Urban dunes

Abstract

Sandy shores worldwide suffer from coastal erosion due to a lack of sediment input and sea-level rise. In response, coastal sand nourishments are executed using ‘Building with Nature’ techniques (BwN), in which the sand balance is amplified and natural dynamics are instrumental in the redistribution of sand, cross- and alongshore. These nourishments contribute to the growth of beaches and dunes, serving various design objectives (such as flood safety, nature, and recreation). Nevertheless, human interference (such as buildings and traffic) along urbanized sandy shores may have significant, yet poorly understood, effects on beach and dune development. Better insight is required into the interplay of morphological, ecological and urban processes to support Aeolian BwN processes for dune formation and contribute to the sustainable design of urbanized coastal zones. This paper aims to bridge the gap between coastal engineering and urban design by formulating design principles for BwN along urbanized sandy shores, combining nourishments, natural dune formation and urban development on a local scale to strengthen the coastal buffer. The first part of the paper analyses sedimentation processes in the (built) sea-land interface and identifies spatial mechanisms that relate coastal occupation to dune formation. Hence a preliminary set of design principles is derived by manipulating wind-driven sediment transport for BwN dune formation after nourishment. In the second part of the paper, these principles are applied and contextualized in two case-studies to compare their capability for BwN in different coastal profiles: the vast, rural, geomorphologically high dynamic profile of a mega-nourishment (Sand Motor); versus the compact, highly urbanized, profile(s) of a coastal resort (Noordwijk). Conclusions reflect on the applicability of BwN design principles within different coastal settings (dynamics, urbanity) and spatial arrangements facilitating BwN dune formation.

ShoreScape

“…Building with Nature is defined as 'the employment of natural processes and resources to serve societal goals, such as coastal safety ' (de Vriend et al, 2014;van Bergen et al, 2021). As an emerging philosophy in hydraulic engineering, it promotes (soft) infrastructure that works with nature rather than against it as an alternative to hard infrastructure.…”

“…The launch of more advanced nourishments, such as the Sand Motor, led to an early definition of BwN as the design of infrastructure that (a) is aligned with natural processes rather than against them; (b) is adaptable to changing conditions, such as sea level rise and climate change; and (c) serves multiple purposes (de Vriend & Koningsveld, 2012). This definition, which closely links BwN to ecological research ('by nature for nature'), initiated the second generation of hybrid BwN solutions (van Bergen et al, 2021) serving a wide range of purposes, including coastal, lakeside, port and urban solutions (Ecoshape, 2021).…”

“…One of the key elements of BwN is the employment of natural processes to serve societal goals through self-regulation (de Vriend et al, 2014(de Vriend et al, , 2015van Bergen et al, 2021). Here, natural processes are the vehicle to establish an intervention for crucial goals as coastal safety.…”

“…By matching nourishment types and urban typologies to specific types of dune formation, returns on nourishments can be increased. Specific spatial arrangements (e.g., shadow dune formation, blowouts) can direct and stabilize sediment, contributing to the coastal buffer (van Bergen et al, 2021). This requires a design process that mediates between the relevant intervention scales and dynamics involved, to tune land-shaping processes for dune formation.…”

“…The core values and principles of Studio Coastal Quality are closely linked to the functionality and values of BwN. In BwN projects, functional quality is related to the 'employment of natural processes and resources' to serve societal goals, such as flood safety (de Vriend et al, 2014;van Bergen et al, 2021). Therefore, BwN boasts three main values:…”