Recent years have seen a succession of serious incidences of flooding and gloomy predictions for the future from climate researchers. This has prompted local authorities and communities to look urgently at how technology can help in flood control. IFAT 2008, which takes place in Munich from 5 to 9 May, is the world´s largest environmental technology trade fair, and this year it is including a new section, on coastal protection and flood control. This dedicated exhibition area covers technology and services in the categories of mobile flood relief, flood prevention and equipment for disaster relief and emergencies.

Probably the most effective way of controlling flood water is to allow the water masses to extend as freely as possible onto unbuilt land. As the water spreads over the meadows, its speed of flow is lessened and the water does not reach the levels it would otherwise have done. In towns and villages, however, flood control equipment is essential. In designing effective flood control plans, the experts are currently combining the local built protection measures, such as earth dykes and walls, with mobile equipment.
 
Dykes and protective walls are often pierced by openings, which at normal water levels allow access to the water. At high water these openings can in many cases closed off with barrier systems. Here, teams of workers fix planks across the opening, slotting them into existing frames. The resulting barrier can be raised as required, by adding more planks, to suit the pertaining flood levels.
 
Traditionally sacks filled with sand were a common type of mobile flood-prevention equipment. In the past these were often used to raise or repair dams and dykes. It is a method which requires a lot of material, time and man-power. And of course after the flood there is the job of disposing of the sacks, some of which may have been contaminated with escaping heating oil. A number of alternatives to the traditional sand sack are now available on the market, for example, plastic tubs filled with water that can be set out in rows, or stacked up. Increasingly, local authorities are using mobile flood walls. These are dismantlable, vertical posts between which wall units, mostly of aluminium or plastic, can be fixed.

Common to all the mobile systems is that they can be set up in just a few hours. For such systems to be effective, of course, you also need an efficient flood-warning service and enough time before the arrival of the high-water mark to erect the barriers. For this reason they are only really sensible alongside larger expanses of water.
 
In addition to the mobile systems, there are also permanently fixed protective systems, with panels (manually or electrically opening), window closures, protective gates or slider devices to secure freshwater and wastewater pipe networks. In Germany the city of Cologne has the most extensive flood-protection measures in place. By the end of this year, the culmination of a ten-year project, the city will have invested 400 million euros along a 60-km stretch of river in danger of flooding; this includes ten kilometres of mobile flood walls. This may seem like an enormous sum, but it has to be set against flood damage estimated at several billion euros which can be incurred once every two hundred years, when record flooding happens, say the experts at the flood competence centre of Cologne.
 
For all the diversity and performance capabilities of the systems on the market, it must be remembered of course that technology can only do so much to control flooding. There will always be the possibility that the next flood is higher than the measures put in place to contain it. In the long term the causes have to be tackled at root, and that is a much wider task for our society. The German Ministry of the Environment, for example, has made a start by introducing, in 2002, a Five Point Programme targeted at preventing floods. It includes measures such as not only leaving more room for the rivers, but also reducing any future damage potential, by adapting building development plans correspondingly.