A few years ago, the City of Fort Lauderdale adopted a new seawall ordinance. The old maximum seawall height of 3.9 feet NAVD (click here to learn about vertical datums) became the new minimum overnight. It was a huge step forward in preparing for sea level rise.Now, Broward County is getting ready to make the change county-wide. A proposed County land use amendment aims to set a minimum elevation for all seawalls in Broward County at 4 feet NAVD by the year 2035, and 5 feet NAVD by the year 2050, all in the name of sea level rise and resilience. With nearly 200 miles of seawalls in Fort Lauderdale alone, the majority of which are privately owned, this may be the only way to ensure that no single property owner causes their entire neighborhood to flood during a king tide event.
This new County-wide policy is going to mean a lot of new seawalls. It could mean contractors working faster to build more seawalls in shorter time spans, and it could mean using designs that don’t consider site specific resilience and the local effects of rising seas and stronger storms.
Typically, seawalls are built with about a 30- to 50-year lifespan in mind. Fifty years ago, water levels were fairly similar to what they are today. But in another fifty years, water levels in South Florida could be as much as three feet higher than they are today. Though in most cases it doesn’t make sense to build that much higher right now, any new waterfront construction needs to be designed accordingly so it can be modified for future conditions with minimal effort or expense.
After hurricane Irma hit the gulf coast of Florida in 2017, the City of Punta Gorda suffered severe seawall failures throughout the community, even though the storm made landfall 75 miles farther south. Irma’s winds drove the water out of Charlotte Harbor like a reverse storm surge. Data shows the water level in Fort Meyers dropped by almost four feet. That water level drop, combined with the buildup of rainwater on the land side, caused the seawalls to fail.
Waterfront construction is a specialty that many engineers are not experienced in. Knowing how to determine the proper coastal and environmental loading conditions from sea level rise and hurricanes is even less understood. It is critically important for property owners to know about these issues and ask questions before building their new seawall.
For Broward County to be successful in rolling out its new seawall regulation, local designers and plans reviewers need a comprehensive resource regarding water depths and retrofitting details. This will help to reduce the cost burden on property owners and to make sure that seawalls are designed appropriately. Until then, it is a good idea to retain an experienced coastal/waterfront engineer to help answer some of those questions. At Brizaga, that’s what we do. Contact us here to learn more about our services.
Here are 5 tips when getting ready to upgrade your seawall:
- Pay attention to how deep the seabed is. Be sure that a drop in water levels won’t cause the wall to fail.
- Ask if vinyl is possible for your new wall. It may require some additional work on the land side, but it will last a lot longer than concrete panels.
- Ensure that the wall design includes adequate provisions for raise the cap in the future. You’ll want to be sure that it can be raised with minimal disturbance, and still look good.
- Approach your neighbors about doing a joint project. It could reduce the cost per foot of the wall, and might even lead to expedited permitting.
- Do your homework when selecting a contractor. You’ll want to be sure you receive quality work in a timely fashion.