What is a function provided by a simple rooftop disconnection?

A simple rooftop disconnection primarily serves to reduce the annual runoff volume. This practice involves directing rooftop drainage away from impervious surfaces and allowing the water to be absorbed by vegetated areas or permeable surfaces, such as lawns or gardens. By doing so, the volume of stormwater runoff generated from impermeable surfaces is minimized, leading to less water entering storm drains and potentially causing flooding or water quality issues downstream.

This method not only helps manage stormwater effectively but also supports groundwater recharge and can improve local water quality by allowing for natural filtration processes in the soil and plants. The reduction of runoff volume is a key aspect of sustainable stormwater management strategies, making rooftop disconnection an important practice in urban environments where impervious surfaces are prevalent.

The other choices do not correctly represent the main purpose or benefit of rooftop disconnection. For instance, while carbon dioxide reduction could be a secondary benefit of increased vegetation, it is not the primary function of this practice. Soil degradation and impervious surface expansion are counterproductive outcomes that contradict the goals of effective stormwater management strategies.