What does the phrase “no net increase in runoff” mean?

The phrase “no net increase in runoff” refers to the concept that stormwater management practices aim to maintain runoff rates that are equivalent to what they were before any development occurred. This means that developments should not cause an increase in the volume or rate of stormwater runoff entering the drainage system or surrounding areas compared to pre-development conditions.

This approach is critical for reducing the impacts of urbanization, such as flooding and water quality deterioration, by ensuring that the natural hydrological cycle is preserved as much as possible. Maintaining pre-development runoff rates helps to mimic the existing landscape's ability to manage stormwater properly, which is essential for effective erosion and sedimentation control.

In contrast, the other choices do not align with the principle of no net increase in runoff. Eliminating runoff entirely during the rainy season would not be practical or reflective of natural systems, while allowing runoff only during specific times of the year does not account for the need for consistent management across seasons. Finally, permitting increased runoff as long as it is documented fails to adhere to the intent of maintaining overall runoff rates within allowed limits. Therefore, the correct response highlights the fundamental goal of managing stormwater effectively through consistent oversight and regulation of runoff rates.