Spongy Gainesville: reimagining stormwater management

OPINION

BY KIM TANZER

Gainesville’s recently persistent rainfall, along with the catastrophic flooding in the northeastern United States, has me thinking about what urban designers and engineers call “stormwater management.”  Locally, we have instructive successes and unfortunate failures in our community’s ability to manage rainfall. Before highlighting local examples, let’s review some basics.

The mechanics of rainfall

When rain falls, it may be absorbed on the site where it falls or run off. 

The first principle of stormwater management is to reduce runoff, holding it on site for long enough to sink into the ground where it falls. The more absorptive the ground is, the better. Forests absorb more rainfall than lawns or golf courses; lawns absorb more water than hard surfaces like roofs, sidewalks, parking lots, or paved streets. Urban areas typically have more hard, non-porous surfaces than more rural areas.

There are two general ways to reduce water runoff in urban areas. First, more “pervious” (absorbent or permeable) surfaces can be incorporated into landscape designs. This might include naturalized areas like groves of trees or groundcovers, permeable paving, or gravel. Second, “containers” like stormwater ponds, raingardens, or cisterns can be incorporated into designs. In either case, qualified experts are required to calculate how much rain will be held on site, and for how long.

A second, obvious principle is that water flows downhill. At the scale of an individual property, the two methods described above are intended to hold water uphill until it is absorbed. If more rain falls than can be held or absorbed on site, it will impact sites downhill.

This suggests an important third principle: rainfall ignores property lines. During and after really large rainstorms, water flows to the lowest point and stays there until it is absorbed–no matter who owns the property.

There is a fourth principle: topography matters. Unlike watersheds in many parts of the world, very little of Alachua County’s water flows to the sea. (Water flowing to the Santa Fe River, then the Suwannee and Gulf, is an exception.) Almost all our rainfall drains from perimeter hills, or rims, downhill to independent centers–like dozens of bathtubs, large and small–then filters directly into the Floridan Aquifer. 

Gainesville’s topography

Our urban area has many watersheds, with two distinctly different landforms. Some watersheds are characterized by city-wide creek systems, while others just look like rolling hills. Each has uplands—where water drains from–and lowlands or floodplains—where water drains to. 

Much of central Gainesville is threaded with creeks leading to four different major basins. Almost all water east of Waldo Road flows into Newnan’s Lake. From the Duckpond south, and between Main Street and 13^th Street, water flows through Sweetwater Branch and Tumblin’ Creek into Depot Park or Bivins Arm, then to Paynes Prairie. Most water on the University of Florida campus flows into Lake Alice. Otherwise, between 13^th Street and about 43^rd Street, water flows into Hogtown Creek and its tributaries, and ultimately into Lake Kanapaha. These are relatively large watersheds, and several watershed-scale solutions have been successful. 

To preserve absorptive uplands, the City created the Hogtown Creek Headwaters park north of 53^rd  Avenue and south of Home Depot. To manage flooding along University Avenue and 34^th Street, the City built an urban stormwater pond where Newberry Road and SW 2^nd Avenue separate and channelized nearby Hogtown Creek. Then, to reduce flooding from the Hogtown Creek floodplain, the City built a large berm along the south edge of the Sugarfoot/Englewood neighborhood. Perhaps the City’s most popular stormwater management project is Depot Park, which collects much of downtown’s stormwater in one series of holding ponds, so individual properties do not need on-site retention ponds. 

Private businesses have also created successful urban amenities within these creek systems. Walmart, on Waldo Road, and Butler Plaza North feature popular stormwater ponds serving as urban lakes. Each is appreciated by walkers, joggers, and bikers, while reducing impacts on their downstream floodplains.

In the western part of our urban area, another type of topography predominates. Here, watersheds, defined by their drainage basins, are much, much smaller. Some of the flooding occurring in west Gainesville neighborhoods is very local but tragic for those experiencing it. 

Watersheds as neighborhoods

As described above, almost all of Gainesville’s land surface is shaped like “dimples” of various scales—larger and smaller shallow depressions, each draining to its center, then into the aquifer. 

Could we begin to envision each dimple—a watershed in reality—as a new kind of neighborhood, with neighbors responsible for each other’s well-being? Then we would regulate across property lines to consider neighbors downhill but within the same drainage basin. We would begin to think of each watershed’s lowest area as a public amenity when dry and a flooded safety valve when inundated with water. Floodplains, a naturally occurring landform, would become public centerpieces rather than dreaded leftovers.

This is the concept many contemporary urbanists have adopted. We have a few examples here in Gainesville, but we could do more, especially in the west part of Gainesville.

Spongy urbanism

Recently urbanists have begun using the term “spongy urbanism” to describe civic features that absorb rainwater. We’ve seen informal examples of stormwater ponds serving as local neighborhood centers, but few have been planned. 

In addition to Depot Park, which serves the downtown “neighborhood,” a series of stormwater features line SW 9th Street in the Innovation District. These architecturalized ponds are built of “tough” materials like concrete, stone, and metal grating, along with local ornamental grasses. They drain and clean the stormwater from a smaller urban area in the Tumblin’ Creek watershed, and we might imagine similar features, with appropriate designs, being built in other neighborhoods across the City. 

Reimagined stormwater retention and flood control projects can provide public spaces while they cleanse stormwater to protect our drinking water and help us celebrate our semi-tropical rainfall. As added benefits, they also provide wildlife habitats, create shade, and reduce urban heat islands. 

The more our area urbanizes, the more valuable a strategic approach to spongy urbanism will become.

Kim Tanzer lives in Gainesville. She is a former UF architecture professor, who was also dean of the University of Virginia School of Architecture.

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