Port Bay

Overview

On the southern shore of Lake Ontario, Port Bay, NY is an active residential community with recreation opportunities like boating and fishing, including ice-fishing for northern pike and yellow perch when safe ice forms. Working closely with New York Department of Environmental Conservation (DEC) and Port Bay Improvement Association (PBIA), Healthy Port Futures aided in the design, implementation, and monitoring of a passive dredge management pilot project to create a bell-shaped sediment pile known as the Cobble Bell that feeds the eroded nearshore.

Development and the continued attempts at controlling the natural erosive/transport environment has contributed to reductions in sediment movement and breached in many of the protective barrier bars.

Development and the continued attempts at controlling the natural erosive/transport environment has contributed to reductions in sediment movement and breached in many of the protective barrier bars.

The geography of the southern shore of Lake Ontario is one of eroding drumlin bluffs that transport sediment across bays and protects communities them from the high-energy lake environment.
The geography of the southern shore of Lake Ontario is one of eroding drumlin bluffs that transport sediment across bays and protects communities them from the high-energy lake environment.
In these bay communities, the amount of sediment dredged per event is relatively small (1,000- 5,000 cubic yards), but occurs with high frequency, at least once per year. These small but high frequency operations can provide opportunities to develop alternate ways to place dredge material.
In these bay communities, the amount of sediment dredged per event is relatively small (1,000- 5,000 cubic yards), but occurs with high frequency, at least once per year. These small but high frequency operations can provide opportunities to develop alternate ways to place dredge material.
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Purpose

Over the last century, jetty construction and shoreline armoring have altered the shoreline, interrupting west to east longshore transport, widening the western barrier bar, and thinning the east barrier bar considerably. Storm waves now breach the eastern bar and deposit sediment over the bar creating secondary semi-permanent inlets, flooding the bay, and threatening important habitat and real estate. The barrier bar needed to be reconstructed, but using machinery to spread dredge over the bar would have been expensive and not a long-term solution.

Over the past few decades, the upland placement of dredge sediment, construction of pier, and armoring of the west bar have contributed to a decrease in sediment transport. As a result, the natural, unprotected eastern barrier bar has shifted back, and become noticeably thinner (losing almost 70’ in shoreline width)

Over the past few decades, the upland placement of dredge sediment, construction of pier, and armoring of the west bar have contributed to a decrease in sediment transport. As a result, the natural, unprotected eastern barrier bar has shifted back, and become noticeably thinner (losing almost 70’ in shoreline width)

Concept

Our plan uses wave energy to spread material from a designed-to-erode drumlin structure (sediment pile) along the protective barrier bar that serves as a feeder bluff. It will erode naturally via wave energy and transport material to strengthen the eastern barrier bar. This less-costly and less-disruptive process was created within known parameters considered in the design: wave direction, water depth, sediment type and amount, available machinery, contractor and knowledge expertise, and time. And because Port Bay is dredged annually, this plan removes additional costs to the community and allows us to assess and calibrate the process each year.

The feeder bluff, made of locally dredged cobbles will serve as a temporary icon of the local geology and the erosive processes that make the region unique.

The feeder bluff, made of locally dredged cobbles will serve as a temporary icon of the local geology and the erosive processes that make the region unique.

Design

The Cobble Bell was made from locally dredged sediment, which consists of a material mix of sand and cobblestones. An example of passive sediment management, the concept represents responsive-design practices applied to the specific landscape. It considered local use and regular practices of the community, like annual dredging, to discern where natural forces can replace machinery use. Geological surveys showed dredged material coarse enough to stack and push with a bulldozer. The Cobble Bell’s placement was determined to minimize the amount of travel distance needed by equipment. Inspired by the geologically unique drumlins whose erosion feeds the nearshore, the Cobble Bell was built perpendicular to the angle of wave activity. The Bell’s steep sides facilitate the feature’s quick erosion and transport dredged sediment along the eastern bay and strengthen the barrier bar.

The intervention at Port Bay is the construction of a feeder bluff made from the annually dredged sediment. Analogous to what happens across the region, the bluff will erode through wave energy and transport material to the east, fortifying the weakened barrier bar

The intervention at Port Bay is the construction of a feeder bluff made from the annually dredged sediment. Analogous to what happens across the region, the bluff will erode through wave energy and transport material to the east, fortifying the weakened barrier bar

Process

Physical modeling helped determine the form of the Cobble Bell and how the annual dredging team will move material. Working on a small, tangible scale, we tested various wave conditions to observe erosion patterns and the effect of wave direction and shoreline. The physical model is not a definitive, predictive approach, but it helped generate inferences, reveal patterns, and uncover questions.

The actual sediment pile will be calibrated through responsive design once installed, which is made easier because Port Bay is dredged at a similar time each year by the same contractor.

Healthy Port Futures studied data collected from 1974-2014 at the closest Wave Information Study (WIS) station 91054, to understand the predominate direction of the wave events. In the dredging season, the majority of the large waves that would move the coarse dredge material are from the northwest direction.
Healthy Port Futures studied data collected from 1974-2014 at the closest Wave Information Study (WIS) station 91054, to understand the predominate direction of the wave events. In the dredging season, the majority of the large waves that would move the coarse dredge material are from the northwest direction.
The wave table was set up to simulate basic conditions at Port Bay, including predominate wave direction, slope, and sediment size.
The wave table was set up to simulate basic conditions at Port Bay, including predominate wave direction, slope, and sediment size.
The drumlin shape increased the erosion rate of the pile. The steep side slopes helped facilitate active sediment erosion. This process mimicked the morphological developmental phases of drumlin bluffs seen along the coast.
The drumlin shape increased the erosion rate of the pile. The steep side slopes helped facilitate active sediment erosion. This process mimicked the morphological developmental phases of drumlin bluffs seen along the coast.
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Monitoring

We developed a monitoring plan to study the movement of the dredge material and its impact on the form of the Eastern Bar. The results will be monitored through drone imagery and RTK survey techniques. ​​The project and subsequent monitoring efforts will provide valuable information into wave-driven dredge placement and movement, and provide a prototype for similar small communities in the region. We will look to supplement the ongoing qualitative data that has been observed by local residents over the last decade and provide insight into how material placed in the nearshore environment around Port Bay moves in response to wave and wind energy.
Within a week, the feature had visibly eroded and there was a measurable effect along the sand bar. Despite extenuating circumstances, initial monitoring data shows that concept worked- material was moved from west to east, and was especially successful in thickening thinning areas of the East Bar that have been historically susceptible to breaching.
Within a week, the feature had visibly eroded and there was a measurable effect along the sand bar. Despite extenuating circumstances, initial monitoring data shows that concept worked- material was moved from west to east, and was especially successful in thickening thinning areas of the East Bar that have been historically susceptible to breaching.
Much of the initial accretion directly east of the feature eroded four months later, suggesting continued migration across the bar, albeit more slowly. The material continued to migrate eastwards across the bar, filling in concave areas of shoreline.
Much of the initial accretion directly east of the feature eroded four months later, suggesting continued migration across the bar, albeit more slowly. The material continued to migrate eastwards across the bar, filling in concave areas of shoreline.
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Sean Burkholder
seanburk@design.upenn.edu
Brian Davis
mudlands@virgina.edu
Tess Ruswick
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