August 12, 2013
How fish and other marine life benefit from tidal creek restoration.
Rain falls from the sky and eventually drains into the ocean. Sounds simple, but the process has become anything but, for West Central Florida's tidal creeks.
Estuaries, the cradle of life for coastal environments, depend on tidal creeks to balance salinity levels through the timing and distribution of freshwater flows. Moreover, creeks provide essential nursery habitat for a variety of sport fish and the forage they consume. Unfortunately, urbanization has negatively impacted many of the Tampa Bay area's 100-plus tidal creeks.
In his role as Chief Environmental Scientist at the Southwest Florida Water Management District, Brandt Henningsen, Ph.D, oversees the Surface Water Improvement and Management (SWIM) program, in which Tampa Bay is one of 10 priority water bodies. Henningsen lists the main causes of tidal creek peril as physical destruction (filling), channelization, alteration of natural flow and rerouted storm water.
Compounding these detriments, the clearing of native coastal habitat has opened the door to fast-growing non-native plants like Brazilian pepper and Australian pines, which can replace a once complex native plant community of 20 to 100 species with one or two dominant species.
This, Henningsen said, greatly reduces a creek's habitat value for shorebirds and other wildlife. “The first rule of ecology states that everything is connected to everything else,” Henningsen said. For an urbanized region like Tampa Bay, the remedies for disrupted, disturbed or altered creeks are somewhat limited by development and access, so SWIM has had to work within these limitations. For example,
the Little Manatee River's Marsh Creek needed renovation, so in 2009, staff and volunteers worked from Hillsborough County- owned land on the creek's north bank to clear dense, non-native plant growth and remove a large volume of trash.
Most recently, SWIM restored healthy flow to Clam Bayou, where a cluster of previously existing tidal creeks that once drained into Boca Ciega Bay (a Pinellas County offshoot of Tampa Bay) had been turned into channelized ditches. With raw storm water and the usual assortment of hitchhiking refuse flowing directly into Clam Bayou, the site was an environmental nightmare with a more challenging scenario than Marsh Creek's straightforward clear-and-clean.
“We cannot restore the original creeks because there has been so much alteration of the watershed and development as an urban landscape,” Henningsen said. “What we can do is use that stormwater to mimic what a tidal creek would do. We can put that stormwater into the system to, hopefully, provide some of the functions that the original tidal creeks provided when they were there.”
Between April, 2010 and April 2012, Henningsen's team accomplished this by giving Clam Bayou a facelift that included the creation of three stormwater treatment ponds with trash skimmers and as many tidal lagoons for coastal habitat restoration. The project also returned the bayou's main drainage ditch to its natural sinusoidal (curving) creek configuration and converted mosquito ditches and adjacent spoil mounds into a series of shallow ponds linked to the main creek via small channels. Known as “the string of pearls,” this network of ponds carries storm water through another level of natural cleansing before it's released into the bay.
“There used to be tidal creeks here at one time and we have put back at least some of the original functions of those tidal creeks, in that we do have fresh water now that has a chance to go back into that system, lower the salinity and make the habitat a little more nursery-friendly,” Henningsen said. “That water will just make its way into the open water of Clam Bayou and eventually flow into Boca Ciega Bay.”
In these and other projects, Henningsen said that SWIM projects are based on normative forecasting—an ecosystem planning tool that establishes the vision for a desired future reality and defines the steps required to reach that reality. This practice, he said, provides a framework for managing growth and balancing it against environmental resources.
Essential intangibles, Henningsen said, are patience and persistence. “Various planning groups and interested parties around Tampa Bay have spent a lot of time trying to figure out what we want the bay to be like in 100 years,” he said. “What do we want our water quality to be? What nutrient levels do we want? How many acres of sea grass, salt marsh and mangroves do we want to have? Those goals have been defined and we have taken on the next steps of, ‘How do we achieve these goals?'
“Ecosystems typically don't just change overnight. They change slowly over time as we continue to modify them. It takes time to reverse some of those human changes.” FS
First Published Florida Sportsman August 2013