Posted on April 24, 2023
In the span of just one day of stormy weather in January, so much sediment had clogged the entrance to the Santa Cruz Harbor that you could walk across the channel.
Since the harbor is directly down the coast from the San Lorenzo River, all of the debris and sand from the channel flows right toward the harbor’s entrance, blocking the waterway and preventing vessels from entering and exiting.
“When there are really heavy rains, all that sand comes our way and we’re the first place it stops,” said Assistant Harbormaster Sean Rothwell.
Enter the Santa Cruz harbor dredge. The system is unique in the United States: Santa Cruz is the only small-craft harbor in the country with its own dredge.
Port Director Holland MacLaurie explained that many other harbors will contract with the U.S. Army Corps of Engineers on an annual basis to perform dredging work over a span of about two months. But because Santa Cruz’s harbor is located so close to the mouth of the San Lorenzo River, the constant outflow of sediment and mountain debris requires crews to continuously dredge for six months out of the year.
The current moves material like sand and driftwood directly toward the jetty. Once it reaches the edge of the harbor, the sediment circles around the jetty and settles at the harbor mouth.
“The location of the harbor has pretty much everything to do with our greater need,” said Rothwell, adding that the fact that the harbor is manmade contributes to shoaling — the formation of a sandy elevation at the bottom of a body of water.
The Army Corps reimburses about a third of the harbor’s annual dredge expenses of $1.6 million — a total of $525,000.
The dredge itself looks like a floating excavator. The blue, white and yellow structure appears like a large crane attached to a boat, but the dredge is essentially just a barge without a motor. That means it requires a system of movable anchors that can be shifted in any direction to pull the metal crane-boat hybrid to the necessary work site — an area where a large amount of sediment has accumulated. A large mechanical arm will submerge what is essentially a huge suction cup into the water, and suck up the excess sediment into a series of pipes that run beneath the water and onto the adjacent beach, releasing it back into the ocean.
It sounds like a gargantuan effort, but really, the dredge is of modest size. The passing O’Neill Sea Odyssey boat is likely bigger than the dredge.
On a sunny day in mid-April, the dredge is positioned just about 30 feet from the jetty where locals jog and walk their dogs. Two men are stationed on the dredge, one manning the controls from the overlook, and the other walking the perimeter. When the suction cup lifts out of the water, it’s caked with waterlogged kelp, driftwood and manmade materials. The crewmember on the perimeter yanks all the debris off and tosses it to the side.
“That can happen quite a bit, maybe like 10 times a day,” said Rothwell. “If they get into some really bad debris pockets they’ll be doing that every half-hour.”
Given the intense runoff from the San Lorenzo River during the winter storms, the potential for rapid shoaling at the harbor mouth was high. That meant keeping the mouth clear was the top priority. Though the crewmembers manning the dredge are still working 10-hour shifts to ensure the harbor mouth stays clear, they have taken care of the shoaling, allowing boats to navigate the channel obstacle-free.
“To have the entrance in the condition that it is now is a testament to how well they do what they do,” said MacLaurie.
“It’s mainly based on species protection for migrating fish,” said MacLaurie. “We need to allow the migration to continue and not interfere with its natural pattern.”
Although the dredge’s main task is to keep the harbor travelable for pleasure craft, fishing boats and others, its operations have a direct impact on local beaches, too. Since the dredge allows sand to drift down the coast, it moves sand onto jetty-adjacent Harbor Beach and Twin Lakes State Beach, maintaining the shore.
The results of the dredge crew’s work goes beyond the 50-hour weeks and beyond mitigating impacts of stormy weather. Dredging at the Santa Cruz Harbor is vital to keeping local beaches accessible to locals and visitors, and therefore preserving the area’s coastal landscape.
“Without the dredge operation, [Harbor] Beach would not be built back in there for everyone to enjoy,” said MacLaurie. “[The crew] are kind of the unsung heroes.”