Building hard defense mechanisms in the water might protect our coast, but such infrastructure could be harmful, as well.
SOUTHERN CALIFORNIA — Policymakers, nonprofit organizations, private businesses, academics, scientists and interested individuals up and down the California coast have been engaged in a nonstop series of talks on climate change and sea level rise. Failure to take action now, many argue, could result in frequent flooding events or higher sea levels, directly affecting homes, harbors and other key infrastructure located on or close to the coast. Some methods to defend against phenomena such as coastal flooding or sea level rise include forms of coastal armoring.
What if some of the defense mechanisms to coastal flooding or sea level rise – which could negatively impact harbors and marinas – are canceled out by the negative effects of coastal armoring?
What is coastal armoring?
Before diving into some of the practical applications of coastal armoring it makes sense to first explain and understand the phrase.
The California Coastal Commission, as part of its Regional Cumulative Assessment Project, or ReCAP, has an entire chapter within its policy guidance publication dedicated to defining and explaining coastal (or shoreline) armoring.
“The term shoreline armoring … refers to hard protective structures such as vertical seawalls, revetments, riprap … and bulkheads,” the policy guidance publication stated.
A fact sheet published by the National Oceanic and Atmospheric Administration (NOAA) stated erosion from coastal armoring, which results in the loss of shoreline sediment, is often a strategy implemented by coastal managers and private property owners to “stabilize coastal land and protect residential and commercial infrastructure along the coast … to hold back the sea.”
“Armored shorelines can prevent sandy beaches, wetlands, and other intertidal areas from moving inland as the land erodes or sea levels rise, but they also have the potential to eliminate habitat for marine organisms and beach front for the public by restricting the natural movement of sediments,” NOAA stated in its fact sheet on coastal armoring. “The key to shoreline stabilization, if it is required, is to use a site-specific stabilization method that balances the needs of the public and the needs of the natural system.”
What are the effects of coastal armoring?
An interactive infographic published by KQED TV cited a Surfrider Foundation report stating about 86 percent (950 miles) of California coast was, as of 2003, “actively eroding. Coastal armament, the infographic hinted, was partially responsible for such erosion.
A Stanford Law School report on coastal armoring in 2015 stated armored infrastructure currently occupies more than 110 miles, or roughly 10 percent, of California overall coastline. Coastal armoring is even more profound in Southern California, where such infrastructure occupies 33 percent of the coastline, according to the Stanford Law School report.
“A common perception is that seawalls and revetments protect the coast. Although such armoring structures may temporarily protect property from encroachment by the sea, they accelerate erosion of existing beaches and coastal habitats in the areas where they are located, limit beach access, and impede coastal recreation,” the Stanford Law School report continued. “Scientific evidence shows that coastal armoring structures prevent coastal ecosystems from migrating inland and cut off sand supply by preventing natural erosion processes.”
At least two areas in Southern California – Long Beach’s Naples Island and Newport Beach’s Balboa Island – are looking to rebuild aging seawalls to protect local homes from predicted sea level rise. Both communities are saturated with private boat slips and recreational vessels – be it boats, kayaks, paddleboards or otherwise.
Coastal armoring, while potentially beneficial to individual properties close to the water, could have severe (and negative) repercussions to nearby marine life and infrastructure. Types of coastal armaments include breakwaters, jetties, ripraps, seawalls and temporary seabags.
UCSB’s Marine Science Institute added the presence of invasive species would likely increase with coastal armoring, as the use of artificial structures to protect against invading waters create ideal habitats for nuisance organism. Invasive species is a thorny problem for boaters, meaning any situation allowing such organisms to exist in the vicinity of recreational vessels would prove to be a problem for boat owners.
Coastal armoring could also have negative repercussions on local tourism, according to UCSB’s Marine Science Institute.
The University of California-Santa Barbara’s Marine Science Institute hosts a website dedicated to beach health and coastal armoring. The website details many of the negative costs associated with coastal armoring.
Beach erosion, biodiversity reduction, habitat loss and less space for habitats to relocate inland should sea level rise become a reality.
NOAA, in listing similar effects, stated armoring our shorelines could actually speed up coastal erosion and sea level rise, even though such events could naturally occur on their own.
“While coastal erosion is a natural process, the rate of erosion can be greatly influenced by human activities. Natural factors that contribute to erosion include sediment supply; geologic characteristics; changes in sea level; and the effects of waves, currents, tides, and wind – all of which vary by location,” NOAA’s fact sheet on coastal armoring stated. “Human activities that can alter natural shoreline processes include beach nourishment (adding sand), dredging of ports and coastal approaches, construction of harbors and sediment-trapping dams, and the use of shoreline armor.”
Beach erosion and dredging obviously go hand-in-hand. What affects, if any, would coastal armoring have on dredging projects should the ocean defense mechanism facilitate beach erosion hear harbors?
Public policy on coastal armoring is still taking shape, of course. The topic of coastal armoring was on the California Coastal Commission’s August agenda. A private residence in Laguna Beach was permitted to build a seawall to protect it from the ocean. The Coastal Commission came down hard on the homeowner, ruling the seawall – which measured 11 feet high and 80 feet long – must be removed since it caused more harm to its surrounding environs than benefit to the residence.
“The seawall … is already causing public access impacts,” Coastal Commission staff stated in a report to commissioners. “Little dry sand is left during certain times of the year, and in the two years since the reconstruction [of the private residence] began, the seawall has already trapped a quantity of sand approximately equal to 18 large dump trucks behind it, unable to erode and nourish the beach.”
California ultimately regulates coastal armoring activities via the state constitution and Coastal Act of 1976. Enacted policies are implemented or enforced by the Coastal Commission or State Lands Commission. Resource protection and public access to the water drive policy decisions, according to the Stanford Law School report cited earlier.
The same report recommended agencies such as the Coastal Commission take a more proactive approach in developing policies to protect sensitive habitats and public access. State and local agencies should also pursue sustainable adaptation strategies while also discouraging armoring, the Stanford Law School report stated.