Experimental and Numerical Modelling of Climate-Change Adaptive Vertical Seawall Structures

Abstract

The performance of coastal structures will be affected as climate change drives sea level rise and increasing storminess. When re-designs are not possible, engineers may need to retrofit existing coastal structures to account for harsher design conditions. Previous research at the National Research Council of Canada (NRC) investigated how adaptations to traditional coastal revetments reduced wave overtopping, forming the basis of the current investigation.

A literature review revealed that, while design guidance exists for retrofits like parapets and toe berms, an otherwise limited amount of guidance exists regarding retrofitting vertical structures. However, all relevant studies used physical modelling to some degree, stressing the importance of physical experimentation in this regard.

This study investigated how retrofits to vertical structures (bulkhead, caissons, seawalls, etc.) improves their wave overtopping resistance under rising sea levels. Experimental modelling was conducted at the Coastal, Ocean, and River Engineering (OCRE) Laboratory of the National Research Council (NRC) in Ottawa to investigate several conventional and novel adaptation concepts: crest extensions, low-crested eco-friendly breakwater, revetments, perched sandy beach, perched cobble beach, landward drainage swales, and secondary wall/stilling wave basins. To the candidate's knowledge, the research presents a novel application of ECOncrete Coastalock armour units. Also, the implementation of a perched beach, and drainage swales as retrofit structures are also novel. Test results revealed that crest extensions are powerful retrofit solutions. Existing wave overtopping design equations were also modified to account for the addition of key adaptations.

In addition, a two-dimensional numerical model (IH2VOF) was assessed for its ability to replicate key experimental test cases. The numerical modelling results had acceptable accuracy compared to the experimental results when both were individually scrutinized against EurOtop (2018) prediction equations. The study aimed to contribute to the knowledge base of vertical structure retrofits, and to design guidance.