Flood management in highly developed areas: problems and proposed solutions.

Water-related disasters have increased considerably worldwide in recent years. While certain trends are global (like climate change), some actions to cope with these problems have to be taken locally. In any case, land characteristics need to be known and analysed in order to cope with the hazards and avoid their transformation into damage or disasters when exceptional events occur. In this study, risk analysis procedures are described, which consist of the systematic actions in a cycle of preparedness, response and recovery where an integrated flood risk management is required. Then, flooding problem characteristics, policies and related measures adopted by different Countries to decrease the risk of floods are considered. Lessons learnt from flood defence are analysed, highlighting that more room for rivers is required, and the balance between present and foreseeable future spatial requirements of both water and people is pointed out. In addition, definitions about the concepts of hazard, vulnerability, risk and damage/disaster are presented, with special attention paid to flood problems, because there is a certain lack of uniformity in the use of terms, which sometimes causes confusion. In this study, structural and non-structural actions that should be performed are analyzed and their significant differences are commented. Furthermore, with regards to the city of Jeddah, the rainfalls which caused the floods in 2009 and 2011 are analyzed and their return period is estimated. It is therefore demonstrated that while under certain conditions it is possible to design structural defences, in other conditions this is not possible and non-structural defences should be designed. Examples for some application of both structural and non structural defence measures in different Countries are shown.