Fighting water with water

Cloudburst events of the scope witnessed by Denmark in recent years can result in massive flooding, putting the infrastructure on hold and causing millions of DKK of damage. Fighting the massive amounts of water is therefore an important part of the municipalities' emergency preparedness.

So far, emergency response has typically involved the use of pumps and sand bags, however in recent years several mobile dam solutions have emerged on the market as a supplement to these pumps and sand bags. The mobile dams can quickly be moved to where the risk of flooding is greatest. Following the cloudburst on 2 July 2011, both the City of Copenhagen and the City of Frederiksberg invested in the NoFloods Mobile Barrier technology, which has proven effective and relatively simple to manage in both real and tested situations.

The NoFloods Mobile Barrier consists of two flexible and parallel hoses/booms. When filled with water, the hoses form a dam to prevent water from passing. The hoses are up to 200 meters long and  can be joined together with special couplings to provide the lengths required to control a flood. Deploying the mobile dam takes considerably less time than stacking up sand bags. Besides deploying the hoses as long booms, the hoses can also be used to build large mobile reservoirs to collect surface water and wastewater.

Following flooding of various public buildings during the cloudbursts in 2010 and 2011, the City of Frederiksberg took a good look at the possibilities for climate change adaptation and preparedness.

"The City of Frederiksberg resolved to buy 1,200 meters of the NoFloods Barrier system of varying lengths, including couplings and fittings. The idea is that the mobile dams will be used on both small and large scale. For example, fifty meters are enough to shield off particularly vulnerable entrances to residential blocks," said Brian Huss Eriksson, who was the fire and rescue chief when the municipality decided to invest in the NoFloods Mobile Barrier.

The sports centre is of special concern for the emergency services in Frederiksberg. The base of the sports centre is below ground level and the floors have had to be replaced on several occasions after flooding.

"We have now installed a pump well adjacent to the sports centre. When the water comes, we can use this to pump water into the mobile dam that had been deployed to form a reservoir. We have prepared laminated action cards for sport centre employees, so that no one is in any doubt about what to do when it's time to act fast," said Brian Huss Eriksson, who today acts as the emergency management chief in the Municipality of Brøndby.

A huge benefit of the NoFloods Mobile Barrier system is that the mobile dam can be deployed very quickly.

"It takes around 16 man hours to deploy a one-kilometre dam, which can hold off at least 80 centimetres of flood water. This corresponds to only a fraction of the resources required to deploy sand bags along the same stretch. In other words, we use only 16 man hours and a single lorry, whereas it takes 7,000 man hours, 149 lorries as well as 2,500 cubic meters of sand to deploy sand bags; a task which has proven unrealistic on many occasions," said Anders Philipsen, who is managing director of Environment Solutions which started developing the NoFloods Mobile Barrier in 1999.

Anders Philipsen points out that the mobile dams are also a cheaper and more effective alternative to other solutions, such as lowering roads so that they can serve as channels or sewer extensions.

"These are very expensive solutions which can be difficult to finance. With our product, public emergency response services, and others who want to safeguard against excessive water, can rapidly relocate dams to areas under threat," he said.
Environment Solutions has just extended its contract with the French emergency response service Sécurité Civile by an additional four years up to 2017. As a client, Sécurité Civile has been active in the development of the NoFloods Mobile Barrier system since 2005.

Here are some price examples for the NoFloods Mobile Barrier:

- 1,000 meters of TwinTube 60 A complete solution which can retain up to approximately 40cm flood water costs DKK 480,000.

- 1,000 meters of TwinTube 125 A complete solution which can retain up to approximately 80cm flood water costs DKK 720,000.

The system can also be rented for a period of 24-60 months