Shared-use of flood defences

Abstract

Many regions face an increasing flood risk as a result of sea-level rise, climate change, and a growing population in flood prone deltas. Introductionuses present either directly or indirectly (Adams, Adger, & Nicholls, 2018;van Wesenbeeck et al., 2014).Accelerating sea-level rise as a result of climate change is further increasing flood risk, with annual global flood costs expected to reach up to US$ 210 billion by 2100 without new or reinforced flood defences (Hinkel, van Vuuren, Nicholls, & Klein, 2013). If new coastal flood defences were to be constructed and existing defences were maintained economically, globally the population at risk of flooding is estimated to reduce by as much as a factor of 500 and annual flood costs would reduce by a factor of 5 by 2100 compared to business as usual (Hinkel et al., 2013).When improving flood protection, it is often considered whether the flood protection zone could also be combined with other needs and services for the area like nature, recreation, or urban development. As of yet, there is little guidance on how such activities will affect the safety provided by the flood protection measures.Multifunctional use can exploit synergies between uses, for example when excess heat from industry is used to heat houses (Weinberger, Amiri, & Moshfegh, 2017). Other times combining uses concentrates adverse effects so these are more easily managed or mitigated, for example when bundling line infrastructure like highways, rail lines, pipelines, and power lines, to concentrate noise pollution and nuisance during maintenance. Similar beneficial combinations of uses for flood Spatial optimisation Structural integration Functional integration Robust dike Super levee Hybrid defence Eco-engineering, natural foreshores Parallel dikesLópez, Warmink, Schielen, & Hulscher, 2018b;Vuik, van Vuren, Borsje, van Wesenbeeck, & Jonkman, 2018b). The approaches of previous studies are discussed in detail below.Ways of probabilistically assessing specific types of multifunctional flood defences were explored by Aguilar-López (2016). The effect of two multifunctional uses (a pipeline and a road) were assessed for two failure mechanisms (piping and overtopping). The strategy employed by Aguilar-López ( 2016) follows a similar First Order Reliability Method (Level II) Vuik et al. (2018b)The shift to a full probabilistic approach allows for optimisation of dike designs as knowledge and uncertainties of local conditions and uses can be incorporated directly in the safety assessment. However, there is little experience how to apply the probabilistic approach in cases of multifunctional use. Still, by 2050 all primary flood defences, including those with multifunctional elements, must conform to the new safety standards in the Water Act.