Race and Stormwater in LA County

Los Angeles County as we know it today is mostly covered in asphalt and concrete. But travel around the county and you can see that certain neighborhoods have more of these impervious surfaces, and other neighborhoods have more parks, trees, and plants. This unequal distribution of impervious surfaces, along with their environmental and social consequences, is a legacy of historic racist policies. But how much do impervious surface levels still vary by race today? And how much is it solely because of race and not something else? Here, we empirically answer these questions.

Our results highlight how institutional racism has shaped neighborhoods, which can elicit anger, sadness, and frustration. However, we hope that our results will be viewed as an opportunity for the public and decision-makers, including the Los Angeles Regional Water Quality Control Board, to act. The region faces an unprecedented drought, hotter temperatures, and chronically impaired waters, among other environmental challenges, and residents experience environmental impacts unequally. Thoughtful targeting of green stormwater infrastructure can help the county address these challenges while also helping to correct systemic injustices.

Los Angeles County wasn't always covered with asphalt and concrete. It was once lush with forests and marshlands that supported multiple indigenous populations, including the Gabrieleños, Gabrielino/Tongva, Fernandeño Tataviam, Chumash, and others before them. When the Spanish began colonizing California in the mid-1700s, there were at least 310,000 indigenous people organized into about 500 political units and was one of the most linguistically diverse places in the world.

Despite the Spanish enslaving and murdering indigenous people in the mission system, and government-sponsored militias hunting them down in the 1800s, they resisted, and as a result, their descendants survive today. However, the landscape and the populations here underwent massive transformations.

By the early 20th century, LA was where people from other parts of the U.S. and around the world came in search of opportunity.

But opportunities weren't available equally for all. In 1892, Lee Sing sued the city of Ventura for restricting Chinese people from living in the city. Federal courts ruled that while municipalities could not discriminate, individuals could. Then in 1902, the first racial housing covenant was filed in LA, which kept non-white people from purchasing property. The LA Realty Board then campaigned to put racial housing covenants on as many new developments as possible. 

The Home Owners Loan Corporation, which operated from 1933-1951, issued home loans across the country according to a rating system where green and blue neighborhoods were desirable, yellow was in decline, and red was considered hazardous, which is where the term “redlining” comes from. Homogenous white neighborhoods were favored while neighborhoods with more people of color were rated poorly. It was more difficult for residents in undesirable neighborhoods to obtain home loans, and they received less favorable terms if they did, effectively  blocking communities from creating intergenerational wealth .

Meanwhile, as LA County grew, more and more roads were paved to accommodate automobiles and development.

Also, in order to tame the flood-prone LA River, the U.S. Army Corps of Engineers began paving over the river in the 1930s, transforming it into concrete-lined channel to move stormwater quickly out to the ocean.

Growing swaths of asphalt and concrete went hand in hand with the growth of LA County. However, as with other cities across the US, the distribution of impervious surfaces also happened unevenly, with richer, whiter neighborhoods able to have more parks and trees, and therefore, less impervious surfaces ( Locke et al. 2021 ,  Nardone et al. 2021 ,  Zhou et al. 2021 ,  McDonald et al. 2021 ,  Watkins and Gerrish 2018 ).

While these impervious surfaces allowed for urban development, they have also led to adverse environmental impacts. Among them is polluted stormwater runoff. When it rains, pollutants get washed off streets and buildings and into channelized rivers like the LA River and into the Pacific Ocean. Every rain event is also a missed opportunity to capture stormwater and replenish groundwater aquifers, important sources of local water. This has become increasingly important as climate change has brought the region its most severe drought in at least 1,200 years.

Large areas of impervious surfaces also lead to urban heat island effects, as the asphalt and concrete get hotter and retain more heat than natural and vegetated surfaces. In cities across the U.S., including  Los Angeles , the poor and people of color bear the brunt of urban heat ( Hoffman et al. 2020 ,  Benz and Burney 2021 ,  Hsu et al. 2021 ).

Green stormwater infrastructure can act as natural sponges that not only help with capturing stormwater and reducing polluted runoff, but also provide an array of other benefits, such as reducing urban heat and flood risk, improving air quality, increasing wildlife habitat, improving neighborhood aesthetics, and increasing recreational opportunities when installed thoughtfully. Below are some diagrams of green stormwater infrastructure. More information and examples are available at  U.S. EPA .

As for race data, percentages of racial groups by Census tract were calculated for the county's largest racial groups - Hispanic, white, Asian, and Black. Unfortunately, Native American and Pacific Islander groups were not analyzed due to low population numbers leading to statistical limitations. Populations by race were divided into quintiles, with each quintile representing each 20th percentile of a population, i.e. the first quintile represents the lowest 20th percentile and the fifth quintile represents the highest 20th percentile. How do impervious surface levels fall along these quintiles?

But race is unfortunately correlated with other factors, like median income and population density, which also affect impervious surface levels. How much is neighborhood impervious surface explained by race when we control for these other factors?

To answer this question, we compiled data on other determinants of imperviousness – median income, owner-occupied rates, and population density from the U.S. Census American Community Survey, as well as land use variables (percent single-family homes, multi-family homes, commercial, industrial, and agricultural) from the Southern California Association of Governments. We also controlled for influences from neighboring Census tracts. For example, residents may see neighbors adding greenery to their properties and may get inspired to do the same. These neighbor effects were accounted for with spatial autoregressive combined (SAC) regression models.

Climate change is making our region experience more extremes. It has not only been getting hotter and dryer, but we are also more likely to experience extreme storm events and flooding. The need for the co-benefits provided by green stormwater infrastructure, such as increased local water supply, decreased urban heat, and flood mitigation, will only increase. Decisions on where to install green stormwater infrastructure should account for race and in general be targeted to areas with higher populations of people of color. This should be done for both moral and practical reasons, as it would help correct for racial inequities while also capturing and treating stormwater where there is most opportunity. While there are existing efforts, like the  Safe Clean Water Program , to put stormwater projects in areas with higher populations of people of color and in lower income communities,  Los Angeles Waterkeeper  has found that there has been little progress on replacing impervious surfaces with natural surfaces. More still needs to be done to expand the distribution of green infrastructure throughout Los Angeles County.

Addressing stormwater pollution, especially through the lens of racial equity, requires a multifaceted response. One great thing about green infrastructure is that it can be incorporated into something you probably already care about. Here are some ideas:

Participate in meetings of the  Safe Clean Water Program  for your local Watershed Area Steering Committee if you want a say in a variety of regional stormwater projects, such as retrofitting parks and creating Green Streets.

If you feel strongly about greening schools, you can get involved with the  Los Angeles Living Schoolyards Coalition . The Los Angeles Unified School District is the largest landowner in the greater Los Angeles area, and greening all schools would make a major impact on capturing stormwater and reducing the urban heat island effect. It would also create better learning environments for students by reducing stress and improving educational outcomes and health.

Or maybe you want to focus your efforts on increasing the urban tree canopy. Get involved with a nonprofit, such as  City Plants ,  TreePeople ,  Northeast Trees ,  Pacoima Beautiful , or any others you feel would be a good fit.

Or perhaps you also care about land use or transportation in your neighborhood. You can attend public meetings of your local departments of planning, parks and recreation, or transportation, and advocate for more green infrastructure to be incorporated in your municipality’s plans. 

Or do you want to address stormwater where you live? Consider installing green infrastructure on your property, or talk to your landlord about this, especially if you live in an area without much greenery. If your property has a lawn, think about taking advantage of  turf replacement rebates  and replace your lawn with a rain garden. The rebates in LA County require installment of a  rainwater capture feature . You’ll help conserve water too!

These are just some ideas and certainly do not encompass everything that can be done. Furthermore, the organizations mentioned here are just a few examples of the many community-based and environmental organizations in LA County. The most important thing is that you get engaged and push for opportunities for green infrastructure, especially in neighborhoods that need it most.