Second-Guessing Nature : Small Model of Batiquitos Lagoon Is Designed to Solve Big Problem
Researchers who have tested everything from America’s Cup yachts to waterlogged rocket modules are trying everything on the fake Batiquitos Lagoon they built to figure out how to unclog the real one.
For three weeks, engineers in landlocked Escondido have watched artificial waves lap at their 55-by-90-foot replica’s concrete shore, hoping to find ways to deflect the rocks that gather at the Carlsbad wetland’s mouth and block ocean tides from flushing them out.
Although it seems a little like floating toy boats across a bathtub, modeling can predict what will happen under real-life conditions, said Ian Collins, vice president of Arctec Offshore Corp. in Escondido, which has a $180,000 government contract to conduct the study.
“Generally it works,” said Collins, a civil engineer. “Of course, we can’t model all possible combinations of tides and storm conditions. We zero in on the standard conditions and we look at (structures’ performance) under the worst storms and the most severe conditions.”
When the study concludes in two weeks, the researchers expect to know where to build a pair of jetties to divert the cobbles away from the lagoon mouth, yet not block the flow of sand to the area’s shrinking beaches.
In search of that data, they have created in their pseudo-lagoon squalls and 24-foot waves, high tides, low tides and nasty winds from all directions. They even recreated the devastating storms of 1983 and 1988 along the 50-foot faux beach.
The real lagoon covers about 600 acres. That’s about 2,500 times bigger than the model. The small scale makes things happen seven times faster, Collins said.
“We could have gone with the numerical models, but this is the next level to give you more confidence in your design,” said Gary Wayne, Carlsbad assistant city planner. “That’s an art, creating a model that will really predict what will happen out there in nature.”
Others, however, were not so confident.
“It’s like anything that deals with computers--garbage in, garbage out,” said Joan Jackson, national coastal committee chairwoman for the Sierra Club, which has filed a lawsuit to block the lagoon’s unblocking. “That (model) is only as good as the information they’re putting into it.”
During its 22 years in Escondido, Arctec has sought answers to diverse and little-pondered questions through its models: Can a hunk of a rocket survive when it hits the ocean? And if it does, can you tow it behind a boat without ruining it? Which kind of keel works best on a Mississippi River towboat? How deep can you sink an offshore oil-drilling platform?
The company has tested military submarines, systems to monitor oil fields in the North Sea, and makeshift docks to aid military landings.
Last year, Arctec suspended half a ton of stinking tuna fish in a gill net to see how many would get away. Next to its Batiquitos model, the engineers are running a model of Logan International Airport, hoping to find a way to prevent Boston Harbor from flooding the runway during a storm. Arctec is also a major testing site for America’s Cup contenders.
Many of the experiments happen in its 295-foot-long, 48-foot-wide indoor basin that has artificial waves big enough to surf on. It’s the “widest commercial towing and seakeeping facility in North America,” the company newsletter boasts.
From its Batiquitos model, Arctec hopes to collect data that will help shape a massive, somewhat controversial government plan to reverse the lagoon’s natural evolution into a meadow.
Left alone, Batiquitos, considered one of California’s last unspoiled wetlands, would become a marsh and eventually a meadow, following a course that many lagoons take.
“We’re looking strictly at the physical feasibility of having an opening (between the ocean and the lagoon) and maintaining it on a year-round basis,” Collins said.
Led by the city of Carlsbad, the $45-million project includes installing two jetties, one on either side of the lagoon’s opening into the ocean, reinforcing four bridges that cross the lagoon and replacing a fifth, and building a buried rock retaining wall parallel to the beach to protect Carlsbad Boulevard during storms.
Officials plan to begin the project in the fall of 1993 or 1994, working around the nesting season of the endangered Belding’s savannah sparrow and the California least tern.
As Arctec continues to jot down data, weigh migrating cobbles and meddle with computerized wave-makers, a longstanding debate rages over the unbottling of Batiquitos.
The city of Carlsbad, the California Coastal Commission, the federal Environmental Protection Agency and numerous government agencies say a regularly ocean-flushed lagoon will provide a better habitat for some wildlife and save the lagoon from filling in with sediment.
“The lagoon’s basically dying,” said Gary Wayne, Carlsbad’s assistant planning director. “It’s drying up.”
But environmentalists--including the Sierra Club and the Audubon Society--say the city is “fixing” the lagoon only because the Port of Los Angeles is footing the $45-million bill.
Los Angeles officials cannot proceed with their own project that will destroy wildlife habitat in the San Pedro Bay unless they enrich wetlands elsewhere. In this case, elsewhere is Batiquitos Lagoon.
“We shouldn’t be managing our sensitive resources in this manner,” Jackson said. “Our lawsuit is based on the fact that they’re going in and making extreme changes to an ecosystem that is working.”
Although city officials strongly deny it, environmentalists also claim the city is getting pressure to clean the lagoon from developers, who view the wetland as a stagnant eyesore and not a natural resource. Environmentalists also say that letting too much water in will harm bird life.
But Wayne says five years’ and stacks of environmental reports support the city’s position.
“In 30 to 50 years, 65% of the lagoon will be gone,” Wayne said. “And short of this project, there’s no technological way of preventing it.”
