Flood risk reduction aims at minimizing losses in low-lying areas. One of the ways to reduce flood risk is to protect land by means of flood defences. The Netherlands has a long tradition of flood protection and, therefore, a wide variety of guidelines and technical reports have been developed for designing and assessing typical flood defences. These documents have been prepared by the Dutch Technical Advisory Committee for the Flood Defences (Technische Adviescommissie voor de Waterkeringen, TAW) and generally apply to dunes, lower and upper river dikes, lake and sea dikes, water-retaining hydraulic structures, etc. These documents contain methods and criteria to determine the reliability of flood defences, based on the present state of technology and research.
Due to continuously expanding urban activities and the need to improve the present protection level, flood defences are often combined with structures that serve other functions than flood protection. Examples of these multifunctional flood defences are parking garages in quays, houses whose facades retain water and wind turbines on dikes. However, the current TAW guidelines are not suitable to multifunctional structures. The problem is that the present guidelines assume specific shapes of flood defences, like gates or embankments. Multifunctional flood defences, conversely, consist of atypical structural elements that require a different approach. The lack of officially approved documents causes difficulties in estimating whether these multifunctional flood defences are sufficiently reliable or not. Consulting engineers and research institutes like Deltares have acknowledged this gap. This problem was also observed by Knoeff et al (2013) and mentioned by Van Mechelen (2013).
Due to continuously expanding urban activities and the need to improve the present protection level, flood defences are often combined with structures that serve other functions than flood protection. Examples of these multifunctional flood defences are parking garages in quays, houses whose facades retain water and wind turbines on dikes. However, the current TAW guidelines are not suitable to multifunctional structures. The problem is that the present guidelines assume specific shapes of flood defences, like gates or embankments. Multifunctional flood defences, conversely, consist of atypical structural elements that require a different approach. The lack of officially approved documents causes difficulties in estimating whether these multifunctional flood defences are sufficiently reliable or not. Consulting engineers and research institutes like Deltares have acknowledged this gap. This problem was also observed by Knoeff et al (2013) and mentioned by Van Mechelen (2013).