Impervious Surfaces

Definition

Impervious surfaces are man-made materials that do not allow water to penetrate into the ground, leading to increased runoff and affecting local hydrology. These surfaces include roads, rooftops, sidewalks, and parking lots, all of which play a significant role in urban environments by altering the natural water cycle. The prevalence of impervious surfaces is a critical factor in urban hydrology as they contribute to flooding, erosion, and the degradation of water quality in nearby bodies of water.

5 Must Know Facts For Your Next Test

1. About 30-50% of urban areas can be covered by impervious surfaces, significantly affecting local ecosystems and water cycles.
2. Impervious surfaces can lead to increased peak flow rates in streams during storms, which raises the risk of flooding.
3. Water quality is often compromised by runoff from impervious surfaces that carries pollutants like oils, heavy metals, and nutrients into waterways.
4. The presence of impervious surfaces contributes to urban heat islands, where cities become significantly warmer than surrounding rural areas due to heat retention.
5. Incorporating green infrastructure can help mitigate the negative impacts of impervious surfaces by enhancing infiltration and reducing runoff.

Review Questions

• How do impervious surfaces impact the hydrological cycle in urban areas?
  • Impervious surfaces disrupt the natural hydrological cycle by preventing water from infiltrating into the ground. Instead of soaking into the soil, rainwater runs off these surfaces, leading to higher volumes of surface runoff. This not only increases the risk of flooding but also reduces groundwater recharge and alters stream flow patterns. As a result, urban areas often experience more intense and frequent flooding events due to this change in water dynamics.
• Evaluate the effectiveness of different strategies to manage the challenges posed by impervious surfaces.
  • Effective strategies for managing the challenges associated with impervious surfaces include stormwater management techniques such as retention ponds, bioswales, and permeable pavements. These solutions aim to reduce runoff volume and improve water quality by allowing water to infiltrate or be treated before reaching storm drains. While traditional drainage systems can efficiently move water away, these green infrastructure approaches can provide additional ecological benefits, enhancing urban resilience against flooding while promoting biodiversity.
• Propose a comprehensive plan for reducing the environmental impact of impervious surfaces in a city experiencing frequent flooding.
  • To reduce the environmental impact of impervious surfaces in a flood-prone city, a comprehensive plan could involve retrofitting existing infrastructure with green technologies such as green roofs, rain gardens, and permeable paving materials. Implementing zoning regulations that promote mixed-use developments with adequate green spaces would also be beneficial. Additionally, public education campaigns can encourage residents to adopt practices such as rainwater harvesting. This integrated approach would help enhance water infiltration, reduce runoff rates, improve water quality, and ultimately create a more sustainable urban environment.

Related terms

Runoff:

The flow of water that occurs when excess stormwater, meltwater, or other sources flow over the ground surface rather than being absorbed.

Stormwater Management:

The process of controlling the quantity and quality of stormwater runoff to reduce flooding and prevent pollution in waterways.

Green Infrastructure: A network of natural and semi-natural systems that provide environmental benefits and help manage stormwater through techniques like permeable pavements and green roofs.