Urban and Suburban Lands

Urban and suburban lands—developed lands that range from major cities to small, single subdivisions—are a major source of pollution to the Bay. Everything we do on the land—from driving our cars to fertilizing our lawns—has an impact on the health of the Bay and its tributaries. Because of rapid population growth and related development, nitrogen, phosphorus and sediment from urban and suburban lands is the only pollution category in the Bay watershed that is still growing.

Polluted Runoff

Stormwater runoff from urban and suburban lands is now the fastest-growing source of pollution to the Bay. Sources of pollution from urban and suburban runoff include:

• Lawn and garden fertilizers
• Pet waste
• Septic tanks and wastewater treatment facilities
• Improperly discarded chemicals, such as motor oil
• Airborne nitrogen and chemical contaminants from automobiles, gas-powered lawn tools, industries and other sources
• Litter

When it rains, water either runs off the land or filters into the ground. In urban and suburban areas, where roads, rooftops, parking lots and other impervious surfaces are common, most stormwater runs off the hardened surfaces and into local streams and storm drains, and eventually to the Bay.

• As water runs across hardened surfaces, it picks up these pollutants, which can be harmful to aquatic life.
• Increased amounts of stormwater can also erode stream banks, contributing more sediment to the Bay and degrading stream habitats.

Septic Systems and Sewage Treatment

When development occurs in existing urban and suburban areas, wastewater generated by new residents is typically treated by a public wastewater treatment plant. But when new homes are built far from public infrastructure, their wastewater is usually treated by on-site septic systems.

Discharges from septic systems depend on a variety of technological and geographic factors; however, on average:

• Municipal wastewater treatment plants annually deliver about 3.1 pounds of nitrogen per person to the Bay and its rivers.
• Septic systems annually deliver about 9.5 pounds of nitrogen per person.

Fertilizer Use

Unlike many farmers using nutrient management plans, suburban residents often over-apply fertilizer to their lawns and gardens. The soil in residential developments is also highly compacted, so less fertilizer is absorbed into the ground. Instead, excess fertilizer runs off lawns into storm drains and streams, and is eventually carried to the Bay and its tributaries.

Air Pollution

What goes up, most come down; just like anything else, pollutants released into the air will eventually make their way down to the earth's surface. In particular, airborne nitrogen is a major contributor to poor water quality in the Bay and its tributaries. Scientists estimate that one-quarter to one-third of the nitrogen that enters the Bay comes from air deposition.

• Vehicles, gas-powered lawn tools, factories, power plants, dry cleaners and gas stations all release nutrients and chemical contaminants into the air.
• These airborne pollutants eventually fall back to the ground, where they can be carried by stormwater to the nearest water source.
• By removing forestland to make room for urban and suburban development, there are less trees to absorb harmful pollutants before they can make their way to the Bay.

Forest Fragmentation

Roads, subdivisions and other human uses divide 60 percent of Chesapeake forests into disconnected fragments surrounded by other land uses. Forest fragmentation isolates animal and plant populations into smaller areas, and makes forestland more vulnerable to development, fires and invasive species.