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Soil, Stormwater, and City Parks

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 tenth installment in a series of 20 posts.

Across the country, and across all sizes and shapes of parks, there are a few key elements to getting green infrastructure right. Some of them begin in the site survey and design process. These considerations include getting the soil right, creating or ensuring that there is enough space for the planned improvements, and the maintenance of green infrastructure, which can have both pros and cons when compared to traditional “gray” infrastructure. In this week’s post, we will discuss ways in which soils can be modified to improve the water management qualities of a park.

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Pounding feet compacts the soil in parks, often preventing it from performing properly. Amended or otherwise modifed soils can ensure proper filtration and drainage. (Flickr user Humanoide)

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Renovating Existing Parks With Stormwater in Mind

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 ninth installment in a series of 20 posts.

Existing parks can offer all of the same benefits as brand new parks designed with stormwater in mind, but may need to be upgraded or modified slightly in order to be most effective. Certainly it makes sense to first approach parks that are severely affected by flooding, washouts, or erosion, but even parks without significant water issues can benefit.

Mill Creek Canyon credit City of Kent

Mill Creek Canyon Earthworks Park was renovated to manage flooding, and has remained a popular attraction for both residents and visitors. (City of Kent)

Modifying a current park to handle stormwater has advantages and disadvantages. On the upside, the land is available at no cost. On the downside, the park’s existing features and uses may be sacrosanct to current users who then resist any design or management changes. The process, therefore, requires a strong administrative hand, a good public information process, and top-notch scientific analysis and explication. Chances are that there is a strong legal or financial justification to take remedial steps since stormwater from the park is negatively affecting downstream resources.

A typical passive stormwater management features modifications that keep rainwater within the park for a longer period of time. Doing more than that – filtering and absorbing water from beyond the park’s boundary – generally requires more space or more complex systems, as at Echo Park in Los Angeles.

Echo Park Lake collects stormwater from a large surrounding uphill neighborhood – a swath of about 770 acres. The 125-year-old facility, which began as a reservoir of drinking water from the Los Angeles River but is now a discharging pond to that same waterway, was renovated in 2014 to handle more runoff and improve water quality through sediment traps, constructed floating wetlands, and better circulation. The upgrade improved the look and smell of the park and also allowed more boating. However, the lake can only manage rainfall from smaller storms; in a major deluge it can hold only about 25 percent of the neighborhood’s water, with the rest shunted straight to the river.

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The new design of Echo Park Lake has improved the water quality, helping to bring back the beloved but dwindling lotuses, among other benefits. (KCET)

In Milford, Connecticut, Eisenhower Park along the Wepewaug River was vastly improved when Connecticut Light & Power Corp. agreed to invest $800,000 as mitigation for installing a new overhead transmission line. The company paid to convert an unattractive and unusable abandoned gravel pit in the park into an ecologically active artificial wetland. The wetland served as such successful water storage that the old river levee could be partially punctured, reconnecting the Wepewaug to its historic floodplain. Kent, Washington, did something similar, though with more artistic flair, at Mill Creek Canyon Earthworks Park (pictured above). In the early 1980s, faced with the need to protect its downtown from flooding by Mill Creek, the city rejected the idea of building a traditional engineered dam and opted for a park that could do the same thing. The 2.5-acre, sculptural earthwork park contains enough detention basins and berms to accommodate a 10,000-year storm, and grassy lawns and hillocks provide an attraction to residents and visitors alike during the majority of times without flooding.

The renovation of Discovery Park in Seattle started with a minor departmental work order to repave a parking area. But when environmental engineer Andy Sheffer discovered that culverts under the park were washing out, the repair was completely re-conceived. The city tore out the culverts, brought the water back to the surface, stabilized the slope, and transformed the creek into a cascade of pools. “This began as a maintenance project but it resulted in an accessible water feature,” explained Sheffer. “It’s been highly acclaimed. People love hearing that good environmental deeds are being done, but above all, they really love watching moving water. As soon as we daylight a stream, people want to see more of the riparian corridor exposed. These projects catalyze park projects further downstream.”

When faced with problems such as flooding, runoff, washouts, or poor quality water features (to list only a few), an existing park may be renovated for water management and greatly improved. It can be challenging to work with already established places, but often has benefits for everyone involved.

Islands in the Street: Turning Gray Space Green

Each month, City Parks Alliance names one “Frontline Park” as a standout example of urban park excellence, innovation and stewardship from across the country. In recognition of its partnership and community engagement efforts, Avalon & Gage Park has been named a Frontline Park.

AG1IntAvalon & Gage is a vibrant, eco-friendly oasis and public green space situated on a traffic island at a busy intersection in South Los Angeles. Built in partnership between the City of Los Angeles, the Los Angeles Neighborhood Land Trust (LANLT), and nearly a dozen local organizations and businesses, this 1/3-acre lot has been transformed from a barren plaza into a welcoming neighborhood park with amenities for all ages.  Continue reading

Designing New Water-Smart Parks: Two Stories From California

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 eighth installment in a series of 20 posts.

When it comes to green infrastructure, the easiest parks to work with are new ones — facilities that don’t yet exist and can be specifically designed with stormwater management in mind. Every park is different, from size to geography to the surrounding culture and politics, but when it comes to water-smart parks there are three main issues to be considered:

  • Is the physical relationship of the park to the surrounding community such that a redesign could reduce neighborhood flooding or the pollution of downstream waterways?
  • Does the park have any available space for water flow and storage?
  • Is the composition of the existing soils, water table and underlying rock such that the park can absorb a significant amount of water in the necessary amount of time?

    Tujunga pathway and stream - credit Water Education Foundation

    A recreated streambed at Tujunga Wash in Los Angeles helps revive depleted aquifers. (Water Education Foundation)

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The Goals of Combining Parks and Stormwater

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 seventh installment in a series of 20 posts.

City parks departments and water agencies both stand to benefit from designing parks for stormwater management. However, it isn’t always easy to meet the needs of both parties, as well as those of the citizen users of a park. For one thing, stormwater has a complex range of impacts, and the techniques for dealing with those impacts are not easy to carry out, or even to explain to the public. There are also many different kinds of park users who have vastly different opinions about what makes a park great and what degrades it. Continue reading

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