Riverscour Prairies: The Rare Grasslands That Whitewater Keeps Alive on the New and Gauley Rivers

Walk a riverbank and you might find an old tire, a sneaker sole, a tomato plant escaped from a garden — or an endangered species. The floodplains of the New and Gauley rivers in the Appalachians hold nearly 40 kinds of plant community, from mature silver maple forest to small beds of plants in shallow, slow water. More than a dozen are globally rare — found in very few places on Earth and at risk of disappearing — and the floodplains are home to nearly 50 state-rare plant species and one federally threatened species.

Two of those rare communities are the riverscour prairies.

Prairie, in the Appalachians

"Prairie" calls up bison, rolling grassland, a covered wagon. These prairies are far smaller, but they grow the same tall grasses as the Midwest: big bluestem, Indian grass, switchgrass and little bluestem.

A riverscour prairie at New River Gorge. NPS / Stephanie Perles

They grow only in particular spots: shorelines of cobbles or small boulders beside whitewater rapids. The rapids of New River Gorge and Gauley River National Recreation Area are world-famous for swallowing kayaks and tipping out rafters — and they also keep the prairies alive:

1. At high water, the rushing rapids strip weeds from the cobble bars and knock down small trees and shrubs.
2. That clears space, and the prairie grasses resprout from their deep, strong roots.
3. Without regular flood scour, trees and shrubs move in, shade out the grasses, and the prairie turns to forest.

These sunny openings are habitat for rare plants such as Virginia meadowsweet (Spiraea virginiana) and Monongahela Barbara's buttons (Marshallia grandiflora).

Three threats

Invasive plants. Non-native species that grow or spread fast and crowd out native plants turn up at low levels at many prairie sites: sericea lespedeza (Lespedeza cuneata), purple loosestrife (Lythrum salicaria), Japanese knotweed (Polygonum cuspidatum), autumn-olive (Elaeagnus umbellata) and multiflora rose (Rosa multiflora). Watching whether they increase or spread is critical. In 2012, the monitoring crew found sweet autumn virgin's bower (Clematis terniflora), an invasive never before recorded in the park, in a New River prairie. Park managers removed it, treated the spot so it wouldn't resprout, and searched the surroundings for more. Catching invaders before they spread is a cost-effective way to protect natural areas.

Collecting vegetation data at a riverscour prairie in New River Gorge. NPS / Stephanie Perles

Regulated rivers. The Bluestone Dam on the New and the Summersville Dam on the Gauley hold back floodwater, so floods come less often — and with them the scouring that clears weeds and young trees. The monitoring tracks young trees and shrubs to make sure the prairies don't become forest.

Recreation. Rafting, kayaking, fishing and riverside camping are all popular here, and they can trample shoreline plants down to bare rock, sand or soil at the busiest sites. Cobbles are hard to walk on, so many prairies are unlikely to be heavily used — but heavy uses, such as guided rafting lunch stops and hangouts near rapids, should be put where they will do less harm to rare riverside plants.

How the monitoring works

The Eastern Rivers and Mountains Network (ERMN) monitors natural-resource "vital signs" for nine national parks in the Appalachians, and these prairies are one of them.

How the long-term monitoring is laid out at a riverscour prairie.

The results tell park managers how the prairies are changing, so they can protect them and the rare plants that depend on them. More: rare riparian prairies monitoring and the Eastern Rivers and Mountains Network.

Sources

Based on "Riverscour Prairies Love Whitewater Too...," a January 2016 summary by the Eastern Rivers and Mountains Network, National Park Service; a work of the United States government in the public domain. Misspellings of "meadowsweet" and "multiflora" are corrected. Rewritten in hubnx's own words.