The following is an excerpt from City Parks, Clean Water, a report by the Trust for Public Land’s Center for City Park Excellence that examines the role of urban parks in managing stormwater. This is the thirteenth installment in a series of 19 posts.
Finding space isn’t the only difficulty in designing water-smart parks. Green infrastructure needs to be kept green in order to function properly and to remain attractive. Swales, rain gardens, and detention ponds are critical components for stormwater management. Long-term aesthetics may take a back seat, especially for wastewater utility staff focused primarily on regulatory compliance, but many such landscape components that are beautiful in initial design renderings will over time start to look mangy. To keep these park areas attractive, experts must choose plants carefully and support good maintenance. Smart planting design (choosing a mix of woody, evergreen, and perennial plants, for example) and rigorous attention and maintenance—especially in the first few years—are important to the success of a water-smart park.
And what about maintaining the rest of a park’s green infrastructure? Managing water in a park requires commitment even after construction ends. The good news about maintenance is that green infrastructure is easily accessible, not somewhere deep below a utility cover. The bad news is that, compared to other park spaces, it often requires more attention because of specialized plant material and because sediment buildup can become debilitating. Infiltration basins require annual or semi-annual mowing, weeding, and removal of debris and dead plants.
Failing to anticipate the maintenance can undermine a successful design. Ann Arbor learned that lesson when pollution- and volume-controlling swales and wetlands in West Park under-performed. The runoff treatment areas were designed to utilize deep-rooted vegetation to withstand high water volumes, but understaffing at the parks department reduced upkeep and allowed shallow-rooted vegetation—less effective at slowing the water flow—to take over the site. With advance planning, the park department might have been able to get staffing or financial assistance from the water department or city council for better maintenance.
No matter how big or small a park is, it is important to perform regular maintenance to ensure that all water management features are functioning properly. Despite these difficulties, cities around the country are rising to meet the challenge with creative policy measures and designs in their urban parks.
It is especially important to factor in the cost of maintenance for a park operating within a floodplain. Buffalo Bayou Park, in flat, rainy Houston, has greenway trails that are inundated regularly – about six times a year. “We’re on a coastal plain, so when water levels get to a certain height, our bayous [streams] flood for a long way,” says Trent Rondot, conservation and maintenance director of bayou greenways for the Houston Parks Board. “Cleaning up the silt and debris is just par for the course.”
The cleanup costs aren’t insignificant. For the full 75-mile bayou greenway system, the city of Houston budgets regular maintenance and also earmarks a reserve of $914,000 to cover potential cleanup costs from a large (once-every-10-years or larger) storm event. (Any unused funds roll over to the city’s capital project reserve at the end of a fiscal year.) For the busiest 2.3 miles of the waterway downtown, the Buffalo Bayou Partnership – a different organization – budgets another $100,000 annually to remove the periodic deposits on two trails.
But paying for more maintenance workers is by no means an unmitigated burden. The very fact of having more staff visibly out in parks is good for residents and visitors in many ways – making the park seem and feel safer, providing a mechanism to report problems and issues, helping people with wayfinding, answering questions, receiving feedback, and more.
There are sometimes countervailing factors that actually cut costs. Some sites require less maintenance than a typical garden because of less frequent watering. Also, in contrast to traditional underground gray infrastructure, the inspection burden can be lower. The University of New Hampshire’s Tom Ballestro says, “It’s easy to determine if it’s working—just walk out there when it’s raining, or after it rains, to see if the water is draining.”
How long components will last with good installation and appropriate maintenance is often an unknown. But with a growing interest from landscape architects in monitoring the performance of stormwater projects, displaying information in real time by using embedded sensors, projections on the realistic lifespans of the components will become more readily available.
Filed under: facilities, green infrastructure, maintenance/management, partnerships, planning Tagged: | Ann Arbor, buffalo bayou park, Center for City Park Excellence, City Parks Clean Water, green infrastructure, houston, maintenance, parks, stormwater, stormwater management, Trust for Public Land, urban parks, West Park