Method for limiting freshet levels and controlling floods

Abstract

A process for limiting the level of flooding of a watercourse, notably a wide river, a narrow river and/or one of its tributaries, consisting of injecting into the said watercourse at least one friction-reduction agent.

Claims

1. A process for limiting the level of flooding of a watercourse consisting of injecting into the said watercourse at least one friction-reduction agent in the form of a water-soluble polymer, wherein the quantity of the water-soluble polymer injected into the watercourse is between 10 and 1000 ppm; wherein the watercourse comprises at least one of a wide river, a narrow river, and a tributary to a river.

2. The process in accordance with claim 1, characterized by the fact that the watercourse has a velocity greater than 1.5 meters per second.

3. The process in accordance with claim 1, characterized by the fact that the friction-reduction agent in the form of a water-soluble polymer is injected upstream of the site to be protected.

4. The process in accordance with claim 1, characterized by the fact that the water-soluble polymer is in powder form.

5. The process in accordance with claim 1, characterized by the fact that the water-soluble polymer is dispersed by a centrifugal pump and injected directly into the watercourse.

6. The process in accordance with claim 1, characterized by the fact that the water-soluble polymer is an acrylamide-based polymer or an ethylene polyoxide.

7. The process in accordance with claim 1, characterized by the fact that the water-soluble polymer is an acrylamide-based polymer obtained by co-polymerization of the acrylamide with at least one of the following monomers: acrylic acid; ATBS (2 -acrylamido-2 -methylpropanesulfonic acid); diallyl dimethyl ammonium chloride (DADMAC); dialkylaminoethyl acrylate (ADAME); dialkylaminoethyl methacrylate (MADAME); their acidified or quaternized salts; N-vinyl pyrrolidon.

8. The process according to claim 1, characterized by the fact that when the water-soluble polymer is an acrylamide-based polymer, its molecular weight is between 5 and 30 million g/mol.

9. The process in accordance with claim 1, characterized by the fact that the watercourse has a velocity greater than 2 meters per second.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) Obviously, the application to the problem of flooding is new, and requires thorough studies taking account of flow rates and profiles. In particular, the measurement of a velocity over a distance does not take account of obstacles (bridges, narrowings, jammed objects, etc.), which strongly accelerate the velocity and create turbulence effects in which the instantaneous velocity is several times the average velocity.

(2) One also has to take account of the fact that floodings are very different on plains, where the warning time is sufficient for taking action and the torrential flooding is very fast, with very considerable peaks. One can cite flooding on the Var at 3800 m.sup.3 per second, whereas flooding on the Seine rarely exceeds 2200 m.sup.3 per second. In certain cases, auxiliary phenomenaparticularly windreduce or accelerate the water velocity.

(3) Obviously, each case is particular, and a study involving both modeling and testing is necessary.

(4) Furthermore, the addition of a chemical product into the river can have undesirable ecological effects. A thorough study of the problem will be necessary, taking account of the enormous stakes.

(5) This is because while polyacrylamide by itself is not in any way toxic, a low residue of monomer (acrylamide) can be questionable. Fortunately, acrylamide is easily biodegradable, and the streaming on water-saturated surfaces should not constitute a pollution hazard for the water tables. This issue must be verified with objectivity.

(6) The following example illustrates the invention and the resulting advantages.

(7) City of Paris

(8) The major floodings of the Seine that have occurred in Paris are the severe floodings of 1176, 1658 (8.96 m level) and 1740. But the most-spectacular floodingbecause it was relatively recentlywas that of January 1910, during which the level reached 8.42 m, compared with the normal average of 3.60 m. This flooding lasted 20 days, with a return to normal after 45 days. The flow rate observed was 2000 to 2200 m.sup.3 per second.

(9) The Seine by itself, upstream of its principal tributaries, is a small river that notably receives:

(10) TABLE-US-00001 The Yonne average 92 m.sup.3 per sec flooding 960 m.sup.3 per sec The Marne average 110 m.sup.3 per sec flooding 650 m.sup.3 per sec The Aube average 41 m.sup.3per sec flooding 330 m.sup.3 per sec The Loing average 18 m.sup.3 per sec flooding 315 m.sup.3 per sec The Eure average 26 m.sup.3 per sec flooding 140 m.sup.3 per sec The Seine in Paris average 450 m.sup.3 per sec flooding 2000 m.sup.3 per sec

(11) The velocity of the Seine is, on average, 1 to 2 km per hour (0.3 to 0.6 m per sec). At the beginning of flooding, it increases to 4 km per hour (1.1 m per sec), stabilizing at 5-7 km per hour during flooding (1.4 to 1.9 m per sec). However, the instantaneous velocities can be practically double in narrower sections and depending on turbulences, which strongly decrease the flow rates. The flood reservoirs currently constructed absorb approximately 60 cm of flooding, without preventing it.

(12) The use of a drag-reduction agent in amounts to be specifiedaround 50 to 100 ppm, would enable an increase in average flow rate of 20 to 30% at peak. Obviously, the quantities necessary seem enormous. With a flow rate of 2000 m.sup.3 per second, at 100 ppm, one needs 0.2 tonnes of product per second, namely 720 tonnes per hour, 17,280 tonnes over 24 hours, and 172,800 tonnes over 10 days. However, the cost would by around 500 million euroslow in relation to the cost of a one-in-one-hundred-year flooding, also taking account of the fact that the 2000-m.sup.3-per-second level can be exceeded in a catastrophic situation.

(13) One can also cite the floodings of the Danube and the Inn which, in 2002, caused enormous damage estimated by the authorities at 7.5 billion euros. The evacuation of a part of the population is additional to this.

(14) France's Barnier Law of 1995 made provision for a Prevention Plan for Flooding Hazards [Plan de Prvention pour les Risques d'Inondation (PPRI)] that plans a stoppage of public transport at 6.20 m, the evacuation of 850,000 people for 30 to 40 days, and the maintenance in-situ of 1.5 million people, probably without heating and electric power for 30 to 40 days. Additionally, the RATP [Rgie Autonome des Transports Parisien, or Paris Public Transport Corporation] has planned for the construction of rubble walls around metro stations; at a certain height and depending on network shortcuts, the metro system could be totally flooded.

(15) In 1910, there were 65,000 electrical power customers in Paris. Today, and taking account of the more-sophisticated electronics employed, which are more-sensitive to water than the power grid of 1910, the time required for replacement of facilities in a situation of equipment shortages is unknown.

(16) The other problem is the evacuation of automotive vehicles to non-floodable areas, with return journeys over large distances in flooded areas and without public transport systems.

(17) ParisRoll-Out of the Project

(18) A study with simulation of the project will enable the parameters to be specified: effectiveness of the product at different doses; effectiveness at different velocities; effectiveness at different velocities, taking account of turbulences; advantageous points of injection; advantageous time window for injection.

(19) It will probably come to the fore that the injections have to be done at the tributaries, taking account of the fact that the dissolution time for a polyacrylamide in powder form is approximately one hour. The injection program itself will be variable, according to the duration, the flow rate and the level.

(20) The storage of the product in silos similar to grain silos poses no problem, but it will be necessary to periodically verify the aging of the product, which should be usable for more than 10 years in the case of high-quality polymers.

(21) Dispersal in rivers can be done by dispersal in a cone of water raised by centrifugal pumps. A centrifugal pump capable of 500 m.sup.3 per hour can disperse 5 tonnes of product per hour directly into the river.

(22) Obviously, this possible new development must undergo optimization studies taking account of the fact that the process itself has been validated by past studies and operations with much lower flow rates.