9.5.1 Fall Line Most people know the fall line as a geomorphological rupture between the metamorphic rock of the Piedmont plateau and the sedimentary ground of the coastal plains. It is visible and dramatic in places like Washington, Fredericksburg, and Richmond. But the fall continues down from there across a number of terraces each defined by a scarp until it reaches the Chesapeake Bay.
Fall Line
I-95
As the James River traverses this thickened fall line, it traces a gradient from holding across a rocky surface to flowing nearer the sea, transitioning from a world of bedded rocks to buoyant ships. It is a gradient repeated in smaller measure by the numerous creeks that enter these rivers and by the streams that enter those creeks. It is also a gradient traversed by a number of organisms including the shad, blueback herring, and menhaden.
RICHMOND
JAMESTOWN
James River
COAL TERMINAL
Figure 9.19: West Frontier: James River via the Fall Line Figure 9.18: Fall Line Frontier
FORT MONROE
153 SCR Phase 1: Context, Site, and Vulnerability Analysis February 2014
BEDDED
BUOYED
HOLDINGS
FLOWS
FIRST WINTE R AT SE A
SECOND WINTE R AT SE A
THIR D WINTE R AT SE A
NORFOLK
OPEN SEA
R ETUR NS TO SEA
RE TURNS TO SPAW N
HATCH ED FR ESH WAT ER
FIFT H SP RING
TERRACES
JA MESTOWN
FALL LINE
AMERICAN SHAD L IF E STAGES ALOSA SAPIDISSIMA
ROCK
SEDIMENT
Figure 9.20: Fall Line Gradients: Operational, Material, Temporal, Spatial, and Ecological
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Off-Sites: Terraces in Jamestown and Poquoson Along the James River to the Chesapeake Bay are a series of marshy terraces striated by marginally higher grounds inhabited by communities—human, animal and plant—that are vulnerable to sea level rise and subsidence. These striations of firmer sediment can be raised and new ones laid to protect historic sites such as Jamestown, enhance inland and off-shore habitats (particularly oyster reefs that have anchored here for millennia), use dredge spoils from adjacent navigation channels, and provide new grounds for socially and physically vulnerable communities in Poquoson. At Poquoson there is the opportunity of building up these striations, not merely for each to be a gradient from land to sea or bedded grounds to surface attenuators; but also for them to perform cumulatively as a protective barrier for communities inland. This multi-layered protective barrier begins at Plum Tree Island National Wildlife Refuge on the Bay, a critical point on the Atlantic Flyway and site of unexploded ordnance from the 1950s that can be defused strategically and the Refuge made available gradually to the public. It works from here inland across a series of fingers of high ground to the City of Poquoson and Langley Air Force Base. HISTORIC JAMESTOWN
PLUMTREE ISLAND NATIONAL WILDLIFE REFUGE
HOG ISLAND
MULBERRY ISLAND
POQUOSON
LANGLEY AIRFORCE BASE
NEWPORT NEWS
RAGGED ISLAND NORFOLK
Figure 9.22: James River terraces and potential high grounds.
Figure 9.21: Fall Line Research Plot
155 SCR Phase 1: Context, Site, and Vulnerability Analysis February 2014
A B
C
E D
Figure 9.23: Historic Jamestown
Figure 9.24: Plan and Sectional Index
G
H
F
Figure 9.25: Poquoson and Plum Tree National Island Wildlife Refuge
Figure 9.26: Plan and Sectional Index
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1
2
3
4
5
6
7
Figure 9.27: Fall Line Horizons: I-95, Route 1 and River Crossings 1 2 3 4
Interstate-95 Occuquan River Fredericksburg, Virginia Rappahannock River
5 Route 1 6 James River 7 Richmond, Virginia
157 SCR Phase 1: Context, Site, and Vulnerability Analysis February 2014
Figure 9.28: Typological Sections A Farm Upland Forest Ferry Jetty B Algae Raceway Jetty Oyster Shoals C Historic Jamestown Lookout Living Levee D Algae Raceway Migratory Bird Nesting Ground Algae Flume E Upland Pine Forest Overlook Biotic Cleansing Naval Ghost Fleet Spartina Gradient F Airforce Runway Public Boat Ramp Marina G Salt Marsh Upland Forest Lowland Forest H Shelter in Place Future Housing Boat Ramp Lookout LOOKOUT Pier
UPLAND FOREST FERRY JETTY FARM
SECTION A
FARM DITCH
JETTY
SECTION B
ALGAE RACEWAY
LOOKOUT
OYSTER SHOALS LIVING LEVEE
SECTION C
HISTORIC JAMESTOWN
NESTING GROUND
SECTION D ALGAE FLUME
ALGAE RACEWAY UPLAND FOREST
OVERLOOK
SECTION E
BIOTIC CLEANSING GHOST FLEET
SPARTINA GRADIENT
SECTION F
RUNWAY BOAT RAMP
MARINA
UPLAND FOREST LOWLAND FOREST
SALT MARSH
SALT MARSH
SHELTER IN PLACE
FUTURE HOUSING
BOAT RAMP
SECTION G
PIER
SECTION H
Figure 9.29: Project Gradients
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