Significant development has occurred in the upper Cahaba watershed in the last few decades. In 2002, the EPA published GIS land use data indicating that in 1998, 38% of the Cahaba watershed was categorized as “disturbed,” up from 8.8% in 1990. In the same study, Buck Creek, a major tributary to the Cahaba River, had a watershed that was 63% “disturbed.” Loss of riparian habitat around the Cahaba River increases stream flow rates and volumes, causing erosion of the river banks and flooding of home sites downstream in many areas. For example, effects of flooding and erosion can be seen today downstream of the Liberty Park at the I-459 and Highway 280 corridor and downstream of the Hwy 280 bridge crossing.
Not only does an increased flow volume during wet weather events cause erosion and flooding, it is also an indication of an increase in impervious cover in the headwaters of the Cahaba. Impervious cover contributes additional threats to the river system, including temperature changes, non-point source runoff of pollutants and toxicants (oils, metals, combustion products, etc.), as well as additional risk of flooding and erosion. With increased flow volumes, streams and rivers are channeled and slowed, contributing to increased temperatures and lower dissolved oxygen in the water, threats to species diversity. In 2000, at least one 122 sq. mile segment of the upper Cahaba watershed was covered with almost 20% impervious cover.19