Flood Mitigation Project Improves Little Tobacco River Intercounty Drain

The Little Tobacco River Intercounty Drain begins just northeast of US-10 at the Tobacco River in Grant Township in Clare County and travels nearly 2.83 miles through Clare County, southwest through the historic downtown in the City of Clare to Dunlop Road, which is the Isabella County Line. Its waters flow into the Tittabawassee River, the Saginaw River, and ultimately the Saginaw Bay.

The drain was established in 1897 and is maintained by the Little Tobacco River Intercounty Drain Drainage Board. The Little Tobacco River Intercounty Drainage District services approximately 7,007 acres and consists of many different land uses.

Demolition of the Great Lakes Central Railroad Crossing on the Little Tobacco River Intercounty Drain

Historically, the City of Clare had been built-out within the existing drain right-of-way and special flood hazard area for the Little Tobacco River Intercounty Drain. Businesses and residences were located directly next to the drain, which crosses beneath 13 bridges within the City. Flooding surrounding the drain was a proven and historical threat.

To mitigate this, the City of Clare petitioned the Little Tobacco River Intercounty Drain Drainage Board to develop an improvement and maintenance project to improve the drain and significantly reduce the possibility of flooding.

This project was found necessary by the drainage board in 2013 after a public hearing where the board listened to the residents and stakeholders about the flooding concerns along their property and on roadways. This project was also found necessary after inspections of bridges throughout the City of Clare that crossed the drain were found to be at the end of their life expectancy and required replacement.

For the next few years, the drainage board worked with the City and other stakeholders to make the project design adequate to mitigate the risk of flooding and cost-effective for taxpayers.

Multiple options on how to improve the drain and solve flooding issues were brought forward to the drainage board.

After a hydraulics study was completed by Spicer Group, it was determined the bridges and drain were inadequate to support the 100-year storm floodplain. To reduce flooding and improve the drain, all the bridges would have to be replaced, increased in size, and the drain channel would need to be increased to convey the water downstream and avoid flooding during significant rain events. However, this solution was cost-prohibitive for the municipality as their budget would not be able to sustain it.

An alternative solution was proposed to replace the bridges while also pursuing funding through the Federal Emergency Management Agency’s (FEMA) Pre-Disaster Mitigation Grant program. This program provides funding for municipalities to purchase property from owners at a fair market value to then remove the structures from the special flood hazard area, creating an open greenspace and floodplain.

Finished box culvert replacement on the Little Tobacco River Intercounty Drain along McEwan Street (Bus-127) in the City of Clare.

The drainage board worked with Spicer Group to determine that 26 landowners with properties within the City were eligible for the grant process. The Drainage Board worked with the landowners to use the grant to voluntarily move from the floodplain area. Once vacant, these homes and buildings were removed from the floodplain, reducing the risk from the 100-year stormwater levels.

The design incorporated two innovative approaches. The first approach included maintaining the original depth and features of the drain channel and constructing a flood shelf to provide the additional conveyance capacity required to ensure that the flooding was contained within the channel. The second design approach utilized the FEMA Pre-Disaster Mitigation Grant to remove several houses and structures from the floodplain in conjunction with replacing the bridges, which helped the project become a financially feasible undertaking for the municipality and stakeholders.

This portion of the project focused on restoring the floodplain by increasing the cross-sectional area of the drain’s channel, restoring floodplain connectivity, and reducing the risk of property flooding throughout the City of Clare while also enhancing the environment along the drain.

The bridge-replacement portion of the project included the replacement of 11 bridges that crossed the drain. These bridges were at or near life expectancy – some having been built more than 80 years ago—posing a potential risk to those that traveled them every day. These bridges were replaced with new and improved structures, creating safer, more sustainable roadways.

In seven of the bridge replacements, three-sided precast concrete bridges with pedestal footings or pilings were used. These pedestal footings were specially designed by Spicer Group and Northern Concrete Pipe and were the first of their kind implemented on a three-sided structure. This design allowed the drain’s natural stream bed to be retained, rather than be replaced with a flat-bottomed stream bed typically used in a four-sided box culvert crossing. In addition, the footings allowed for manageable loads of precast materials to be shipped to the site by lessening the need for a greater scale three-sided precast concrete bridge.

Spicer Group, along with Wade Trim and Fahey Shultz Burzych Rhodes, assisted the Little Tobacco River Intercounty Drain Drainage Board with managing the improvement project, maintaining a high level of communication and coordination throughout the entirety of the project, designing the replacement bridges, designing the drain improvements, applying for the grant, administering the grant, constructing the improved drain, demolishing the buildings within the floodplain, and constructing the greenspace and floodplain shelf.