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

Stormwater runoff is rainwater that flows over the ground, sometimes with extreme force, picking up mud and other pollutants in its path and depositing it into surrounding waterways.  Unlike water collected through sewage treatment facilities, stormwater runoff goes untreated directly into rivers and streams. In addition to the dangers of pollutants in untreated rainwater, mud and clay runoff accumulates on stream bottoms and in wetlands from levels of a few inches to a few feet.  This accumulation smothers plants and bottom dwellers, such as snails and mussels, on which larger fish and birds feed. The result can be the devastating loss of vital ecosystems. According to the National Weather Service, Alabama receives one of the highest average annual rainfalls in the United States. Widely regarded as a top threat to water quality nationwide, stormwater is, therefore, a particular threat to Alabama’s waterways, especially in the upper Cahaba watershed. As growth and development continue to challenge waterway health and supply, as well as local habitat, many citizens remain largely unaware of the damaging effects of what is commonly accepted as progress. Providing education for citizens, and especially engineers and contractors, about the dangers mud and pollution from development pose to Alabama’s waterways is vital. Once builders begin to understand how to protect the environment from pollution and that their onsite activities are being monitored by an educated public, they are more likely to decrease overall violations of the Clean Water Act. The ultimate goal of stormwater management is to improve the water quality of the state’s rivers and streams, all of which eventually flow on to Mobile Bay and into the Gulf of Mexico.

Numerous federal reports, regional studies, and state and local conservation organizations recognize increased sedimentation from non-point source pollution, primarily from development in the upper Cahaba basin, as the primary threat to water quality and species diversity in the Cahaba River. When surface sediments are disturbed during construction activities, nutrients often follow sediments in runoff. Sedimentation reduces available dissolved oxygen and the runoff of nutrients increases algae bloom; both types of runoff add to the assault on species survival.

In 2002, the U.S. Environmental Protection Agency (EPA) documented findings that sedimentation and nutrient loading were adversely affecting the biology of the Cahaba.¹⁷ There has been on official survey in the ensuing years. Since 2002, numerous instances of sedimentation disturbance have occurred in the Cahaba, especially in the headwaters of the watershed where development is increasing. After a sufficient rain (>0.50 inches) in the headwaters, the river at the Highway 280 bridge crossing often requires five to seven days to recover from turbid conditions.

As a result of the persistent lack of enforcement of clean water laws by ADEM, many private citizens have turned to the legal system for relief from the impacts on their enjoyment of the Cahaba River, costing both plaintiffs and defendants money and resources. Some non-profit conservation organizations, Cahaba Riverkeeper among them, actively advocate against adverse sedimentation and turbidity impacts from construction in the upper Cahaba. Cahaba Riverkeeper also advocates for ADEM reform and tighter EPA oversight for the administration of Alabama’s water quality enforcement program.

 

Almost four dozen municipal plants treat wastewater from homes, schools, and businesses and then discharge the effluent into the Cahaba. In increasing numbers, self-contained, packaged sewage treatment plants, serving residential subdivisions and commercial developments, are also proliferating in the area. Several industries also have permits to dispose treated wastewater into the river. Discharges of treated wastewater have increased over the last two decades in this high-growth area. The river also receives discharge from storm water drainage systems throughout the watershed.^{2-3, 6-7,10}

Fifteen wastewater treatment plants in the upper Cahaba Basin above Centerville, Alabama, are permitted by ADEM to discharge more than 41 million gallons per day of treated wastewater into the river. (See Maps) The wastewater treatment systems along the Cahaba each day discharge treated, partially treated and raw sewage (e.g., during storm sewer overflow) to the flow of the river. Discharge from treatment plants are why pathogens in many of the upper sections of the river are named as negative impacts to water quality on the ADEM 303(d) impaired waters list.

Farm animals, with access to the river and its primary tributaries, can also contribute pathogens, especially in the lower Cahaba where agriculture is more prevalent.

Uniquely, Cahaba Riverkeeper tests, documents and disseminates information on bacteriological pollution through social media outlets for rapid communication to the general public.