Since this report is navigation resilience, it will focus more on structural measures (e.g. concrete and embankments in the ground). It is noted that a broader and more integrated flood risk management approach that strikes a balance between structural and non-structural measures is applicable for FDS in general. Past examples have shown that some structural flood control systems may have exacerbated rather than reduced the amount of damage from flooding, for example, when levees created a false sense of security that lead to excessive development in floodplains.
rnrnThe guidance provided in this report is applicable for most FDS, not just for FDS embedded within navigation structures. A fully integrated water basin perspective would also include many non-structural methods that can be developed to give rivers more room and reduce the speed of flood water. Inland navigation needs to be developed in an environmentally friendly way where river training methods are reassessed without the straightening of rivers. For example, polders are low-lying flood plains enclosed by embankments, separated from the river and are used on the Rhine River to allow for floods to be alleviated. Storing water by means of vegetation, soil, ground and wetlands, all of which are capable of retaining water, should have priority over swift water run-off. Every cubic meter of water not drained away immediately to the next body of water is a gain for the water regimen. An efficient flood risk management system needs to be complemented with integrated watershed management, retention zones, restricted developments in flood plains, land use planning, awareness raising, flood resistant construction, drainage and water storage improvement, effective evacuation planning and other measures. It is emphasised that embankments or levees (the focus of this report) are only one part of a fully functioning sustainable system.
rnrnThe purpose of this report on resilience to overloading is the compilation of lessons learnt. Knowing the inevitable that the structure may fail at some point, weather due to degradation, overloading, or design error, this report summarises what can be done to minimize consequential damage and risks if this happens. The report includes recommendations for minimum system performance and public safety aspects of navigation systems integrated with FDS which have the potential to malfunction or fail during major storm or flood events and thereby cause loss of human life, create catastrophic environmental hazards that endanger public health, disrupt lifeline services or destroy critical infrastructure needed for emergency response. This Working Group report introduces performance requirements covering the minimum public safety aspects for navigation structures integrated with FDS. The performance requirement statement will lead the design team in how the system will perform for various loadings throughout its life. While many of the examples shown are for embankments or flood walls, the concept of resilience to overload shown in this document applies to the design, construction, operation, inspection and assessment of most FDS. (Dams and Tsunamis are beyond the scope of this report.) Resilience is about designing systems that ?fail gracefully? when overloaded, to avoid catastrophic failure but to allow for time to evacuate.
