Today, with the launch of The Trust for Public Land’s ParkScore, it became easier to answer these questions – and more importantly, to begin to develop solutions to park shortages. ParkScore is the most comprehensive park rating system ever developed, combining advanced GIS analysis and data collected by the Center for City Park Excellence.

San Francisco came out on top of the ParkScore rankings, edging out Sacramento, Boston, and New York. Credit: Flickr user Phillie Casablanca.

The Trust for Public Land analyzed the park systems of the nation’s forty most populous cities, and ranked them according to three categories:

Acreage: a city’s acreage score is based equally on two data points – median park size and the percentage of the city’s area covered by parkland.

Access: a city’s access score is based on the percentage of the city’s population that lives within a half-mile walk of the nearest park, taking into consideration the layout of the road network and barriers to access such as railroads, freeways, and fences.

Service & Investment: a city’s service & investment  score is based equally on two data points – total spending per resident and playgrounds per 10,000 residents.

Park access in Dallas, which placed 21st overall in ParkScore. Areas without walkable park access are either red (very high need) or orange (high need), depending on three demographic factors: density, income, and presence of children. Interactive maps for all cities are available at the ParkScore website.

Combined, these factors provide a fair and comprehensive basis for comparison within cities, between cities, and over time. ParkScore is designed to help city residents quantify their need for more and better parks, and for city governments to craft effective and efficient plans to create excellent park systems.

There is a wealth of information in ParkScore that we will delve into in much greater detail in the coming months. For now, here’s an overview of the best urban park systems and those most in need of improvement. Visit the ParkScore website for all the in-depth rankings, maps, and information.

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When it comes to urban infill projects – and urban infill park systems – in the San Francisco Bay Area, the colossus is Mission Bay. Almost one out of every six acres of the brand new community is slated to become parkland.

Located in east-central San Francisco, along San Francisco Bay and not far from the Financial District, the 303-acre site was a former industrial area, port rail terminal and warehousing center that suffered through decades of decline. Finally, the pendulum swung back, the area’s intrinsic value was recognized, and in 1998 the San Francisco Board of Supervisors voted to establish the Mission Bay North and South Redevelopment Project Areas. It then turned the vast project over to the San Francisco Redevelopment Agency. The area is eventually scheduled to contain 6,000 residential units, 6 million square feet of commercial space, a hotel, a university campus, retail – and 49 acres of new parkland.

Mission Creek Sports Courts, the first of many new parks that will be built within Mission Bay. Credit: Ning Deng, Marta Fry Landscape Associates

The first of the new parks to come on line is 3-acre Mission Creek Sports Courts, a facility designed to specifically activate land and water spaces partially under a freeway. Its development cost was approximately $7.2 million, its gestation period was 10 years, and it officially opened to the public in mid-2008.  As is usually the case with redevelopment projects, the story of Mission Creek Sport Courts is complex.

By the 1990s most of the land of Mission Bay was owned either by the City of San Francisco or by Catellus, Inc., a land development company associated with the Southern Pacific Railroad. Under normal circumstances, since the area was uninhabited, the company would have had a relatively free hand to develop the large site more or less as it wished, which might have meant a modest amount of parkland. However, there was a small but historic and vociferous community living in houses that literally floated in Mission Creek itself, and that group pressed for parks.

“We weren’t going to let them move ahead without a significant commitment to parks and recreation in our area,” recalls Corinne Woods, a local resident who formerly worked for the Neighborhood Parks Council. Years earlier, ideas for the Mission Bay area had included a sterile collection of concrete water channels and high-rise towers that residents had rejected. This time was different, said Woods. “I’ve got to say that they really stepped up to the plate.”

A major reason that so much more was done at Mission Bay is because the developer wanted, and was dependent on, special financing from the Redevelopment Agency to fund public infrastructure. The city, the agency and the community therefore had considerable leverage to require that land be dedicated to public parks, affordable housing and other benefits.  Without public financial help, the entire project would not have been feasible.

Basketball courts in front of new residences. Courtesy Mission Bay Development Agency.

“This is the value of public/private partnerships,” explained Kelley Kahn, project manager with the San Francisco Redevelopment Agency. “We bring powerful public financing tools to the table, the developer brings private land, and together with the community a plan with important public benefits is negotiated.”

Ultimately the redevelopment agency and the master developer (formerly Catellus, now a company called FOCIL-MB) agreed to create 0.45 acres of parkland for every 1.0 net acres of physical development (i.e., acreage not counting streets). This will translate into 41 acres of parks (plus 8 more acres promised within the new campus being built for the University of California at San Francisco). Moreover, under the agreement, the parkland has to be brought on line at a rate equivalent to the development of buildings — that is, park construction cannot be held back while residents are awaited.

Park funding in Mission Bay is provided by way of two sources: from a community facilities district (CFD, also known as a Mello-Roos District), and from tax increment financing – additional tax monies generated because of redevelopment in the area. A CFD is an area where a special property tax on real estate, in addition to the normal property tax, is imposed. The district then sells bonds to finance public improvements and services (which, in addition to parks, could pay for streets, water, sewage and drainage, electricity, schools or police protection.) The tax paid is used to reduce the principal and interest on the bonds.  Similarly, tax increment bonds are issued against future tax increment to pay for parks and other public infrastructure.

The CFD, which runs until the year 2043, and the tax increment financing – a key tool of redevelopment – make all the difference. If it weren’t for the district, Mission Bay (like San Francisco itself at the current time) would not be financially able to create any parks. Moreover, if Mission Creek had contained a large number of small landowners, it is unlikely that they would have voted to spend more of their money by way of a community facilities district. Since Catellus wanted it and was the primary owner, the company was able to make it happen.

Today the park contains courts for basketball, volleyball and tennis, a dog run, a small boat launch for human-powered vessels (kayaks and canoes), a walkway, a bikeway, and a multipurpose lawn. Maintaining and programming the Sports Courts costs about $400,000 per year. A separate community facilities district was formed to fund park maintenance and operations. The cost of this (and other parks) comes to $10,650 per acre for undeveloped land and just over $18,000 per acre for developed land (which is pro-rated by the number of units on each acre). For individual units, the fee generally came to between $150 and $200 in 2010.

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Windsor, a town of 27,000 almost 30 miles north of San Pablo Bay, is the site of one of the newest central parks in the Bay Area. Interestingly, the Windsor Town Green grew not from the needs of a park-starved citizenry, but from a community’s desire to reclaim a largely abandoned downtown, provide a public gathering place – and, not least, compete with nearby towns for Sonoma County wine country tourists.

Even before Windsor incorporated in 1992, there was momentum behind the idea of transforming the underutilized downtown area into a public plaza. That vision, first articulated by Sonoma County in 1986, remained in place after incorporation and served as the foundation for turning the downtown, once a wine processing and railroad hub, into a true walkable civic center anchored by shops and residences.

A crowd gathers on a summer night in Windsor's Town Green. Photo courtesy Windsor Department of Parks and Recreation.

Windsor decided to develop the Town Green, as well as its new municipal center, on the grounds of a vacant junior high school campus, thus fortunately eliminating any opposition from neighbors.  Owned by the Sonoma County Office of Education, the 21-acre site was broken into two parts and sold — 7.5 acres of buildings to the town (for a new town hall), and 13.5 acres to a private developer, subject to a town planning process.

In 1999, after the exact location of the Town Green had been selected, the Windsor Redevelopment Agency purchased the 4.84-acre park site for $1,142,670, which included more than $450,000 in matching grants from the Sonoma County Agricultural Preservation Open Space District. The remaining funds came from the agency’s capital fund, which is replenished by the collection of the tax increment in the growing area. Two years earlier, the Agricultural Preservation and Open Space District had acquired another small part of the property to protect a stand of historic oaks. The remainder of the land has been (or is in the process of being) redeveloped for housing and retail around the park.

Finding a private developer willing to gamble on a unique project in an area of traditional subdivisions was not easy, even with the redevelopment agency spending $2,900,000 to build the park, widen sidewalks, bury utilities, and improve the surrounding streets.

“The town had been promoting the concept of mixed use for a long time,” says Senior Planner Rick Jones, “but no one was willing to take the risk” on a new urbanist development. Finally, in 2001, a developer named Orrin Thiessen took the plunge. In addition to the park, Windsor provided Thiessen with some other incentives. He was given the right to develop his three properties at higher densities than code allowed, and also to encroach on sidewalks for restaurants and commercial use. He was also given an expedited planning review process and reduced parking requirements. By now, almost 14 acres of colorful three-story townhomes with commercial space below have been built.

The Town Green itself features a stage, covered pavilions, a playground, a plum tree orchard, a fountain, reflecting pools, and a historical time-line walk. (The historic oak grove is directly adjacent.) The park, as well as the adjacent restaurants and businesses, are supplied with a Wi-Fi network. In 2008, a community member offered to help underwrite the expansion of the stage, which is now outfitted with a sound system, used for the numerous programs held on the green. Programming is varied and popular, and all events are free. The Summer Nights on the Green concert series is expected to attract 40,000 attendees in 2011. Other regular summer events include the Farmers Market, Tuesday Night Kid Movies and the outdoor Shakespeare Theater on the Green.

But the Bay Area is also thinking of sustainability in terms of smarter growth throughout the region as a whole. The Association of Bay Area Governments (ABAG) has identified Priority Development Areas to encourage infill development, combining housing, amenities, and transit in a walkable environment.

These increasingly dense areas will need carefully planned parks. Some jurisdictions have done little more than hope for additional green space, while others have worked diligently but unsuccessfully to acquire parkland. Still others have succeeded in creating new parks but now have difficulty funding their maintenance.

To provide some guidance, The Trust for Public Land’s Center for City Park Excellence performed a study for ABAG, one component of which was identifying examples of how recently-completed infill parks were financed. We will be publishing each of the four case studies over the next several weeks. First up is Doyle Hollis Park in Emeryville.

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Tiny Emeryville, squeezed between Oakland, Berkeley and the Bay Bridge, has 10,000 residents and 20,000 daytime workers on only 1.2 square miles of land. For most of the 20th century it was an industrial center, famous for meatpacking plants and a Sherwin-Williams paint factory. It has since evolved into a hub for biotech and software companies, including Pixar Animation Studios, as well as a major shopping destination.

Emeryville has a dearth of parkland, particularly parkland away from San Francisco Bay, east of Interstate 80, since that highway is a significant physical and psychological barrier to the enjoyment of green space along the waterfront. The city also has a demand for auto parking because of the daily commuter influx. Doyle Hollis Park grew out of the competition between these two forces.

The park site was slated to become a parking structure. Credit: MIG, Inc. Courtesy Emeryville Planning and Building Department.

In 1999, when the city’s planning department began to develop the North Hollis Area Plan, situated in the transition zone from commercial to residential, it focused upon a warehouse in the block bounded by Doyle and Hollis Streets. In 2002, the warehouse site was slotted for a parking structure and steps were taken to relocate the tenant and arrange acquisition.

During this time, citizen opposition to the idea of a parking structure in the geographic heart of the North Hollis Area grew. The proposed six-story, 700-vehicle building abutted a low-density neighborhood and stood across from a middle school that lacked playing fields. It would have also shaded the new Emeryville Greenway and a pocket park.

“We first considered putting the garage beneath the park,” said Planner Diana Keena, “but the site is so narrow that just the entryway would have consumed a third of the space.” The city also considered building a smaller structure or allowing diagonal street parking around the perimeter of the park, but those, too, would have swallowed most of the park.

Neighbors, who had coalesced a few years earlier to redesign the greenway as a park rather than as a tree-lined auto-oriented street, arose again, voicing opposition to the parking structure, lobbying individual councilmembers, and gaining the support of the school board. “With persistence and a lot of hard work, we eventually convinced the City Council that a park — not a parking structure — was the right thing for the neighborhood,” recalls Jim Martin, one of the original leaders of Doyle Street Neighbors. The group ultimately convinced the City Council to rezone the block to open space.

Kids playing at Doyle Hollis Park. Credit: MIG, Inc. Courtesy Emeryville Planning and Building Department.

From then on, things moved relatively quickly. In 2005 the site, which had already been on the city’s acquisition list, was bought by the Emeryville Redevelopment Agency for $5.1 million, using capital improvement funds from a combination of tax revenue and bond proceeds. That same year, Economic Development Coordinator Ignacio Dayrit, now with the non-profit, San Francisco-based Center for Creative Land Recycling, secured a U.S. Environmental Protection Agency (EPA) brownfield assessment grant for Emeryville, $75,000 of which was applied to the Hollis Doyle parcel. (The site was found to have some petroleum contamination.) Also in 2005, Gates Associates was hired to do planning and community workshops for the park. Later, a $200,000 brownfield cleanup grant was used for site remediation, along with a $500,000 loan from the EPA’s Brownfield Revolving Fund, which was matched with $100,000 from the redevelopment agency. (The loan has since been repaid by the city.)

Design, construction, and remediation added up to $5.25 million, some of which was paid for through the city’s community development block grant program ($109,557), the California workforce housing benefits program ($37,000), and the StopWaste.org Bay-Friendly Landscaping program ($25,000). All told, $10.35 million was spent on the park. Day-to-day park maintenance is handled by the Emeryville Department of Public Works and costs approximately $53,000 a year.

Basketball court at Doyle Hollis Park, with fountain in foreground. Credit: MIG, Inc. Courtesy Emeryville Planning and Building Department.

Opened in 2009 after a year of construction, the 1.25-acre park includes a children’s play area, restrooms, a recreation lawn, a basketball court, a rain garden that processes 85 percent of stormwater runoff on-site, and a striking public art fountain designed by artist Masayuki Nagase. It opened “to great fanfare,” according to City Manager Pat O’Keefe, and Diana Keena remembers that eager children crawled under the construction fencing to play on the climbing structures before it was dedicated.  Since then, park use has exceeded all expectations. “During lunchtime on a sunny day the place is packed with workers, kids, and food vendors,” notes Jim Martin.

As for the existing parking concerns, the city is attempting to address them through transit improvements, including the free Emery-Go-Round shuttle that links downtown to the MacArthur BART station one mile away, partnering with developers in providing public parking components to private parking structures, and prodding employers to offer their workers free transit passes. Finally, Emeryville plans to install meters for all street parking to nudge more drivers into existing garages that traditionally have been underused. The efforts are already successful – recent statistics show that the single-occupancy-vehicle commuting rate of employees to Emeryville is only 36 percent, well below the East Bay average.

He sees parks as a way to increase density without sacrificing beauty and creativity. This is a somewhat of a twist on the usual tension between density and open space, in which cities have to force developers to include parks as an offset to residential and commercial projects (in a future article, we’ll discuss Seattle’s Green Factor codes, which require new developments in dense areas to provide publicly accessible and visible landscaping).

In Toronto, Lamb wants to build a slender 47-story residential tower and replace the podium space of other towers with a tiny park (the entire lot is only 62 by 200 feet). The building is between two historic buildings and the park would feature a lawn, benches, and a fountain.

His plans, though, face some opposition from city planners. This is certainly not the first time that open space and density have struggled to coexist.

Justin Herman Plaza, San Francisco. Credit: Kenneth Lu (Flickr Feed)

San Francisco’s Proposition K, otherwise known as the Sunlight Ordinance, was the source of a recent clash between parks advocates and proponents of dense, transit-oriented city living. Passed in 1984, the ordinance bans the development of any building over forty feet that would cast a shadow on an existing park.

The Sunlight Ordinance halted the development of a group of residential towers, part of the high-profile remake of the Transbay Transit Center, when it was discovered that two of the towers would cast a shadow on nearby parks. The shadows would have fallen on St. Mary’s and Portsmouth Squares for an hour a day in the spring and fall, and on Justin Herman Plaza for an hour around lunchtime in the middle of winter.

The project, designed by Pelli Clarke Pelli Architects, eventually got the go-ahead, in part because developers agreed to pay $10 million for park improvements and to offset the impact of the shadows by building a 5.4-acre rooftop park over the transit center.  The park, which according to this video has the potential to match the grandeur of Chicago’s Millennium Park, will feature an open air amphitheatre, gardens, a trail for running and walking, open grass areas for picnics, lily ponds and more.

It will also provide significant environmental benefits by minimizing the heat island effect, regulating interior temperatures, and absorbing and filtering pollutants rising from the terminal, which will connect 11 regional transit systems and accommodate 100,000 passengers each day.

With more people yearning to move into cities, it is critical to ensure that densification and parks are mutually reinforcing. And in the end, there is no reason why they should not be: people in dense areas need nearby parks for health and relaxation, and parks benefit from a lively atmosphere that comes from being close to homes, shops, transit and workplaces. With the recent success of Chicago’s Millennium Park and New York’s High Line, cities such as Los Angeles , Seattle and San Diego are recognizing the potential of elevated parks to encourage density while also generating excitement and boosting livability.

St. Mary's Square, San Francisco. Credit: BrokenSphere (Wikimedia Commons)

New York landscape architect Thomas Balsley delights in promising to show friends what he calls “the greatest untapped open space opportunity in America.” He then takes them to the top of the Empire State Building and points to the ocean of rooftops visible to the horizon in every direction.

A city receives exactly as much sunlight and rainfall as it did before development when the area was a virgin forest or grassland, but now much of the meteorological action is off the ground on top of structures. Although most individual houses have sloping roofs that are perhaps better suited for solar collectors or conduits for rain barrels, most large institutional or residential buildings have flat ones that could potentially be used for parks. Rooftops represent the rare resource that is increasing. Most are private, but a significant number are publicly owned. And some of those are large–the tops of schools, libraries, government office buildings, post offices, concert halls, convention centers, parking ramps, and bus stations can all extend to well over an acre. Moreover, large private rooftops, such as those on shopping centers, big box stores, and warehouses, are purchasable or leasable, just like any other private property.

The green roof movement, still in its infancy, is mushrooming in popularity along with the green building movement in general. But merely being green does not make a roof a park. That oft-cited Chicago City Hall green roof is a marvelous creation but it isn’t a park, just as the much older green roof on the Time-Life Building in New York City isn’t a park–neither is freely open to the public. There are already thousands of rooftop gardens, pools, and recreational facilities on top of luxury condominiums, apartment buildings, office buildings, and hotels across the country, but they are private facilities for residents, workers, guests, and members only. They are the vertical equivalent of parks inside gated communities.

At present the majority of rooftop parks are ones at ground level built over subsurface parking garages–places like Millennium Park in Chicago, Hudlin Park in St. Louis, and Yerba Buena Garden in San Francisco. This wonderful urban solution is referred to, at Boston’s Post Office Square, as “Park Above, Park Below.” Older facilities are of relatively conventional ornamental design; new ones increasingly incorporate more ecological features. Both Nashville’s new Public Square and Austin’s new City Hall collect all the gathered rain for later use as pumped irrigation water.

Putting parks on rooftops higher than street level is, thus far, much rarer. For one thing, keeping the plant material alive is a challenge because of more extreme conditions of wind, sunlight, thin soil, and lack of trees. For another, there are concerns about the structural strength of buildings and potential water leakage as well as issues of human access and security. Also, what park uses are appropriate on rooftops? Flower gardens, lawns, benches, and pathways? Courts (surrounded by cages) for basketball, tennis, and volleyball? Community gardens? Playgrounds? Dog parks? Miniature golf?

These are complex questions that require a good deal of research–both into the issue of “rooftops” and of “parks.” Some of the investigation is generic, some of it needs to be highly specific, on a city-by-city basis. How many flat rooftops does, say, Miami have? What is the total combined acreage? How many are on public buildings and what is that combined acreage? How many of them are large, say, an acre or more? How many of those large ones are relatively uncluttered with air conditioning units and other paraphernalia? How many are accessible by the public? How many happen to be in areas underserved by parks? This entire field of inquiry is so new that there are almost no data available, although there will be breathtakingly quick progress now that aerial photography is so widely available through Internet programs.

One of the most famous, and one of the oldest, rooftop parks is NCNB Plaza (also called Kiley Garden) in Tampa, Florida. Rarely known for urban innovation, Tampa backed into its moment of leadership as a result of authentic civic outrage over the sale and destruction of its historic rose garden for the erection of a 33-story bank tower. In a creative (and expensive) gesture of repair, North Carolina National Bank agreed to restore the lost green space by putting a park on top of the new tower’s parking deck. Designed by (and named after) prominent landscape architect Dan Kiley and opened in 1988, the plaza is 8 feet above ground level.

Kiley Garden represents all that is great and all that is problematical about rooftop parks. On the positive side, it provides outstanding views of Tampa’s downtown and of the Hillsborough River and its riverwalk. It came into being in a high-land-value location which, under other circumstances, would never have yielded a public park. On the other hand, there were design and construction shortcomings that ultimately–nineteen years later–forced a total and complete renovation, including the removal of every tree, shrub, and blade of grass, as well as the many architectural elements. Of course, almost every aspect of technology has evolved in the past two decades, and the lessons of Kiley Garden can be used to help make rooftop parks more successful in the future.

The two places that have taken rooftop parks the furthest are New York and San Francisco–not surprisingly, since they are the two most crowded big cities in the country.

At 28 acres, New York’s Riverbank State Park is so large that it contains a pool, a skating rink, a theater, four tennis courts, four basketball courts, a wading pool, a softball field, a football field, four handball courts, a running track, two playgrounds, a weight room, a boat dock, and a restaurant. It was built on the roof of a new sewage treatment plant on the Hudson River and provides an exciting template of how large public buildings can be constructed to do double duty.

San Francisco has St. Mary’s Square, a full-fledged, off-the-ground, up-in-the-air park amid the high rises in the Financial District. Moreover, St. Mary’s Square will soon be getting an addition (on another rooftop) thanks to a far-reaching law–Proposition K, The Sunlight Ordinance–passed by voters in 1989. That ordinance, aimed at preventing the proliferation of shadows in already-chilly San Francisco, restricts any new construction that would block sunlight on a public park. (Among other things, the law gave birth to a unit of measurement that has probably never existed anywhere else in history: the “solar-year square-foot-hour of new shade.”) St. Mary’s is the place where the irresistible force of San Francisco’s development pressure met the immovable object of the arc of solar radiation.

Because of its location and open-space importance to workers and residents, St. Mary’s was given the most stringent designation under Proposition K: zero tolerance. The square could not have a single additional square-foot-hour of sunlight taken away. An office tower was proposed that would have blocked a small amount of sunlight–only in the early morning, four months out of the year–but that was enough to kill the proposal, until a wonderful solution was proposed. The developer offered to create a public park on the second-floor roof of the building’s garage. The 5,000-square-foot roof was located in such a way that it received much more sunlight; in fact, the developer calculated that the amount of sunlight hitting the rooftop park addition would be 40 times greater than the sunlight lost to the old park by the building’s shadow. And, because of the steepness of the site, the second-story location actually intersected with the ground plane of a portion of St. Mary’s Square, removing the need for steps or handicap accessible designs.

Overcoming the hurdles of rooftop park technology and getting people up off the ground can be challenging. But rooftop parks could make a big difference when it comes to urban beauty, livability, and recreation. This abundant resource beckons, particularly in extremely dense communities that are very short of parkland.

The bayside city enjoys sunshine for two-thirds of the year, and the balmy summers turn to mild winters. But it’s not just pleasant weather that makes San Francisco so ideal for its active residents. The city has set aside 18% of its land for parks and spent $268 per resident on parks-related projects in the fiscal year 2007.

Those reasons combined are why San Francisco ranks as the best city for the outdoors for the second consecutive year. In general, Californians are a lucky bunch: San Diego, San Jose and Sacramento all ranked in the top 10, while Los Angeles tied for 11th with Austin, Texas.

View the full list and accompanying story here.