What is a primary concern associated with increased impervious surfaces?

The primary concern associated with increased impervious surfaces, such as roads, parking lots, and buildings, is indeed higher rates of stream erosion. When surfaces become impervious, rainwater cannot infiltrate the ground as it would in a natural, vegetated landscape. Instead, this water flows directly over these surfaces, increasing the volume and speed of stormwater runoff.

This rapid runoff can lead to a significant increase in the energy of the water reaching nearby streams and rivers. As a result, this higher flow rate can erode stream banks and beds, leading to sedimentation, habitat loss, and diminished water quality. Stream erosion can also alter the physical characteristics of waterways, potentially leading to further ecological impacts and destabilizing the stream ecosystem.

In contrast, increased infiltration of groundwater would typically decrease with more impervious surfaces, not increase. Similarly, soil moisture tends to be reduced in areas with greater impervious cover due to less water being able to permeate the soil. Lastly, urban areas with more impervious surfaces often experience higher temperatures due to the urban heat island effect, rather than lower temperatures. Thus, the concern with increased impervious surfaces primarily relates to the impact on streams and erosion rates.