Urban runoff

When rain falls, the water goes several places. It percolates down through the soil and ends up as groundwater. It soaks into the soil, is drawn up through plant roots and released into the atmosphere by transpiration. It also flows over the land surface into a local body of water like the St. Johns River. When this third process occurs in urbanized areas, with water flowing over streets, parking lots, construction areas, and golf courses, it is termed urban runoff. Human-caused sources of overland flow, such as sprinklers, are also included in the definition of urban runoff.

Urban runoff is a concern to all of us because it is often heavily polluted. In fact, in some areas it is believed to be the main cause of water pollution. Rainwater can become contaminated in the process of flowing across the urban landscape. Sources of this contamination include the following:

• Motor oil (dripping cars, dumping of used motor oil)
• Antifreeze or coolant (dripping cars, dumping of used antifreeze or coolant)
• Other automobile fluids and greases
• Rubber dust from tires
• Pet wastes
• Fertilizers and pesticides
• Paints and thinners (disposed of improperly or dumped down a storm drain)
• Dirt from construction sites or unpaved roads
• Industrial yards
• Litter

The urban pollution problem is characterized by many individuals all contributing a little bit to make a large problem.

There are several important differences between runoff in an urban setting and runoff in a more natural setting. In an urban area, cement, asphalt, and other impermeable surfaces (surfaces that water cannot pass through) cover more land area. Water that would soak into the ground in natural areas runs off in urban areas. A much greater volume of water runs off urban areas than rural areas. Because pavement moves water efficiently, urban flows tend to move much faster, peak sooner, and have more scouring power than rural flows. So not only are more contaminants (such as pesticides, fertilizers, oil, and grease) found in urban areas, but the rapidly moving water is more capable of picking up contaminants, even when attached to soil particles, and washing them into a nearby water body.

One of the major factors contributing to urban runoff pollution is simple ignorance of stormwater systems and storm drains. Storm drains, the metal grates seen along curbs and in streets, do not lead to water treatment plants. They drain directly to the St. Johns River via ditches, streams, or drains. Storm drains are installed to prevent flooding. They are designed to drain rainwater off the streets and put the water as quickly as possible into local lakes or rivers.

The only treatment that exists for stormwater is retention/detention ponds. These ponds remove a certain amount of pollutants and sediments found in urban runoff but often do not remove pesticides or nutrients. Additional treatment of runoff would be expensive and require the construction of additional treatment facilities.

Grades 6–8

Mathematics
Algebraic Thinking
Standard 1: The student describes, analyzes, and generalizes a wide variety of patterns, relations, and functions.
MA.D.1.3.2: The student creates and interprets tables, graphs, equations, and verbal descriptions to explain cause-and-effect relationships.
Data Analysis and Probability
Standard 1: The student understands and uses the tools of data analysis for managing information
MA.E.1.3.1: The student collects, organizes, and displays data in a variety of forms, including tables, line graphs, charts, bar graphs, to determine how different ways of presenting data can lead to different interpretations.

Science
Processes that Shape the Earth
Standard 2: The student understands the need for protection of the natural systems on Earth.
SC.D.2.3.2: The student knows the positive and negative consequences of human action on the Earth’s systems.
How Living Things Interact with Their Environment
Standard 2: The student understands the consequences of using limited natural resources.
SC.G.2.3.2: The student knows that all biotic and abiotic factors are interrelated and that if one factor is changed or removed, it impacts the availability of other resources within the system.
SC.G.2.3.4: The student understands that humans are a part of an ecosystem and their activities may deliberately or inadvertently alter the equilibrium in ecosystems.

Social Studies
People, Places, and Environments (Geography)
Standard 2: The student understands the interactions of people and the physical environment.
SS.B.2.3.6: The student understands the environmental consequences of people changing the physical environment in various world locations.
SS.B.2.3.9: understands how the interaction between physical and human systems affects current conditions on Earth.

Grades 9–12

Mathematics
Algebraic Thinking
Standard 1: The student describes, analyzes, and generalizes a wide variety of patterns, relations, and functions.
MA.D.1.4.1: The student describes, analyzes, and generalizes relationships, patterns, and functions using words, symbols, variables, tables, and graphs.
Data Analysis and Probability
Standard 1: The student understands and uses the tools of data analysis for managing information.
MA.E.1.4.2: The student interprets data that have been collected, organized, and displayed in charts, tables, and plots.

Science
Processes that Shape the Earth
Standard 2: The student understands the need for protection of the natural systems on Earth.
SC.D.2.4: The student understands the interconnectedness of the systems on Earth and the quality of life.
How Living Things Interact with Their Environment
Standard 2: The student understands the consequences of using limited natural resources.
SC.G.2.4.6: The student knows the ways in which humans today are placing their environmental support systems at risk (e.g., rapid human population growth, environmental degradation, and resource depletion).

Social Studies
People, Places, and Environments (Geography)
Standard 2: The student understands the interactions of people and the physical environment.
SS.B.2.4.4: The student understands the global impact of human changes in the physical environment.