Final Project Report

Healthy Streets Program Analysis for Savannah, Georgia CP 6213: Urban Environmental Planning and Design

MAY 2 , 2022

List of Figures

Figure 1 City of Savannah, Georgia Boundary

Figure 2 Urban Heat Risk of Savannah, GA

Figure 3 Impervious Surface Coverage of Savannah, GA

Figure 4 Five Classes of Urban Heat Risk by Census Block of Savannah, GA

Figure 5 Five Classes of Stormwater Runoff by Census Block of Savannah, GA

Figure 6 Five Classes for Social Vulnerability Index by Census Block of Savannah, GA

Figure 7 Combination of Heat Risk and Stormwater Risk of Savannah, GA

Figure 8 Climate Vulnerability for the Most Socially Vulnerable Blocks

Figure 9 Healthy Streets Program Priority Site 1: Museum

Figure 10 Healthy Streets Program Priority Site 2: Creek

Figure 11 Healthy Streets Program Priority Site 3: Residential

Figure 12 Site 1

Figure 13 Site 1 Strategies

Figure 14 Reference Images for Blue Street Strategies

Figure 15 Pervious Surfaces on Site 1

Figure 16 Public Space Strategies for Site 1

Figure 17 Rooftop Impervious Surfaces on Site 1

Figure 18 Urban Agriculture Reference Images

Figure 19 Site 1: Before and After Visualizations with the Interventions

Figure 20 Site 2

Figure 21 Site 2 with Pervious Surfaces

Figure 22 Site 2 with Indicated Interventions

Figure 23 Site 2: Before and After visualizations with the Interventions

Figure 24 Site 3

1.0 Introduction

The U.S. Infrastructure Investment and Jobs Act, signed into law on November 15, 2021, aims to update various types of infrastructure throughout the country. One outcome of the legislation is the Healthy Streets Program, which allows municipalities to apply for up to $15 million each. Funding aims to support urban heat risk assessments, stormwater runoff assessments, and green infrastructure strategies

The city of Savannah, Georgia was selected to explore how the Healthy Streets Program may be implemented in a local context First, Savannah’s current and projected climate change hazards were researched. Next, geospatial assessments were performed for Savannah’s urban heat risk, stormwater runoff, and equity considerations. These three assessments were geospatially combined to identify three priority areas within the city that are the most physically and socially vulnerable to negative climate change impacts. To help mitigate the negative impacts, urban design and green infrastructure strategies are proposed for the three priority sites Co-benefits are identified for the proposed intervention strategies.

2.0 Current and Projected Climate Hazards

2.1 Historical Background

The founding of the colony of Georgia by James Oglethorpe started with the coastal city of Savannah. Before Oglethorpe's arrival, the land around the Savannah River was home to the Yamacraw people. The Yamacraws had to resettle afterwards, and multiple sources state they were able to resettle peacefully, becoming strong allies to the colonists (Sweet, 2020). Oglethorpe’s vision for Savannah drew on Thomas More’s previous ideology of a utopian society. Disparaging the European society they had left behind, which both More and Oglethorpe critiqued as flawed in its political, religious, economic, and social aspects, they hoped for something bigger and better (De Vorsey, 2012). Modern day

Savannah is most likely not what Oglethorpe had envisioned when he originally founded it, but it holds that utopian atmosphere and dreamy idealism he would have appreciated. Savannah, between the Savannah River and Ogeechee River, is about twenty miles upriver from the Atlantic Ocean. Figure 1 shows Savannah's municipal boundaries within the state of Georgia. Savannah has a humid, subtropical climate which allows the lush greenery and fauna it is known for. Throughout American history, Savannah has maintained its reputation for cultivating both urban and rural planning elements; it is upheld as a city within a large garden. However, Savannah is facing irreversible damage from the consequences of climate change, which especially impact coastal cities.

2.2 Climate Hazards

The regional summary for the Southeast in the Fourth National Climate Assessment (NCA) warns of a variety of risks that are made more likely and/or more severe by climate change. It warns of increasing daily low temperatures, increased prevalence of vector borne diseases, higher flood risk due to both sea level rise and more extreme precipitation events, increased frequency and severity of wildfires and hurricanes, and more extreme drought (U.S. Global Change Research Program, 2019). Not only will the physical infrastructure be devastated, but the groundwater and natural habitats, such as wetlands and marshes, will be impaired.

Savannah is at risk for all of these climate hazards Large forests exist west of Savannah and are primarily managed by the Fort Stewart-Hunter Army Airfield Forestry Branch (FS-HAAF). The FS-HAAF manages a yearly prescribed burn program, the largest on a single plot of land in North America (Dickerson, 2021) This serves the military’s training purposes without starting wildfires. In addition, the keystone species in these longleaf pine forests, the gopher tortoise, relies on wildfires for a suitable habitat (Texas A&M NRI, 2017) However, Georgia has millions of acres of privately-owned forests in the

Savannah and Ogeechee River watersheds If these forests are not diligently managed, potential wildfires could bring large amounts of ash and debris to Savannah via air and surface water

If society continues consuming fossil fuels in a business-as-usual scenario (i.e., Representative Concentration Pathways [RCP] 8.5), NASA projects that by 2100 there will be just under three feet of sea level rise locally for Savannah (NASA, nd) There are different RCP scenarios for climate models that estimate the concentration of greenhouse gases (GHGs) in the atmosphere. RCP 8.5 is the scenario in which there is little to no behavioral change and humankind continues to emit GHGs at or close to the current rate. The 8.5 in RCP 8.5 stands for the radiative forcing expected. It is estimated that under the business-as-usual scenario, the radiative forcing would average 8.5 Watts per square meter (NOAA, 2013). Tidal flooding is a regular issue on the highway from Savannah to nearby Tybee Island and is likely to become an issue for Savannah with projected sea level rise (Union of Concerned Scientists, 2016).

The main climate issues addressed in this evaluation are increased heat, especially in terms of the urban heat island effect, and stormwater runoff management from increasingly severe precipitation events. The NCA predicts that there will be 100-150 nights per year with a minimum temperature greater than 75o Fahrenheit (U.S. Global Change Research Program, 2019). This is important because if people cannot recover at night from daytime heat exposure, they are much more likely to succumb to heat illness (Grey & Hennen, 2016) Anything that can be done to mitigate the urban heat island effect will serve as heat relief for Savannah residents, especially those with the lowest adaptive capacity like the unhoused or those without air conditioning.

Stormwater management from more severe storms, both in Savannah and the vast Savannah and Ogeechee River watersheds, is another important adaptation measure (U.S. Global Change Research Program, 2019) The Savannah River runs from the convergence of Georgia, South Carolina, and North

Carolina along the Georgia-South Carolina border to the Atlantic Ocean. There have recently been costly flood-related damages from large rainfall events up-river in Augusta, Georgia (Lepp & Jones, 2022) Adapting for heavy rainfall events to slow and direct water to strategic outlets will lower flood damages in the future.

2.2 Savannah’s Mitigation Plan

As of 2019, Savannah is home to approximately 145,403 people (Deloitte, 2022). Already at risk for tropical storms due to its location and climate, Savannah has worked diligently on mitigation plans. The city understands that rising global temperatures and sea levels will negatively impact their infrastructure and residents. Savannah’s flood mitigation plan, last updated in September 2021, was written under the guidance of the Federal Emergency Management Agency (FEMA) as well as the Floodplain Mitigation Planning Committee (FMPC) (City of Savannah, 2021). It contains four major goals: protect Savannah’s residents and infrastructure from flood hazards, address areas that experience repetitive loss, improve flood-related education and outreach efforts, and monitor future changes in climate and weather conditions to adapt and implement potential plans (City of Savannah, 2021). These four goals will be pursued through both public and private sector efforts, including the Healthy Streets Program, and they aim to lessen potential damage that Savannah may face in the future.

3.0 Methods and Assessments

To assess Savannah’s climate hazard risk and identify priority areas, publicly-available geospatial and census data, in the format of Geographic Information Systems (GIS) files, were obtained. Three assessments were performed: urban heat risk, stormwater runoff, and equity. A series of steps were taken in esri’s ArcPro 2.8.6 to conduct the analysis. The analyses were performed at the 2020 census block level. This spatial resolution was chosen because of the 30-meter raster cell size, as explained further below. Georgia census blocks were obtained from 2020 TIGER/Line Shapefiles (U.S. Census

Bureau, 2022). These datasets were clipped to the City of Savannah boundary using the Savannah Area Geographic Information Systems (SAGIS) “Municipality” of Chatham County layer (SAGIS, 2022). Rasters were clipped using the tool Extract by Mask, and vectors were clipped using the tool Clip. Clipping the datasets bounded the extent of the analyses. Some of the clipping steps resulted in anomalous geometries and null values. For example, select roads and City boundary edges. For ease of analysis and interpretation, these anomalies were removed from the dataset.

3.1 Urban Heat Risk Assessment

To assess urban heat risk, the Trust for Public Land’s Urban Heat Island Severity for U.S. Cities layer was obtained. The 30-meter raster, sourced from ArcGIS Online, was created with Landsat 8 imagery band 10 (ground-level thermal sensor) from summers 2018 and 2019 (ArcGIS Online, 2022). The layer reports heat risk on a relative scale of 1 to 5 using the Jenks Natural Breaks classification method, with 5 being the most at-risk areas. Figure 2 shows the heat risk for Savannah. The tool Zonal Statistics as Table, using census block boundaries as the zone layer, was used to calculate the median heat risk value per block.

3.2 Stormwater Runoff Assessment

To assess stormwater runoff, the Multi-Resolution Land Characteristics (MRLC) Consortium’s Percent Impervious layer was obtained. The 30-meter raster, sourced from the MRLC website, reports the percentage that a surface is impervious on a scale of 0 to 100, with 100 being 100% impervious (MRLC, 2022). Figure 3 shows the percent impervious layer for Savannah. The tool Zonal Statistics as Table, using census block boundaries as the zone layer, was used to calculate the average percent impervious value per block. The Rational Method for runoff was used to calculate runoff at the census block level:

Q = CiA

Q = Flow rate (cubic feet per second [cfs])

C = Land cover coefficient (Impervious =0.95; Vegetative = 0.35) i = Rainfall intensity (2.19 inches per hour for a “2-year” storm in Savannah)

A = Land cover area (acres, apportioned by impervious and vegetative cover)

Rainfall intensity for Savannah was obtained from the Georgia Stormwater Management Manual, Volume 2, Technical Handbook (Atlanta Regional Commission et al., 2001). The land cover coefficient values used are consistent with industry practices. It was assumed that everything not impervious was vegetation (i.e., 1 – percent impervious = vegetative). To standardize the stormwater runoff values by area, flow rate was then divided by square feet per census block. This approach was taken in order to highlight areas that have high impervious cover rather than highlight especially large areas with high runoff values. The resultant unit, cubic feet per second per square foot, is less physically meaningful than standardized resultant values, which indicate relative stormwater runoff severity.

3.3 Equity Assessment

The Healthy Streets Program prioritizes equity by focusing funding toward mitigating disproportionate negative health impacts on low-income and disadvantaged communities In fact, proposed sites are to be located in areas where at least 30% of residents live below the poverty line

Given that the 2019 poverty rate in Savannah was 21.9%, social vulnerability in a spatial context is a key data input to identify potential priority sites (Deloitte, 2022).

To assess equity, the Social Vulnerability Index (SVI), created by the Centers for Disease Control and Prevention (CDC) and Agency for Toxic Substances and Disease Registry (ATSDR), was obtained. The layer is in vector (polygon) format at the census tract level. The SVI aggregates social vulnerability factors, such as socioeconomic status (e.g., income, employment status), household composition (e.g., age, disability status), minority and language status, housing type (e.g., multi-unit structure), and transportation ability (ATSDR, 2022). The tool Spatial Join was used to obtain an SVI value for each census block.

3.4 Combination

These three layers were combined to identify areas for Healthy Streets Program prioritization. An ordinal combination, concatenation approach, was performed. A rating system was developed for each of the input variables. The Jenks Natural Breaks method was used to bin each variable into five classes. Figure 4 shows census blocks colored by the five bins for urban heat risk. Figure 5 shows census blocks colored by the five bins for stormwater runoff. Figure 6 shows census blocks colored by the five bins for SVI. Table 1 presents the rating schedule for each variable.

Then, each bin was reclassified into values 1 through 5 for ease of concatenation. Finally, an expression was used in the Field Calculator to concatenate the three variables. Higher concatenations (e.g., 5,5,5; 4,5,4) signify more vulnerability.

Table 1: Rating Schedule for Each Variable Considered

3.5 Results

Figure 7 shows the resultant combination layer displayed by climate vulnerability assessed (i.e., urban heat and stormwater runoff). Because of how data were binned, the SVI indicator is not reflected in this map. Figure 8 is a variation of the combination, which shows census blocks that are in the fourth and fifth social vulnerability rating categories. Therefore, these blocks represent the most socially vulnerable groups for Savannah. The color gradient shows climate vulnerability for these most socially vulnerable blocks.

Three priority sites were objectively selected by identifying the three highest concatenation values. Note that one census block rated 5,5,5 was not selected because upon inspection, it was an uninhabited area between highways. Figure 9 shows Site 1, located near museums. Figure 10 shows Site 2, located near a creek. Figure 11 shows Site 3, located in a residential neighborhood.

To verify that our sites included the most socially vulnerable areas in Savannah, and therefore met the goals of the Healthy Streets Program, the following SVI data summarize demographics for the census tract that our sites are in: greater than 40% of the population lives below the poverty line; 25% unemployment rate; greater than 80% of the tract identifies as a minority; high ratio of occupants to rooms; $14,429 average per capita income; 34.5% of adults above the age of 25 do not have a high school diploma (ATSDR, 2022).

4.0 Urban Design Strategies

To help mitigate the negative climate change risks assessed, urban design and green infrastructure strategies are proposed for the three priority sites. Each intervention strategy provides co-benefits, meaning that the strategy affords benefits to multiple sectors, including social, environmental, economic, climate adaptation, and climate mitigation benefits.

4.1 Site 1: Museum

Site 1, shown in Figure 12, focuses on a total of three city blocks on both sides of Jones Street in the Kayton/Frazier Area neighborhood. A railroad museum and a children’s museum are in the northern blocks of the study area, and one of the blocks on the south contains a church (indicated in the figure). Since these blocks surround and include public spaces, community and public oriented strategies are proposed. Apart from mitigating environmental issues, these strategies aim at creating a larger public realm.

The first strategy is a “blue street” design along Jones Street. Google Earth was used to obtain elevation profiles of the blocks, and stormwater runoff for the area is estimated as shown by the blue arrows in Figure 13. Green infrastructure like bioswales, stormwater check dams, and native vegetation are aimed to soak the stormwater to better attenuate runoff and also improve street aesthetics. Figure 14 presents reference images for blue street strategies. In addition to these low impact developments, street trees are an important addition to the street to help mitigate the urban heat island effect. These street interventions create a better environment for people to navigate as pedestrians, especially because it is an arterial street connecting key public buildings. This strategy offers the opportunity to develop the site into a walkable place with better aesthetics.

Image Sources: https://www.urbangreenbluegrids.com/measures/bioswales/ and https://www.fastcompany.com/90379081/cities-aregetting-hotter-but-we-can-redesign-them-to-keep-us-cool

The second strategy is to increase vegetative cover, tree canopy, and pervious pavement surface for the public spaces and parking lots identified in Figure 15. Increased green space and tree canopy are proven approaches to abate the urban heat island effect In addition, stormwater runoff can better infiltrate into the ground with more pervious surfaces. Greening in this way offers a more cohesive public realm between the natural and built environment, improving human and nonhuman quality of life By the creation of accessible public spaces along the public buildings (i.e., the museums and church), we hope to attract more people and revenue to the buildings, creating an identity as a tourist destination in the city. Figure 16 shows locations identified for this intervention.

The third strategy is to add green roofs and rooftop gardens to buildings with large building footprints, as indicated on Figure 17. Urban agriculture provides several co-benefits, including additional greenspace, rain infiltration, social opportunities to garden, a healthy food source, community ability to be self-sustainable in terms of cultivating their food, and potentially a financial source if the food is sold.

Reference Images

All three strategies include climate adaptation measures, by designing for hotter temperatures and more intense storms, and climate mitigation measures, by adding carbon-sequestering vegetation.

4.1 Site 2: Creek

Site 2, shown in Figure 20, is a plot of land north of West Gwinnett Street and east of Stiles Avenue in the Carver Heights neighborhood. A creek runs just east of the site. The creek was viewed as an opportunity to create a public and educational space, which was the primary design strategy for this site In addition, certain currently impervious surfaces, shown in Figure 21, would be vegetated or made pervious This intervention would help mitigate the volume of stormwater runoff entering the creek, as shown in Figure 22.

Vegetation also absorbs and filters chemicals and nutrients that may be present in urban stormwater, thus decreasing the load entering the creek and later the Savannah River. Increased green space and tree canopy can help to decrease the urban heat risk The space would provide several environmental, social, and economic benefits. For example, it would increase physical accessibility to nature and surrounding streets, as well as attract tourism and future development. Figure 23 presents before and after visualizations for the proposed interventions.

4.1 Site 3: Residential

Site 3, shown in Figure 24, is a city block in the West Savannah neighborhood bounded by Millen Lane on the west, Golden Street on the north and south, and De Lyon Street on the east. Given the residential nature of the site, design strategies were focused on the surrounding streetscape and incentives for residents.

A “blue street” design along the aforementioned streets is proposed. Google Earth was used to obtain elevation profiles of the block, and stormwater runoff for the area is estimated as shown by the blue arrows in Figure 25. Green infrastructure like bioswales, rain gardens, and native vegetation would better attenuate stormwater runoff and improve street aesthetics. Along with this, the area in the middle of the block, marked in green on Figure 26, was seen as an opportunity for water collection from the rooftops of each residence. Collected rainwater could be stored in an underground tank with a filtration system. This could potentially help residents store rainwater, reducing their water bills and dependency on the municipal water supply. This space could also become a community space where residents come together and socialize.

Lastly, a policy to subsidize residents’ “cool material” construction (such as light-colored roofing, paint, siding, and paving) is proposed. Doing this would increase albedo and thus decrease surface temperatures. The hope is that if this proposal is successful for one block, it can be used as a prototype for other blocks Figure 27 shows a map of the block’s rooftops.

5.0 Conclusion

This analysis demonstrated how the Healthy Streets Program may be implemented in a local context for the city of Savannah. Savannah’s current and projected climate change hazards were researched. Geospatial assessments were performed for Savannah’s urban heat risk, stormwater runoff, and equity considerations. The assessments were combined to objectively identify three priority sites with the most physical and social climate change vulnerability. To help mitigate the negative impacts, urban design and green infrastructure strategies were proposed for the three priority sites. Each site demonstrates strategies to mitigate urban heat risk and stormwater runoff risk in the most socially vulnerable areas of Savannah, providing a range of co-benefits. The primary co-benefits from these strategies are social, environmental, economic, climate adaptation, and climate mitigation benefits

6.0 References

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=4f6d72903c9741a6a6ee6349f5393572 https://www.atsdr.cdc.gov/placeandhealth/svi/index.html https://www.savannahga.gov/2364/Flood-Hazard-Mitigation-Plan https://datausa.io/profile/geo/savannah-ga/

Atlanta Regional Commission et al., 2001. Georgia Stormwater Management Manual, Volume 2, Technical Handbook, First Edition. August 2001.

ATSDR, 2022. “CDC/ATSDR Social Vulnerability Index.” Centers for Disease Control and Prevention, and Agency for Toxic Substances and Disease Registry. Accessed April 15, 2022.

City of Savannah, 2021. “Flood Hazard Mitigation Plan | Update.” Accessed April 22, 2022.

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De Vorsey, Louis, 2012. “The Origin and Appreciation of Savannah, Georgia’s Historic City Squares.”

Southeastern Geographer, vol. 52, no. 1, 2012, pp. 90–99, http://www.jstor.org/stable/26228997. Accessed May 1, 2022

Dickerson, 2021. “Fort Stewart controlled burns program keeps soldiers training in the woods.” Stars and Stripes. Accessed April 23, 2022. https://www.stripes.com/branches/army/2021-0623/Fort-Stewart-controlled-burns-program-keeps-soldiers-training-in-the-woods1783784.html

Grey & Hennen, 2016. “Overnight heat can be more deadly than daytime.” CNN. Accessed on April 23, 2022. https://www.cnn.com/2016/07/22/weather/dangerous-nighttime-temperaturesheat/index.html

Lepp & Jones, 2022. “Significant flooding along Savannah River, 5th Street Marina.” WJBF. Accessed on April 23, 2022. https://www.wjbf.com/csra-news/significant-flooding-along-savannah-river5th-street-marina/

MRLC, 2022. “2019 CONUS Impervious Surface.” Multi-Resolution Land Characteristics Consortium. Accessed April 15, 2022. https://www.mrlc.gov/viewer/

NASA, nd. “Sea Level Projection Tool.” Accesss April 23, 2022. https://sealevel.nasa.gov/ipcc-ar6-sealevel-projection-tool

NOAA, 2013. “Climate Model: Temperature Change (RCP 8.5) - 2006 – 2100.” NOAA. Accessed May 1, 2022. https://sos.noaa.gov/catalog/datasets/climate-model-temperature-change-rcp-85-20062100/

SAGIS, 2022. “Welcome to SAGIS.” Savannah Area Geographic Information Systems. Accessed April 15, 2022. https://data-sagis.opendata.arcgis.com/

Sweet, Julie, 2020. "Yamacraw Indians." New Georgia Encyclopedia, last modified Jul 15, 2020. https://www.georgiaencyclopedia.org/articles/history-archaeology/yamacraw-indians/

Texas A&M National Resources Institute, 2017. “Protecting military readiness and the gopher tortoise at the same time.” Accessed April 23, 2022. https://nri.tamu.edu/blog/2017/april/protectingmilitary-readiness-and-the-gopher-tortoise-at-the-same-time/

Union of Concerned Scientists, 2016. “Sea Level Rise and Tidal Flooding in Savannah and Tybee Island, Georgia.” Accessed April 23, 2022. https://www.ucsusa.org/resources/sea-level-rise-and-tidalflooding-savannah-and-tybee-island-georgia

U.S. Census Bureau, 2022. “TIGER/Line Shapefiles.” U.S. Census Bureau, Geography Division. Accessed April 15, 2022. https://www.census.gov/cgi-bin/geo/shapefiles/index.php

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Esri, HERE, Garmin, FAO, NOAA, USGS, EPA

City of Hinesville, Savannah Area GIS, Esri, HERE, Garmin, SafeGraph, METI/NASA, USGS, EPA, NPS, USDA

Savannah City Boundary

City of Hinesville, Savannah Area GIS, Esri, HERE, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS, EPA, NPS, USDA

Esri Community Maps Contributors, Savannah Area GIS, © OpenStreetMap, Microsoft, Esri, HERE, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS, EPA, NPS, US Census Bureau, USDA, City of Hinesville, Savannah Area GIS, Esri, HERE, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS, EPA, NPS, USDA

Esri Community Maps Contributors, Savannah Area GIS, © OpenStreetMap, Microsoft, Esri, HERE, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS, EPA, NPS, US Census Bureau, USDA, City of Hinesville, Savannah Area GIS, Esri, HERE, Garmin,