The prime culprits are human use of the creek and coastal development—and the ensuing “impervious cover,” meaning any surface that cannot absorb or infiltrate rainfall. For centuries, the creek was bordered by farms. Today, neighborhoods, business parks, and paved roads have replaced the soft ground that previously allowed rainwater to slowly absorb into the soil.
Given that a one-acre parking lot produces 16 times more runoff than a one-acre meadow, one begins to understand how, in dense areas like Mount Pleasant, some 75 percent of rainwater runoff now finds its way to creeks. This water is flushed through culverts and across people’s yards, carrying with it fertilizers, pesticides, gasoline, motor oil, heavy metals, and animal waste.
In The World of The Salt Marsh: Appreciating and Protecting the Tidal Marshes of the Southeastern Atlantic Coast (University of Georgia Press, 2013), author Charles Seabrook illustrates how impervious cover has rapidly altered the Lowcountry landscape in recent decades: “Thousands of people bought or built houses in subdivisions along the creeks, primarily to enjoy sweeping views of water and tidal marsh,” he states, explaining that the spin-off “secondary” development, such as new streets and shopping centers, engulfed the land six times faster than the rate of population growth.
Seabrook also notes how watersheds went from being designated as “forested” to “suburban” so quickly it happened “as fast as researchers could amass field data.” It took less than seven years for the impervious cover at Horlbeck Creek, off the Wando River, to jump from two percent to more than 16 percent. In the same study, the impervious cover affecting Shem Creek leaped from 35 to 55 percent.
Mummichogs & Macrobenthos
Shem Creek twists its way through marshlands some two miles inland to its headwaters in the area where Bowman Road intersects Highway 17 North. Here, the creek is narrow, not more than two or three feet wide at high tide and a mere trickle when the tide is out. The headlands surrounding or draining into the creek are now partially covered by asphalt, concrete, houses, and the overpasses of Highway 17.
“The headwaters are vital to the health of the entire creek,” explains Dr. Denise Sanger, marine scientist with the Marine Resources Research Institute at the S.C. Department of Natural Resources. “This is where you find the small minnows, called ‘mummichogs,’ as well as other small fish, shrimp, and crabs that use the creeks and salt marsh as nurseries. There are also marine organisms that live in the mud, called ‘macrobenthos’—primarily worms and small crustaceans, they are ‘fish food’ and near the bottom of the food web. They are good indicators of habitat health since they cannot move like a fish. When the environment becomes impaired, their numbers and diversity change. These changes can, in turn, impact the use of these systems by the small fish and crustaceans.”
Sanger compares their testing of the headwaters to the canary in the coal mine: “The upper reaches of a creek are a first-warning system, like the birds sent into the mines to measure air quality. When the bird died, the miners knew the air was toxic. Similarly, when the water and sediment quality levels of the headwaters are poor, then we have reason to be concerned about that creek as well as the larger estuary.”
For years, DNR studies of Shem Creek’s headwaters have come back with poor ratings. Many people driving on multi-lane Bowman Road don’t realize that they’re crossing the beginning of the same picturesque creek where they just went kayaking or enjoyed dinner.
Don't Fall Off that Paddleboard
Shem Creek’s water, sediment, habitat quality, and overall biological condition show continued impairment in the various tests run by DNR and other agencies. “On a positive note,” says Dr. Sanger, “a few marine animals are very pollution-tolerant. They live and even thrive. Yet the downside is that the contaminants remain inside them. They can be transferred to the shrimp, fish, birds, shellfish, and humans who feed on them.”
Perhaps the most troubling pollutant for the creek’s recreational users is the high level of enterococci bacteria (typically found in intestines and feces) present. The source may include wildlife, pet waste, malfunctioning septic tanks, sanitary sewer overflows, vessel discharges, leaking sewer infrastructure, and storm- and flood-water runoff. Aside from the obvious aversion to swimming in such tainted waters, fecal bacteria can carry disease.
Charleston Waterkeeper is a member of the international Waterkeeper Alliance, a nonprofit group of on-the-water advocates who patrol and protect more than 100,000 miles of rivers, streams, and coastlines throughout the world. Working with the College of Charleston’s Environmental Geochemistry Laboratory, Charleston Waterkeeper measures the enterococci bacterial levels of frequently used locations, such as Shem Creek, each week from May to October. Based on their data going back to 2013, Shem Creek has regularly not met water quality standards for safe recreational use.
Charleston’s Waterkeeper Andrew Wunderley finds this unacceptable. “One of our main purposes is to let people know they are safe when they’re in or on the water,” he explains. “We sample a number of Charleston’s most popular tidal areas weekly from May to October. Our results are published as soon as the data is complete so people can make an informed decision about where they go swimming or put their kayak or paddleboard in the water.”
Charleston Waterkeeper recently took the matter to the S.C. Department of Health and Environmental Control (DHEC) with an urgent call to reclassify Shem Creek as Class SA, which has the state’s most protective bacterial water quality standards. The change would also make the creek a higher priority for cleanup work. “Unfortunately, DHEC’s funding was cut across the board several years ago,” says Wunderley. “They have not sampled the waters of Shem Creek since 2011.”
Even if DHEC decides to reclassify Shem Creek, the process will take years. After it passes staff approval, the request has to be voted through by the state legislature and then sent to the Environmental Protection Agency for review. In the meantime? Wunderley suggests that if you find yourself swimming in Shem Creek, either purposely or accidentally, you should shower off afterwards as quickly as possible. “Try not to swallow the water,” he says. “Watch the weather. The bacteria levels will be higher after a hard rain with runoff.”
To read the next section, “State of the Fututre,” click here.