City of Chicago Flood Claims Against Tree Canopy Access by Neighborhood Area
Purpose
This map looks to illustrate a spatial pattern between tree canopy access and flood risk in Chicago neighborhoods. While it does not represent a strictly causal relationship, it can be used to represent a correlation between the two factors. Neighborhoods with low tree canopy coverage also tend to be lower income, with higher risk of soil or air contamination, higher flood susceptibility, and worse topsoil conditions. By illustrating some elements of this relationship, this map helps paint a broader picture about neighborhoods most in need of ecological restoration, and the economic/environmental consequences of failing to do so. As this map was created as an early semester project, it does not include more complicated or in-depth methods of data analysis to statistically identify the strength of the correlation.
Rather than introduce that data analysis into this piece, it was kept largely as submitted, to represent an early step and pattern of growth across my GIS course load, project work and education.
Background
Chicago is often lauded as a city in a region uniquely well situated to deal with the struggles of climate change. However, this commonly obscures the region’s incoming struggles. While other regions are expected to become hotter and drier, losing access to water - Chicago is expected to become wetter, and experience more severe storm water and flooding conditions over the next half century. Some Chicago neighborhoods, typically on the north side are better prepared than others to deal with this change, with better topsoil, tree canopy to capture the water before it hits the ground, and better outcomes historically from flooding conditions. South and West side neighborhoods tend to fare far worse. This map illustrates a correlation between tree canopy access and flooding on a neighborhood level. While a lack of tree canopy does not represent a causal relationship, it does clearly represent a mitigating factor.
This data was cleaned to avoid problems created by NA values or inconsistent data entry.
Methodology and data sources
This map uses data sets from the Chicago Community Health Atlas. This includes all data and map elements including the Chicago Community Boundaries and the Chicago City Boundary, as well as Tree Canopy Coverage and Flood Claims. Vitally, this analysis is descriptive rather than inferential — it identifies a spatial pattern but does not quantify the strength of the relationship.
Tree Canopy coverage is calculated as a percent of coverage for a community area. This means that if a community area shows 20% coverage, it is 20% shaded by tree canopy. Meanwhile, flood claims are calculated by rate, showing a percent of adults in a given area who have reported flooding of their residences. This data set does not include commercial or business properties which have flooded; it is limited to households, apartment complexes, and other kinds of residences. With little change, this map could be made to include other factors such as economic well being, and other data points derived from census data and the atlas.
Maps
The maps below are of tree canopy coverage and flood data. Both were taken from the Chicago Community Health Atlas and therefore only show data at the community level. More detailed analysis of tree canopy access does exist - I highly recommend viewing the Morton Arboretum’s tree canopy priority and equity maps, found here: https://mortonarb.org/plant-and-protect/chicago-region-trees-initiative/priority-maps/
The flood data map shows residential flooding incidence claims by neighborhood. This is broken down by the percentage of adults in a community area. So, if South Lawndale’s rate is 28.8 plus or minus 5.7% of adults, 28.8 percent of adults living in residences in the South Lawndale area reported that their residence flooded at least once in the last year, plus or minus 5.7%.
This map shows tree canopy coverage as a percent of area coverage at the Chicago community level. While this map is specifically observing tree canopy access against flood claims, it is important to note that tree canopy equity is an important spatial equity indicator correlating to reduced ambient noise, reduced ambient heat, and several other factors of spatial equity.
As this is an early semester project, this analysis does not include more in-depth data analysis methods which could measure tree canopy access and flood claims against other measures of equity. However, this map does illustrate a correlation between the two.
This map shows flood claim incidents as a percent of adults for each community area. As noted above, this means that if South Lawndale’s rate is 28.8 plus or minus 5.7% of adults, 28.8 percent of adults living in residences in the South Lawndale area reported that their residence flooded at least once in the last year, plus or minus 5.7%.
As this is an early semester project, this analysis does not include more in-depth data analysis methods which could measure tree canopy access and flood claims against other measures of equity. However, this map does illustrate a correlation between the two.
Analysis at a Glance
While flood incidence and tree canopy equity are commonly correlated, this project does not conduct any data or statistical analysis to identify the strength of that correlation. At a glance, we can identify community areas on the west side that deal with both low tree canopy coverage and high incidence of flooding. However, the north and south sides complicate the picture. Both regions include areas of high tree canopy coverage, with some of the highest coverage neighborhoods actually on the south side. However, nearly all south side neighborhoods report higher incidence of flooding than their north side counterparts. This suggests that tree canopy may be a mitigating factor in flood risk reduction, but not a determinative one: soil permeability, drainage infrastructure, and topography would all need to be studied for a complete picture.