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Flood forecasting

FREQUENCIES AT THE HEART OF FLOOD FORECASTING 

Frequencies are extensively used to face flooding. Over 700 sensors, spread over the different rives in continental France are used by the flood forecast services. They measure the water level and transmit data to the prefectures. Normally, the transmissions are sent every hour, but they increase when it rains and can occur every 5 minutes.  If major flooding is rare, its important effects mean that they have long been noted in the national registers.  The most important flooding on the Seine occurred in February 1658: 8.96 m converted to the modern scale (Austerlitz bridge), or 34 cm higher than the 1910 level. Indeed, in Paris, systematic readings have been taken since the mid 19th century using a scale located at the Austerlitz bridge. The torrential flooding in the Gard in 2002 accelerated the redesign of the flood warning system, which changed to a flood forecast system on the main rivers in continental France.  A flood forecast and warning system requires a central operational service to communicate with the decentralised stations and with all people in contact with the service.  Joint expertise between meteorologists and hydrologists was also needed, resulting in the creation:

  • of the Central Hydro-Meteorology and Flood Forecast Support Service (SCHAPI) in 2003. It is in charge of displaying the risk at the national level (maps "vigicrues") and is located in Toulouse, as is Météo-France. It reports to the risk prevention general department (DGPR).
  • of 19 Flood Forecast Services (SPC) which are in charge of the specific watch for their territories.  

To coordinate operations at a local level, the Regional Environmental, Planning and Housing departments (DREAL) are in charge, for each basin Prefect, of organising and implementing the directives. They are the main information relay to local authorities.

The relays used to monitor floods operate in the 70/80 MHz band and collect the data from sensors installed at the river level: it is these level sensors that can operate using ultrasounds or use pulse radar technology operating in the 24 GHz band.  The relays can either receive alarms sent spontaneously by the sensors or query them following a request from an operator or according to a pre-defined cycle.

The sensors provide rainfall or river level readings which contribute to the overall flood forecast and warning process.  

The degree of interference between the radio relays must be sufficiently low not to put into doubt the reliability of the communications, which requires the assignment of several frequencies for the equipment controlled at the basin level. 

This information is then re-transmitted to the prefectures in order to inform or warn populations. The transmission can use the phone network, optical fibre or even microwaves in the 1.4 GHz band. 

Flood control is also a fundamental part of dam safety, in particular in areas around nuclear power stations. Some additional stations are thus operated by EDF.  

Finally, flood prevention requires international cooperation and alert sharing. Thus, in 1993 in the north of the Aisne department, the Oise floods caused flooding and showed the importance of warning populations of the arrival of floods soon enough, including in the Belgian Hainault region.

Signature des actes finals de la CMR-19 #ITUWRC https://t.co/hPSsuZYNWL

ANFR a Retweeté

#ITUWRC identifies additional frequency bands for #5G https://t.co/t0FxsBSwaT https://t.co/m9q6Mrdf45

En direct de la CMR-19 ! La plénière est toujours en cours... Un thread pour donner les principales conclusions adoptées #ituwrc https://t.co/1Oh1zDOccu

En route pour la plénière d’approbation des derniers textes de la CMR #ITUWRC https://t.co/Util4aGiGu

A partir du 1er juillet 2020 , l’affichage du DAS (tête , tronc et membre)sera renforcé et devra figurer sur l’ensemble des équipements radioélectriques. L'@anfr assurera le respect de cette nouvelle règlementation.

👉https://t.co/86dBrcuORB https://t.co/hqcRI2Yp6y

@anfr @ITU @uit Entre satellites, 5G, usages scientifiques, transports, les débats sont vifs à Charm El-Cheikh. Mais, désormais, les textes passent en plénière, et cela durera jusqu’au petit matin du jeudi 21 novembre. Le suspense reste entier sur les derniers arbitrages ! https://t.co/PkuVgkJzkn

@anfr @ITU @uit Au cours d’une CMR, tout peut arriver : il suffit que les Etats tombent d’accord pour que le texte s’inscrive dans le RR. L’ordre du jour est donc fixé à l’avance, pour canaliser les débats. Des commissions permettent de décanter les résolutions avant de les proposer en plénière. https://t.co/CtXpmP4j5H

@anfr @ITU @uit Une CMR, ce n’est pas une conférence classique, avec des orateurs sur scène. C’est une assemblée qui crée une nouvelle loi. Tous les Etats se réunissent en un seul lieu pendant 4 semaines, pour tenter de se mettre d’accord sur un nouveau RR. Chaque Etat dispose d’une voix. https://t.co/h8fM11LVRi

@anfr @ITU @uit Mais voilà, les services sans fil sont toujours plus nombreux. TNT, Galileo, 5G… : le RR doit être actualisé. Si c’était une loi, il faudrait l’inscrire à l’ordre du jour du Parlement. Mais aucun Parlement ne siège au niveau mondial ! L’@UIT organise donc une CMR tous les 4 ans. https://t.co/SphUomlKb9

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