Flooding the Swamp
Reversing a legacy of ditching and draining to reconnect the Pocomoke River to its floodplain wetlands.
Floodplain wetlands play a critical role by storing and filtering water. During large storms, rivers like the Pocomoke overflow their banks into the adjacent lands, or floodplain.
The water spreads out and is slowed by vegetation. Sediment settles out of the water and nutrients are absorbed by plants and trees. The Pocomoke floodplain’s saturated soils support some of the most biodiverse wetland habitats in the region.
After the storm, when the river’s water level subsides, the “filtered” floodwaters slowly return to the river. The whole process helps to reduce erosion and improve water quality.
DRAINING THE SWAMP
The 73-mile-long Pocomoke is the easternmost river that flows into the Chesapeake Bay, draining water from four counties in Delaware, Maryland, and Virginia. Ditching the land for agriculture began during the colonial era, but dramatically increased post-World War II to meet the food demands of a booming population.
While the surrounding cropland was being ditched to more rapidly transmit water off the land after heavy storms, an 18-mile section of the Pocomoke River mainstem was dredged and channelized. The dredged material was piled along each side of the river’s edge creating “spoil banks”, further disconnecting the river from thousands of acres of floodplain.
The announcement of a ribbon cutting ceremony initiating the dredging of the Pocomoke in 1946 provides a perspective from Delmarva at that time: “The flat farmland in this area must be drained by ditches which empty into the Pocomoke River. After hard rains the water backed up into the drainage ditches, and fields were sodden for days, making the ground barren and unprofitable as farmland.”
Today, consequences of the Pocomoke Drainage Project are apparent. The ditching of the floodplain, and the channelization of the river, converted what was historically a groundwater-dominated system into a surface water-dominated system.
The channelized Pocomoke transmits water more rapidly off the land and into the Chesapeake Bay, without giving that water an opportunity to spill into the full floodplain where nitrogen, phosphorous and sediment are filtered. Nitrogen, phosphorous and sediment are all major contributors to “dead zones” in the bay, which can suffocate marine life.
The largest dead zone is most pronounced in the deep waters of the bay’s mainstem during warm summer months. Between 1985 and 2010, the duration of the dead zone fell from five months to four, suggesting efforts to manage nutrient pollution are working. The 2016 dead zone was smaller than average because of low river flow and reduced springtime nutrient-rich runoff. Restoration efforts like the Pocomoke will help even more.
FREEING A TRAPPED RIVER
In 2017, partners came together to restore in initial section of the channelized portion of the Pocomoke River while not impacting the needed drainage to residents upstream. The scale of the Pocomoke floodplain restoration project is massive – encompassing roughly 4,000 acres of floodplain along 9-miles of the river.
The restoration itself is focused on a narrow band of dirt, the spoil banks, which were piled over 12-feet high in some areas along the river’s edge during earlier dredging operations.
Heavy construction equipment was brought in and operated by local contractors to carve breaches, some up to 100-feet in length, through the spoil banks. When the project is completed the number of breaches will exceed 100. Different methods of stabilizing the breaches from erosion are being tested, including the planting of native vegetation.
Working with Partners
The Pocomoke River Restoration Partnership includes the U.S. Fish and Wildlife Service (USFWS), the U.S. Department of Agriculture’s (USDA) Natural Resources Conservation Service (NRCS), the Maryland Department of Natural Resources (MD DNR), the U.S. Geological Survey (USGS), the France-Merrick Foundation, the National Fish and Wildlife Foundation (NFWF), and The Nature Conservancy.
The partnership has led to one of the largest ecological restoration efforts in Maryland’s history, and each partner plays a critical role: The NRCS secured easements and financial incentives for interested landowners and engineering of restoration, USFWS provided technical expertise to design effective restoration techniques, MD DNR provided project support and financial investment. The USGS monitored water quality.
The Conservancy’s work to advance outreach, implementation and monitoring was supported through the generous support of our private donors including the France-Merrick Foundation and the Maryland Chesapeake and Coastal Bays Trust Fund. NFWF has leveraged the great work of this project to support targeted restoration in other areas of the Chesapeake Bay.
A Critical Component
People are always a critical component of the environmental conservation equation. With the number of federal, state and local government decision-makers involved, the private landowners whose participation is essential to the effort were at risk of being overwhelmed with information.
TNC is investing the time to engage landowners to help them identify a restoration plan that works for them whether that is enrolling in a government program, placing an easement on their property, or entering into a private agreement with the Conservancy. As one landowner partner noted, “The Nature Conservancy has been great to work with. They keep me informed when they’re working on the property, which is especially important during hunting season when we have a lot of people hunting on the property.”
Mike Dryden, restoration specialist with the Conservancy, and our project partners have successfully engaged 24 landowners in the 9-mile stretch, enabling us to restore 75% of the floodplain area.
“It’s really important to educate the community on this program, to make people feel comfortable about enrolling in the program. We want to let them know that they’re restoring the land so that future generations can enjoy it,” says Dryden. Mike continues to talk with the remaining landowners about future restoration.
GUIDED BY SCIENCE
In 1998, USGS started studying the Pocomoke River to understand the effect that channelization was having on water quality for the Chesapeake Bay. What they found with those early studies is that channelization did make a big difference on water quality. The channelized floodplains trapped very little phosphorous, nitrogen and sediment compared to the natural floodplains further downstream.
Today, we continue to collaborate with USGS and USDA scientists to further understand how floodplain function varies in relation to how near or far it is from the headwaters of the river and the health of the wetland.
At six sites along the Pocomoke River, a network of monitoring equipment has been installed in strategic positions to evaluate restoration benefits: two monitoring devices are in sections of the river that remain channelized, three set along sections that have been restored, and one set within a naturally connected river channel.
The monitoring program will enable us to gather data on water level fluctuations and the impact the floodplain reconnection is having on flood reduction for downstream communities. The data will enable us to track how long water remains in the floodplains and the impact that natural storage and filtration process is having on water quality improvement for the bay.
And the initial monitoring results are exciting. We’re seeing from the monitoring that this floodplain reconnection project is providing the anticipated benefits.
As the Conservancy and our restoration partners work to engage more landowners in our ongoing restoration efforts, there is one partner whose job is just getting started – nature itself will eventually take over.
LIFE IN A CYPRESS SWAMP
The cypress swamp forest and wetlands that are fed by the Pocomoke’s natural flooding patterns are a biodiversity hotspot. The river itself, while altered, is home to numerous species of resident and migratory fish including herring and shad.
The Pocomoke watershed support more than 60 recorded species of migratory songbirds, including high priority species such as the wood thrush, Swainson’s warbler, Kentucky warbler, Louisiana waterthrush, worm-eating warbler, Acadian flycatcher, yellow-throated vireo, prothonotary warbler, red-headed woodpecker, barred owl, and great-blue heron.
The wild and scenic Pocomoke River also drives a tourism industry that has become one of the largest economic sectors in Worcester and Wicomico counties. The state parks, state forests, wildlife management areas, and nature preserves bordering the 73-mile-long river offer recreational activities almost as varied as the species that inhabit the swampy floodplain.
Restoring the river’s natural beauty, and preserving the watershed’s fragile and captivating ecosystem is in everyone’s best interest.
LOCAL TO GLOBAL
We believe the Pocomoke floodplain restoration is replicable and scalable to other channelized rivers in the Chesapeake Bay watershed, and other sites across the country and around the world.
As a global organization, The Nature Conservancy has a network in place that allows us to share our monitoring data with other regions that can look to the Pocomoke restoration as a best practice. TNC Watershed Scientist Dr. Kathleen Boomer has shared our Pocomoke story in China, translating the science into a watershed management plan that will help address similar water resource concerns.
This local-to-global sharing is an exciting example of the Conservancy’s international science leadership, and reinforces the importance of international collaboration to address global environmental issues.
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