Restoring river edges could help keep floodwaters at bay

The plan to restore the rapids to the Grand River has long been in the limelight, but the concomitant resolution to restore the river’s banks and riparian buffers has unassumingly occupied the shadows. Yet the latter guidelines are integral to aquatic habitats and flood mitigation strategies, and could also contribute to recreation opportunities—an element that successfully captured and held the public’s eye in the rapids restoration project.

Flood protection has traditionally occupied an integral place in city and county planning—for obvious reasons—and now the City is seeking ways to achieve it without increasing the height of floodwalls. One of the proposed solutions is to restore natural river edges, wherever possible, through introducing terraces or increased green space between the river and city infrastructure. 

“If you think of all the different functionalities you can put on a slope or a terrace—certainly there’s no way that a floodwall is going to provide that,” said Christopher Reader, co-chair of the Green Grand Rapids Committee. “There’s no human space on a floodwall—there’s no place to handle the stormwater or to create amenities. It’s one of those things where, even though it may be more expensive [to implement a terrace or greenspace], your payoff is certainly, in the long term, much greater.”

Wetland_terrace

A wetland terrace is one riverbank option explored by the GR Forward Downtown and River Action Plan Draft (DGRI, July 2015).

Riparian zones—those slender shoulders of land bordering waterways—are, according to Schrems West Michigan Trout Unlimited, “among the most diverse biological systems on earth.” They  provide considerable ecosystem services to people, and indispensable habitat services to ecosystems. Some of the most significant ecosystem services a strong riparian zone provides is erosion and runoff control—a natural water quality insurance.

Riparian zones, narrow though they are, tend to support a high diversity of organisms. Large animals are drawn to rivers as consistent water sources, while plant species thrive in the wet environment, fueling both terrestrial and aquatic ecosystems by providing food, shade, and woody debris—which serves as shelter for aquatic species.

Lyon_square_concept

A conceptualized design for Lyon Square’s river edge includes space for various riverfront activities (DGRI).

“The protection and restoration of natural systems should be viewed as a primary public investment,” reads the Green Grand Rapids Master Plan. “Whenever possible, greenways along tributary streams should include public access easements and walk/bike trails.” However, the plan emphasizes that “riparian buffers should be protected or restored whether or not public access can be provided.” Riparian zones are a public investment even when they’re inaccessible to the public. Human recreation is not the only service provided by riparian zones—they are also a means of flood protection. 

Riparian_buffer_widths

Grand Rapids River Corridor Guidelines provides suggestions for ideal buffer widths along the river.

The restored riparian zones will be designed, in places, as a series of terraces in place of the current single slope model. Preserving this additional open space along waterways is an efficient means of flood mitigation—flood risks will be reduced through preservation and extension of the floodplain area and, more importantly, its elevation. This model also benefits many native species, both aquatic and terrestrial. Native vegetation through an extended riparian zone provides both a wildlife corridor for terrestrial species, and shade for the waterway and its coldwater fish species.  

Nichol DeMol, Project Manager for the Rogue River Home Rivers Initiative of Schrems West Michigan Trout Unlimited, emphasizes the importance of preserving coldwater refuges for species like trout.

“If the water’s warmer, they’re trying to cool themselves down, so all of their energy is going into that,” she said. “If there’s a one degree difference in water temperature, you can see a huge change in the fish communities from cold to warmer water species.”

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