Wednesday, July 17, 2024

$400K grant to fund watershed studies to improve flooding near Northchase, ILM

Flooding on a street in the North Chase neighborhood. (Port City Daily photo/Mark Darrough)
The Northchase community is one of the areas being studied in New Hanover County for ways to improve flooding. (Port City Daily/file)

NEW HANOVER COUNTY — A nearly half-a-million state grant will assist New Hanover County in studying ways to mitigate flooding in highly impacted locations.

READ MORE: New flooding research shows most vulnerable areas in Cape Fear

The New Hanover County Board of Commissioners will consider accepting two grants totaling $400,000 from the North Carolina Department of Environmental Quality at its Monday meeting. The county received the maximum allowable amount to any municipality for the purposes of performing watershed planning studies.

The funds — covered 100%, with no local match required — come from NCDEQ’s Division of Water Infrastructure for local stormwater improvements, which commissioners supported applying for last fall. The county was notified as a recipient Aug. 11.

The money will go toward assessing two specific areas: Acorn Branch, near the Wilmington International Airport, and Pumpkin Creek, which handles water flow from the Northchase development, near the intersection of interstates 140 and 40.

A watershed plan is the first stage of a larger process to mitigate runoff, county engineer Timothy Lowe said. The study is intended to address ways to decrease stormwater, improve floodplain capacity, restore bank stabilization and develop strategies for more resilient development.

“[It’s] intended to increase the county’s understanding of the drainage infrastructure to better inform future decisions,” he said. “It is difficult to say what exactly it will identify or what solutions could be considered until this work is complete.”

The grant money will be used to hire a consultant the county intends to select by January 2024, with work to begin by March 2024.

The chosen professional will review current conditions, address concerns of drainage infrastructure and analyze data to address future conditions as it relates to potential changes in the community and environment. A baseline capacity will be established using NOAA rainfall data, and future conditions will be estimated for 50 years beyond the study to account for full build-out in line with current zoning and land-use plans.

The county’s future land use map designates community and urban mixed-use for the land surrounding Northchase, as well as a potential employment center, indicating additional growth is headed to that area.

The chosen consultant will build on work and data collection the county has already been doing, including mapping drainage infrastructure throughout the unincorporated areas, Lowe said.

“This work was unassociated to the grant funding and continues to be ongoing,” he said. “However, the mapping that has already taken place within Acorn Branch and Pumpkin Creek will be helpful in reducing some of the data gathering work required to develop watershed plans in those watersheds.”

The goal is to recommend ways to improve the flow and identify any channels that do not meet the needed capacity for 25-year and 100-year rainfall events.

During Hurricane Florence, I-40 — in the Pumpkin Creek watershed — was completely under water with more than 30 inches of rain, cutting off Wilmington from the rest of the state for over a week with no way in or out.

The Northchase area and commercial development within the Prince George Creek watershed saw the highest concentration of impacted structures during and after Hurricane Florence, according to the county’s agenda.

“We also have several FEMA buyout properties in this area, which we look to as one of the indicators that is measurable for purposes of applying for these grant funds,” Lowe explained.

Other areas in the county did not report as high of a concentration in a similar spatial area, he added.

Within the Pumpkin Creek watershed, north of 100 private properties have been impacted in some way by flooding. 

“A lot of the questions involve a dive into details that we hope to understand better through the course of developing the watershed plan so it is difficult to give a clear or definitive answer at this time,” Lowe said.

There are two main outlets for water to drain — north to Pumpkin Creek and South toward Smith Creek. Pumpkin Creek, near Castle Hayne, is cut with encroachments, making it difficult for the water to flow properly.

The Castle Hayne area was recently noted in UCNW’s research on green infrastructure to support flood mitigation as one of the most vulnerable. The research team took into account income, race, education level, access to transportation and households with single earners to pinpoint its target areas. The solution was to avoid more “gray” infrastructure, such as pipes and concrete channels, which allows stormwater to travel faster and lead to erosion and flooding.

In Acorn Branch, the data is limited, but anecdotal information through community residents noted water accumulates there as well, Lowe said, though did not have specifics.

The neighborhoods of Acorn Branch are located upstream of the airport and have experienced widespread flooding leading to property loss and operational impacts to the airport. While ILM was not involved in the grant application, Lowe said it was included as a critical piece of infrastructure in major storms and a desire to ensure it stays protected in future events.

Cape Fear Public Utility Authority operates a major sewer line with lift stations along Acorn Branch.

The sewer pump station has been inundated and partially submerged by flooding during hurricanes Floyd in 1999 and Florence in 2018, CFPUA spokesperson Cammie Bellamy confirmed.

“The biggest problem there is stormwater flowing over infrastructure during major storms,” CFPUA spokesperson Cammie Bellamy said.

She noted CFPUA staff have had some issues accessing sewer outfall lines during very wet conditions. The lines in that area have drip pans installed to keep stormwater from infiltrating during creek and drainage overwash.

“One of the outcomes that we hope to be a byproduct of the watershed planning in this area is to capture and provide more data and clarity to flooding and drainage concerns in that part of the county,” Lowe said.

Finding out the reasons why these particular areas are vulnerable is part of what the watershed plan will do.

“Watershed plans are intended to explore background conditions, analyze different scenarios, and provide potential solutions to background issues and additional scenarios that are analyzed,” Lowe told Port City Daily. “As the background conditions and future scenarios are explored, we will be able to increase the amount of data that we have and gain a clearer picture of the scope/magnitude of the issues in these areas.

According to data from NOAA, sea levels are expected to rise 10 to 18 inches by 2050 and 17 to 79 inches in the next 100 years. UNCW professor and researcher Narcisa Pricope studied the financial impact of climate change and noted New Hanover County property value losses would reach $4.9 million by 2070, with a $22.4 million residential tax base loss.  

The reimbursement-style grant will pay back the county at periodic intervals throughout the process as it expends funds. No work has occurred yet, but Lowe anticipates the $400,000 to cover the work.

It will take two years for the data to be collected and reviewed before a watershed plan it presented in spring of 2026.

The board of commissioners will consider approval of the grant Monday at 9 a.m. at the New Hanover County Historic Courthouse, 24 N. Third St. The meeting can be livestreamed on NHCTV and YouTube.

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