Correlation impact in piping erosion for safety assessment of multi-functional flood defences

Introduction Adaptation to climate change is one of the main concerns for cities in deltaic areas. For a country such as the Netherlands where two thirds of the land are located under sea level, reliability of the flood defence system is a top priority. Flood defences are exposed to different deterioration processes (also known as failure mechanisms) which might compromise the water retaining capacity during a flood event. In the state of the art of safety assessment for flood defences, a failure mechanism known as “Piping erosion” is considered one of the most probable and uncertain threats for the Dutch dike system. This type of failure consists in the formation of longitudinal cavities in aquifers located underneath the foundation of flood defences. This type of failure is one of the challenges that planners and engineers must cope with when high reliable flood defence systems are conceived. Multifunctional flood defences are one of the many solutions proposed for urban areas, where factors such as sea level rise, global warming and demographic explosion are the main concerns in future planning. In principle, the addition of extra functions and the strengthening of the existent flood defence system will signify an increase in the dimensions such as height and width (Fig 1.)