The future of downtown Riverhead depends in large measure on the town’s ability to mitigate and plan around the flooding that occurs when severe weather impacts the region and the Peconic River rises and breaches its banks.
Extreme flooding from weather events like Superstorm Sandy, which struck the region nearly a decade ago, inundated the downtown riverfront and surrounding streets. Floodwaters reached as far upland as Main Street. With continuing sea-level rise and other impacts of climate change, severe storms will likely become more frequent and downtown flooding more extreme.
Riverhead Town, which has been developing the downtown riverfront with new multifamily buildings and is currently planning a new town square on the riverfront, has been working with the Army Corps of Engineers on ways to address downtown flooding, an initiative commenced by Supervisor Yvette Aguiar after she took office in early 2020. At her request, Rep. Lee Zeldin asked the Army Corps in February 2020 to conduct a site visit in downtown Riverhead. That led to a study by the Army Corps’ Floodplain Management Services, which was begun in October.
The Army Corps gave an initial presentation to town officials and planners last month. The presentation outlined possible flooding severe storms could bring to downtown and the riverfront. It is being used to help the town apply for various project grants and inform the design of the town square project.
The presentation, dated July 13, included a hydraulic and hydrologic analysis of possible flooding impacts.
For example, a 100-year flood, which has a 1% chance per year of occurring, has a high likelihood to bring flood water to 12.2 feet, according to the report. The largest storm the report measured, a 500-year flood, which has a .2% chance per year of occurring, has a high likelihood to bring flood water to 15.64 feet. Either of these storms would flood the riverfront and parts of Main Street, graphics in the presentation show. The analysis does not take into account flooding from rainfall.
The economic impact of the flood will be measured through a cost-benefit analysis, comparing the cost of flood risk management measures to potential flood damages. The cost-benefit analysis is not yet complete.
The Army Corps presentation outlines different measures the town can implement to mitigate flooding. They fall into three different categories. Structural measures are “human-designed to reduce occurrence and/or severity of the event,” such as seawalls, bulkheads and flood walls. Natural and nature based features are measures “most appropriate for higher frequency, lower intensity flood events,” and include wetlands and open areas to mitigate flooding. Nonstructural measures, which “remove the structures from flood damages or reducing the degree of vulnerability to the event,” include a wide array of options ranging from physical changes like structure elevation, to more systemic changes like implementing evacuation plans and zoning code changes.
“People have talked about flooding downtown for many, many years and how it’s going to impede redevelopment. What are they going to do about flooding? What are they going to do about parking? Well, this is the answer,” Community Development Administrator Dawn Thomas aid.
Town officials and Urban Design Associates, the firm Riverhead hired to design the town square project, have been using the preliminary presentation in the design of the town square and to apply for the grants Riverhead hopes to win to fund the project, Thomas said.
“The more certainty we can give the state in information, and the more detail and certainty we can give them, and what the costs and what’s expected in terms of the scope of the project, the better we are in our grants,” Thomas said.
The town applied for a $25 million Federal Alternatives Transportation grant in mid-July and is waiting to hear the results. Officials are also in the process of completing the application for New York State’s $20 million Downtown Revitalization Initiative grant, which is due on Sept. 15. Riverhead’s downtown project was a finalist for the DRI grant — previously a $10 million grant — in three prior years and has gotten very positive feedback, Thomas said.
The town square and transit-oriented development plan around the LIRR station will be the two major economic redevelopment projects listed in the Downtown Revitalization Initiative grant application, Thomas said. Some of the money will be used for flood mitigation measures, she said.
“Adaptation and resiliency is important because we can’t control what others do [about climate change], we can only control what we do here,” Barry Long of Urban Design Associates said during a town square update on Aug. 5. “We will do our part, but we’re going to look forward and make sure that we work with the Army Corps and we plan for the future of downtown, so that it will be an asset and amenity for future generations in Riverhead.”
Thomas said the full report from the Army Corps is expected by the end of the year.
The town has also commissioned its own consultant, Street Sense, to draft a market report on downtown’s economics to help determine what businesses could line the town square and better inform the town’s risk assessment measures. Th Street Sense report is expected before the end of the month.
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