The four components to combine flood protection with other functions

Multifunctional flood defence systems combine flood defence functions with elements in the flood protection zone that fulfil other functions like nature, housing or agriculture. The wide range in possible combinations of dike configurations and functions complicates a unified approach for designing and assessing multifunctional flood defences. The aim of this paper is to describe how multifunctional elements and flood protection can be linked in an integrated design. We analyse three cases: a typical Dutch riverine dike, the Wide Green Dike in the Dollard estuary, and the Double Dike project at Eemshaven-Delfzijl. These cases include additional functions ranging from nature, to clay mining, and saline agriculture among others. From these examples a framework connecting multifunctional use to flood risk was developed. Such other functions affect flood risk by interacting with four general components of the flood defence: 1) the foreshore 2) the geometry of the flood defence system, 3) the (state of) materials used for flood protection elements, and 4) objects in, on or near the flood protection zone. For the first three components assessment procedures for monofunctional dikes can be followed. Objects require new procedures as these can introduce new modes of failure, directly interact with the hydraulic loads and generate new loads.