Assessing performance of ZCTA-level and Census Tract-level social and environmental risk factors in a model predicting hospital events

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Goetschius, Leigh G., Morgan Henderson, Fei Han, Dillon Mahmoudi, Chad Perman, Howard Haft, Ian Stockwell. 2023. “Assessing performance of ZCTA-level and Census Tract-level social and environmental risk factors in a model predicting hospital events.” Social Science & Medicine 326 (2023): 115943. doi:10.1016/j.socscimed.2023.115943


In the US, a lot of health data is analyzed using zip codes: they can easily be derived from addresses. Address zip codes are not addresses. They are mail carrier routes. The Census publishes Zip Code Tabulation Areas (ZCTAs), however, these aren’t the same as carrier routes. Both ZCTAs and carrier routes change quite a bit. So what happens if we geolocate addresses and then aggregate to the Census Tract level?

Results showed that increasing the granularity of area-based risk factors did not dramatically improve model fit or predictive performance. However, it did affect model interpretation by altering which SDOH features were retained during variable selection. Further, the inclusion of SDOH at either granularity level meaningfully reduced the risk that was attributed to demographic predictors (e.g., race, dual-eligibility for Medicaid).

The Modifiable Areal Unit Problem (MAUP) strikes again.

Mapping for Whom?

Communities of Color and the Citizen Science Gap

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Mahmoudi, Dillon, Chris L. Hawn, Erica H. Henry, Deja J. Perkins, Caren B. Cooper, and Sacoby M. Wilson. 2022. “Mapping for Whom? Communities of Color and the Citizen Science Gap.” ACME: An International Journal for Critical Geographies 21 (4): 372–88. ACME open access link


In this paper, we examine the geography of the citizen science project Community Collaborative Rain, Hail and Snow Network (CoCoRaHS). This project is an important project because it is used to produce national rainfall data. Capturing rainfall data is also important because of increase in hyperlocalized precipitation events. Using a zero-inflated hurdle model, we find that the geography of the rain gauges are in primarily wealthier, white neighborhoods, leaving communities of color and low-income communities unrepresented in weather models.

Scholars have shown that communities of color and low-income communities are most vulnerable to the impacts of climate change, and without intervention, scientists will miss localized events in these neighborhoods and these communities might go unrepresented in rainfall models, further exacerbating the disproportionate impact.

This paper should be construed as a critique of the important work by CoCoRaHS and its volunteers. Instead, it should be a call for deliberate engagement of “missing geographies and people” in all participatory/citizen science projects. We argue social and natural geographies are co-constructed, and thus if we are measuring only part of a social geography, then the natural science we produce from that geography may only serve one part of society.


Citizen science harnesses the power of nonscientist observations, often resulting in a vast network of data. Such projects have potential to democratize science by involving the public. Yet participants are mostly white, affluent, and well-educated, participants that contribute data from their residence or places they frequent. The geography of the United States is heavily segregated along lines of race and class. Using a Census Tract-level hurdle model, we test the relationship between the locations of the rain gauges from the citizen science project Community Collaborative Rain, Hail, and Snow Network (CoCoRaHS) with continuous variables for percent non-Hispanic white and median household income. We find whiter and more affluent Census Tracts are significantly more likely to have a rain gauge. The highly localized nature of precipitation combined with the uneven geography of storm-water infrastructure make data missing from citizen science projects like CoCoRaHS of vital importance to the project’s goals. We warn that scientific knowledge created from citizen science projects may produce scientific knowledge in service of wealthy, whiter communities at the expense of both communities of color and low-income communities.


Baltimore, Maryland and Portland, Oregon and the geography of tracts with rain guages.

One way to visually see the difference is by looking the geography of rain gauges with the percent BIPOC in Baltimore and Portland. On the left, Baltimore has numerous >80% BIPOC tracts with no rain gauges. The wings of the “black butterfly” are mostly unrepresented with the exception of rain gauges at large parks near the western city border. On the right, Portland’s inner eastside, where there is a cluster of tracts that are >80% white, are also well represented by rain gauges. Conversely, there are no tracts that are >80% BIPOC, but the 5 tracts that are 60%-80% BIPOC have no rain gauges. The areas that are 40-60%, especially outer east Portland, are not well represented. The paper has a more in-depth discussion and includes the hurdle model.

Doing Critical GIS

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Mahmoudi, Dillon, and Taylor Shelton. 2022. “Doing Critical GIS.” ACME: An International Journal for Critical Geographies, 21 (4): 327–336. ACME open access link


In 2019, Taylor Shelton and I organized a series of events at Red Emma’s Bookstore and Cafe. This paper is the attempts to bring together many of the themes we saw in the presentations. We focus on “what” we map and “how” we map. For example, how might we think about absences and presences on a map? Why is it that, for example, poverty are present in some places and absent in others⁠—and what is the relationship of those two (this is one of the core questions of the Relational Poverty Network)? And what is the process of critical mapping? Towards what end?

Doing Critical GIS Workshop and Conference

The full schedule and itinerary is available from the 2019 workshop and conference. UMBC hosts the workshop and conference website.

ACME Vol 21 No 4 Doing Critical GIS

ACME: An International Journal for Critical Geographies hosts the special issue. Major appreciation to the incredible ACME collective for working with us and the authors during COVID to get these papers out.

Doing Critical GIS
Dillon Mahmoudi, Taylor Shelton

What Can GIS Do?
Nick Lally

Situated Mapping Visualizing Spatial Inequality between the God Trick and Strategic Positivism
Taylor Shelton

Digital Cartographies of Displacement Data as Property and Property as Data
Erin McElroy

Mapping for Whom? Communities of Color and the Citizen Science Gap
Dillon Mahmoudi, Chris L. Hawn, Erica H. Henry, Deja J. Perkins , Caren B. Cooper, Sacoby M. Wilson

Mapping Violence against Indigenous Women and Girls Beyond Colonizing Data and Mapping Practices
Annita Hetoevehotohke’e Lucchesi

Pressing Pause, “Doing” Feminist Mapping
Meghan Kelly, Amber Bosse

Toward Queering the Map 2.0 A Conversation with Michael Brown, Larry Knopp, and Bo Zhao
Jack Swab, Jack Jen Gieseking

Toward a Fourth Generation Critical GIS Extraordinary Politics
Sarah Elwood

Mapping Juvenile Justice

Identifying Existing Structural Barriers to Accessing Probation Services

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Fountain, Erika and Dillon Mahmoudi. 2021. “Mapping Juvenile Justice: Identifying Existing Structural Barriers to Accessing Probation Services.” American Journal of Community Psychology 67 (1-2): 116-129. doi:10.1002/ajcp.12474


This paper was part of a special issue in the American Journal of Community Psychology which explicitly sought to engage in interdisciplinary approaches to community psychology. Our paper incorporates insights from human geography and GIS to identify the landscape of mobility for justice-involved youth in Baltimore. We argue that practitioners and lawmakers need to think spatially about uneven development to reduce the number of justice-involved youth that end up in prison because they could not get to court-mandated Department of Juvenile Services locations.

The majority of justice-involved youth are placed on probation; however, many of those same youth struggle to comply with probation requirements and are subsequently confined. In Baltimore, a full 20% of newly committed youth were detained for violations of probation. While there are various reasons youth fail to comply with probation requirements, there have been recent calls to consider the impact of structural and spatial barriers to accessing probation programs and services. In this study, we take a novel, interdisciplinary approach to identifying structural or spatial barriers facing justice-involved youth in Baltimore, MD. Specifically, we explore transportation barriers (i.e., vehicle access) and spatial disparities between youth residences and probation office locations. Our findings suggest that there are several barriers facing Baltimore’s justice-involved youth that may impact access to and engagement with juvenile probation. Specifically, we found that 1 in 3 youths reside in areas with extremely low levels of vehicle access and where the median household income is 25% below the city median. We also find that the majority of youth live beyond walking distances; many would require lengthy transit commutes. These findings highlight the structural and spatial barriers facing justice-involved youth that may impact access to and engagement with probation services.

Our findings indicate there are various spatial and structural barriers that justice-involved youth in Baltimore City face. First, a majority of youth live in areas marked by concentrated poverty and where many residents do not have access to a vehicle. About a third of the youth sampled live in areas marked by the most disadvantage; these youth live in areas where the median household income falls 30% below the Baltimore City median household income, and where between 30 and 70% of workers do not have access to a vehicle. Furthermore, almost all of these youth live beyond walking distance from DJS probation locations, effectively requiring them to use public transit or costly alternatives to attend regular meetings with their probation officer.

Reproducing Spatial Inequality

The sustainability fix and barriers to urban mobility in Portland, Oregon

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Mahmoudi, Dillon, Amy Lubitow, and MacKenzie A. Christensen. 2020. “Reproducing spatial inequality? The sustainability fix and barriers to urban mobility in Portland, Oregon.” Urban Geography 41(6), 801–822. doi:10.1080/02723638.2019.1698865


We explore how the language of “just sustainability” may become subsumed into a sustainability fix strategy, depoliticizing the utility of concepts such as justice and/or equity. Building from critical GIS insights,we combine digitized spatial data from participatory mapping exercises and community-organization-based focus group in Portland, Oregon, regarding a proposed six-mile biking and walking path around downtown. We find that 80 percent of participants’ typical travel destinations are outside of downtown Portland and that participants experience planning and sustainability in a highly localized manner, challenging the equity rationale of downtown investment. We argue the top-down planning model, which presumes that the spatial diffusion of benefits is equitable, is inherently ahistorical and fails to benefit those in historically marginalized neighborhoods. Finally, we argue for the value of community-oriented research, which, in this case, inspired a coalition of community organizations to formally oppose a city-led project based on the inequitable distribution of infrastructure benefits.

We show how development based on a sustainability fix hinders an equity evaluation whose primary metric is access to central city amenities, where “access” is perceived to be a mechanism that serves traditionally marginalized populations. The uneven spatial structure of the city instead reveals that wealthier, white central city residents have much higher rates of access to the proposed project than those connected to the project later through bike and pathway development.

When asked about their typical travel concerning the central city, participants either didn’t want to travel downtown or found that there were barriers to doing so. Traveling to and from the central city was not of immediate interest for a clear majority of our participants, despite the Green Loop project’s goals of creating infrastructure that would serve a large share of Portland residents. As one participant put it:

And the reality is that a lot of people who now live here don’t or can’t work downtown because toward downtown requires higher education. And it requires you being in very specific industries . . . a lot of folks are working in blue-collar industries . . . So a lot of our folks who live here, downtown isn’t where people are going to work.

Critical Geographic Information Science (GIS)

What is Critical GIS?

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Mahmoudi, Dillon. 2020. “Critical Geographic Information System.” In International Encyclopedia of Human Geography, edited by Audrey Kobayashi, 2nd edition, 3:31–36. Thousand Oaks, CA: Elsevier. doi:10.1016/B978-0-08-102295-5.10530-X

This article is a revision of the previous edition article by N. Schuurman, volume 2, pp 363–368.

We also published commentary in EPA covering the topics and discussions at the 2014 Revisiting Critical GIS workshop and conference.


Critical GIS combines the technical field of geographic information science (GIS) with heterodox social theory. The result is a rich field whose technical focus incorporates cartography, computation, big data, and information science, with theoretical moorings in critical human geography, feminism, STS, and scholar-activism. A series of critiques of the technoscientific nature of traditional GIS undergird the formation of critical GIS as a subdiscipline and continues to contribute to its evolving definitions. One notable challenge for any definition of a critical GIS is the continued development of the technologies of GIS itself and the social, political, and economic transformations that reflect and feedback into the continued evolution of technology. Critical GIS is thus dynamic but has rich histories that include critiques and contributions of scholars that mirror science and technology studies (STS), feminism and GIS, ontology, research, and participatory GIS (PGIS).

Revisiting Critical GIS

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Thatcher, Jim, Luke Bergmann, Britta Ricker, Reuben Rose-Redwood, David O’Sullivan, Trevor J. Barnes, Luke R. Barnesmoore, et al. 2016. “Revisiting Critical GIS.” Environment and Planning A 48 (5): 815–24. doi:10.1177/0308518X15622208

Top image: taking the ferry to Friday Harbor, WA from Anacortes, WA. Bottom image: participants enjoying sun as we debrief and discuss next steps.

I also updated the Critical GIS entry in the Encyclopedia of Human Geography.


This paper recounts many of the insights and discussions from the Revisiting Critical GIS conference/workshop in 2014. At this event, thirty researchers met at the University of Washington’s Friday Harbor Laboratories to revisit the spirit of ‘critical GIS’ in approaching questions both emerging and enduring around the intersection of the spatial and the digital. While the 1993 gathering at Friday Harbor, like much early work in critical GIS, can be read as ‘peace talks’ brokered between warring factions, with wary GIScientists and cautious Human Geographers on opposite sides of the table (Schuurman, 2000), more than a decade into the 21st-century, our meeting drew an open field of scholar-practitioners bursting with questions, varied experiences, and profound concerns.

Socio-spatial Differentiation in the Sustainable City

A mixed-methods assessment of residential gardens in metropolitan Portland, Oregon, USA

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McClintock, Nathan, Dillon Mahmoudi, Michael Simpson, and Jacinto Pereira Santos. 2016. “Socio-Spatial Differentiation in the Sustainable City: A Mixed-Methods Assessment of Residential Gardens in Metropolitan Portland, Oregon, USA.” Landscape and Urban Planning 148 (April): 1–16. doi:10.1080/01944363.2015.1135072

See other related articles on Nathan McClintock’s website.


As cities take center stage in developing and brokering strategies for sustainability, examining the uneven distribution of green infrastructure is crucial. Urban agriculture (UA) has gained a prominent role in urban greening and food system diversification strategies alike. Despite that it is the preeminent form of food production in North American cities, residential gardening has received little scholarly attention. Moreover, research on the intra-urban variability of home gardens is sparse. In this paper, we use a mixed-methods approach to assess the scale and scope of residential gardens in Portland, Oregon, a metropolitan region renowned for its innovations in sustainability. Using a combination of mapping, spatial regression, and a mail survey, we compare residential UA and the characteristics and motivations of gardeners in two socioeconomically differentiated areas of Portland and one of its major suburbs. Results demonstrate that engagement in UA is differentiated along both spatial and socioeconomic lines, with more educated respondents engaging for environmental reasons and more low-income respondents relying on their gardens for food security. We contextualize our findings within broader urban processes, e.g. reinvestment in the urban core and displacement of poverty to the periphery.

For policymakers, our results suggest the need for sustainability messaging that is sensitive to a variety of motivations and that resonates with a diverse population. For a city to reach a broader population, it may need to reframe its sustainability goals in new ways, while attending to the structural constraints to food access that cannot be resolved through local food production alone.