Stormwater runoff

Definition

Stormwater runoff is the flow of excess rainwater or melted snow that does not infiltrate into the ground but instead travels over impervious surfaces, such as roads, parking lots, and rooftops, eventually entering streams, rivers, or storm drains. This phenomenon is particularly significant in urban areas where natural land cover has been replaced by man-made surfaces, leading to increased volume and velocity of runoff, which can contribute to flooding and water pollution.

5 Must Know Facts For Your Next Test

1. Stormwater runoff can carry pollutants like oils, heavy metals, and nutrients from urban surfaces into local water bodies, leading to degradation of water quality.
2. Increased stormwater runoff due to urbanization can lead to erosion of stream banks and habitat loss for aquatic life.
3. Green infrastructure practices, such as rain gardens and permeable pavements, can help mitigate stormwater runoff by promoting infiltration and reducing the volume of water entering storm systems.
4. Regulatory frameworks often require cities to manage stormwater through permits that enforce the implementation of control measures to protect waterways.
5. The volume of stormwater runoff can be influenced by factors such as rainfall intensity, duration, land use patterns, and the condition of the urban drainage system.

Review Questions

• How does the presence of impervious surfaces in urban environments affect the quantity and quality of stormwater runoff?
  • Impervious surfaces significantly increase both the quantity and speed of stormwater runoff in urban environments. Since these surfaces do not allow water to infiltrate into the ground, rainwater flows directly into drainage systems or nearby bodies of water. This increased runoff can lead to higher pollutant loads because it picks up contaminants from roads and other urban areas before discharging into streams or rivers, ultimately degrading water quality.
• What role do best management practices (BMPs) play in managing stormwater runoff in urban settings?
  • Best management practices (BMPs) are crucial for managing stormwater runoff in urban areas by reducing its quantity and improving its quality. BMPs include techniques like green roofs, bioswales, and rain gardens that promote infiltration of water back into the ground. By implementing these practices, cities can mitigate flooding risks, decrease pollutant loads in waterways, and enhance overall urban resilience against storm events.
• Evaluate the impacts of increased stormwater runoff on local ecosystems and urban infrastructure due to urbanization.
  • Increased stormwater runoff due to urbanization has significant negative impacts on local ecosystems and urban infrastructure. The higher volumes of runoff can lead to severe flooding, causing damage to roads, bridges, and buildings. Ecosystems suffer as sedimentation disrupts aquatic habitats, while increased nutrient loading can cause algal blooms that deplete oxygen in water bodies. Overall, these effects create a cycle of degradation that threatens both biodiversity and human safety in urban areas.

Related terms

Impervious surfaces: Surfaces that do not allow water to infiltrate into the ground, such as concrete, asphalt, and buildings.

Runoff coefficient: A numerical value used to represent the fraction of rainfall that becomes runoff from a specific surface, influenced by land use and surface type.

Best management practices (BMPs): Techniques or strategies employed to manage stormwater runoff and reduce its negative impacts on water quality and quantity.