Challenges in Sustainability | 2016 | Volume 4 | Issue 1 | Pages 39–53
DOI: 10.12924/cis2016.04010039
ISSN: 2297–6477
Challenges in
Sustainability
Research Article
Siting Urban Agriculture as a Green Infrastructure Strategy for
Land Use Planning in Austin, TX
Charles M. Rogers* and Colleen C. Hiner
Department of Geography, Texas State University, San Marcos, TX, USA
Submitted: 1 February 2016 | In revised form: 19 July 2016 | Accepted: 19 July 2016 |
Published: 22 August 2016
Abstract:
Green infrastructure refers to a type of land use design that mimics the natural water cycle by
using the infiltration capacities of vegetation, soils, and other natural processes to mitigate stormwater
runoff. As a multifunctional landscape, urban agriculture should be seen as a highly beneficial tool for urban
planning not only because of its ability to function as a green stormwater management strategy, but also
due to the multiple social and environmental benefits it provides. In 2012, the city of Austin adopted a major
planning approach titled the “Imagine Austin Comprehensive Plan” (IACP) outlining the city’s vision for
future growth and land use up to 2039. The plan explicitly addresses the adoption of green infrastructure as
a target for future land use with urban agriculture as a central component. Addressing this area of land use
planning will require tools that can locate suitable areas within the city ideal for the development of green
infrastructure. In this study, a process was developed to create a spatially explicit method of siting urban
agriculture as a green infrastructure tool in hydrologically sensitive areas, or areas prone to runoff, in east
Austin. The method uses geospatial software to spatially analyze open access datasets that include land
use, a digital elevation model, and prime farmland soils. Through this method a spatial relationship can be
made between areas of high surface runoff and where the priority placement of urban farms should be sited
as a useful component of green infrastructure. Planners or geospatial analysts could use such information,
along with other significant factors and community input, to aid decision makers in the placement of urban
agriculture. This spatially explicit approach for siting potential urban farms, will support the integration of
urban agriculture as part of the land use planning of Austin.
Keywords: GIS; green infrastructure; urban agriculture; urban planning; watershed protection
1. Introduction
1.1. Green Infrastructure and Urban Agriculture
The federal Clean Water Act (CWA) of 1972 provided a
basic framework for the regulation of pollutant discharges
with the intent of protecting water quality and human health
in the United States (U.S.) [
1
]. To further the protective
benefits of the CWA, the Environmental Protection Agency
(EPA) enacted its Combined Sewer Overflow Control Policy
in 1994 [
2
]. This policy initiative established guidelines by
which municipalities could better manage environmentally
harmful stormwater pollution events that occurred as a re-
sult of infrastructural challenges in handling both sanitary
sewage and stormwater runoff in the same sewer system
during precipitation events. In response, many cities im-
c
2016 by the authors; licensee Librello, Switzerland. This open access article was published
under a Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/).
librello
plemented green infrastructure measures to help mitigate
urban stormwater runoff as an alternative to expensive wa-
ter main upgrade projects. Green infrastructure can be
defined as the management of runoff through the use of
natural systems, or engineered systems that act as nat-
ural systems, to allow stormwater to infiltrate the ground,
recharging the water table and decreasing run-off. Accord-
ing to the EPA, Green infrastructure uses vegetation, soils,
and natural processes to manage water and create health-
ier urban environments. At the scale of a city or county,
green infrastructure refers to the patchwork of natural ar-
eas that provides habitat, flood protection, cleaner air, and
cleaner water. At the scale of a neighborhood or site, green
infrastructure refers to stormwater management systems
that mimic nature by soaking up and storing water [
3
]. While
this definition of green infrastructure is structured on water
management, there are broader definitions of green infras-
tructure that focus on aspects such as clean air, wildlife
habitat, and preservation of forests and grasslands.
With the industrialization of our food systems, most
cities, whether intentionally or not, have developed in such
a way that farms have become incompatible with the urban
environment. There is, however, a tremendous amount of
resurgent interest in urban farming and community garden-
ing across the country. In general terms, urban agriculture
refers to “the growing, processing, and distribution of food
and nonfood plant and tree crops and the raising of live-
stock, directly for the urban market, both within and on the
fringe of an urban area” ([
4
], p. 2500; [
5
], p. 4). As evi-
denced by the recent growth of municipal urban agriculture
land inventories as a method to integrate urban agriculture
into sustainable land management policy [
6
], we can infer
that municipalities value the multi-beneficial attributes that
urban agriculture offers. Urban agriculture has been char-
acterized as a multifunctional land use because, through
its versatility as a landscape, it offers a range of benefits
to densely populated areas [
4
]. For example, the ecolog-
ical functions of urban agriculture provide environmental
benefits in the form of biodiversity, nutrient cycling (com-
post), or wastewater re-use (stormwater and greywater);
the cultural functions improve the quality of a neighborhood
or community through its visual appeal, recreational use,
or the provision of rare foods to immigrant communities;
the socio economic functions provide access to nutritious
fresh produce for underserved communities in food deserts
facing obesity and diabetes [4].
In fact, evidence suggests that incorporating appropriate
types of urban agriculture into the urban environment will
greatly improve the overall sustainability of U.S. cities [
4
,
7
].
The EPA, in collaboration with experts from academia, state
and local governments, and nonprofits, released a general
listing of the benefits of urban agriculture:
•
Increases surrounding property values, beautifies va-
cant properties, increases a sense of community, and
provides recreational and cultural uses [8].
•
Increases infiltration of rainwater, reducing stormwa-
ter overflows and flooding, decreases erosion and
topsoil removal, improves air quality, and reduces
waste by the reuse of food and garden wastes as
organic material and compost [8].
•
Increases physical activity and educates new garden-
ers on the many facets of food production from food
security to nutrition and preparation of fresh foods [
8
].
While the positive ecological and environmental impacts
of urban agriculture have been acknowledged, minimal re-
search has been conducted to determine the feasibility of
urban agriculture as a green infrastructure strategy to man-
age stormwater. Green infrastructure strategies include
a list of practices that have been studied and quantified,
making their engineering and performance outcomes pre-
dictable and reliable [
3
]. A lack in such quantification, or of
carefully researched sets of best management practices,
leads to a further lack in the promotion of urban agriculture
as a green infrastructure strategy. As Dunn ([
9
], p. 58)
argues: “Being able to quantify the effectiveness of green
infrastructure on a small scale is one way to promote regula-
tory and enforcement acceptance, which thereby enhances
its appeal to city officials”. As a productive, multifunctional
landscape, urban agriculture offers answers to complex
infrastructural challenges that are facing many cities.
1.2. Urban Agriculture Land Inventories
Over the last decade a variety of municipalities have begun
the process of inventorying and assessing land to determine
the potential for a broad range of urban agricultural initia-
tives. This effort is driven by a diverse range of community
stakeholders, each with an interest in growing food locally,
including capturing the social and environmental benefits
urban agriculture provides. Yet, despite the realized and
potential benefits for individuals and communities, urban
agriculture is largely overlooked in urban and regional plan-
ning [
4
,
10
]. Instead of considering opportunities to preserve
farmland or to integrate it as part of a land use management
strategy in urban environments, agricultural landscapes are
often considered by land use planners as areas for future
development [4].
As part of the urban planning process, land inventories
have been used and recognized as a basic tool for land
suitability and site selection [
11
]. Many municipalities and
researchers are now employing this tool to promote urban
agriculture, integrating it into public policy and planning as a
land management strategy. Horsts’ (2011) paper “A Review of
Suitable Urban Agriculture Land Inventories” provides a brief
overview of urban agriculture land inventories in various cities
[
12
]. Inventories have been performed in Portland, Vancou-
ver, Seattle, Cleveland-Cuyahoga County, Detroit, Chicago,
Toronto, New York City, Cincinnati, Oakland, and San Fran-
cisco [
12
]. Some of the inventories primarily focus on public
vacant land and some open up their inventory to include
private lands or residential lands such as lawns or rooftops.
Decisions made as part of urban agricultural land in-
ventories typically require the input of multiple criteria in-
volving social, economic, and environmental considerations
40
[
6
,
13
,
14
]. The success of multiple criteria decision making
depends on an array of knowledgeable stakeholders mak-
ing informed decisions [
15
]. Using this model, inventories
rely upon the explicit use of an advisory committee with rep-
resentation from municipal staff, non-profit organizations,
urban gardeners, and academic researchers. Many inven-
tories emulate the Portland model, wherein an advisory
committee guided the inventory throughout the process,
particularly in establishing evaluation criteria and reviewing
preliminary results. Mendes et al. [
6
] points to Portland’s
inventory as more successful when compared to Vancouver
due to the way Portland engaged many community part-
ners throughout the entire process, from design to imple-
mentation, while Vancouver lacked community involvement.
Mendes et al. [
6
] suggests this represents what the schol-
arly literature identifies as a “networked movement”, where
participation in local decision making is inclusive and citi-
zen engagement is fully accepted, similar to Arnstein’s [
16
]
highest rungs in the ladder of citizen participation (Partner-
ship, Delegated Power, Citizen Control). Likewise, Oakland
established a Community Advisory Committee throughout
the project that provided citizen input in a number of ar-
eas: the location of potential sites, criteria for selection of
potential sites, and feedback on what type of information
would be useful in the finished inventory [
17
]. The best as-
set mapping has been described, especially in the case of
urban agricultural land inventories, to be a multi-stakeholder
process for action planning and policy design [4,6,18].
Many of the inventories have involved multiple stake-
holders in research and analysis phases, but have been
less inclusive when performing technical analysis includ-
ing Geographical Information System (GIS), aerial imagery
assessment, and site visits or ground-truthing [
19
]. The
key actors during this phase of inventory development have
been municipal staff, experts from food policy councils and
non-profits, and students [
12
]. The partnership among
stakeholders from the city governments and student re-
searchers from local universities has created synergistic
opportunities. In Portland, Vancouver, Oakland, Seattle,
and Cleveland among others, graduate students worked
in partnerships with local municipalities to complete the
inventory, thereby gaining valuable experience while the
respective cities received cost-effective results.
Generally, the vacant land inventories followed a frame-
work of identifying vacant or open land by ownership type,
categorized as public or private, assigning suitability criteria,
then eliminating the unsuitable sites and highlighting the
best. Within this generalized framework, most inventories
created suitability criteria for urban agriculture addressing
physical and socioeconomic factors, assigned a ranking or
scoring system for criteria, presenting the study results as
publicly available reports [19].
The technical work for most inventories made use of
one or a combination of methods including aerial photo
assessment, GIS analysis, remote sensing, and site visits.
Some efforts relied extensively on GIS analysis or remote
sensing as in New York and Philadelphia [
20
,
21
]. The
potential exists for expanding the use of GIS and remote
sensing for urban agricultural land inventories from other
approaches developed by urban land use researchers. For
example, Myeong et al. [
22
] developed vegetation indexes
that estimate vegetation coverage and bare soil, criteria
that usually requires labor-intensive visual assessment, us-
ing multi-spectral and hyper-spectral data to identify urban
green areas [
21
]. Other inventories have made use of the
satellite imagery from the National Agricultural Imagery Pro-
gram (NAIP) overlaid onto the GIS city parcel data of vacant
land in order to select parcels containing potentially arable
land [
23
]. A more specific use of geospatial data in the Hal-
ifax, Canada inventory used the LiDAR data to model sun
exposure, an important aspect of most inventories suitability
criteria for potential urban agricultural sites [23].
As the practice of inventories is evolving, there are ar-
eas for improvement. In particular, many authors noted
limitations because of incomplete data, limited availability
of data, and frequency of updated data [
13
,
21
,
23
,
24
]. A
common limitation expressed by researchers stemmed from
low resolution and accuracy of the aerial imagery that re-
sulted in possible visual interpretation errors [
13
,
23
]. As
a result, researchers advised that post-analysis ground-
truthing of potential sites would be necessary to quality
check geospatial analysis [
13
,
23
]. Additionally, establish-
ing a measure of community support is also an area that
many inventories acknowledged needed further research
to identify variables such as cultural preferences, skills and
willingness, demand, resources, and the presence of local
leaders [
21
,
24
,
25
]. Inventories with community advisory
committees also noted that site visits, community outreach,
and consultation with city staff are necessary to evaluate
characteristics like soil quality, community interest, and se-
curity [
6
,
14
,
23
]. Soil quality, in particular, is an issue in
many urban areas that was recognized by most inventories
as an area for further research and analysis. In Oakland, for
example, the completed inventory inspired further research
about lead (Pb) contamination in the soil of potential urban
agricultural sites. This research assessed Pb levels at over
a hundred different sites identified in the inventory [26].
Beyond land identification, land inventories have been
an effective tool to integrate urban agriculture into urban
policy and planning as a land management strategy [6]. As
a part of the planning process land inventories can identify
opportunities for urban agriculture initiatives that result in
positive changes. Some impacts have included increasing
awareness and political support for urban agriculture, ad-
vancing social and ecological sustainability, and enhancing
public involvement [
6
,
17
]. For example, Toronto, Seattle,
and Portland experienced notable changes resulting from
vacant land assessments. In Toronto, local zoning regula-
tions and guidelines were altered to help guide an increase
in urban agriculture [
19
]. In Seattle and Portland, the col-
laborative process increased community involvement and
inclusion of urban agriculture into city sustainability planning
[
6
]. Stakeholders have also built upon these assessments
and conducted more targeted in depth studies that relate
41
to issues of public health, economic development, food
security, and environmental sustainability [
19
]. As a tool,
land inventories do not have to function in isolation and can
be employed in conjunction with other strategies, such as
surveys or scenario planning, to advance municipal goals
such as stormwater management, reducing carbon emis-
sions, increasing food access, and supporting workforce
development [6].
Urban agriculture land inventories have been a useful
step for many cities in evaluating the potential for urban agri-
culture, though the process and resulting impacts are unique
to each city. The type of parcels considered, criteria applied,
and stakeholders involved differ depending on the objective.
The delineation of potential urban agriculture sites is only a
preliminary step in a long process of mapping the potential
of urban agriculture in a city [
23
]. That being said, such
demarcations can be a useful starting point as cities begin
to incorporate urban agriculture into community planning.
The tools involved with a land inventory have the potential
to facilitate participatory planning by bringing together com-
munity participants such as local residents, food activists,
academic researchers, and farmers with city planners and
government officials, in an effort to better plan and man-
age land use [
4
]. Nevertheless, the politics of negotiating
competing uses of land is inherently complex and difficult.
The viability of utilizing urban agriculture land inventories for
planning will depend upon identifying and negotiating the
varied interests of multiple stakeholders [23].
1.3.
Can Urban Agriculture identify as Green Infrastructure
in Austin, TX?
In 2012, the City of Austin adopted a major planning
approach titled the Imagine Austin Comprehensive Plan
(IACP) that outlines the vision for future growth and land
use in the city until 2039. The plan explicitly addresses the
adoption of green infrastructure as a targeted future land
use with urban agriculture specifically being included as a
component of the green infrastructure network.
The IACP identified eight priority programs, ranked in
order of importance, which will guide policy and implemen-
tation of the plan. The fourth priority proposes the use of
“green infrastructure to protect environmentally sensitive
areas and integrate nature into the city” [27]:
1. Invest in a compact and connected Austin.
2. Sustainably manage our water resources.
3.
Continue to grow Austin’s economy by investing in our
workforce, education systems, entrepreneurs, and lo-
cal businesses.
4.
Use green infrastructure to protect environmentally
sensitive areas and integrate nature into the city.
5. Grow and invest in Austin’s creative economy.
6.
Develop and maintain household affordability through-
out Austin.
7. Create a Healthy Austin Program.
8.
Revise Austin’s development regulations and pro-
cesses to promote a compact and connected city.
The building block actions listed as methods to imple-
ment the green infrastructure priority program include several
references to urban agriculture (below; emphasis added):
•
Integrate citywide and regional green infrastructure to
include such elements of preserves and parks, trails,
stream corridors, green streets, agricultural lands,
and the trail system into the urban environment and
the transportation network [27].
•
Incentivize appropriately-scaled and located green
infrastructure and public spaces, such as parks,
plazas, greenways, trails, urban agriculture and/or
open spaces in new development and redevelopment
projects [27].
•
Expand regional programs and planning for the pur-
chase of conservation easements and open space
for aquifer protection, stream and water quality pro-
tection, wildlife habitat conservation, and sustainable
agriculture [27].
•
Extend existing trail and greenway projects to create
an interconnected green infrastructure network that
includes such elements as preserves and parks, trails
stream corridors, green streets, greenways, and agri-
cultural lands that link all parts of Austin and connect
to nearby cities [27].
•
Permanently preserve areas of the greatest environ-
mental and agricultural value [27].
This study looks at east Austin where there is 1) an
established urban and peri-urban farm presence and 2)
high future development potential of agricultural land due
to the Austin-Round Rock Metro Area’s rapid growth (110
people per day) [
28
] and lack of land use constraints lead-
ing to urban sprawl [
28
]. Since the late 1990s, the City of
Austin has viewed the eastern side of the metro area as a
prime area of growth and development. Without an urban
growth boundary most of what the city has determined as
the “desired development zone” (DDZ) falls into much of
east Austin (Figure 1) and beyond into the Austin’s Extrater-
ritorial Jurisdiction (ETJ). The opening of the SH130 tollway,
conceived of as a north-south alternative route to interstate
35 on the east side of Austin, has further opened up large
areas of available land for new jobs, housing, and services
for Austin’s rapidly growing population. The Imagine Austin
plan conceives of growth corridors around the city, with the
SH130 corridor representing one of those growth corridors
in east Austin. According to 2012 land use data from the
City of Austin, 94,961 acres of undeveloped land, much of
it in agriculture, existed in the suburban portion of the DDZ.
Information from the 2015 State of the Food System Report,
released by the City of Austin’s Office of Sustainability, put
the loss of farmland each day in Travis County at 9.3 acres
and a 25% loss in farmland over the last 11 years [29].
42
Figure 1.
The Decker Creek and Elm Creek Watershed
study areas, located in Austin, Texas in Travis County, re-
side completely in the Suburban DDZ, an area promoted
for growth and development by the City of Austin.
Furthermore, the hydrologic environments in east Austin
are already under much pressure as a result of being located
downriver from the impervious cover of the central business dis-
trict and at the bottom of several highly urbanized watersheds,
effectively making east Austin the hydrologic drain for the city
[
30
]. The creeks and watersheds within east Austin have ex-
perienced significant erosion problems and flooding associated
with the increasing development and impervious cover seen
upstream over the last half century [
30
]. Further exacerbating
the erosion problems have been urban development patterns in
the suburban DDZ that situated buildings on small lots close to
the creeks. The Austin City Council itself has underscored the
potential implications of increasing development and its effect
on eastern watersheds:
“The eastern watersheds, with broader floodplains and more
erosive soils, pose unique challenges to creek and floodplain
protection. Development is currently being placed in close prox-
imity to erosive creek banks in headwaters areas and creating
future problems requiring significant and unsustainable public
expense to maintain and repair. This development will likely
accelerate as build-out proceeds along SH-130” [31].
As a response to city-wide watershed threats, the City Coun-
cil updated the watershed protection policies in 2013 with Phase
One of the new Watershed Protection Ordinance (WPO). The
new WPO increased stream buffers and erosion hazard zones
to ensure development is not built to close to waterways for over
400 miles of smaller headwater streams [
32
]. Phase Two of
the WPO began in January 2015 with a Green Infrastructure
Working Group as part of the City’s land development code
rewrite process, called CodeNEXT, to discuss how to achieve
the Imagine Austin goals of “integrating nature into the city and
creating complete communities through revisions to our zoning
and environment codes’ [
32
]. Currently, green infrastructure
techniques in the Watershed Department’s manual for best man-
agement practices include rain gardens, bio- filtration areas, and
vegetative filter strips; however, there is no reference to urban
agriculture as a green infrastructure strategy for new develop-
ment or as a stormwater management strategy in the city.
Nevertheless, within the last twenty years there has been
a proliferation of urban agriculture in east Austin. A variety of
urban agriculture exists in the city, ranging from community gar-
dens to small market farms (defined as farms operating on less
than one acre within the city’s full jurisdictional boundary) to
larger urban farms (over one acre) within or on the periphery
of the city. In addition, the Austin City Council has encouraged
urban agriculture by authorizing relaxed zoning regulations for
private urban farms. For example, the current land code allows
for urban farming in all zoning classes, and, at this time, there
are 23 urban farms in the city of Austin, classified either as
“market farms” if less than one acre and as “urban farms” if
more than one acre, and 52 community gardens [
29
]. Further-
more, in 2009, the Austin City council created the Sustainable
Urban Agriculture and Community Garden Program with the
expressed purpose of streamlining the process for establishing
community gardens and sustainable agriculture on city land,
further endorsing urban agriculture in the city.
Much of the land in the suburban DDZ is in Texas Blackland
Prairie Geographic Region and contains prime farmland soils
according to the classification by the National Resources Con-
servation Service (NRCS) (Figure 2). The soils in this region
are known for being deep and rich with organic material, mak-
ing them valuable for agricultural use [
33
]. With the quality of
the soils, good drainage, and flat surface, prime farmland also
serves as ideal land for development. Indeed, many new devel-
opments are going to occur in prime farmland as a result of the
city’s priority to develop in the suburban DDZ and the substantial
amount of open space in that part of the city. As a matter of de-
bate, the question is how much of the land to develop and what
positive and negative impacts are expected to occur. However,
the City of Austin, through its Imagine Austin plan, has indicated
that preserving a portion of different classifications of open land
is important for making Austin a sustainable city. The function of
urban agriculture in this plan, thus, has significance in terms of
protecting and valuing the environmental, social, and economic
well-being of Austin. Most significantly for this study, though,
is the role of urban agriculture as a means to conserve prime
farmland and serve as green infrastructure in Austin.
1.4. Purpose of Study
Urban agriculture acts as a multifunctional landscape with a
variety of benefits including the ability to offset many facets of
environmental degradation including preventing excessive runoff
[
34
]. The increase of new development and predominance of
urban farms in east Austin, combined with the rise of green
infrastructure as a stormwater management focus in the city,
makes east Austin an ideal study area for evaluating the poten-
tial role of urban agriculture as a green infrastructure strategy.
While this is the narrow aim of this study, the true value of urban
agriculture as green infrastructure can only be better understood
by placing the results of this research into a wider systems frame-
work that encompasses the multiple environmental, economic,
and social benefits offered by urban farms.
43
Figure 2.
Prime Farmland Soils in Austin, Texas almost
exclusively exist in east Austin, where the City of Austin is
encouraging growth and development to occur as part of
the Suburban DDZ.
The Imagine Austin plan explicitly addresses the
adoption of green infrastructure as a targeted future
land use with urban agriculture as a component of the
green infrastructure network. Addressing this area of
land use planning will require tools that can locate suit-
able areas within the city where urban agriculture can
best act as green infrastructure. In this study, a process
was developed to create a spatially explicit method of
siting urban agriculture as a green infrastructure tool on
hydrologically sensitive areas (HSAs), or areas prone to
runoff, in east Austin. The method uses geospatial tech-
nology to spatially analyze open access datasets that
include land use, a digital elevation model, and prime
farmland soils. Through this method a spatial relation-
ship can be made between areas of high surface runoff
and where the priority placement of urban farms should
be sited as a useful component of green infrastructure.
Planners or geospatial analysts could use such informa-
tion, along with other significant factors and community
input, to aid decision makers in the placement of urban
agriculture. Creating a spatially explicit approach for
siting potential urban farms will support the integration
of urban agriculture as part of the sustainable land use
planning of Austin.
2. Data and Methods
2.1. Study Area
This study examines the sub-watersheds of Decker
Creek and Elm Creek in east Austin (Figure 1). These
two watersheds were chosen because they are smaller
watersheds that both exist completely within the sub-
urban DDZ and reside in either the Full Purpose Ju-
risdiction or ETJ of Austin, whereas other eastern wa-
tersheds do not fit within those parameters. In ad-
dition, the SH130 growth corridor cuts through both
watersheds as well as the FM 969 growth corridor.
The impact of growth in the region and the expected
loss of prime farmland and agricultural land use make
these two watersheds ideal areas to study. Decker
Creek watershed is 17 square miles and Decker Creek
runs 12 miles from the top of the watershed to the out-
let. Decker Creek watershed is less developed than
other watersheds in Austin containing more agricultural
land, but is projected to experience a rise in population
growth from 3,156 people in 2000 to 12,341 people in
2030 or a 391% projected increase [
35
]. Elm Creek wa-
tershed totals only 9 square miles and Elm Creek runs
10 miles from the headwaters to the outlet [
35
]. Elm
Creek watershed is comprised mostly of agricultural
land, though with development looming there will be an
expected increase in population of 180%, or from 3,136
residents in 2000 to 5,643 residents in 2030 [
35
]. By
analyzing these watersheds, the study examines where
current farmland can best be preserved for urban agri-
culture, especially in light of the area’s continued de-
velopment, and provides insight into the functionality
of urban agriculture as a way to reduce surface runoff
pressure on developing watersheds.
2.2. Data Sourcing & Methods
The entirety of the data for the geospatial elements of
this project were sourced from open access datasets
(Table 1). Data was pulled from the “GIS Downloads”
website managed by the City of Austin. Other data was
pulled from federally managed “Data Download” map
viewers. The digital elevation model (DEM) was down-
loaded from the National Map Viewer managed by the
United States Geologic Survey. Soil data was obtained
from the Web Soil Survey Map Viewer managed by
the National Resources Conservation Service (NRCS).
Aerial imagery was downloaded from the National Agri-
culture Imagery Program (NAIP) and land cover data
came from the National Land Cover Database (NLCD).
Additional data and information about study area context
were derived from informal interviews with urban farm-
ers and City of Austin leadership, together with a site
visit to an urban farm within the study area. The human
subject’s portion of this research was approved by the
Institutional Review Board (IRB) exemption request on
October 15, 2015 with ID # L4567180.
44
Table 1. Data layers used to inventory urban agriculture and create a topographic index at a watershed scale.
GIS Layer Format Source
Land Use 2012 Vector-polygon City of Austin GIS Downloads (2012)
Watersheds Vector-polygon City of Austin GIS Downloads (2013)
Digital Elevation Model (DEM) 10 meter/raster National Elevation Dataset- Geospatial Data Gateway
Soil Conductivity Vector-polygon Soil Survey Geographic Database: National Resources Conservation Service.
Soil Depth to Restrictive Layer Vector-polygon Soil Survey Geographic Database: National Resources Conservation Service.
Prime Agricultural Soils Vector-Polygon Soil Survey Geographic Database: National Resources Conservation Service.
Aerial Imagery 1 meter/raster Texas Natural Resources Information System: National Agriculture Imagery Program
2.3. Geospatial Database Development
For use in this analysis, all datasets were projected to the
North American Datum 1983 (NAD83), State Plane Texas-
4203 with a Lambert Conformal projection to coincide with
data from the City of Austin. Both the soils and land use
data had to be transformed from vector to raster to cor-
respond with other raster layers. In particular, the prime
farmland data and the land use data needed transformation
to perform a simple urban agricultural inventory that would
be combined with another raster dataset.
Furthermore, a topographic index was performed to de-
lineate HSAs, areas that are prone to generate surface
runoff, within the Decker Creek and Elm Creek watersheds.
The topographic index is determined with a GIS and re-
quires a digital elevation model, soil hydraulic conductivity,
and depth of soil to restrictive layers [36–38].
2.4. HSA Delineation
The topographic index (
λ
) is formed from two components.
The first component is a steady state wetness index, formu-
lated from slope (
β
) and drainage area (
α
) of the watershed
[
36
–
38
]. This index determines the potential for surface
runoff within the contributing area and for each cell within
the raster. The steady state wetness index is defined as:
ln
α
tanβ
(1)
where
α
is the drainage area per unit contour length in
meters and β is the slope in radians.
The second component is soil water storage, derived
from soil hydraulic conductivity (
K
s
) and soil depth to re-
strictive layers (D) [
36
–
38
]. Soil water storage determines
the saturation probability for each cell in the raster. Soil
water storage is expressed as:
ln(K
s
D) (2)
where is the soil hydraulic conductivity in meters per day
and is the soil depth to restrictive layers in centimeters. In
general, the deeper the soil depth or topsoil, and the higher
the value of the soil hydraulic conductivity or the speed at
which water percolates through the ground, the lower the
likelihood of producing surface runoff [39].
The two components combine to make the soil topo-
graphic index equation, below, to determine the hydrologi-
cally sensitive areas in the watershed:
λ = ln
α
tanβ
− ln(K
s
D) (3)
To calculate the steady state wetness index, a 10-m
resolution DEM, clipped to the watershed, was processed
by an open source tool, called the Compound Topographic
Index (CTI), as part of an ArcGIS extension toolset. This
extension allows the user to simply input a DEM into the CTI
tool automatically calculating the steady state wetness in-
dex according to the first component of the soil topographic
index equation. The CTI operates exactly like the steady
state wetness index component of the equation above and
can be shown as:
CT I = ln
α
tanβ
(4)
where
α
is drainage area “calculated as (flow accumulation
+ 1)
×
(pixel area in m
2
)” [
40
] and
β
is “the slope expressed
in radians” [40].
At this point, the raster layers for each component part
of the topographic index equation were entered into the
ArcGIS Raster Calculator to calculate the HSAs of the wa-
tersheds. The resulting raster layer indicates areas within
the 10-m grid that are more or less likely to become satu-
rated when a storm event occurs. The higher topographic
index (TI) values correspond to areas most likely to become
saturated and act as a source of surface runoff, also indi-
cating the location of hydrologically sensitive areas [
37
,
39
].
During a storm event, runoff would likely accumulate and
disperse in areas with higher topographic indices than any
areas with lower topographic indices [39].
Hydrologically sensitive areas are areas most prone to
surface runoff and must be delineated in a watershed by
some threshold criteria to identify as distinct from the lower
topographic indices that are less likely to produce runoff
[
36
–
38
]. Many techniques have been used to derive such
conclusions. Agnew et al. [
36
] proposes using the average
saturation probability to determine HSAs. Others have used
the delineation tactic of targeting 20% of the watershed with
the highest topographic index values to prevent overland
flow from reaching streams [
39
]. Community and stake-
holder involvement also represents a method of delineating
45
HSAs based on funding, feasibility, or local expertise. Qui
[
39
] selected an HSA threshold level for illustrative purposes
considered as reasonable and Martin-Mikle [
37
] expanded
upon that criteria by selecting TI values 1.5 standard devia-
tions above the mean as HSAs. Following similar protocol,
HSAs in this study were delineated by selecting topographic
index values 1.5 standard deviations above the mean for
each respective watershed. Decker Creek watershed TI
values have a mean of 11.65, resulting in a threshold TI
value level of 15. Any grids in Decker Creek with a TI value
greater than or equal to 15, therefore, are delineated as
HSAs. The threshold value for selection of HSAs in Elm
Creek is anything above 14, or 1.5 standard deviations
above the mean value of 10.20.
2.5. Delineation of Prime Farmland on Agricultural Land
Use
To determine where current land use is best suited for tran-
sitioning into some form of urban agricultural opportunity, a
simple urban agriculture land inventory was performed in
both watersheds. This land inventory was derived from two
datasets: City of Austin land use data and prime farmland
soil data from the National Resources Conservation Service
SSURGO soil database. Utilizing the ArcGIS 10.2 overlay
analysis tools on the aforementioned datasets resulted in a
new dataset of potential land suitable for urban agriculture.
The inventoried lands suitable for potential urban agriculture
are located on prime farmland soils and have an agricultural
land use classification.
2.6.
Combining HSAs with Land Use and Prime Farmland
Data to Prioritize Locations for Urban Agriculture as
Green Infrastructure
To prioritize locations for urban agriculture as a green
infrastructure tool, the urban agriculture land inventory,
composed of land use and prime farmland data, had to
be converted to a raster layer to enable a combination of
the delineated HSAs in each watershed with TI values
1.5 standard deviations above the mean. In the Decker
Creek watershed, TI values greater than or equal to 15
were overlaid onto the potential areas for urban agricul-
ture to find HSAs located on agricultural land use and
prime farmland soils. In the Elm Creek watershed, TI
values greater than or equal to 14 were overlaid onto
the potential areas for urban agriculture to find HSAs
located on agricultural land use and prime farmlands
soils. The resulting datasets showed where in each wa-
tershed agricultural land use and prime farmland soils
should be considered as areas for potential urban agri-
culture as a green infrastructure tool according to the
spatial relationship with HSAs in the watershed. To
further prioritize the sites considered as potential sites
for urban agriculture as a green infrastructure strategy
and for conserving prime agricultural land in Austin, an
additional step derived the top ten areas in each water-
shed holding the most HSAs in acreage according to
Travis County Appraisal District (TCAD) parcels. TCAD
parcels identify bounded property lines in Travis County
and their owners.
2.7. Combining Prioritized Locations of Urban Agriculture
with TCAD Parcels to Identify Sites with the Most HSA
Acreage
TCAD parcels from the City of Austin were downloaded
and clipped to each respective watershed to delineate the
boundaries of the parcels within the watershed. The ap-
plication of the ArcGIS spatial analyst tool zonal statistics
derived how many 10 meter pixels of HSAs on potential
urban agriculture sites were located within the boundaries
of individual TCAD parcels. Parcels with no HSAs were
eliminated from analysis. Calculations utilizing the field cal-
culator in ArcGIS were then made on the parcels containing
HSAs to derive the total amount of HSAs acreage within
each parcel. Through sorting, a ranked list of parcels con-
taining the most HSAs acreage was generated for each
watershed. This list shows the most viable parcels so that a
structured attempt can be made to identify those landown-
ers that hold the most HSAs in an effort to conserve areas
of prime agricultural land from incoming development and
locate possible urban agriculture opportunities as a method
of green infrastructure.
3. Results
3.1. Delineated HSAs on Agriculture Land Use and Prime
Farmland
The derived TI values for Elm Creek watershed range
from 3.5 to 23.3, while the TI values for Decker Creek
watershed range from 3.3 to 27.0. In Elm Creek water-
shed, areas with TI values greater than or equal to 14 (1.5
standard deviations above the mean) are delineated as
HSAs (Figure 3). In Decker Creek watershed, areas with
TI values greater than or equal to 15 (1.5 standard devia-
tion above the mean) are delineated as HSAs (Figure 4).
HSAs indicate areas prone to surface runoff as a function
of a topography’s slope and drainage area and a soil’s sat-
uration potential derived by soil hydraulic conductivity and
soil depth. To prioritize where potential urban agriculture
sites could serve as a green infrastructure strategy in both
watersheds, HSAs were combined with areas deemed as
agricultural land use by the City of Austin and those con-
taining prime farmland soils. The total area of agricultural
land use on prime farmland for Elm Creek watershed is
1218 acres and 1504 acres for Decker Creek watershed
(Table 2). The areas of the delineated HSAs within poten-
tial sites for urban agriculture as a green infrastructure
tool are 62.7 and 111.7 acres for Elm Creek and Decker
Creek, respectively. HSAs represent 5.1% and 7.4% of
the total agriculture land use on prime farmland in Elm
Creek and Decker Creek, respectively.
46
Figure 3.
The spatial distribution of hydrologically sensitive areas (HSAs) in
Elm Creek Watershed in Austin, TX. HSAs in Elm Creek watershed have
topographic index (TI) values 1.5 standard deviations above the mean or
greater than 14. These particular HSAs are on potential urban agriculture
sites as determined by their location on land deemed agricultural by the
City of Austin and considered prime farmland by the National Resources
Conservation Service (NRCS).
Figure 4.
The spatial distribution of hydro-
logically sensitive areas (HSAs) in Decker
Creek Watershed in Austin, TX. HSAs
in Decker Creek watershed have topo-
graphic index (TI) values 1.5 standard de-
viations above the mean or greater than
15. These particular HSAs are on poten-
tial urban agriculture sites as determined
by their location on land deemed agri-
cultural by the City of Austin and consid-
ered prime farmland by the National Re-
sources Conservation Service (NRCS).
Table 2.
Potential urban agriculture land totals in Elm Creek and in Decker Creek watersheds: agricultural land use on
prime farmland, HSAs on prime farmland with agricultural land use, and HSAs on prime farmland with agricultural land
use without Critical Water Quality Zone (CWQZ) restrictions.
Elm Creek Watershed Decker Creek Watershed
Total Acreage of Agricultural Land Use with Prime Farmland 1504 acres 1218 acres
Total Acreage of HSAs on Agricultural Land Use with Prime Farmland 62.7 acres 111.7 acres
Total Acreage of HSAs in CWQZ 20.4 acres 17.5 acres
Total HSAs left after CWQZ restrictions omitted 42.3 acres 94.2 acres
3.2. Delineated HSAs Protected Under Current Land Use
Control
The Critical Water Quality Zone (CWQZ) restrictions
set forth by the City of Austin’s 2013 watershed protec-
tion ordinance restricts development around waterways
by establishing a buffer associated with the size of the
waterway [
41
]. The suburban DDZ watersheds, includ-
ing Decker Creek and Elm Creek watersheds, maintain
unique buffer classifications associated with the size of
the waterways. In minor waterways, CWQZ boundaries
are located 100 feet from the centerline of a waterway
[
41
]. Intermediate waterways retain CWQZ boundaries
200 feet from the centerline of a waterway [
41
]. Finally,
major waterways have a restriction of no development
within 300 feet of the CWQZ [41].
The areas of the delineated HSAs found on prime
farmland with agricultural land use that are already pro-
tected under CWQZ restrictions total 20.4 acres for the
Elm Creek watershed (Table 2) and 17.5 acres for Decker
Creek watershed (Table 2). With the Elm Creek water-
shed that leaves 42.3 acres of HSAs on prime farmland
with agriculture land use unprotected from potential devel-
opment (Table 2). While, in the Decker Creek watershed
94.2 acres of HSAs remain unprotected from future de-
velopment (Table 2).
47
3.3. Prioritized HSAs on TCAD Parcels
In an effort to include tangible results for the City of Austin
(as suggested by the Food Policy Manager at the Office of
Sustainability) so that they may reach out to landowners
about conserving portions of their land to incoming devel-
opmental threat, TCAD parcels were sorted into a “top ten
list” of areas that contain the most HSAs. These areas
not only hold the potential to serve as urban agricultural
opportunities, protecting prime farmland, but also to act as
a green infrastructure land use control that further protects
the watershed beyond the CWZQ zone.
In both watersheds, the spatial distribution of the HSAs
in the parcels varies because the parcels are based on an
individual’s ownership. As a result, some of the parcels
show an even spread of HSAs throughout the parcel, while
other locations show clusters of HSAs only in portions of
the parcel. As a means of validation, aerial imagery from
the National Agricultural Imagery Program (NAIP) and land
use data from the National Land Cover Database (NLCD)
were used to identify land use within the parcels to validate
potential urban agriculture sites.
The top ten parcels in Elm Creek watershed contain
51.5 acres, or 82%, of all HSAs. The total acreage for
HSAs ranges from 10.7 acres in Parcel 1 down to 1.9
acres in Parcel 10 (Table 3). In Parcel 1, a mid-size
parcel containing 57 acres, the HSAs spread throughout
the parcel in an even density, while in most others the
HSAs cluster in certain areas of the parcel. Parcel 1
encompasses 41 acres of prime farmland and 26% of
that land contains HSAs. With the relative density of
HSAs in Parcel 1, this parcel may best be conserved as
an entire plot suitable for a large urban farm. Verification
with NAIP imagery and land cover data from the NLCD,
demonstrates that this plot contains a large pasture and
hay field with HSAs (Figure 5). In contrast, Parcels 2
and 3 contain 8.9 and 7.3 acres of HSAs, respectively,
but include only a minimal percentage of HSAs relative
to their total percentage of HSAs on agricultural land
use with prime farmland. For example, Parcel 2 has 132
acres of agricultural land use on prime farmland but only
6.8% contain HSAs. The HSAs are highly clustered in
the southeast portion of the parcel and, through NAIP
and NLCD verification, the densest network of HSAs
lies on cultivated fields (Figure 5). In this case, it would
make sense to target the portion of the land with HSAs
for conservation, adding protection to the watershed by
allowing it to remain free of development, enabling it to
become a potential site for urban agriculture.
In contrast to Elm Creek, the top ten parcels in Decker
Creek watershed encompass a total of 57.5 acres of HSAs,
or 51%, of all delineated HSAs in the watershed. Delineated
HSAs in the Decker Creek watershed parcels range from a
total of 11.1 to 2.9 acres (Table 4). The spatial distribution of
HSAs in the Decker Creek watershed parcels vary, though
in the northwest corner of the watershed five parcels fea-
ture somewhat evenly spread out HSAs. Through validation
with NAIP imagery and NLCD data, Parcels 6 and 7, in
the northwest corner, contain HSAs primarily on cultivated
fields, and have 4.6 and 4.0 acres of HSAs, respectively
(Figure 6). Parcel 6 contains only prime farmland and 93%
of the land in parcel 7 is prime farmland (Table 4). The per-
cent of HSAs on prime farmland is 14.5% for parcel 6 and
18.9% for parcel 7. These two parcels, taken together as
an urban agriculture site, could protect 8.6 acres of HSAs
and 52.8 acres of prime farmland. As a contrast, parcel 8
contains 2.9 acres of HSA, but when verified through NAIP
imagery and NLCD data, most of the HSAs are located
on uncultivated fields within deciduous forest and scrub-
land (Figure 6). While maintaining this area as open land,
protected from development, still has benefits for the water-
shed, its use as a potential site for urban agriculture as a
green infrastructure strategy may not be the best use of the
land. Rather, leaving the land undeveloped arguably poses
the greatest benefit to the watershed.
Figure 5.
TCAD parcels in Elm Creek watershed. TCAD
parcel 1 shows an even spread of HSAs across the land
area, while TCAD parcel 2 shows a clustering of HSAs in
the southeast portion of the parcel.
Table 3.
Potential urban agriculture sites in Elm Creek
watershed relative to their affiliation with TCAD parcels
and the HSAs located on agricultural land use with prime
farmland (Prime Ag).
Elm Creek Watershed
TCAD
Parcel
HSAs
acreage
Total
Land
Acreage
Prime
Ag
Acres
Percent of
HSAs on
Total Land
Acreage
Percent of
HSAs on
Prime Ag
Acres
1 10.7 57.4 41.3 18.60 26.00
2 8.9 147.3 132.3 6.10 6.80
3 7.3 275.4 256 2.70 2.90
4 5.4 165.1 154.3 3.30 3.50
5 4.4 82.2 60.5 5.40 7.30
6 4 29.5 19.2 13.60 20.80
7 3.5 79 75 4.40 4.70%
8 2.8 27.2 9.2 10.10 29.90
9 2.6 42.4 33.2 6.10 7.80
10 1.9 20.6 20.6 9.40 9.40
48
Figure 6.
TCAD parcels in Decker Creek watershed. TCAD
parcel 6 and 7 show an even spread of HSAs across a cul-
tivated land area, while TCAD parcel 8 shows an uneven
spread of HSAs mostly in a landscape of deciduous forest
and scrubland.
Table 4.
Potential urban agriculture sites in Decker Creek
watershed relative to their affiliation with TCAD parcels
and the HSAs located on agricultural land use with prime
farmland (Prime Ag).
Decker Creek Watershed
TCAD
Parcel
HSAs
acreage
Total
Land
Acreage
Prime
Ag
Acres
Percent of
HSAs on
Total Land
Acreage
Percent of
HSAs on
Prime Ag
Acres
1 11.1 89.1 66.8 12.40 16.60
2 8.5 66.4 48.1 12.70 17.60
3 7.8 72 46.9 10.80 16.60
4 7.1 100.3 68.9 7.10 10.30
5 5.7 38.1 31.7 15.10 18.10
6 4.6 31.7 31.7 14.50 14.50
7 4 22.6 21.1 17.70 18.90
8 2.9 66.3 32.3 4.40 9.10
9 2.9 101.3 89 2.90 3.20
10 2.9 31.5 13 9.20 22.20
3.4. Delineated HSAs on Urban Farms
Green Gate Farms is a five-acre farm and the only classi-
fied urban farm in the Elm Creek watershed. The owners
currently rent the land to farm from an owner who holds
106 acres of the land in the Elm Creek watershed. Analysis
of the HSA data in the Elm Creek watershed results in no
delineated HSAs within the boundaries of the farm. When
HSAs are classified as existing on prime farmland with a TI
value greater than or equal to 14, there are still no HSAs in
the farm boundary, but there are 7.7 acres of HSAs within
the wider 106 acre boundary under scrutiny. The densest
network of HSAs resides within just 150 feet of the farm
boundaries in an open field adjacent to the farm. When the
CWQZ is accounted for, 2.5 acres of HSAs are protected
from development leaving 2.2 acres of HSAs unprotected
still within a dense network neighboring the farm.
Tecolote Organic Farm is the only urban farm within the
Decker Creek watershed. It comprises 65 acres in total and
contains 0.5 acres of HSAs on prime farmland. There are
only two 10m pixels within the CWQZ accounting for protec-
tion of four one-hundredths of an acre. In effect, Tecolote
Organic Farm is protecting 0.46 acres of HSAs on prime
farmland or 92% of the total HSAs. When HSAs are delin-
eated solely by a TI value greater than or equal to 15 and
not according to land use classification or prime farmland,
HSAs total 2.1 acres on the farm.
4. Discussion
The Decker Creek and Elm Creek watersheds reside on
the periphery of Austin and remain relatively undeveloped
at this point. However, city projections suggest the water-
sheds will be rapidly urbanizing in the near future as Austin
continues to increase in population and expand its urban
impervious cover. The implication that much of the land in
the suburban DDZ will be developed at some point poses a
significant threat to those watersheds and open land within
them including areas that hold value as prime farmland.
Given population growth demands, it will be important to
grow smartly, identifying areas best suited for development
and organized around interconnected open spaces that pro-
tect the environment and add a social and economic benefit
as integrated elements of a community, neighborhood, and
city. The IACP provides the framework for this type of smart
growth in Austin but will need to be implemented through
new sets of land use controls and tools that allow planners
and decision makers to make informed decisions about
where to develop and where not to develop. As the city
redevelops its land development code and initiates Phase
Two of the WPO concerning green infrastructure, tools such
as the one outlined in this research can provide valuable
information to incorporate urban agriculture as part of the
green infrastructure strategy in Austin.
4.1. Implementation of Urban Farms on HSAs: Best
Management Practices (BMPs)
The approach outlined in this research prioritized HSAs
by their spatial connection to potential urban agriculture
sites that could act as a green infrastructure tool. HSAs
in a watershed generate overland runoff and require land
uses that limit the amount of water resource degradation.
High-intensity urban land uses placed on HSAs such as a
commercial development or low-density residential develop-
ment have a significant impact on watershed degradation.
For example, an increase in impervious cover increases the
amount of stormwater runoff already generated in the area
resulting in potential floods, incised creek beds, or more
non-point source pollutant loads from residential lawns,
leaking septic systems, or carbon particulates from streets
and parking lots [
38
]. Furthermore, common stormwater
infrastructure such as catch basins, detention basins, pipes
and culverts quickly disperses polluted stormwater runoff
to downstream waterways. Urban farms can decrease the
49
amount of surface runoff that would otherwise flow to an
already overwhelmed storm drain by remaining as unde-
veloped land and increasing the amount of water that the
land can soak up. HSAs on potential urban agricultural land
protect the watershed by keeping it as low-intensity land
use, with the proper BMPs.
Traditional farming techniques typically have negative
impacts on water quality due to farming practices such as
fertilization along with pesticides and herbicide use. As a
result, HSAs in agricultural land uses have a higher poten-
tial to export pollutants from agriculture fields to streams.
If HSAs were to be located on potential sites for urban
agriculture, it would be necessary to implement BMPs that
provide risk reduction techniques to reduce contamination
of stormwater runoff from urban farms. Below are some of
the best practices for urban agriculture [38,42,43]:
•
Use organic farming principals that require no syn-
thetic pesticides or fertilizers;
•
Construct berms along the edges where the im-
pervious surface and farm meet to prevent erosion
and runoff;
•
Incorporate bio swales and retention ponds to collect
runoff and promote infiltration;
•
Use crop rotation and plant cover crops to hold soil
in place;
•
Avoid input of animal manure, instead use organically
produced compost as a fertilizer;
•
Install a rainwater re-use system that captures rain-
water then filters it into an underground tank for
irrigation use.
Real Food Farm is an example of a farm that integrates
stormwater management practices into urban farming. The
farm is located in Baltimore, Maryland, in the Chesapeake
Bay watershed, a watershed affected by the urbanization of
the area leading to large amounts of polluted stormwater
runoff. The farm installed a rainwater re-use system that
captures rainwater off the hoop houses and stores it an
underground cistern. Additionally, the farm incorporated a
retention pond and constructed bio swales and berms to
help mitigate stormwater runoff from the farm [43].
Another BMP model that the City of Austin could poten-
tially implement for urban farms is a sediment and erosion
control plan. Seattle’s urban farm code requires a man-
agement plan if an urban farm exceeds 4,000 square feet
[
44
]. One provision included within that plan states a given
proposed sediment and erosion control program for farm-
ers to follow. To approve a farm, the city considers the
potential impacts and mitigation of how a farm’s proposed
sediment and erosion control measures will affect the im-
pacts of runoff on the surrounding watershed. In addition,
Seattle resides in the King County Conservation District
which provides free soil nutrient testing on up to five sam-
ples, including compost [
44
]. This program allows farmers
to use soil amendments wisely in an effort to reduce water
pollution from over-fertilization.
In a sheer size comparison, traditional farms compared
to urban farms also typically have a broader footprint on the
surrounding environment. The larger the farm the higher
the potential to export non-point source pollution into wa-
terways. In Austin, urban farms (again, classified as farms
over one acre) average only 4.5 acres in total land area,
and, moreover, the actual plots that produce food occupy
fewer acres. Often embedded within the total land area
are woods, pasture, and fallow ground. If these areas re-
main undeveloped they may occupy space where HSAs
are located. Hence, potential urban farms using BMPs
and occupying space around future development in the two
researched watersheds can provide valuable community
benefits in the form of providing access to healthy food,
enriching green space, and protecting prime farmland, as
well as the added environmental benefit of leaving HSAs as
undeveloped land.
4.2. Opportunities at the Local Scale
The situation at Green Gate Farms in Elm Creek watershed
offers an instructive view of the pressures current and po-
tential urban farms confront as development encroaches
into the rural-urban fringe of Austin. In addition, Green Gate
Farms shows the value urban farms bring to a community
and why urban agriculture in the City of Austin should be
considered as a valuable land management tool.
Green Gate Farm is an organic farm occupying five
acres of leased land on a larger parcel of land that also con-
tains a large RV park and undeveloped land. The land sits
in an area experiencing major growth with the construction
of new subdivisions. An informal interview with one of the
farmers provided the following information. The farmers of
the land have been farming on it for the last 10 years paying
rent to one owner. Recently, the land was sold to a new
owner who hopes to develop an upscale RV park and man-
ufactured homes on the farmstead. Until recently, the two
original farmers lived on the land in an old farmhouse, but a
new condition applied by the current landowner stipulated
that the house can longer be used as a residence, forcing
the farmers to move off the land. The farmhouse now oper-
ates as an office for the farm and a non-profit called New
Farm Institute with a mission “to educate, assist and inspire
citizens and a new generation of sustainable farmers, with
a focus on the urban fringe” [
45
]. Currently, the farmers are
still under lease until summer 2016 and continue to operate
the farm, but whether or not they will be able to continue to
farm the land is uncertain.
Furthermore, the farmer indicated that the mission of
the farm has always been community oriented. As former
health professionals, the farmers’ priorities have been to
provide fresh produce to underserved families living in a
part of east Austin that is recognized by the USDA as a food
desert, an area with limited access to fresh food or exist-
ing one mile or more from a grocery store [
46
]. As part of
the mission to create a community resource for neighbors
of all incomes, the farm accepts Supplemental Nutrition
Assistance Program (SNAP) benefits (i.e. food stamps)
and Women, Infants, and Children (WIC) vouchers so that
50
citizens in the community can buy healthy local produce.
In addition, the farm has a robust community supported
agriculture (CSA) program that provides boxes of organic
produce, meat, eggs, and flowers to participating individ-
uals that choose to enroll in a weekly, monthly, or yearly
subscription service. During an on-site observation of the
farm, it became clear that community involvement is some-
thing that is not just talked about, but actually exists. Many
people dropped by on a Saturday afternoon to purchase
certified organic vegetables, dairy, meat, and eggs from the
farm stand, which is open to the public Tuesday, Friday and
Saturday. At least two families purchased produce with food
benefit cards. In addition, they have an open-door policy
that allows the public to experience a working urban farm
providing educational opportunities as wells as a relaxing
environment. On this particular Saturday, the farm hosted
a children’s birthday party surrounded by volunteers and
workshare members preparing the fields for Fall planting.
To protect beneficial urban farms like Green Gate Farm
and ensure that future urban agricultural opportunities exist
on prime farmland within the suburban DDZ, the Austin Sus-
tainable Food Policy Board (SFPB) serve as advisors to the
Austin City Council and the Travis County Commissioners
Court to improve the food system in Austin. As part of the
land development code update in Austin (CodeNEXT), the
all-volunteer SFPB working group is working with commu-
nity and board members“to improve upon the existing code
in a way that meets the needs of communities, farmers,
and regulators in the interest of a healthy, safe, secure, and
sustainable food system for all of Austin” [
47
]. The group’s
work includes providing recommendations on desirable land
use policies in the suburban DDZ [47] (below):
• Prioritize preservation of prime farmland;
• Establish limits on sub-dividing farmland;
•
Utilize community gardens in new housing developments;
•
Allow for conversion of underutilized industrial
sites/strip-malls into urban farms.
The Green Infrastructure working group in Austin is also
currently working on integrating green infrastructure as part
of land development code update to meet the provisions
set forth in the Imagine Austin Comprehensive Plan. The
SFPB working group and the Green Infrastructure working
group both provide paths by which their recommendations
can be integrated into the code revision process and ensure
that urban agriculture is considered a viable asset in the up-
dated land development code. The methods outlined in this
research to delineate HSAs on potential urban agricultural
sites as a green infrastructure strategy could prove useful
to both working groups as they look for ways to conserve
portions of Austin’s green space.
For example, consider the situation at Green Gate Farm
again: while the five acre farmstead does not contain any
prime farmland soils nor HSAs, the undeveloped fields next
to the farm do contain 2.2 acres of HSAs on prime farmland
that are not protected under the CWQZ. If an updated land
development code existed establishing land use controls that
“prioritized preservation of prime farmland” to include HSAs
as a part of the criteria that functions as green infrastructure
tool in the WPO then a portion of this land could be protected
from development and potentially be used as urban agricul-
ture site. Under this type of land management scenario
there could be an opportunity to move Green Gate Farm
onto the adjacent prime farmland that occupies the HSAs
in order to preserve environmental and social functionality
and services offered by the farmstead when the new owner
builds the RV Park. The protection of Green Gate Farm
would serve not only the underserved communities’ needs
with continued healthy fresh produce but also provide critical
watershed protection from the incoming development.
4.3. Limitations of the Research
The ability to remotely prioritize HSAs and potential ur-
ban agriculture sites is one advantage of employing a GIS
based approach as opposed to the costly and time con-
suming practice of visiting all sites. While the soil data
collected provides the necessary components to complete
the soil topographic index, it would be ideal to have on-site
collected data of the soil infiltration rates and soil depths as-
sociated with urban agricultural land in east Austin, enabling
a comparative analysis that quantifies exactly how much
urban farms help to reduce stormwater runoff. Furthermore,
ground truthing HSAs on the prioritized sites to verify that
there is a potential for surface runoff would further validate
the GIS based approach of delineating HSAs. Additionally,
2014 aerial imagery from NAIP was used to verify selected
sites in this study where cultivated cropland could be recog-
nized as potential urban agricultural land. It is also possible
to ground truth data using Google Earth, similarly to Taylor
and Lovell [
48
], who used this method to identify backyard
agriculture in Chicago. Nonetheless, before making any
policy decisions, on-the-ground site-checking of selected
HSAs on potential urban farms should be a necessary com-
ponent of any urban agriculture land inventory [13].
Another possible limitation of this study are the derived
threshold criteria determining the HSAs in both watersheds.
In this study, the threshold criteria for selecting HSAs are
TI values greater than or equal to 1.5 standard deviations
above the mean. This approach follows well-researched
methods from Mickle et al. [
37
] and Qui [
39
] who use sim-
ilar derivations. However, more information is needed on
the local characteristics of the watersheds in Austin that
could possibly determine a more suitable threshold value.
This could result in either leaving the value the same, or
increasing or decreasing the delineations of HSAs in the
study area depending on if that value is equal to, greater
than, or less than the value used in this study.
Another limitation of the study is the lack of analysis of
other important factors related to the feasibility of urban agri-
culture. When determining land use for future development,
urban agriculture faces strong competition from housing
and commercial developers; simply creating urban farms
instead of housing or businesses could decrease affordable
housing options or minimize job creating commercial devel-
51
opments. Like the set of BMPs urban farms use to mitigate
stormwater runoff, BMPs should also be created that prop-
erly locate urban agriculture without hindering access to
affordable housing.
5. Conclusion
While urban agriculture is a valuable tool in a city’s toolbox
of methods which can be used to create a more sustainable
city, it is by no means a solution to all the problems a city
endures. This study will add only one piece of knowledge to
an ongoing discussion and debate about urban agriculture’s
role in developing more sustainable cities. Nevertheless, this
research may help to further establish urban agriculture as
part of the discussion about strategies that could lead to a
more sustainable city. The social and economic benefits of
urban agriculture are well established and well known, but
the scientific inquiry into the environmental benefits of urban
agriculture is still lagging behind current needs and popular
enthusiasm. This research aims to add a spatially explicit
method to urban agriculture’s potential as a green infrastruc-
ture strategy that demonstrates the ability of urban farms to
mitigate surface runoff and provide environmental benefits to
a city. By validating urban agriculture as green infrastructure
it will help to integrate urban agriculture into public policy and
urban planning as a land management strategy.
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