This earthcache takes you to Plum Point Park and teaches you about how the City of Norfolk used this site to help mitigate shoreline erosion, wetlands loss, and stornm water runoff. The park is only accessible off the Elizabeth River Trail, but street parking is available nearby at the waypoint. Bus and WAVE access available at the nearby Fort Norfolk stops. Please note and comply with the park rules posted at the entrance.
There is no physical cache container to find; to log this earthcache, you will need to message or email us the answers to the questions below.
HUMBLE ORIGINS
It's not clear how Plum Point got its name, but most agree that this area got its origins when the nearby Midtown Tunnel was built in the early 1960s. As the bottom of the Elizabeth River was excavated, the sand, rock, and mud ended up here, eventually sprouting into a weedy meadow with a marshy fringe. Over time, other objects accumulated, even a rusted out barge! Although various plans were proposed for development, the site was never built on, and it existed as an undeveloped meadow (and dumping ground) until plans were proposed in the late 1990s to develop it as a park. Ten years and $1.5 million later, Plum Point is now a green space in the middle of an industrial waterfront, helping to mitigate both coastline erosion and improve water quality.
COASTAL EROSION
It is somewhat inevitable that land eventually erodes into the sea, and that natural forces reshape shorelines. Rain loosens soils, gravity washes the soil and water down to rivers and seas. Waves, tides, storm surges, and river currents can work to continually shift shore lines. Human development can amplify the natural process. When water flows off sidewalks and streets, it picks up more speed and therefore can strip more soil away if it comes in contact with soil surfaces. With so many Virginians living on the Chesapeake Bay and depending on it for survival, the Commonwealth and its cities and counties have taken steps to preserve the coastline as much as possible and promote water quality in the Bay area.
HARDENING THE SHORE
One of the most common steps to preserve existing coastlines against erosion is called hardening. There are two examples visible from the coordinates: revetments and sills.
The first band of granite riprap along the edge of the grassy area of the park is an example of a revetment, an onshore structure designed to protecting the shore from erosion. Revetments are frequently placed at the shoreline and backfilled to create a limited sloping backshore. But that should not be the only solution. If a revetment is placed on an eroding shore, and erosion continues to move the shoreline towards the revetment, the original intertidal habitat - such as marsh areas that are exposed at low tide and submerged at high tide - will be lost to open water, and the revetment will become the shoreline.
Here, then, you can see (at lower tides, anyway) a second line of stone riprap further out, called a sill. On this side of Plum Point, there was an existing area of marsh grass, but runoff from stormwater discharge threatened to wash it away. By adding a sill at the fringe of the marsh area, the marsh is protected and can act as an additional buffer to protect the main shoreline.
The park and its marshy fringe help with air and water quality. First, by creating a vegetated space, local runoff is slowed down and has a chance to trickle through soil, rather than quickly run on concrete surfaces and plunge into the river. Second, by preserving marsh land, sediments can build up and be filtered out of the water by the marsh habitat. Third, trees and other plants can draw carbon dioxide and other pollutants out of the air.
LOGGING THIS EARTHCACHE: This earthcache was designed so it could be answered without referring to the signs in the park, but they will hopefully add to your understanding of coastal erosion and preservation efforts.
To log this earthcache, message or email us and copy and paste these questions, along with your answers. Please do not post the answers in your log, even if encrypted. There's no need to wait for confirmation from us before you log, but we will email you back if you include your email address in the message. Group answers are fine; just let us know who was with you.
1. The name of this earthcache: Plum Point Park Earthcache
2. Observe: Look at the grassy area between the sign and the revetment (the closest band of stone riprap). Can you see any signs of erosion behind it? Based on that, how well do you think the revetment is protecting against erosion?
3. Observe: Was the area of marsh grass visible between the inner band of riprap (revetment) and the outer band (sill)? If so, can you see any signs of erosion in the marsh area? Based on that, how well do you think the sill is protecting against erosion?
Pictures of your visit are not required to log this cache, but are highly encouraged.
SOURCES
US Army Corps of Engineers, Coastal Risk Reduction and Resilience
Woods Hole Institute, The Spectrum of Erosion Control Methods
The National Academies Press, Mitigating Shore Erosion Along Sheltered Coasts, 2007 (please note, no subscription or membership is required to download this document, you can download it as a "guest")
Tim McGlone, "What's in a name? Plum Point Park in Norfolk," The Virginian-Pilot, May 10, 2010