Stormwater Map

Trees act as straws, pulling water from roots to leaves along urban streams, as well as on city streets. Explore the difference in stormwater runoff in neighborhoods with dense, healthy tree canopy compared to those without.  

The proportions of tree canopy relative to hard surfaces in a neighborhood influence the amount and speed of runoff entering urban streams and floodways. Trees planted along roadways, in parking lots, retention basins, and on the sides of streams can benefit communities by slowing and reducing fast runoff. The more runoff is reduced due to tree canopy, the less local flooding. 


For reference, an Olympic-sized swimming pool contains 2,500 cubic meters of water. The lightest shade of blue on the GIS Stormwater map receives over 200 Olympic swimming pools worth of water every year that could have been intercepted by trees and held in plant tissue and roots underground! The Federal Emergency Management Agency (FEMA) publishes maps of the relative risk of flooding in urban communities across the United States. In the Birmingham study area, floodways (rivers and streams) are shown as teal green and 500-year flood zones are shown in purple.

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