unflooded areas and modifications to the electricity network and devices aiming at separating flooded and unflooded parts and being able to supply a part of the building with electricity-generators. © Société Hydrotechnique de France, 2011.

Erpicum S.,University of Liège | Lodomez M.,University of Liège | Savatier J.,ISL Ingenierie | Archambeau P.,University of Liège | And 2 more authors.
6th International Symposium on Hydraulic Structures: Hydraulic Structures and Water System Management, ISHS 2016 | Year: 2016

To mitigate the negative effects on the water quality in the downstream river of a projected large dam, and in particular to increase the dissolved oxygen concentration during low flow periods within the first 10 years of dam operation, an aerating weir has been designed and tested on a physical model at the Laboratory of Engineering Hydraulics (HECE) of the Liege University. The design of the structure considers data from the literature. The selected solution is a 3 m high stepped spillway designed to operate in nappe flow conditions within the range of design discharges (25-100 m3/s). To validate the design, a physical model representing a section of the weir at a 1:1 scale has been built and operated in the laboratory. A chemical dissolved oxygen removal technique has been applied upstream of the model to be able to measure the weir aerating efficiency. The physical model results show that the proposed structure is able to maintain, in the range of discharge in the river from 25 to 100 m3/s, a minimum 5 mg/l oxygen concentration downstream, whatever the upstream oxygen concentration. The paper presents the design process of the weir, the scale model features and the results of the validation tests on the physical model. The prototype construction will take place in 2017 and the water quality will be monitored.

Labyrinth and Piano Key Weirs II, PKW 2013 - Proceedings of the 2nd International Workshop on Labyrinth and Piano Key Weirs 2013 | Year: 2014

The Rassisse Dam (Tarn - France) is a 60 year old arch and gravity dam. Following previous studies made by the CEMAGREF and Coyne et Bellier, theTarn Prefet - State representative - obliged the owner (Syndicat Intercommunal pour l'Aménagement Hydraulique du Dadou - SIAH) supplying drinking water to the nearby communities to lower the normal reservoir level by 2.9 meters and upgrade the dam (stability and flood protection). Main issues are the present spillway capacity to withstand extreme floods and the stability of the dam in case of very high water elevation level. An upgrading project was derived, that had to take into account a design flood twice (431m3/s) as high as the present gated spillway capacity, considering also that Max Water Level (MWL) has to be kept under elevation NormalWater Level (NWL)+1.20 m, little space to accommodate for the new spillway, requirements of low costs and low environmental impacts and the need to dismantle the present gated spillway, 3.30 meter under NWL, without modifying the arch dam load on its abutments. ©2014 Taylor & Francis Group.

This report intends to underline the limitations of usual flood design criteria for dams. It also intends to investigate whether other criteria, based on pobability of failure, could be of practical interest. The report gathers results from recent incidents or experience, results from published failure reports and results from a simple mathematical analysis. It leads to some practical conclusions: there is a need to better account for uncertainty in flood computations, either with adapted computations or simply by « testing » how would behave a dam exposed to a flood twice as large as the design flood, the freeboard design should be adapted so as to give adequate flood safety: classical formulas are sometimes too cautious and sometimes not enough, spillways (and freeboard) could usefully be designed based on failure probability or rather based on FN curves; this can be done with reasonably simple tools and leads to quite different results than the classical criteria, specific care should be given to flood mitigation dams: these dams turn out to be far less safe than classical reservoir dams. © Société Hydrotechnique de France, 2010.

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