Significant floods in Europe in 2013 have tested the learning from earlier floods, some as recent as 2002. One of the “new” learnings has been the utility of temporary structures which can be installed when floods are imminent and removed once flood waters recede. Such systems require pre-installation and sufficient early warning to set them up, but they can offer a reasonable defense if no other solutions are available or affordable.

“These types of mobile barriers have proven effective in Austria and along the Rhine, and the Aare river in Switzerland. However, careful planning and training is necessary for their deployment, as well as reliable early warning systems, and adequate emergency planning … At several locations along the Danube and the Elbe rivers, inaccurate and/or late warnings, along with inadequate or inoperable equipment – for example, electric water pumps in areas that lost power causing the entire system to fail – underscore that emergency planning and regular training is needed for these measures to work.”

European floods: using lessons learned to reduce risks
http://www.zurich.com/internet/main/sitecollectiondocuments/insight/european-floods-using-lessions-learned-en.pdf