South Jersey: the coastline of birds
When it comes to birding, there’s probably no state with a greater disconnect between image and reality than New Jersey. Many people think of New Jersey as suburbs, factories, turnpikes, and seaside tourist towns like Atlantic City. It is true that it’s the most densely populated state, but it’s just as true that New Jersey encompasses a wide and rewarding array of habitats and natural areas.
However, overall bird populations continue to decline, for a variety of reasons.
And with the start of the annual beach season, one endangered species in particular is put even more at risk: the piping plover. Crowding of beaches, among other factors, has put these birds at risk of extinction.
Coastline sediments: Muddy and Sandy
The Delaware Estuary has been extensively modified by urban and industrial development over the past two centuries. Since the late 1800s, providing access for waterborne commerce has necessitated the construction and deepening of navigation channels and berths, resulting in the dredging of large quantities of sediment.
Since 1955, the vast majority of dredged material has been placed in upland CDFs located along the banks of the Delaware River. Dredging plays a dominant role as a sediment sink, which permanently removes sediment from the estuarine system. The sediment Basis is land source sediments, including sandy mud. Not the mouth of Maurice River have higher sand content.
South Jersey’s Tidal plain loss
River inputs, bottom erosion and marsh erosion appear to be significant contributors of sediment within the system while predominant sinks removing sediment from the system include dredging, accumulation by marshes, and subtidal shoal development. The balanced sediment budget might be subsidized by enhanced erosion of bottom habitats and coastal wetlands.
Sediment supply from the watershed is likely to increase due to projected increases in precipitation by 7-9% by 2100 and the current consensus is that sea level will rise by 0.5 to 1.5 meters or more by 2100. Sea-level rise will result in larger tidal volumes that bring more salt water up the estuary.
Retreating coastline near Maurice River
Since river inputs of sediment have been decreasing and maintenance dredging of navigation channels represents a major sediment sink, there should be less sediment currently in the system than historically. And in the future, due to decreasing amount of sediments available and sea level rise, the tidal marshes forming the final bends of Maurice river is eroding away into the estuary. From 1940 to 2000, the final 2 U shape bends are completely gone. Tidal habitats are shrinking, and remaining ones pushed closer to developed area.
The loss of the bends is irreversible. The river channel now directly passes through the place where there used to be a peninsula. Should the erosion extend further inland, the loss of the habitats and coastal industrial and recreational land will be permanent.
To the east of the high flow speed zone, an island is covered by salt marsh, with its southern part dissolving into the mudflat. This trend may also be related to the deeper river trough splitting into two parts coming out of the high speed bend. Thus, the shallower area between them and the shoreline maybe potential areas to set up a plan to catch sediments and create a more stable mudflat environment.
From railroads to sea
There used to be human activity on the lost land. South Jersey Railroads and Central Jersey Railroads have two spurs built in late 19th Century to reach the fishing ports of Bivalve and Matts Landing, the later completely vanished by now.
The change is continuing to happen. Sea level rise already renders many places inland below high tide. Impoundment are leaking, causing road flooding. The end of the sea dike also falls apart, being under a higher sea level.
Sediment evidence
In this 1971 Aerial photo, a feature worths inspection: Tidal channels cutting the peninsula and created a tidal lagoon inside. It was from this point that the erosion sped up. It suggests differentiated erosion process might be happening.
From 1971 and 1991 aerial photos, existence of sandy material can be confirmed. Although the bay is dominated by mud, it shows there are still some natural source of larger grain size sediments.
The NJ Government Sediment project also indicate that the mouth of Maurice River is rich in sandy debris.
INITIAL HYPOTHESIS
If more habitat needs to be created for the endangered piping plover, then built infrastructural elements will be strategically placed to filter out fine sediments and retain larger particles in the island of interest
If these structural elements retain sand and minimize velocity towards the island, then newly established flats will form connections to the neighboring wildlife sanctuary and begin to stretch the ecology of the island across the bay.
HOW CHEVRONS + J VANES WORK TO TRANSFER SEDIMENT
CHEVRONS:
Chevrons are triangular structures used in rivers and streams to manage water flow and sediment distribution.
They redirect water towards the channel's center, reducing erosion along the banks by reducing the water's velocity. This redirection also helps in redistributing sediment, maintaining deeper channels for navigation, and creating diverse aquatic habitats.
J VANES:
J-Vanes are strategically positioned in the water to change the direction of flowing water.
J-Vanes are typically installed in a series, angled relative to the flow direction to redirect water flow to lessen erosion in sensitive areas and reduce water velocity, allowing sediment to settle and build up where needed.
DESIGN AND PLACEMENT:
The shape, size, and alignment of the chevrons and j vanes with respect to the prevailing wave direction are critical to their performance.
LOCAL HYDRODYNAMICS:
The local wave climate, tide ranges, and sediment supply must be well understood to design an effective chevron system.
ENVIRONMENTAL IMPACT:
Like any coastal engineering structure, chevrons and j vanes can have unintended consequences on coastal ecosystems and sediment transport patterns, potentially affecting areas down-current.
Proposal and experiment
STRATEGY C | Extending from Island Peninsula
Further exploration
After analysing previous results, we are considering a new possibility of controlling water flow, as a patterns of periodically switching back and forth between tide-dominated environment, experiencing forces in perpendicular directions.
The backwater phenomenon leads to an increase in the water surface level of upstream regions, thereby imposing the threat of submergence during flood events and affecting the longitudinal extent of the river reach.
The effect can be utilized to create favourable aquatic movements to push back against rip current taking away sediment.
Finally, some drone photos of the area of interest.
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