Wednesday, October 8, 2014  |  0 Comment(s)  |   Email   Print

Strategic placement of urban greening projects to ensure success

by Ryan Mackin and Joseph F. Koonce

 

The location of an urban greening project has a big impact on its eventual success. For that reason, it’s important to consider the goals of an urban greening project up front and ensure that those goals are incorporated into the process of selecting a project site. As a case study in site selection, we consider here our Vacant to Vibrant (V2V) project, which used a standardized methodology for selecting parcels for green infrastructure in three cities. Our project goals, as described in our introductory post, included a mixture of both ecological and social outcomes. Using a standardized site selection process, we tried to identify the best possible locations for our green infrastructure installations, develop an optimal match of experimental and control parcels to evaluate effectiveness of green infrastructure installations, and provide a method for green infrastructure site selection that will be useful for other projects in the Great Lakes region.

Each of our three cities required three experimental sites, three control sites, and one nursery site. Depending on the city, anywhere from hundreds to thousands of parcels were initially available for project use. The overall approach to selecting a final set of just seven parcels used a nested set of criteria for neighborhoods, block groups, and individual parcels, with unique sets of attributes applied to each level.

Download a list of generic site-selection criteria that may prove useful to other projects.


Neighborhood and Block Group Selection Methods

Initially, we considered a variety of neighborhoods within each municipality. To narrow it down to neighborhoods where green infrastructure would be both appropriate and successful, at the level of the city we considered neighborhood stabilization target areas, stormwater management priority areas, and areas that had designated green zoning that permitted urban greening as a land use. The types of data that we considered for these three criteria varied among the three cities, but generally we considered neighborhoods that had received investment of federal, state, and/or local dollars for economic stabilization or redevelopment; identification by local sewer authorities or US EPA of priority stormwater management areas where flooding or combined sewer overflow (CSO) were problems; and neighborhoods that had active urban farming, land reuse programs, or formal green zoning designation.

We anticipated that alignment with other projects and organizations would be important to the success of Vacant to Vibrant, so we also considered existing or potential partnering institutions within each neighborhood. Northside Redevelopment and federal Hardest Hit programs in Gary were important municipal projects with goals parallel to those of Vacant to Vibrant, and alignment with existing organizations—People United for Sustainable Housing (PUSH) and Buckeye Shaker Square Development Corporation—influenced our selections in Buffalo and Cleveland.

Once a neighborhood was chosen, the next step in the selection process focused on census block groups and used census data and other georeferenced data from USGS and TIGER for environmental, socioeconomic, and cadastral attributes to narrow down block groups of interest for our project. Environmental considerations included high-volume CSOs, location in the watershed and sewershed, access to green space (walkability), and visually-assessed slope and contour of the area. Social and economic data retrieved from the 2010 Census SF1 and 2011 ACS databases factored in block group and census tract levels of income, racial makeup, ages, and property and home values. Both census and field survey-based vacancy rates were integral to gaining a realistic assessment of the potential for neighborhood stabilization and environmental justice. Proximity to other community enhancement programs was also an important selection factor, and during this phase we relied on extensive consultation with neighborhood partner organizations. 

Figure 1. Vacant to Vibrant site proximity to future NEORSD projects in the Woodland Hills neighborhood (Cleveland, OH). The final V2V neighborhood selection is shown near surrounding Sewer District green infrastructure sites--to be installed in the next 2 to 5 years. The block group chosen lies in an area where green infrastructure has the potential to become a common theme for the neighborhood in addition to providing collective impact to stormwater management.

 

Parcel Suitability Analysis

To have a common method for parcel selection in each of the selected block groups in Buffalo, Cleveland, and Gary, we developed a set of qualitative and quantitative metrics to guide selection of candidate parcels. The method relies on neighborhood-specific housing surveys and readily available georeferenced input data including: county parcel shapefiles; lidar-derived digital elevation model (DEM) raster files (1/9 Arc Second resolution); and TIGER Census shapefiles for census tracts, block groups, and blocks. From DEM rasters, we derived terrain raster maps for slope, aspect, and curvature at the scale of the underlying DEM. We used a combination of GIS data and field surveys to establish ownership and vacancy status of individual parcels.

From the input parcel shapefiles and terrain raster maps, we calculated a set of quantitative parcel attributes (mean slope, standard deviation of slope, sum of curvature, and mean aspect) for individual parcels and for a 100-ft buffer polygon around each parcel and tallied the number of occupied parcels within the buffer area. Based on neighborhood surveys and images from Street View in Google Maps, we also developed a qualitative suitability metric (QSM) for a subset of vacant parcels in the neighborhood that had public ownership. The QSM was a weighted sum of a series of twelve binary criteria that represented a range of desirable features of a parcel for optimal installation of green infrastructure. We then ranked candidate vacant parcels having public ownership by various combinations of QSM and quantitative parcel metrics. Using these metrics to screen candidate parcels produced a ranked list of parcels that were most suitable for green infrastructure installation.

Pairing treatment and control parcels required more stringent criteria than selection of the nursery parcel. Because paired sets of treatments and control parcels provides greater statistical power to detect an effect of treatment, we developed a quantitative method based on Principal Component Analysis to guide pairing of parcels using standardized scores of the QSM and quantitative parcel metrics.

The parcel suitability method that we developed has application to the more general problem of repurposing vacant land in urban areas. The method adds an important tool for changing behavior of citizens and community planners in strategic decision-making about the scale of green infrastructure installations. By including objective assessments of the suitability of various parcels for green infrastructure treatment, community discussions can focus on criteria for identifying priority areas for treatment and the levels of parcel aggregation or dispersion needed to obtain quantifiable ecological, economic, and societal benefits.

 

 Figure 2. Digital elevation model (DEM) for Northeast Ohio. This sample georeferenced DEM can be downloaded from the USGS National Elevation Dataset website. By using a resolution of 1/9 Arc Second, we were able to analyze parcel and neighborhood topography with changes in elevation readings occurring approximately every 11 feet horizontally. Terrain raster maps for slope, aspect and curvature were created from the DEM and were then used to prioritize prospective project parcels according to site attributes and buffer area attributes.

 

 

Implementation of Parcel Suitability Analysis

We implemented the parcel suitability analysis primarily for selection of parcels in Gary and Cleveland. Unlike Gary and Cleveland, we were not able to obtain DEM raster maps at 1/9 Arc Second resolution for Buffalo. Also, PUSH pre-identified candidate parcels, which were owned by Buffalo Neighborhood Stabilization Corporation and were approved for use in stormwater management projects. This assessment was performed by PUSH's own PUSH Blue green infrastructure initiative that was planning locally for GI before the V2V site selection process began. The low slope terrain of the PUSH neighborhood on the west side of Buffalo was also unsuitable for application of our parcel selection methods. Essentially, all available parcels in Buffalo would have met the selection criteria developed for Gary and Cleveland, where there was substantial variability in topographic features of the neighborhood and individual parcels.

The method for performing parcel suitability analysis is open to inclusion of a variety of approaches to identifying the optimal mix of parcels for treatment and control. In addition to the QSM, we found that number of occupied parcels in a buffer zone around a candidate parcel and the variability of parcel slope were most informative. Our screening strategy first identified the candidate vacant parcels with number of occupied neighboring parcels greater than the median value for all vacant parcels in the neighborhood. We next screened those for the lowest slope variability (standard deviation of parcel slope less than the median value), and then by the QSM (parcels with QSM value greater than median). Sequential application of these screens results in a decreasing set of candidate parcels. From these screens and the analysis of best pairs of treatment and control parcels, we arrived at the recommended set of parcels.

On the basis of these analyses, we recommended fifteen candidate parcels to our Cleveland community partners for permission to obtain leases. For Gary, Indiana, we confined our selection to 23 parcels owned by the City of Gary in the West Aetna neighborhood. Five of those parcels met our criteria for treatment and control parcels. Additionally, the City of Gary proposed adding additional parcels through their Hardest Hit program. The advantage of these additional parcels is that the post-demolition process of grading and filling can be done to specifications of the treatment regime.


Final Parcel Selection

Project partners determined the final sets of project parcels using additional sources of information. In Cleveland, the pool of 15 candidate parcels was narrowed down with parcel information from county databases. Demolition practices and history were an important determinant, as were problematic title transfer histories. The final selection of three experimental and three control parcels relied on their ranking by the parcel selection method and suitability as paired experimental and control parcels. In Gary, the Hardest Hit program moved along concurrently with our selection process. Two post-demolition parcels and one vacant city-owned parcel were selected as our three experimental sites. The remaining controls were all selected based on their quantitative metrics and suitability as pairs for the study. In Buffalo, PUSH Blue GI investigation helped PUSH define the project sites and jump-start the implementation process. Each site was surveyed and the same selection analysis (less LIDAR data) was applied to the Buffalo sites to ensure they met project parameters.

Residents in each community were included in project planning after we narrowed down site selection to 1–2 block groups of interest within a given neighborhood. Fortunately, we did not encounter instances of strong negative feedback about final site placement—though it was common to be asked why we didn’t choose X other parcel for a variety of reasons, and we consistently observed trepidation around potential negative impacts of land reuse of any kind. After sites were selected, residents played a vital role in determining the programmed use on each site. The synthesis of their design input will be shared in future blog entries.

 

Check out the following resources that provide assistance in selecting sites at different stages in your selection journey: 

 

Resource

Location

Description

EPA Great Lakes Areas of Concern

Regional

Working in these established areas may help the bigger picture of increasing ability to support aquatic life, and may also help you secure funding.

NEORSD Green Infrastructure Plan

Cleveland

The Sewer District's GI Plan establishes priority areas where implementation is most effective in mitigating CSO volume (pp. 21-32). If your project goals are in alignment, and your geographic scope is open, these are good locations to consider. All-in-all this resource has a lot of useful information, even beyond site selection and regional implementation.

USGS Maps, Imagery and Publications

National

Download geospatial data, obtain hi-res aerial imagery, and use browser-based applications if you do not have access to mapping software.

Census Bureau TIGER Products

National

Obtain essential geospatial shapefiles and geodatabases at the state, county, city, census tract, block group and block spatial levels.

USGS National Elevation Dataset

National

An essential resource for topographic data. We used USGS LIDAR Digital Elevation Models (DEM) to analyze the topography of our neighborhoods and parcels. Limitations on caliber of data based on location.

Census Bureau American FactFinder

National

Home for a variety of American Community Survey and U.S. Census data. Much of the same data can be obtained through TIGER, but the front end of this website may be more user-friendly in figuring out what you're looking for.

PUSH Blue Building The Blue Economy Report

Buffalo

A great resource with plenty of citations--essential if you're planning to do any projects in the Buffalo area. The report focuses on a community-based GI approach though much of the info and additional resources are universal.

Lake County Assessor

Gary

Though parcel history is not available through the Lake County Assessor, this is likely the most reliable source for current, general parcel information. Choose "Guest Access".

Cuyahoga County Fiscal Officer

Cleveland

The Cuyahoga Fiscal Officer page is the best source in Northeast Ohio for up-to-date parcel information and history.

NEO CANDO / NST

Cleveland

Case Western Reserve University's NEO CANDO site processes a lot of socio-economic data for the region. The Neighborhood Stabilization Team (NST) provides backdoor access to the data used by NEO CANDO and has been an essential tool for a dense amount of parcel and vacancy data.

 

 


Figure 3. Final parcel selection in the Aetna neighborhood (Gary, IN). Orange parcels refer to experimental sites while yellow parcels refer to control sites. The nursery site in Gary will not be located in the Aetna neighborhood.

 

Figure 4. Final parcel selection in the Woodland Hills neighborhood (Cleveland, OH). Orange parcels refer to experimental sites while yellow parcels refer to control sites. Due to information stemming from a Phase I Environmental Site Assessment, the nursery location is being re-evaluated.

 

Figure 5. Final parcel selection in the PUSH neighborhood (Buffalo, NY). Orange parcels refer to experimental sites while yellow parcels refer to control sites. One control parcel on West Delavan Avenue is not shown on this map. The blue parcel refers to the PUSH nursery site.

 

 
 

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