USA - How to Approach Breakwater Maintenance as Water Levels Rise
Many marinas are protected by rubble mound or sheetpile breakwaters, some of which are approaching the end of their life cycles. Regular monitoring and maintenance are paramount if the performance levels of these breakwaters are to be preserved.
This is particularly important for marinas facing sea level rise, along with the more severe storms caused by global warming. As water levels rise, wave overtopping of the breakwater will increase, resulting in agitation in the marina basin that can damage the infrastructure and vessels moored within. Larger storm waves can also accelerate breakwater deterioration and potentially lead to structural failure.
When water levels pass a certain height, the breakwater will become ineffective and no longer safeguard the vessels and infrastructure it was originally built to protect. Adopting an appropriate strategy to monitor breakwater facilities allows a marina owner/operator to make informed decisions on how to maintain the desired protection and performance level in the most cost-effective manner possible.
The first step is having a clear understanding of the conditions for which the breakwater structure was designed. Most existing breakwaters were designed in response to historic averages known at that time for a particular geographic region. What were the known historic high and low water levels and tidal dynamics that informed the design? How did the design account for extreme wave and storm events and their potential impact on structural stability and overtopping? What storm severities/frequencies were assumed?
While there isn’t always specific documentation available to help a marina owner answer these questions, particularly if a facility is very old, in many cases there are relevant examples of similar breakwaters that were built around the same time using similar specifications and materials. Even knowing the typical performance assumptions for a comparable breakwater cross-section can be extremely helpful in evaluating how performance is likely to change as water levels rise and storms intensify.