Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Journey back through time to help manage river floods

11.06.2003


Statistically, there is little likelihood of anybody experiencing a major river flood whose average recurrence interval is one hundred or one thousand years. Predicting and designing of such events involves going back in time, three or four centuries, by scrutinising records of severe flooding. Joint researches by Cemagref hydrologist Michel Lang and historian Denis Coeur have reconstructed the history of three French rivers, the Guiers, Isere and Ardeche, a unique picture which has been incorporated in the European SPHERE project involving French, German, Canadian, Spanish and Israeli teams.



esearch on three rivers

The search began with the Guiers, the historical boundary between France and Savoy. Using a qualitative recension of river floods, a list of the ten largest events recorded over the last 300 years was drawn up. Attention then turned to the Isere, to test the method on a river which had been extensively developed and controlled, and to see if the past could yield insights into the future. Four centuries of data was used. Contemporary eyewitness accounts are not ignored, and can be consulted on the Internet at http://www.lyon.cemagref.fr/hh/base-in/base_in_anglais/isere1859/presentation.htm where there is an illustrated account of the worst river flood, in 1859. The geography of the flood plain made it impossible to calculate river flow from water levels, because the flood plain is too wide and its contours insufficiently documented before the 19th century. Abundant information is available for the Ardeche river. Two sites were given special attention near the gorges, at Vallon Pont d’Arc and Saint Martin d’Ardeche. River flow has been recalculated from 1644 to the present. The largest river flood has been reconstituted with a 50% margin of error, which is comparable to today’s level of accuracy on high streamflows.


Close look

Historical records yield information on the damage caused by a river flood, how the emergency was managed and, sometimes, more technical data on water levels or river geometry. Palaeohydrologists may be called in to take a close look at the sediments and organic material in the flood plain and date the deposits. In the Ardeche area, they inspected caves to look for precious particulates loaded with information and count how many times the water level rose higher than the cave. Working from the historical shape of the river bed and a hydraulic model, the researchers built up streamflow data series and assessed the magnitude of each event. With these long series in hand, it was possible to compare different methods of estimating rare river floods and validate, on the Ardeche, the Gradex method used in France for assessing the safety of large dams.

Risk culture

A combination of hydrologist and historian is vital in addressing flooding so that the riparian population retain the memory of the risks involved. On the Saone river at Lyon, the researchers intend to make historical information available in the form of a column showing the present water level and the levels reached by the most extreme floods, together with the main vagaries of the river. This is in line with the new legislation on risk, making it a duty to mark flood levels on public buildings.

The historical data collected may also help in finding strategies for managing rare events, by optimising emergency plans and setting extreme flood levels more accurately. Methodological guidelines for technicians are being drafted jointly with the European countries taking part in the SPHERE programme.

Michel Lang | EurekAlert!
Further information:
http://www.cemagref.fr/Informations/Presse/indexgb.htm
http://www.lyon.cemagref.fr/hh/base-in/base_in_anglais/isere1859/presentation.htm

More articles from Ecology, The Environment and Conservation:

nachricht Global threat to primates concerns us all
19.01.2017 | Deutsches Primatenzentrum GmbH - Leibniz-Institut für Primatenforschung

nachricht Reducing household waste with less energy
18.01.2017 | FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur GmbH

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>