Experts weigh flood concerns with coho salmon and steelhead habitat
Last summer, stagnant water from the San Lorenzo River seeped into the basement of the Santa Cruz Beach Boardwalk. Maintenance crews struggled to keep the flooding waters out of the basement, but couldn’t remove it fast enough.
“The immediate effect of the flooding is that we have to close rides, but when it gets to the next level of flooding, it floods areas where our maintenance employees work. And if it’s bad enough, like it was this summer, they can be working in two to three feet of water,” says Kris Reyes, director of community relations at the Santa Cruz Seaside Company. “We also have a lot of electrical equipment down in that area, and electricity and water don’t mix.”
For more than 30 years, the Santa Cruz Beach Boardwalk has experienced intermittent flooding of its basement—every time the water levels of the San Lorenzo River lagoon rise high enough to seep in through the retaining walls.
The Santa Cruz Seaside Company, which owns and operates the Boardwalk, has dealt with the mild flooding over the years by pumping it out. But when the lagoon waters rise dramatically, as they did in 2012, and more recently in 2014, the Seaside Company resorts to emergency measures—breaching the lagoon sandbar with bulldozers to release the water into the sea.
Unfortunately, these artificial breachings of the sandbar may be contributing to ever-dwindling populations of threatened steelhead and endangered coho salmon in the San Lorenzo River, biologists say.
In the dry summer months, creeks and rivers along the Central Coast close their mouths to the sea and form lagoons. In unimpaired conditions, the saltwater leftover in the lagoon is slowly pushed out and replaced with more freshwater. The lagoon then becomes a scene of “marvelous biological productivity,” and the freshwater or brackish lagoon becomes a breeding ground for insects, which provides food for the fish eat, according to National Marine Fisheries Service Biologist Jon Ambrose.
The steelhead that spend time in the lagoon grow bigger and stronger, and Ambrose says they are much more likely to return to the same area as adults to procreate. The process has been studied extensively in Scott Creek, just north of Davenport.
“The fish that are rearing in the lagoon during the summer are the small juveniles, but there’s so much food there that these fish grow very large, very fast, versus if they are in a freshwater stream,” says Ambrose. “Size is a critical factor for salmon and steelhead, because if you go out to the ocean as a little fish, you’re more likely to get eaten, but if you go out as a big fish, you’re less likely to get eaten, and come back as an adult.”
The city of Santa Cruz has allocated money to study the best way to handle flooding while taking environmental concerns into account.
When a lagoon-forming sandbar, like the one at the mouth of the San Lorenzo River, is artificially breached, saltwater rushes in, and because there is very little freshwater flowing to the river mouth in the summer months, the conditions become unlivable for the growing fish, Ambrose says.
“You get this wedge of saltwater and this small layer of freshwater on the top. That doesn’t sound like a big deal, but it is,” he says.
After a breach, the freshwater on the top of the lagoon warms the saltwater on the bottom. The vegetation then decomposes, there is less oxygen in the water and the lagoon traps heat—not great salmon conditions.
“What we found at the San Lorenzo River lagoon this year was that there was at least one point in time where that bottom layer was 92 degrees Fahrenheit,” says Ambrose. “That is off the charts. No cold-water fish can live in there.”
The drought conditions over the summer prompted Ambrose and his colleagues to work with the Santa Cruz Water Department to bypass freshwater into the San Lorenzo lagoon, specifically to improve the situation for growing fish. But when the sandbar there was artificially breached to alleviate the flooding in the Boardwalk’s basement, the precious resource was washed out to the ocean.
“You have a community that is doing all it can to conserve water during this drought, and we were working hard with the city’s water department to improve conditions in the lagoon, and then these breaches happen and all those benefits are lost,” Ambrose says.
Prior to 1989, the city of Santa Cruz managed the conditions at the mouth of the San Lorenzo River, and even had a long-term engineering project in mind at the time—similar to the culvert at the mouth of Soquel Creek, according to Santa Cruz Assistant City Manager Scott Collins. But when a woman was swept out to sea after a natural breach in May of that year, suffering brain injuries that resulted in a coma, her family sued the city. Although the case was ultimately dismissed, the city government then stepped away from creating a long-term solution.
“It put a pause on the project,” says Collins. “We didn’t pursue it even though we had plans, we had put money into it, and we had funding coming in from the state.”
Since that time, the sandbar has been breached on an emergency basis.
The San Lorenzo River rose during a storm in March 2012, and changed course toward the Boardwalk. The Seaside Company took action and constructed sand berms to redirect the flow, but the action was unsupervised by authorities, and the company did not acquire an emergency permit from the U.S. Army Corps of Engineers until after the fact.
One of the stipulations of the 2012 emergency permit is that the city of Santa Cruz begin to establish a timetable and framework for a sustainable solution to the flood control problem at the mouth of the San Lorenzo River, but aside from hiring a consultant to study the problem in 2013, no specific long-term plans were established. And in late September 2014, when the Boardwalk basement flooded again for an extended period over the summer, the Seaside Company sought out another emergency permit from the Army Corps of Engineers.
The emergency permit to breach the sandbar was granted, but the Corps of Engineers and other organizations like the National Oceanic and Atmospheric Administration further implored the city to come up with a long-term solution, and offered to work with them through the process.
Earlier this year, the Santa Cruz City Council approved $45,000 in funding to research flood-control solutions, and approved an additional $120,000 to study the problem and create an interim plan, but no specific long-term solutions have been outlined just yet.
The Seaside Company invested roughly $300,000 over the summer to upgrade sump pumps and reinforce the retaining walls near the river, among other infrastructural improvements made to prevent flooding.
“That was one of the things the agencies wanted us to do, take a little bit of control on our end with our facility, and we’ve taken that seriously,” says Reyes.
Collins, who has championed the effort to devise a sustainable solution to the flood-control problem, hopes that with the funding, a permanent strategy will be implemented in the next few years.
“My hope is that the teamwork that’s come together to start this process will continue forward, and that everybody continues to think about what’s reasonable and feasible, and that we would have something in place to address the emergency situations in a very streamlined way for the next year or two, and that we ultimately have a long-term plan that is efficient and effective,” says Collins. “When I say reasonable and feasible, reasonable is both what can actually be accomplished and works, and balances beach access with habitat and flood control with public safety—and I think we’ll get there.”
PHOTO: Scott Collins, assistant to the Santa Cruz city manager, will work on fish-friendly fixes to river flooding. CHIP SCHEUER