Bridging the Gap between Engineering and Ecology: Towards a Common Framework for Conventional and Nature-Based Coastal Defenses

Coastal ecosystems provide multiple, valuable services including coastal protection but are globally threatened by human-induced and natural pressures. Traditionally, coastal protection has relied on hardening the shoreline using structures that are difficult to modify or remove once in place and, frequently have negative impacts on adjacent coastlines and coastal ecosystems. Consequently there is growing interest in the design and engineering of «nature-based solutions» (NBS) as elements of coastal protection that are flexible and sustainable and also help maintain or enhance ecosystem health. Despite the increasing interest and body of scientific research around NBS, there remains a gap with regard to guidance and understanding on how these solutions can be managed and integrated within traditional coastal engineering practice. This is partly due to the fact that NBS straddle two distinct disciplines-ecology and engineering. However, the coastal engineering profession has considerable expertise and experience with tools and approaches that can be applied to ecosystem based solutions. Likewise, the vast knowledge on the ecology of coastal ecosystems can help address many of the challenges raised by the consideration NBS for coastal protection. This work reviews the design approach and process within commonly used coastal engineering frameworks in the context of NBS, to find common grounds and overarching principles. Existing guidelines for traditional engineering structures are compared and contrasted with those for NBS to contextualize the position of NBS within engineering practice. A parallelism is thus drawn between NBS and traditional coastal engineering, acknowledging their differences, to provide insights on ways in which NBS can be integrated with standard coastal engineering practice, ultimately, to achieve the dual goals of coastal protection and habitat conservation.