Case Study

Ohio Creek Watershed Project, Virginia, USA

OHIO CREEK WATERSHED PROJECT

Case Study Summary In the Ohio Creek Watershed project, the city is employing a multi-layered approach to mitigating current and future flooding concerns. The $122-million project aims to help mitigate both regular nuisance flooding and storm-surge flooding in the historic Chesterfield Heights neighbourhood. The strategies deployed will offer city officials valuable insight for future planning while creating best practices that other flood-threatened urban centres can follow.
Sector
           WATER
Key Topics
  • Community engagement
  • Coastal resilience
  • Nature-based solution
  • Ecological uplift
  • Green-grey infrastructure
Project Owner City of Norfolk, Virginia
Project Start/Completion 2016 – December 2022
Location Norfolk, VA
Community Impacted Urban, Coastal
Climate Hazards Mitigated Flooding
Case Study Provided by

In the Ohio Creek Watershed project, the city is employing a multi-layered approach to mitigating current and future flooding concerns. The $122-million project aims to help mitigate both regular nuisance flooding and storm-surge flooding in the historic Chesterfield Heights neighbourhood. The strategies deployed will offer city officials valuable insight for future planning while creating best practices that other flood-threatened urban centres can follow.

About the Project

In Chesterfield Heights, rainstorms regularly cause nuisance flooding on neighborhood streets because ageing infrastructure is unable to handle stormwater effectively. Flooding also raises safety concerns. The neighborhood, which is partly cut off from the rest of the city by Interstate 264, can only be accessed by two streets. During flooding events, those roads may be impassable.

In 2017, the state was able to secure a $112-million resiliency grant through the Dept. of Housing and Urban Development’s National Disaster Resilience Competition. As part of conceptual design, the city and designers worked with the community to devise a strategy that would not only address flooding concerns and make the neighbourhood more resilient, but also provide other improvements for the community.

The final design concept called for a mix of hard infrastructure and natural solutions. Near the shoreline, crews would construct more than 1,000 linear ft of floodwall, along with more than 2,000 linear ft of living shoreline. Based on National Oceanic and Atmospheric Administration sea level rise projections, an earth berm was built to an elevation of 12 ft. It extends from the floodwall, across the shoreline and into the neighbourhood. The combination of floodwall and berm create a continuous coastal defence system for the entire community.

At the foot of the berm along Ohio Creek, the team designed a living shoreline to provide a natural buffer against wave action and surge; the design was largely based on studies of wave energy. Along the side closest to the Elizabeth River, a hardened approach was used, incorporating large areas of rip-rap stone to armour the shore. In areas subject to less wave action, vegetated shoreline was installed. Oyster reefs were also created in some areas with rip-rap fill, providing small breakwaters just offshore. Although the living shoreline is located on the other side of the berm from the neighborhood, the community can walk along the berm or gain access to a new fishing pier to better experience the new shoreline.

Designers added a tide gate to the floodwall that can be operated by city staff, as needed, in the event of a storm. As part of that project, VHB also enhanced an existing marsh on the neighborhood side of the gate, where water will be able to move in and out as needed. Numerous solutions were also designed to help alleviate flooding, including two large pump stations. Stormwater systems were also improved in the neighborhoods, with new large-diameter drainpipes installed along streets that are already prone to nuisance flooding. Planted bioswales and permeable pavers were also added to help convey stormwater.

To address access issues, roadways that regularly flood were raised. Because the neighborhood had limited access to begin with, existing roads needed to be kept open while construction crews built raised roadways on new alignments, including a new 30 ft span precast concrete bridge. Sidewalks and paths were also added to expand transportation options, helping to improve access to a light rail station located just outside the neighborhood.

Green space was converted to ‘stormwater parks’, which also help capture runoff and lessen flooding. The strategy provides a public amenity, too. The largest of the parks is an area adjacent to a school, which has been converted to play fields once the area was graded to alleviate standing water and help better direct runoff.

Achieved Outcomes

The Ohio Creek integrated plan results from the Dutch Dialogues planning process and Norfolk’s participation as a 100 Resilient City member. The extensive participatory effort acknowledged the regional economic, watershed and infrastructure context, resulting in a multifaceted and multidisciplinary project scope.

As determined by the needs of the residents, the watershed project had three goals:

  • Design a coastal community capable of dealing withthe increased risk of flooding
  • Create economic opportunity by promoting the growth of existing and new industry sectors
  • Advance initiatives to connect communities, alleviate poverty, and strengthen neighbourhoods.

The Ohio Creek community is better protected to withstand impacts of weather events such as extreme precipitation and storm surge as well as more intense future weather events. The constructed solutions serve multiple purposes, supporting the community and local ecology. A variety of community amenities have been embedded, including innovative features such as permeable roads which have water quality benefits and a positive effect on water storage capacity, and bioswales which store large volumes of water and form green elements in the community. The natural waterfront edge enhances ecological value over time.

During our dialogue with the community, we toured around the neighborhood and you felt how deep their connection with the water goes. That’s not something you want to take away with a big wall. We wanted them to stay connected.Edgar Westerhof, North America Climate Adaptation Director, Arcadis

Number of vulnerable people made more resilient by this project

2000

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