In 2016, NYSDEC and partners removed Shapp Pond Dam after 50 years of blocking migratory fish. 4 years later, restored habitat showed significant gains in stream health and wildlife

Restoring rivers and streams can help reconnect aquatic habitats, improve ecological conditions, and address problems caused by older structures. Dam removal can be particularly important when a barrier interferes with fish movement, changes natural water and sediment patterns, or creates conditions that favor invasive species. The removal of the Shapp Pond Dam in Dutchess County, New York, provided an opportunity to restore natural stream functions and improve habitat along the East Branch of Wappinger Creek.

A Long-Standing Barrier to Fish Passage

Over 50 years, the 12-foot-high Shapp Pond Dam, situated near the outlet of the East Branch of Wappinger Creek, prevented imperiled migratory fish like American eel from moving through the stream. The dam also interrupted natural flow and sediment regimes and created artificial lentic habitat that favored non-native and invasive species.

The impoundment led to stagnant streamflow, elevated water temperatures, reduced dissolved oxygen levels, and a greater likelihood of harmful algal blooms. Because the structure was also in poor condition, it presented a flood and safety concern for the dam owner and downstream property owners.


The East Branch of Wappinger Creek drains almost 86 square kilometers and is a major tributary of the Hudson River Estuary. Across the watershed, agricultural nonpoint source pollution, urbanization, and hydromodification had resulted to degradation of water quality and aquatic habitat. Other low-head dams also fragmented aquatic habitat and interfered with natural river functions and ecological processes.

Assessment Before Dam Removal

In 2016, the New York State Department of Environmental Conservation (NYSDEC), working with the New York State Water Resources Institute and Cornell University, collected macroinvertebrate and substrate samples and evaluated habitat quality in the impounded portion of the river.

The analysis featured that the dam had negatively affected the stream’s macroinvertebrate community and aquatic and riparian habitat. Fish communities also differed significantly above and below the dam.

The warmer impounded water contained silt that was suboptimal for cold-water species such as trout and fish that prefer gravel substrates that included Longnose Dace and Eastern Blacknose Dace. Researchers also found fewer American eel above the dam than in downstream habitat.

Dam Removal and Habitat Restoration

Using grant funding from the NYSDEC Hudson River Estuary Program (HREP), the Dutchess County Soil and Water Conservation District (SWCD) developed a restoration plan. The plan called for removing the dam while retaining some remnants of the structure and installing erosion control near a home to stabilize the streambank.

Project partners carried out the restoration during the summer of 2016. Following dam removal, the SWCD planted native trees, shrubs, and grasses throughout the formerly impounded region to establish a vegetated corridor.

The restoration also included monitoring designed to document the stream’s ecological recovery. Fish, macroinvertebrate, and substrate conditions were monitored at places upstream and downstream of the former dam.

Improvements in Stream and Riparian Habitat

Monitoring showed significant improvement following the project. Biological Assessment Profile (BAP) scores for the macroinvertebrate community in the formerly impounded section improved from “moderately impacted” before removal to “slightly impacted” afterward.

The pre-removal Stream Visual Assessment score for the impounded section was 6.2 in 2016. It increased to 8.5 in 2017 and 8.7 in 2018. The corresponding Biological Assessment Profile score increased from 3.5 in 2016 to 6.4 in 2017 and 6.3 in 2018.

The formerly impounded section also featured substantial changes in particle size distribution. The streambed became considerably coarser after removal, indicating movement of sediments that had accumulated in the impoundment and a return toward natural lotic benthic habitat.

Improvements were also observed in the unimpounded downstream section. Its Stream Visual Assessment score increased from 7.0 in 2016 to 8.5 in 2017 and 8.8 in 2018, while its Biological Assessment Profile score changed from 7.4 to 7.5 and remained at 7.5.

Funding and Project Support

Engineering, demolition, and streambank stabilization were funded through the New York State Environmental Protection Fund through an HREP grant for Tributary Restoration and Resiliency awarded to the Dutchess County SWCD for $96,408.

Biological and physical habitat monitoring was conducted by researchers from Cornell University, with funding support from the New York State Water Resources Institute totaling $33,401. Riparian planting was supported through the HREP’s Trees for Tribs Program.

Restoring More Than Five Miles of Stream Connectivity

The dam removal restored connectivity to more than five miles of stream habitat. Three years of bioassessment data collected by NYSDEC and Cornell University documented clear recovery in the previously degraded upstream section of the East Branch of Wappinger Creek.

The improvements in macroinvertebrate conditions, stream habitat, sediment characteristics, and connectivity demonstrate the ecological response following removal of the long-standing barrier. The restoration helped return the formerly impounded area toward natural stream conditions while improving habitat for aquatic life.

Source: U.S. Environmental Protection Agency (EPA)

FAQs:

1. What is dam removal?

Dam removal is the process of taking a dam out of a waterway to restore stream connectivity or natural functions. It can also help address habitat and flow-related problems.

2. Why are dams sometimes removed?

Dams can interfere with the movement of fish and other aquatic organisms. They can also change natural water flow and sediment patterns.